Virus Selection for Lithium Ion Battery Formation
Viruses can be genetically modified by manipulation of coat proteins to construct a variety of materials at the nanoscale. Viruses with proteins that are effective at binding cobalt oxide to their coat have been used as anode material in the first generation of batteries.Viruses with proteins that have the highest affinity for iron phosphate and carbon nanotubes were selected and amplified to build a cathode in further studies done. Angela Belcher along with a team of scientist from Massachusetts Institute of Technology (MIT) as well as scientist around the world, have been using M13 bacteriophage viruses to construct high power lithium ion batteries through modification of coat proteins. Belcher et al. have nanostructured lithium ion batteries capable of electron transmission with enough energy capacity to even power a car.
The Idea
In nature there can be found nanoscaled durable materials formed through biological processes from both organic and inorganic substances. Biosystems have the capability of recognition and assembly, which is why organisms can build strong structures from the nanoscale up. For example, the Abalone shell, which is formed by marine gastropods, is built from composing layers of pearl on top of each other with perfect alignment, orientation, and shape from solely minerals in their environment (Belcher,Ted talk). Organism’s with these shells uses calcium carbonate in two distinct crystalline structures, one that grows strongly and one that grows quickly. Magnetotactic bacteria nucleate and organize iron oxide in present vesicles to create a permanent magnetic dipole, which helps them survive in their environments (Flynn, 2003). These organisms are examples of biological agents building a structure from the ground up through recognition and orientation of certain chemical compounds in their habitats (Ross, 2013).
Angela Belcher and team of material scientists from the Massachusetts Institute of Technology, MIT, have studied the abalone shell, and came to the conclusion that if marine snails could materialize such a complex structure, humans should be able to devise a method that could mimic biological processes to make nanoscale structures that we can utilize in our every day life. Belcher believed that she could manipulate organisms in a similar process to natural selection to favor interactions between biomolecules and conductive materials to form devices such as batteries (Whaley, 2000). Nature has provided organisms with limited resources not all immediately accessible depending on their location (Flynn 2003). Belcher found that it could be possible to speed up the evolution of microorganisms, such as viruses, to have more of certain proteins that have a higher affinity for the binding of specific organic and inorganic chemical compounds that are deliberately put into their environments. This could lead to interactions between organisms and their environment that lead to the directed growth of crystals with certain size and face that could be use for electronic devices. Scientists have exploited certain biological factors to create protein coats on viruses that lead to the assembly and nucleation of nanocrystals, wires, and particles, in an organized structured manner. Through genetic control and modifications different structures and compositions can be created, for whatever the desired purpose is (Mao, 2004). This bottom up method of using nature to construct materials is a less expensive and more feasible way to create materials for electronics and one-dimensional systems at the nanoscale. In addition, biological materials have more spatial control at the nanoscale, as well as, self-assembly and correcting methods. Belcher and scientists across the world are modifying viruses by mimicking the evolutionary cycle of material production (Flynn 2003).
Modifiable Viruses
Viruses are ideal for programming due to the small number of genes, which make peptide insertion more feasible. The capsid of a virus contains surface proteins that have peptide sequences than can be manipulated to produce proteins with different properties. Stanley Brown, of the University of Copenhagen, was the first to combine the use of a phage display library for certain peptide sequences with the binding of inorganic materials such as gold and iron oxide. In a phage display library many different genetic sequences are expressed that lead to the formation of different proteins on the coat of viruses. These proteins are displayed on the surface of the viral particle and interactions with the target material in the solution is anaylzed. Brown looked at the M13 virus as well as three others with different structures.
M13
The M13 virus is a phage that infects bacteria but is harmless to humans. It has DNA that is circular and single stranded; 6,407 nucleotide long. The coat of bacteriophage M13 is composed of five proteins encoded by 5 different genes. There are 2700 copies of the major coat protein pVIII along the long axis of the phage. At one end of the phage there are five copies of pIII and at the other, five of pIX; the other proteins are minor. The coat proteins are modifiable through genetic engineering making it possible to create viruses with heterofunctional proteins in different regions on the coat. All four virus studied for nanomaterial nucleation contain a protein coat that can me manipulated through genetic selection and then amplification to produce viruses with the desired binding affinities (Flynn, 2003).
