Essay title - Magnetic Nanoparticles seperation
1.0 Introduction
This review will be investigating the use of magnetic nanoparticles within seperation processes. The motivation for this report is to formulate an investigation into the use of magnetic nanoparticles within seperation and review the current and existing research that has been carried out into this. This will hopefully enable a conclusion to be drawn into whether this technology has a future within seperation processes. It will also create a critical analysis of these articles to construct a formal report on the validity and success of the selected papers.
seperation processes have been evolving for a number of years due to increasing cost and limitations in seperation efficiency. For seperation to occur between components there must be a difference in properties between he species being separated. seperation processes can be controlled by the equilibrium, the rate or by mechanical seperation. For the seperation of miscible liquids three commonly used methods are:
- Distillation – Dependence on difference in volatilities.
- Liquid-liquid extraction – Dependence on difference in solubility in a liquid solvent.
- Freezing – Dependence on difference in melting point.[1]
For many of these processes to occur, an understanding of the fluid dynamics of the vessel, as well as the mass and heat transfer properties of the materials and chemicals being used for the seperation must be appreciated. This type of information can be difficult to find and may need to be produced if there is not a lot known about the materials being separated.
However, for any seperation to be considered, the safety and the impact on the environment must first be acknowledged. The plant must be operated and maintained appropriately to ensure there is a minimum risk to the safety of the workforce and the local community. The plant running the seperation must also take responsibility for conserving natural resources at the same time as ensuring effluent and other potentially dangerous materials are not discharged directly into the environment. This is in conjunction with the efficiency of the seperation taking place and the cost of the process. This is why new methods of seperation are continually being explored. One of these new methods involves the use of magnetic nanoparticles to be attached to one of the components of seperation so that they can be simply removed using a magnetic field.
The main scope for this study will be within the seperation of proteins in the biomedical and pharmaceutical industries. Within theses sectors, there currently exist methods for separating proteins such as electrophoresis, chromatography, precipitation, Ultrafiltration and so on [2]. However, these current seperation systems are usually very complex and involve many time consuming steps, which leads to a low overall process yield and hence, a high product cost. This is why magnetic nanoparticles are being considered as a more effective, lower cost solution to this seperation problem. This method is however, not extensively use within traditional “bulk” chemical seperation. This is because of the small size of the molecules being separated and the combined mass of these molecules meaning that tons of magnetic nanoparticles would be needed for every seperation. This would of course be very expensive and therefore not financially viable in the short or long term. However, since the theory for this type of seperation is sound, there is potential for the use of this method in the near future depending on the number of size of scientific breakthroughs within this field of research.
Previously, it was thought that magnetic materials were solely based on metallic and ionic lattices, however at the end of the twentieth century, scientists discovered that purely organic materials could act as electrical conductors an in some cases as superconductors. The first organic ferromagnetic material was discovered in Japan, based on nitronyl nitroxide (para-nitrophenyl nitronyl nitroxide, NITpNO2Ph), in1991. It was discovered that molecules that contained nitroxides, that have organic radicals localised within a NO group, are relatively stable. It was this relative stability of the unpaired electron that proved to be the breakthrough within molecular magnetics. However, the practicality of using this molecule was not sound. This is because NITpNO2Ph is only ferromagnetically active below 0.6K, which will obviously cost a huge amount of money to obtain and also will not be useful in the seperation of bio-molecules which will clearly not be able to survive at such low temperatures. At the moment, the purely organic magnetic with the highest critical temperature is a sulphur based radical. The will only operate as a weak ferromagnet at temperatures below 35K, which is still a relatively low temperature. These studies proved to be the foundations that lead to the revolutions that can be seen today within magnetic seperation. However, utilising molecular lattices comprising various transition metal ions and also transition metal ion-organic radical pairs, a high temperature ferromagnet was created, using vanadium ions attached to the radical anions of tetracyanoethylene[3]. The molecule was named TCNE- (see figure 1).
TCNE- can operate as a ferromagnet above room temperature and therefore it can be considered as a candidate for use within seperation processes, along with other room temperature ferromagnets such as Prussian blue. The main interest of molecular nanomagnetism for use in seperation processes, however, lies within superparamagnets. Superparamagnetism is a phenomenon by which magnetic materials may exhibit behaviour similar to paramagnetism even when at temperatures below the Curie or the Néel temperature. This is a small length-scale phenomenon, where the energy required to change the direction of the magnetic moment of a particle is comparable to the ambient thermal energy. At this point, the rate at which the particles will randomly reverse direction becomes significant. [4] Superparamagnets have applications within magnetic drug delivery, in magnetic seperation of cells and as a contrast material in magnetic resonance imaging.
