Poly(L-lactic acid) and its copolymers with Dlactic and glycolic acid were used to fabricate various porous biodegradable scaffolds suitable for tissue engineering and drug delivery based on a thermally induced phase separation (TIPS) technique. A variety of parameters involved in TIPS process, such as types of polymers, polymer concentration, solvent/nonsolvent ratio, and quenching temperature, were examined in detail to produce a wide array of micro-and macroporous structures. A mixture of dioxane and water was used for a binary composition of solvent and nonsolvent, respectively. In particular, the coarsening effect of pore enlargement affected by controlling the quenching temperature was used for the generation of a macroporous open cellular structure with pore diameters above 100 m. The use of amorphous polymers with a slow cooling rate resulted in a macroporous open cellular structure, whereas that of semicrystalline polymers with a fast cooling rate generated a microporous closed cellular structure. The fabricated porous devices loaded with recombinant human growth hormone (rhGH) were tested for the controlled delivery of rhGH, as a potential additional means to cell delivery.

Highly open porous biodegradable poly(L-lactic acid) ¿PLLA scaffolds for tissue regeneration were fabricated by using ammonium bicarbonate as an efficient gas foaming agent as well as a particulate porogen salt. A binary mixture of PLLA-solvent gel containing dispersed ammonium bicarbonate salt particles, which became a paste state, was cast in a mold and subsequently immersed in a hot water solution to permit the evolution of ammonia and carbon dioxide within the solidifying polymer matrix. This resulted in the expansion of pores within the polymer matrix to a great extent, leading to well interconnected macroporous scaffolds having mean pore diameters of around 300-400 microm, ideal for high-density cell seeding. Rat hepatocytes seeded into the scaffolds exhibited about 95% seeding efficiency and up to 40% viability at 1 day after the seeding. The novelty of this new method is that the PLLA paste containing ammonium bicarbonate salt particles can be easily handled and molded into any shape, allowing for fabricating a wide range of temporal tissue scaffolds requiring a specific shape and geometry.

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Over several billion years, cyanobacteria and plants have evolved highly organized photosynthetic systems to shuttle both electronic and chemical species for the efficient oxidation of water. In a similar manner to reaction centres in natural photosystems, molecular and metal oxide catalysts have been used to photochemically oxidize water. However, the various approaches involving the molecular design of ligands, surface modification and immobilization still have limitations in terms of catalytic efficiency and sustainability. Here, we demonstrate a biologically templated nanostructure for visible light-driven water oxidation that uses a genetically engineered M13 virus scaffold to mediate the co-assembly of zinc porphyrins (photosensitizer) and iridium oxide hydrosol clusters (catalyst). Porous polymer microgels are used as an immobilization matrix to improve the structural durability of the assembled nanostructures and to allow the materials to be recycled. Our results suggest that the biotemplated nanoscale assembly of functional components is a promising route to significantly improved photocatalytic water-splitting systems.

Biological molecules can be used as versatile templates for assembling nanoscale materials because of their unique structures and chemical diversities. Supramolecular organization of molecular pigments, as is found in the natural light-harvesting antenna, has drawn attention for its potential applications to sensors, photocatalytic systems, and photonic devices. Here we show the arrangement of molecular pigments into a one-dimensional light-harvesting antenna using M13 viruses as scaffolds. Chemical grafting of zinc porphyrins to M13 viruses induces distinctive spectroscopic changes, including fluorescence quenching, the extensive band broadening and small red shift of their absorption spectrum, and the shortened lifetime of the excited states. Based on these optical signatures we suggest a hypothetical model to explain the energy transfer occurring in the supramolecular porphyrin structures templated with the virus. We expect that further genetic engineering of M13 viruses can allow us to coassemble other functional materials (e.g., catalysts and electron transfer mediators) with pigments, implying potential applications to photochemical devices.

Biotemplated synthesis of functional nanomaterials has received increasing attention for applications in energy, catalysis, bioimaging, and other technologies. This approach is justified by the unique abilities of biological systems to guide sophisticated assembly and organization of molecules and materials into distinctive nanoscale morphologies that exhibit physicochemical properties highly desirable for specific purposes. Here, we present a high-performance, flexible nanogenerator using anisotropic BaTiO3 (BTO) nanocrystals synthesized on an M13 viral template through the genetically programmed self-assembly of metal ion precursors. The filamentous viral template realizes the formation of a highly entangled, well-dispersed network of anisotropic BTO nanostructures with high crystallinity and piezoelectricity. Even without the use of additional structural stabilizers, our virus-enabled flexible nanogenerator exhibits a high electrical output up to ∼300 nA and ∼6 V, indicating the importance of nanoscale structures for device performances. This study shows the biotemplating approach as a facile method to design and fabricate nanoscale materials particularly suitable for flexible energy harvesting applications.

A facile synthetic route was developed to make Au nanowires (NWs) from surfactant-mediated bio-mineralization of a genetically engineered M13 phage with specific Au binding peptides. From the selective interaction between Au binding M13 phage and Au ions in aqueous solution, Au NWs with uniform diameter were synthesized at room temperature with yields greater than 98 % without the need for size selection. The diameters of Au NWs were controlled from 10 nm to 50 nm. The Au NWs were found to be active for electrocatalytic oxidation of CO molecules for all sizes, where the activity was highly dependent on the surface facets of Au NWs. This low-temperature high yield method of preparing Au NWs was further extended to the synthesis of Au/Pt core/shell NWs with controlled coverage of Pt shell layers. Electro-catalytic studies of ethanol oxidation with different Pt loading showed enhanced activity relative to a commercial supported Pt catalyst, indicative of the dual functionality of Pt for the ethanol oxidation and Au for the anti-poisoning component of Pt. These new one-dimensional noble metal NWs with controlled compositions could facilitate the design of new alloy materials with tunable properties.

We integrate the adhesive properties of marine mussels, the lubricating properties of pitcher plants, and the nonfouling properties of diatoms into nanostructured surfaces to develop a device called a micro-omnifluidic (μ-OF) system to solve the existing challenges in microfluidic systems. Unlike conventional poly(dimethylsiloxane)-based fluidic systems that are incompatible with most organic solvents, the μ-OF system utilizes a variety of solvents such as water, ethanol, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, n-hexane, 1,2-dichloroethane, acetic acid, 2-propanol, acetone, toluene, diesel oil, dioxane, gasoline oil, hexadecane, and xylene. The μ-OF system is based on a phenomenon called microchannel induction that spontaneously occurs when virtually all droplets of solvents are applied on omniphilically micropatterned regions of a slippery liquid-infused porous surface. Any solvents with surface tension greater than that of the lubricant (17.1 mN/m, Fluorinert FC-70) are able to repel the infused lubricant located on top of the omniphilic microlines, triggering controlled movement of the droplet by gravity along the microlines. We also demonstrated that the μ-OF system is reusable by the nonadsorption properties of the silicified layer. Due to the organic solvent compatibility, we were able to perform organic reactions with high portability and energy efficiency in operation.