Belcher and her team have primarily used the M13 bacteriophage for experimentation and synthesis of nanoparticles and wires due to the multifunctional protein coat’s ability to nanoarchitecture structures and materials (Lee, 2009). Manipulations and additions to the M13 genome affect the five-coat proteins function leading to the creation of better templates for positioning nanoparticles (Nam, 2006). The M13 virus also has a high production rate at 200mg/liter, making it easier to amplify the selected virus through bacteria. The M13 virus is long and skinny so it is more ideal for the formation of nanowires. It is 6nm wide and a micron long; this length to width ratio is ideal for assembly into complex shapes naturally (Ross, 2013). The different modifiable proteins on the virus coat make the M13 phage a multifunctional scaffold for high power battery synthesis (Lee, 2009).
- FIG OF M13 AND MULtIPLE PROTIENS ON COAT
- FIG OF M13 AND MULtIPLE PROTIENS ON COAT
Peptide selection for targeted materials
The five coat proteins make the M13 phage a more versatile virus with modifiable proteins along the filamentous region of the virus, as well as, multiple proteins at each end (Flynn, 2003). The M13 phage has previously been used to identify unknown organic and inorganic substances based off known binding affinities(Ross, 2013). Belcher and fellow scientists have used phage display libraries to determine which gene sequences lead to proteins with certain favorable interactions.
Phage display library
Phage display library's are a collection of clones with different DNA fragments that encode different peptide sequences. The DNA fragments are cloned into the capsid gene, then the peptide for which it encodes is synthesized as part of a capsid protein that is displayed when the virus assembles. A process called biopanning isolates viruses with high binding affinity to the target molecules in a coated plate. The target could be anything from proteins to antibodies to metal ions. The phages that do not bind to the target strongly are washed away at a lower pH.and the remaining phages are amplified though bacterial infection. The biopanning process is repeated again with a more specific target which is harder for non-specific virus proteins to bind to. The Biopanning continues until a phage that has the most effective DNA fragment for binding to the target is selected (Slonczewski & Foster, 2011). This process can take up to three weeks for the ideal virus peptide sequence to be found (Ross, 2013). DNA sequencing is then used to identify the genetically encoded peptide that was binding. Temperature and pH changes are used to solidify that there is a strong interaction between the encoded peptide and substrate (Flynn, 2003).
Utilization of library by Belcher team
Belcher used a M13 phage display library to find peptides that could bind to a range of semiconductor surfaces with a high specificity depending on the orientation and composition of the proteins and metal substrates. The first phage library used was based on a combinatorial library of random peptides with twelve amino acids fused to the pIII coat. This collection of phage variants only cost $300 but provided around one billion different peptides that could react with different crystalline semiconducting materials.. Belcher et al. then looked at the peptide substrate interactions to determine which phages carried the DNA that encoded the specific pIII (Whaley, 2000). Belcher then used the process of direct evolution to amplify the phages with the strongest binding affinities to the metallic substrates.
Initial Experiments
Using phage display libraries and amplification, scientists have been able to genetically modify viruses’ scaffolds to produce crystalline nanowires, particles and arrays. This approach has allowed for the genetic control of semiconducting, metallic oxide, and magnetic materials using the phage as a universal template. Different peptide sequences control the binding phases of crystals depending on the chemical (Flynn, 2000). Mao et al. initially did experiments screening for peptides fused to the pIII coat with affinities for ZnS, CdS, FePt, and CoPt. Incubating the viral template in the metal salt precursors at low temperatures to encourage the uniform orientation of the molecules produced mineralization of CdS and ZnS. The ZnS and CdS nanoparticles formed nanowires when the viral template was melted off at 350°C, which is still below the melting point of these semiconducting metals. A similar experiment was done using CoPt and FePt solutions with the M13 phage library, resulting in the nucleation of these particles and growth of nanowires. Typically, nanowires formed by these metals can only be achieved at temperatures over 550°C. Mao et al. believe that the ordering and orientation of these nucleated particles could only be due to the stability of the peptide fusion and symmetry of the viral coat (Mao, 2004).