However, there have been some key problems with the use of magnetic nanoparticles within seperation processes. First of all, many magnetic materials with strong magnetisation are highly prone to chemical alteration such as oxidation or hydrolysis. This proves to be a major issue during seperation processes and thus deems these materials unsuitable for this purpose. If the reactive surface of the magnetic core is exposed to substrate molecules, it is possible for an undesirable catalytic reaction to take place. This is mostly apparent within application involving bio-catalysis. Furthermore, since there are a restricted number of surface sites on the magnetic particle that are available to carry biological or chemical species, no physical storage of the particles in a significant quantity can be made possible. Since the particles tend to agglomerate during subsequent treatments, the availability of chemical methods for modifying surface properties are limited. These two issues are of high importance within magnetic nanoparticles and must be addressed and resolved before successful applications of nanomagnets can be developed. Fortunately, a lot of work has been done to resolve these issues and there have been some great successes within developing magnetic nanoparticles within the last two years.
This technical review will look at four main scientific reports that are investigating the use of magnetic nanoparticles within seperation processes. These reports will be summarised to give a flavour of what they are concerning, including any significant results and conclusion that have been drawn by the authors. A technical review of the report will then be carried out, reviewing the structure and content of the article, with suggested improvements and changes that could be made. There will also be some comparison made between the selected articles, in an attempt to decipher which article displays the best method of magnetic seperation, or will prove to be the most useful for the future. The referencing system using during this report is the numerical method so when a number appears superscripted in square brackets, the previous quote or passage will have been directly taken from the coinciding article listed in the reference section at the end of the review. Finally, a conclusion will be drawn at the end of the review to bring together the main information gathered and also, to highlight the main developments that could possibly have potential to be explored in the future.
2.0 Technical Review
2.1 Magnetic nanoparticles in biological seperation
2.1.1 Magnetic nanoparticles in the seperation of proteins
2.1.2 Selective seperation of proteins with pH-dependent magnetic nanoadsorbents [6]
Up to now, many solid particulate adsorbents have been developed for various applications [7-13].With the incorporation of magnetite, nanoadsorbents based on magnetic nanoparticles provide a solution to the problem of requiring a small surface area and they can also be easily recovered or manipulate with an external magnetic field [14-19].Two kinds of unique pH-dependent magnetic nanoadsorbents based on silica coated magnetic nanoparticles (SMNPs) and amino-silica coated magnetic nanoparticles (ASMNPs) have been exploited for selective seperation of proteins. With different isoelectric points, silica coated magnetic nanoadsorbents (SMNAs) and amino-silica coated magnetic nanoadsorbents (ASMNAs) can respectively adsorb proteins with different charges. The interactions between proteins and magnetic nanoadsorbents changed with the solution pH. Thus, the adsorption or desorption between proteins and magnetic nanoadsorbents can be controlled by changing the solution pH according to the charge of the proteins. The magnetic nanoadsorbents can be separated and recycled simply with a magnet. All of the other chemicals used were analytical grade reagents, which were used without any further purification; all solutions were prepared with ultra-pure water. The spectra in figure 2(a) show the adsorption profiles for standard solutions of cytochrome c (Cyt-c) and Bovine serum albumin (BSA) individually. The narrow peak for Cyt-c near 400 nm due to the heme group provides a clear distinction between the spectra for the two proteins. The spectra for the effect of SMNAs in the binary protein seperation shown in figure 2(b) revealed that remaining protein solution after adsorption by SMNAs contained little or no discernible Cyt-c, indicating essentially complete removal of this protein from the binary protein mixture. At the same time, the spectra for the effect of ASMNAs in the binary protein seperation shown in figure 2(c), reveal that the remaining protein solution after adsorption by ASMNAs showed little or no discernible difference from the stock binary protein mixture near 400 nm, but a clear decrease at 280 nm, indicating that the selective adsorption of BSA on ASMNAs. The spectra for the eluted protein solution showed only one peak at 280 nm, and also confirmed the high selectivity of ASMNAs in protein seperation. The aforementioned results revealed that the magnetic nanoadsorbents SMNAs and ASMNAs could be used for selective seperation of proteins from the binary protein mixture according to the characteristics of the magnetic nanoadsorbents and the proteins. [6]
The methodology, results and conclusions of this paper must be questioned to obtain an overall critical assessment and to evaluate its successes and failures within the application of seperation using magnet nanoparticles. All of the reagents and instruments have been sourced on the article which would suggest a high level of reliability since all of the products used can be traced back to their original sources. The size of the magnetic nanoparticles was measured with a transmission electron microscope. This is a highly accurate piece of equipment and thus the results obtained using it will also be of high accuracy, therefore the results for the size of the magnetic nanoparticles are of high validity. There are however some problems with the use of TEM, which will be discussed later in this review.
The preparation of the magnetic nanoparticles was achieved by a water-in-oil micro-emulsion technique. This method of preparing magnetic nanoparticles is relatively simple and therefore can be achieved without major complications. This can be seen from figure 3, which shows that the nanoparticles are both uniform spheres, with little variation in size. This would suggest that the method of producing the nanoparticles was successful, however, it is evident from figure 3 (b) that there were some large size variations occurring within the ASMNAs. This is to be expected however could be improved upon. Perhaps looking at a variety of methods for producing the magnetic nanoparticles would yield an even higher uniformity in the particles produced. The seperation of the protein mixtures was measure using a UV-vis spectrophotometer. This would obviously be the best method for measuring the seperation of the binary and tertiary protein mixture since they are routinely used in the quantitative determination of organic compounds such as proteins. The zeta potentials of the two magnetic nanoadsorbents in the different pH solutions were titrated using an automatic titration system. This will eliminate a proportion of the human error from the experiment that is generated when obtaining results manually. Clearly, this will improve the accuracy of the experiment and will therefore render it more credible.
The conclusions drawn from this experiment are obviously positive since the authors are trying to show that their new method will have applications within the seperations sector. The main comment in the conclusion which shows the potential of this process is, “…has good selectivity towards a particular type of protein” [6], which would be of particular interest to a potential investor because it shows that this process of seperation proteins would be specific to a certain type, which would be desirable to anyone wanting to separate that variety of protein. However, the conclusion does not state that this method would be useful to separate all types of protein from a mixture. This is a massive negative point for the paper, because it means that this particular method would not work over more general scope of proteins. On the whole, the methodology, results and conclusions of this article are of a high standard; however the authors could have perhaps added some more information about the specific energy and monetary savings this new process might offer to a potential industrial investor. The general structure and content of the report was good throughout and explanations were clear and concise.
The credibility of the source of information must also be investigated when review an article such as this. Firstly, the country from which it was produced must be looked into. This particular article originated in China, from Hunan University, which would suggest that it is from a reputable source. China is very up and coming within the technology sector and therefore will have a significant amount of state funding to aid it with its scientific innovation. This contributes towards another reason why this source of information can be considered credible. Saying this, a country striving to become a world leader in science an innovation may perhaps put pressure on its scientists to produce results, thus pushing the country further forward. Therefore, the journal the article was published in must be investigated to whether this can validate the credibility of the source of information. This particular article was published in August 2007 in the Nanotechnology journal, by IOP Publishing. Nanotechnology is a highly reputable journal, which publishes work from all over the world. This would suggest that this particular source of information is credible since it was published within a credible journal. A further piece of evidence that makes this article more credible is the fact that it was received by Nanotechnology on 18th July 2007 and was published on 10th August 2007. This is less than a month from receiving to printing, which would suggest that the journal saw this article as a promising and worthy step in the development of seperation using magnetic nanoparticles. Finally, the integrity of the authors of the paper must be reviewed to test whether the paper can be taken as a trustworthy source of information. The collaboration of Chinese scientist that co-wrote this particular paper have been involve in a number of other articles such as “Atomic Force Microscopy” and “Preparation and antibacterial activityof Fe3O4 and Ag nanoparticles” which have been publish and widely receive throughout the world.
As part of this technical review, the impacts on safety, energy and the environment compared to the financial implications will be investigated. The current techniques being used to isolate proteins such as electrophoresis and chromatography are very complicated and involve many time consuming steps. This leads to a low overall yield and high manufacturing costs. Therefore, it can be said that this new method of separating proteins will increase the seperation yield and thus have less adverse effects on the environment. This is because, the higher the yield being obtained from seperation, the less seperation steps will be required to form a certain amount product. This means that less energy will used to obtain the same amount of product. This will obviously be more beneficial to the environment since fossil fuels will have to be burnt at some stage to product that extra energy for the old system of seperation. As it is widely known and advertised, this will produce carbon dioxide which is having a negative effect on global warming. Also, the less energy that is require for the seperation to take place, the less money the company will need to spend in producing a certain amount of the product. This is very good for the company financially, since they will have less production costs and will inevitably make more money if they utilise this new seperation technique. There are a number of chemicals used in the preparation of the SMNPs and ASMNPs that could pose a potential risk to the safety of the operators and could be potentially harmful in the environment. The first of these is ferric chloride which is used to prepare the magnetic ferrofluid. Ferric chloride (FeCl3) is a corrosive solid that can cause serious injury even with a short exposure period. However, with the correct safety measures and precautions taken, it would not pose a serious health risk or a risk to the environment. A second potentially dangerous chemical that is again used in the production of the magnetic ferrofluid is ammonia. This is a hazardous gas that can be caustic and corrosive, expose to which can be deadly. However, is it a commonly use chemical in industry that if correctly controlled will pose no serious health risks. The final chemical used in the preparation of the magnetic nanoadsorbents is concentrated ammonium hydroxide. Ammonium hydroxide (NH4OH) is used to initiate the microemulsion process and is harmful to ones health like the other chemicals, but is also very harmful if released into the environment. This means that measures would have to put in place when disposing of any waste from these processes, so that they do not pose a risk to the environment. This will obviously create an extra cost for an industrial process, however all the other positive aspects massively outweigh this small financial aspect. As for the end product (SMNPs and ASMNPs), they pose no real risks to safety or to the environment. This is a massive benefit when taking to a large scale since there will be no accumulation of toxic materials that would need to be dealt with before being discharged into the environment.