Belcher et al. made specific peptide insertions to the pVIII helical major coat proteins, as well as, insertions to the pIII and pXI proteins at each end of the virus. The pVIII insertions were nanocrystal templates for ZnS and CdS. Nucleated ZnS nanoparticles were nucleated along the length of virus forming nanowires. An advantage to this type of viral engineering is that there is a potential to specify viral length and geometry. Viruses can be conjugated with one-dimensional as well as two-dimensional nanowires and tubes to form nanoelectrodes to be used at the microscale for devices. Nanothick electrodes can be organized to form alternative anode and cathode structures from lithium ion batteries. Belcher et al. developed large scale self- supporting viral films that had smectic structure, well liquid defined crystal layers at lower temperatures. The organization of nanocrystals into fibers and films can lead to promising developments and technological advancements at the nanoscale (Flynn, 2000).
Lithium Ion Batteries
Conventional lithium ion battery synthesis requires toxic chemicals and extremely high temperatures; in addition, it is also expensive. Lithium ion batteries have positive and negative electrodes along with electrolyte material and current collectors. The US Army has funded Belcher et al. research because a cheaper lightweight battery would be beneficial to planes being sent over seas. Currently, the batteries used in the Army’s planes are several grams, however, the batteries Belcher’s team has been able to produce are only milligrams. Belcher et al. have genetically programmed the M13 phage to form square films less than a micron thick that can then be fixed into a stable sheet through chemical cross linkage. Lithium ion batteries function due to the transfer of lithium ions through electrode material. An increase in the transport of ions means an increase in performance (Lee, 2009).
First Generation battery
The negative electrode is formed from a sheet of cobalt oxide (Co3O2) and gold to increase conductivity; the Co3O2 exchanges lithium ions with the battery electrolyte, moving charge from electrode to electrode. A positive electrode sheet is formed (Flynn, 2000).
(I THINK THIS IS HER FIRST BATTERY BUT IT ALSO MAY BE THE negative eletrode) Belcher et al. have manipulated the coat proteins on the M13 phage to be templates for Co3O2 nanostructures. Tertraglutamate was fused to the N terminus of the peptide sequence because glutamate has a carboxylic acid side chain, which attracts positive metal ions and is also important in bio mineralization. Tetraglutamate also helps in the binding of gold particles to the nanowires. The Co3O2 nanowires were made by incubating the viruses in an aqueous cobalt chlorine solution. Co3O2 is lithium active and has a large storage capacity. The system was reduced and oxidized leading to the formation of monodisperse crystalline nanowires along the length of the virus. Belcher et al. found that viruses with out the peptide insert with affinity for Co3O2 did not produce the nanowires. To increase the conductivity of the nanowires, Belcher et al. isolated a gold binding peptide structure so that the phage would both attract Co3O2 as well as gold nanoparticles on the protein coat. Once the most effective virus was found it was then used to infect bacteria and be amplified. The properties of the nanowire were tested using galvanic cycling. When the gold nano particles were added to the structure the capacity of the electrode was increased by 30%. Belcher et al. created an anode with nanowires up to 10cm long and layers as thick as 10nm, while still maintaining the capabilities of anodes fabricated at temperatures above 500°C (Nam, 2006).
(THIS MAY BE THE SECOND or the positive eletrode) Iron phosphate has been found to be a conductive material for the transfer of Li ions. The conductivity of FePO4 nanowires is increased by the addition of carbon nanotubes to the structure. Conventional methods make it difficult to manufacture carbon nanotubes because high temperatures and toxic chemicals are required for the crystallization of carbon, which is why Belcher et al. devised a method to produce these nanotubes using biological systems in an environmentally benign manner. The composition of the FePO4 electrode is based on a two gene system using the pVIII major coat protein and pIII minor coat protein. Carbon nanotubes are known to be highly conductive, so in order to improve the battery system the M13 virus was further genetically modified to have a protein coat with both affinity for F FePO4 nanowire growth and be a template for carbon nanotubes. The pVIII protein was modified to have affinity for FePO4 crystalline growth and the pIII was modified to have affinity for carbon nanotubes. The addition of carbon nanotubes also gives the ions better percolating abilities. The FePO4 pick up the carbon nanotubes to form an array of nanowire growth (Lee, 2009). Electrons then can travel through the carbon nanotube network to the iron phosphate network. The end result was a lithium ion battery formed by viruses that could be charged and discharged at least 100 times without losing capacity (Trafton, 2009).