The possible future developments of this process will be reviewed as an estimate as to whether this process has a future in industrial applications. Firstly, the experiment is run as a batch process, which is clearly not as appealing as a continuous process. Therefore, a possible future development would be to look into the feasibility of running this experiment as a continuous process. This however may not be possible since a continuous process may not give the experiment enough interaction time for the desired proteins to attach to the nanoadsorbents, which would obviously have to be investigated. The experiment clearly shows from figure 4, that the adsorption of the protein occurs more readily at higher pH, especially for the adsorption of Cyt-c on SMNAs. This could create a limitation for the application of this process since proteins are easily broken down at pH extremes. This could potentially decrease the scope for industrial applications of this method. The research conducted within this paper only focuses on the removal of a certain protein for mixture containing the same type of proteins (i.e. binary or tertiary). Therefore, to extend the research, perhaps the success of this method could be investigated with a multi-protein mixture containing lots of protein states. If this could be shown to work, it would vastly improve the applications of this process and thus would find more applications within the industrial market. In the conclusion it states “…SMNAs and ASMNAs can respectively adsorb proteins with different charges.”[6], however, what if the proteins had similar charges or even the same charge? Therefore, this method would not apply to a solution containing two different proteins with the same charge. This could be a potential problem and thus, more research would need to be conducted to test whether this method could be adapted to be ultra-specific when separating a mixture of similar proteins. Finally, this experiment could be expanded to test the success of a variety of silica coated nanoparticles or even investigate whether a different coating would create the same or even perhaps more successful seperation. This would obviously be highly unlikely but might be worth exploring in the long run. Therefore, this process shows an overall mild feasibility for scale up, however since no preliminary test have been carried out, no-one is likely to use this process in the near future. If these experiments were scaled up in the required stages, perhaps it might see a future in seperation processes.
2.1.3 Magnetic seperation and collection of fusion proteins using bio-nano magnetic particles. [20]
Bio-nano magnetic particles obtained from Magnetospirillum magneticum AMB-1 are covered with lipid membrane. The bio-nano magnetic particles have been studied with much interest with reference to many engineering applications. Recently, a protein assembling technique on bio-nano magnetic particles membrane has been established by using an antimicrobial peptide as an anchor molecule. The antimicrobial peptide temporin L was spontaneously integrated into bio-nano magnetic particles membrane and the N-terminus was located on the bio-nano magnetic particles membrane surface. In this study, an assembly of fusion proteins, which was expressed in Escherichia coli transformant, on bio-nano magnetic particles, was examined to concentrate and purify the fusion proteins by simple magnetic seperation. [20]
First of all, the methodology and results published in this article must be reviewed and compared to the last article to gauge whether this method is perhaps better or even possibly worse. This seperation method also looks at the seperation of proteins using bio-nano magnetic particles. However, whereas before the nanoparticles where given a silica coat so that they would act as magnetic nanoadsorbents, the nanoparticles in this study were given a lipid membrane so that they could have other ferromagnetic molecules attached. This includes an antimicrobial peptide temporin L which was integrated into the surface so that seperation could take place with use of a simple magnetic field. This method obviously is more complex than the previous method because you not only have to coat the nanoparticles but you have to attach molecules to this coating. This will clearly lead to a lower efficiency since it will undergoing to two step process as opposed to a single step process. This will mean that there is less chance of the seperation molecule being magnetic and thus, less of the desired product will be separated when a magnetic field is induced. The results back up this prediction and clearly show less seperation taking place compare to the previous method magnetising the target molecule.
Furthermore, the credibility of the source of information has to be taken into account when critically assessing an article such as this one. This particular article was written in Japan and published in the Nippon Kagakkai Koen Yokoshu journal. Japan has a wide technology research base and at the same time is very up and coming in research and development. For this reason, there is a lot of research being conducted in key areas such as this one. Therefore, as with before, the government will be pushing their researchers to produce innovative technologies, which could lead to novel process being created that, are not a lot of use industrially. This is the same as with the previous article that was produced in China, and was published in the Nanotechnology journal. However, this article was published in Nippon Kagakkai Koen Yokoshu, which is a Japanese journal and is not recognised worldwide. For this reason, this particular article can not be considered as useful as the previous article since if this method of utilising magnetic nanoparticles for seperation was particularly profound, then it would have been published in a journal outside of the country it was conceived in. Saying this, the main author of the article (Kokuryu Yoriko) is at the forefront of biological research in Japan. This obviously makes this article slightly more credible since it was written by credible authors, however much of Kokuryu Yoriko’s research is conducted and published in Japan and thus for the same reasons as before, this research will not be considered as credible as the previous example.
Once again, the impacts on safety, energy and the environment compare to the financial gains of a process must be reviewed as a test for the viability of this process. As with the previous method, this process will also be beneficial to the environment for the same reasons. This will obviously make it a very desirable process industrially since it will have an overall lower production cost compare to current methods of bio-seperation which are long and laborious. In terms of safety, this process does not use any potentially dangerous or harmful chemicals to human health or the environment. This is a massive advantage compare to the previous method which uses a number of chemicals that are potentially harmful to the environment and to human health. However, since this method uses more steps to produce the magnetic nanoparticles, it inevitably uses more chemicals, which in turn take more energy to produce, and thus makes the process slightly more expensive to use. This is one of the disadvantages it has over the previous method which used a simple method coating the nanoparticles with silica.
For this process to be of any use, the feasibility of taking to an industrial scale must be explored. This involves looking at possible future developments that might help this seperation process to reach this sort of status in industry. Firstly, as with the previous method, this process runs as a batch operation. Once again, this means that continuous processing is not possible which might make it seem less attractive to a potential industrial investor. Saying that, it would not be a major problem since many industrial application are run as a batch process. Also, this research only looked at the use of lipid coated nanoparticles in the seperation of fusion proteins. This would have vast applications in DNA research and bio-medicine; however, a future development could be to investigate the use of this method to separate other types of proteins or even other molecules. If this was prove to work, the process would find a whole host of new applications for industry to utilise. Also, it might be useful to look at multi-protein mixtures that contain a number of different types of protein. This would obviously test the limitations of the process and perhaps would not be viable since the process could induce a magnetic charge in a different type of protein which would then be separated along with the desired fusion protein. This again would have to be investigated, which would of course depend on financial backing and the existence of other, better novel processes.
2.1.4 Thermosensitive polymer coated nanomagnetic particles for seperation of bio- molecules. [21]
This report looks at the use of magnetic iron oxide particles for use in the seperation of bio molecules. Bovine serum albumin (BSA) was selected as a model protein for the seperation study. Adsorption of BSA on the thermo-sensitive magnetic particles was mainly dependent on the properties of the particles’ surface. By increasing the temperature above the lower critical solution temperature (LCST) of poly N-isopropylacrylamide (PNIPAM), the particles shrank and were able to adsorb larger quantity of proteins, this was subsequently desorbed at lower temperature. The results in tables 1, 2 and 3 show that about 80% proteins are desorbed if the adsorption was done at a temperature near the lower critical solution temperature of PNIPAM. On the other hand, desorption percentage is only 60% when adsorption was conducted at higher temperature 40 °C. This is because at higher temperature proteins will form a complex with the thermo-sensitive polymer. The observed behaviour can also be interpreted as the possible permeation of protein molecules inside the shell network. The mechanical entrapment of BSA molecule by PNIPAM chains during shell shrinkage can also contribute to less percentage of desorption at higher temperature. Results from the experiments so far conducted show that both PNIPAM and MAA-PNIPAM coated core shell nanomagnetic particles can be used for adsorption and desorption of proteins. The adsorption of BSA on PNIPAM magnetic particles is principally governed by hydrophobic interaction above the LCST of the polymer while for MAA-PNIPAM magnetic particles hydrogen bonding is dominant. Comparing the extremes of two interactions, hydrogen bonding is stronger than hydrophobic interactions for MAA-PNIPAM coated particles. The adsorption equilibrium results are fitted well by the Langmuir–Freundlich model. Desorption of BSA from both surface modified magnetic particles was carried out below the LCST of PNIPAM and at alkaline condition which is above the isoelectric point of the protein. More than, 60% desorption efficiency was achieved for adsorption at higher temperature (40 °C) and 80% efficiency was achieved for adsorption at lower temperature (30 °C). The obtained results indicate that these particles can be used for protein isolation and purification by controlling the temperature, thus supplementing other techniques such as precipitation using high salt concentrated medium and gel column system. [21]
For this paper to be critically analysed, the methodology, results and conclusions drawn must be assessed. Firstly, there is a list of the different chemicals that are use in the experiment. This is useful for anyone trying to repeat the experiment, however, gives no mention of where these chemicals were obtained from. This could be a potential problem concerning the validity of the experiment since if the chemicals used were not obtained from a high quality source, they might have caused inaccuracies in the experimental results. This is however only a suggestion; the chemicals purchased for this experiment were most likely of the highest quality. The method of producing the magnetic nanoparticles was different to the other methods described previously. This new method prepares the magnetic particles by a chemical co-precipitation method under an inert environment. The method for the preparation of thermosensitive nanomagnetic particles can be seen in figure 5, which shows the number of complex step that are required to produce these magnetic nanoparticles. Since this method of producing magnetic nanoparticles is far more complex than the two previous methods, it is obviously not as desirable as the previous method, which proved to be simple and therefore less expensive to execute.