- FIG OF BATTERY
(I AM CONFUSED BECAUSE SHE DID MULTIPLE EXPERIMENTS and not sure how to tie them together hardest part for sure) I need to do more research or talk to a battery expert at the keck about this section
Conclusion
Belcher and other scientists have succeeded in creating lightweight flexible lithium ion batteries that can take the shape of basically any compartment, in an environmentally friendly way (Trafton, 2009). Belcher was able to convince viruses to work with a new toolbox and through direct evolution by natural selection, create structures that can be applied for use in our electronics by choosing the viruses that make the strongest batteries (Belcher,Ted talk). Through genetic manipulation electronically active nanowires are able to be organized on the viruses polymer surface. These batteries can be used for devices ranging from portable electronics to hybrid cars (Lee, 2009).
Belcher is currently working on viruses that can be used in making photovoltaic cells more efficient. Belcher sees the need to preserve and make more effective renewable energies such as solar energy. Nonporous solar cells are lower cost and more productive compared to silicon cells. Belcher is using a genetically modified M13 phage as a template for single walled carbon nanotubes on the titanium oxide (TiO2) nanocrystal composites on the protein coat. The carbon nanotubes are once again used here like in the lithium ion battery to provide better conductivity of electrons. Belcher would be the first to incorporate them in photovoltaic cells. The gene for pVIII was manipulated to express foreign peptide inserts that aid in the interaction of coat proteins and carbon nanotubes. The pIII gene was also manipulated to increase affinity for carbon nanotubes. The addition of carbon nanotubes increased the power efficiency of photovoltaic cells when compared to cells with just the TiO2 nanocomposites (Dang, 2011).
By using viruses as scaffolds Belcher and scientists around the world wish to create more technologies from the bottom up. Viruses can be used to detect defects in materials such as airplane wings, and be coated in materials to make them behave as complete transistors and semiconductors through simple genetic modifications. All of this can be done without the use of harsh chemicals and production of toxic wastes (Ross, 2013).
References
Belcher, Angela."Using Nature to Grow Batteries." Caltech, Pasedena, CA. 14 Jan. 2011. TED talks.
Dang, X., Yi, H., Ham, M. H., Qi, J., Yun, D. S., Ladewski, R., Strano M., Hammond P., Belcher, A. M. ."Virus-templated self-assembled single-walled carbon nanotubes for highly efficient electron collection in photovoltaic devices." Nature nanotechnology 6.6 (2011): 377-384.
Flynn, C. E., Lee, S. W., Peelle, B. R., & Belcher, A. M."Viruses as vehicles for growth, organization and assembly of materials." Acta Materialia 51.19 (2003): 5867-5880.
Lee, Y. J., Yi, H., Kim, W. J., Kang, K., Yun, D. S., Strano, M. S., Ceder, G & Belcher, A. M."Fabricating genetically engineered high-power lithium-ion batteries using multiple virus genes." Science 324.5930 (2009): 1051-1055.
Mao, C., Solis, D. J., Reiss, B. D., Kottmann, S. T., Sweeney, R. Y., Hayhurst, A., Georgiou, G., Iverson B., & Belcher, A. M. . "Virus-based toolkit for the directed synthesis of magnetic and semiconducting nanowires." Science 303.5655 (2004): 213-217.
Nam, K. T., Kim, D. W., Yoo, P. J., Chiang, C. Y., Meethong, N., Hammond, P. T., Chaing, Y. & Belcher, A. M."Virus-enabled synthesis and assembly of nanowires for lithium ion battery electrodes." science 312.5775 (2006): 885-888.
Ross, Phillip. "Viral Nanotechnology." Scientific American. 295.4 (2006): n. page. Web. 15 Mar. 2013.
Slonczewski, J. L., & Foster, J. W. (2011). Microbiology, an evolving science. (2 ed.). New York: W. W. Norton & Company.
Trafton, Anne."New virus-built battery could power cars, electronic devices." MITnews. N.p., 02 04 2009. Web. 25 Mar 2013.
Whaley, S. R., English, D. S., Hu, E. L., Barbara, P. F., & Belcher, A. M."Selection of peptides with semiconductor binding specificity for directed nanocrystal assembly." Nature 405.6787 (2000): 665-668.
Edited by (Justine Oesterle), a student of Nora Sullivan in BIOL187S (Microbial Life) in The Keck Science Department of the Claremont Colleges Spring 2013.