The particle size of the prepared nanomagnets was measured using a bright field TEM. Transmission Electron Microscopes are a very powerful tool; however there are some draw backs that might have affected the results. First of all, the structure of the sample can be altered during the preparation process. This means that the sample being measured may not be a true representation of the actual molecule being used in the seperation process. This could lead to miscalculation, especially when dealing with surface area and diameter approximations. Also, the field of view on a TEM is relatively small and thus, the sample being measured may not be true representation of the sample as a whole. This has the same implications as before, since the approximated average diameter of the sample may be slightly different to the actual average diameter of the nanomagnets. The methods of measuring the nanoparticles using a TEM were encompassed by the two previous methods of separating proteins. This would suggest that transmission electron microscopy is the only viable method for measuring nanoparticles. However, that is not to say extended research could not be carried out to look at a new and improved method for measuring the size distribution of nanoparticles. It is evident from figure 6 that the size distribution of the nanoparticles is relatively small. This shows that the method for producing them was very repeatable and hence more desirable than the method used in [6], which produce the wide size distribution that can be seen in figure 3. The adsorption of BSA on the two different magnetic nanoparticles can be seen in figure 7, which shows a good adsorption of BSA, especially at high equilibrium concentrations of the BSA. Also, the adsorption occurred more readily at higher temperatures. However, the maximum temperature used in the experiment was 40°C, which produced the maximum adsorption, and thus, further experiments could have been conducted at higher temperatures to find the optimum temperature for adsorption to take place. Saying this, however, since the material being separated is a protein and proteins have a tendency to denature at high temperatures, it is possible that the temperature could not go above 40°C since the proteins would have been rendered useless at temperatures exceeding 40°C. This however would have to be investigated to see whether the process could be optimised further. One downside of this process is that little or no adsorption takes place at lower concentrations of BSA, which could prove to be a problem if an industrial process was required to separate proteins that were present in a solution in low concentrations. This particular paper also looks at the desorption of BSA from the attached nanomagnetic particles, which is a massive advantage for an industry looking to utilise this process, since the protein would need to be separated from the nanomagnet before being used in another process. This is in stark contrast to the two previous experiments that did not look into the desorption of the nanomagnets in great detail. The results for the experiment show around a 60% desorption at 40°C and around 85% desorption at 30°C. This is not particularly high and it would mean that the efficiency of the seperation process overall would be low since the percentage of BSA adsorbed would not be high. This could prove to be a massive problem for this particular process since it would not appear to be very attractive to potential investors with efficiency as low that describe by the evidence in this experiment.
The conclusion for this experiment states, “…thus supplementing other techniques…” [21], which shows that the author had envisioned that this method should be use in conjunction with current methods of seperation to maximise the overall efficiency of the process. This is a very clever ploy, since the use of two seperation methods working together would vastly reduce the costs of seperation in industry. However, there is no evidence of this being a feasible method and therefore experimentation would need to take place before it can be hailed as a breakthrough in seperation.
Now that the methodology, results and conclusions have been critically assessed, the credibility of the source of the information can be reviewed to see whether this will have an effect on the viability of the process. Firstly, this particular journal was written by N. Shamim et al, in the National University of Singapore. N. Shamim has written a number of journal articles in related areas such as “Thermosensitive-polymer-coated magnetic nanoparticles: Adsorption and desorption of bovine serum albumin” which is directly related to this research. This means that this particular source of information can be considered as credible (based on this evidence), since the authors have obviously received funding to carry out research in related areas. Since the article was written at the National University of Singapore, it can again be considered as credible since this is a very prestigious university that has a wide foundation for research of this nature. Finally, the journal that the article was published in must be scrutinised to see whether it is reputable. The article in question was published in the seperation and Purification Technology journal in 2007. seperation and Purification Technology is an international journal that publishes articles everyday, from all over the world. This makes it an extremely reliable journal and thus, any article published in it can be deemed as credible.
For a full review to be carried out, an assessment of the safety, energy and the environmental implications of this method of seperation must be considered. First of all, it has to be said that the benefits to the environment and to the financial status of a potential investor still apply to this method as were mentioned above in the financial review of [6]. This is the main reason why this method of seperation has had such attention and funding in the research sector. The chemicals in this process are, on the whole, not particularly toxic to human health or the environment. The only two chemicals that pose any risk to the health of the workers are thiodiglycolic acid and methacrylic acid, particularly methacrylic acid which is toxic and flammable, thus causing risk to the health of potential users. This would obviously mean that money would have to be invested to protect the workers; however this would not be as much as that, which would be required for the two previous pathways, since they use many more dangerous chemicals. The process in question also does not create any dangerous chemicals in the form of by-products whilst utilising this pathway. This, combined with the advantage above makes this process seem ethically far more viable that the two previous processes. However, in the synthesis of the magnetic nanoparticles, temperatures of 80 and 50°C are required. This is in comparison to the method used in [6] and [20] which required temperatures of 25 and 30°C respectively. This clearly means that this method would use more energy to produce these temperatures, which would not have a massive environmental or financial impact at experimental stages, however would obviously have larger implications as the process was scaled up to industrial levels.
The final stage in the assessment of a new process such as this one is in the critical evaluation of possible future developments and the feasibility of scale up for the process. First of all, the results seen in figure 6 reveal that the distribution of the average particle size is relatively small compared to the previous two processes. This would mean that the process of preparing the magnetic nanoparticles would be easily scaled up, since the average diameter of the particles remains approximately constant. This is because on a larger scale, this distribution would become more significant and may heavily affect the result of the process if large variations in diameter were occurring. However, there are some disadvantages to this process that may mean it would not become an industrially viable process. The first of these can be seen in tables 2 and 3, that show the adsorption and desorption of the protein from the nanomagnets is miserably low. This would obviously be one of the main scale-up criteria that would be considered if a company was considering initiating this process. From this evidence, this process, at first sight, would not appear to be viable for scale up. However, in the conclusion, the author states “…thus supplementing other techniques such as precipitation…” [21], which would suggest the process would be viable in conjunction with another, current seperation technique. This perhaps would, be an interesting prospect to a potential investor. Also, this experiment only looks at the adsorption and desorption of BSA from the magnetic nanoparticles. This would obviously not be ideal for someone looking to invest the process since it does not show any range of proteins that this method can be applied to. However, this would clearly be a future development of the process to see whether it can be applied to other proteins. If this were possible, this process would become far more attractive to industries looking to scale-up the process. Finally, the research does not show the use of this method within multi-protein mixtures. Within the bio-chemical industry it is clear that the seperation of proteins is likely to take place in the presence of other proteins, and thus this process would need to extended into this area before any scale-up could be considered feasible.
2.1.5 High throughput human DNA purification with aminosilanes tailored silica-coated magnetic nanoparticles. [22]
Current DNA purification methods suffer from several drawbacks that make them unsuitable for the manufacture of pharmaceutical grade. They often involve the use of solvents, toxic chemicals such as cesium chloride, ethidium bromide, phenol, and chloroform, or animal-derived enzymes such as ribonuclease A and lysozyme that are either not approved or not recommended by regulatory agencies. Moreover, the saccharose or cesium chloride, ethidium bromide density gradient ultracentrifugation is time-consuming and difficult to scale up and also use toxic and mutagenic reagents, thus, a new process involving magnetic nanoparticles would be far more appealing. This work described the development of high throughput human DNA purification process with the amino-functionalized silica coated magnetic nanoparticles. The magnetic nanoparticles were synthesized with average particle size of 9 nm and silica-coated magnetic nanoparticles were obtained by controlling the coating thicknesses on magnetic nanoparticles. The silica coating thickness could be uniform-sized in the diameter of 10–40 nm by a sol–gel approach. The surface modification was performed with amino functionalized organic silanes on silica coated magnetic nanoparticles. The spectroscopic measurements such as a FT-IR (ATR-method) and Vibrational Sample Magnetometer (VSM) were used to characterize the chemical structures and magnetic strengths. To elucidate the relationship among the surface area, pore size distribution and reactivity of the materials, XRD, TEM, BET and Zeta potential were used. The use of functionalized self-assembled magnetic nanoparticles for human DNA seperation process gives a lot of advantages rather than the conventional silica based processes. [22]
The methodology, results and conclusion drawn by the authors from this experiment must be investigated and compared to the previous methods of manipulating magnetic nanoparticles as an aid to the seperation of proteins. Firstly, the time period for the adsorption of the DNA was optimise at twenty minutes. This is a massive advantage since twenty minutes is not very long to wait compared to the other potential methods of protein seperation. The report does not mention where any of the chemicals used were obtained. This is not a massive critique, however might create a problem when trying to repeat the experiment since different strength chemicals are likely to be purchased from an alternate source from that used in this experiment. The method for preparing the magnetic nano particles uses temperatures of 100°C for twenty four hours and 130°C for seven hours. This is clearly going to require a lot of energy and hence money to conduct on a larger scale. This is a huge disadvantage compared to the previous three methods that used moderate temperature for shorter periods of time.
The adsorption and desorption efficiencies can be seen in figure 9 in the form of electrophoresis images. They both show reasonable adsorption and desorption of the DNA onto the magnetic nanoparticles, however do not show the quantitative data that was presented in [21]. This is clearly not ideal, since the quantitative data is far easier to read and understand, but mainly it gives a potential investor an actual figure for the efficiencies they can expect to obtain from the seperation process. It can be seen from figure 8 that the particle size distribution is relatively large. The average diameter was calculated using the Scherrer equation and showed the uniform size to be 9±2nm. This is a large deviation from the mean and may cause problems if the process was taken to a larger scale.
The conclusion for this report is incredibly short but does imply some very interesting and valuable information that makes this process look like an attractive prospect. The main one of these is that it implies that the process can be adjusted by manipulating the number of amino groups attached to the MNP. This means that molecules with different functional groups can be attached to the MNP, which in turn implies that this process could be used to separate a number of different protein molecules with varying functional groups. It also states “…in which the range of silica coating thickness was optimised to be interacted with human DNA” [22], which means that the efficiency of the process can be altered depending on the target molecule being separated. This would again be a huge advantage for this process; however it still does not give a quantitative efficiency that this process could expect to obtain.
Secondly, the credibility of the source of information must be scrutinized to see whether this might have an effect on the reliability of the source of information. The article in question was published in Korea at the Korea Institute of Ceramic Engineering and Technology by Moo Eon Park. Korea is one of the least technologically advanced of the Asian countries studied, however still has a lot of research funding, which would suggest that this source is credible. The particular institute that it was published in is also well known for its research and development. The author Moo Eon Park has also produced a number of advanced articles from this particular institute and is at the forefront of research in material chemistry, nanoparticles and catalysis. M E Park did however solely produce this article with only one corresponding author, Jeong Ho Chang. This might explain why the article was lacking in content and did not explore the entire scope for this type of research. This is with respect to things such as quantitative data and explanations of results and conclusions drawn. The article was published in the Materials Science and Engineering journal, which is an international journal that publishes thousands of articles worldwide. It is however not specific to the type of research in this article. This is clearly not good for the credibility of the article, since the previous article investigated were published in specific journals such as Nanotechnology and seperation and Purification Technology.
Now that the credibility of the article has been established, the impact on safety, energy and the environment must be assessed with respect to the financial social and ethical aspects. The current methods of purifying DNA involves the use of toxic and even sometimes mutagenic chemicals which will obviously have a large impact on human health and the environment. Therefore, this new method that does not involve the use of such chemicals will clearly have less of a negative impact on the environment and to human health. The process developed in this article does however use ammonia and Iron Chlorides, which pose a high risk to health in general. Saying this, it is far better than using the previous method that involves the use of many dangerous and mutagenic chemicals. This method does however have a large impact on the environment due to the energy demands the process requires when preparing the magnetic nanoparticles. This is because it requires the solution to be heated to 100°C for 24 hours and then to 130°C for 7 hours. These temperatures would obviously take a large amount of energy to reach and to maintain, particularly if the process was to be scaled up. This will have a negative impact on the environment compare to the other experiments explored in this technical review, but also will cost a lot of money to maintain on a large scale. This would clearly make this process less attractive to any potential investor, however being one of the only feasible large scale processes for separating DNA, could potentially be necessary.
Finally, the possible future developments of the process must be discussed and how this will relate to the feasibility of scale-up for this particular process. From figure 9 it has already been suggested that the particle size distribution is relatively large compared to the other articles reviewed. This would obviously be a disadvantage on scale-up, since the diameter of the nanoparticles would not be certain, which would in turn lead to lower overall efficiencies. This process is however, specific to DNA purification and therefore cannot properly be compared to conventional protein seperation in terms in industrial applications. However, this does mean that it could operate in a niche and be the exclusive process for the purification of DNA. This would be an overwhelming factor in the consideration of scale-up, since it is far better than any processes currently in operation. However, there are some disadvantages to this particular process that would need to be rectified if the process was going to be adopted industrially. The first of these is to do with the potential amount of energy that the process will require. Since the temperatures in the preparation of the nanoparticles are so high, for so long, a lot of energy will be required which will cost a lot of money on a large scale. This could be resolved by investigating the use of a catalyst to lower the activation energy and hence the overall temperature requirement for the reaction. As well as this, the use of inhibitors could be investigated to limit the occurrence of side reactions that will also be using energy and therefore heat input. These future developments could make this process extremely viable on an industrial scale, if they were possible. The final disadvantage of this process is the fact that the article does not make mention of any efficiencies associated with this new process. This would again have to be explored before any companies would look to invest in it since this would be one of the main seperation criteria.
3.0 Conclusion
This report has shown that there is definitely a future for the seperation of proteins using magnetic nanoparticles. This is mainly because the current methods are labour intensive and not always available for scale-up, but also because of the savings gained in terms of energy. The increased ease and efficiencies of seperation mean that less energy has to be inputted into the system for the required seperation to take place. This is in conjunction with the fact that not as many harmful chemicals are required for these processes, meaning that there is less of an impact on the environment. These two advantages also lead to the conclusion that these methods will cost less on a large scale compared to the current methods of seperation. A possible idea for future development in seperation using magnetic nanoparticles would be to attach a positive nanomagnet to one of the seperation materials, whilst attaching a negative nanomagnet to another in the same solution. This could be done by attaching a different functional group to each nanomagnet that would bind to a known site on the respective proteins. Then, if a negative magnetic field was passed through the solution followed by a positive magnetic field, both proteins could be separated simultaneously.
Bibliography
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[4] www.ugr.es
[5] en.wikipedia.org
[6] “Selective seperation of proteins with pH-dependent magnetic nanoadsorbents”
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[21] “Thermosensitive polymer coated nanomagnetic particles for seperation of bio-molecules”, Authors: N. Shamim, L. Hong, K. Hidajat and M.S. Uddin. Source: seperation and purification technology. Published: 25th February 2007. [22] “High throughput human DNA purification with aminosilanes tailored silica-coated magnetic nanoparticles” Authors: Moo Eon Park, Jeong Ho Chang. Source: Korea Institute of Ceramic Engineering and Technology, Published: 4th September 2006. |
