Hen egg white lysozyme acted as the sole reducing agent and catalyzed the formation of silver nanoparticles in the presence of light. Stable silver colloids formed after mixing lysozyme and silver acetate in methanol and the resulting nanoparticles were concentrated and transferred to aqueous solution without any significant changes in physical properties. Activity and antimicrobial assays demonstrated lysozyme-silver nanoparticles retained the hydrolase function of the enzyme and were effective in inhibiting growth of Escherichia coli, Staphylococcus aureus, Bacillus anthracis, and Candida albicans. Remarkably, lysozyme-silver nanoparticles demonstrated a strong antimicrobial effect against silver-resistant Proteus mirabilis strains and a recombinant E. coli strain containing the multiple antibiotic- and silver-resistant plasmid, pMG101. Results of toxicological studies using human epidermal keratinocytes revealed that lysozyme-silver nanoparticles are nontoxic at concentrations sufficient to inhibit microbial growth. Overall, the ability of lysozyme to assemble silver nanoparticles in a one-step reaction offers a simple and environmentally friendly approach to form stable colloids of nontoxic silver nanoparticles that combine the antimicrobial properties of lysozyme and silver. The results expand the functionality of nanomaterials for biological systems and represent a novel antimicrobial composite for potential aseptics and therapeutic use in the future.

This research introduces a method for fabrication of conductive electrode materials with hierarchical structure from porous polymer/carbon composite materials. We describe the fabrication of (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) scaffolds doped with carbon materials that provide a conductive three-dimensional architecture that was demonstrated for application in microbial fuel cell (MFC) anodes. Composite electrodes from PHBV were fabricated to defined dimensions by solvent casting and particulate leaching of a size-specific porogen (in this case, sucrose). The cellular biocompatibility of the resulting composite material facilitated effective immobilization of a defined preparation of Shewanella oneidensis DSP-10 as a model microbial catalyst. Bacterial cells were immobilized via chemical vapor deposition (CVD) of silica to create an engineered biofilm that exhibits efficient bioelectrocatalysis of a simple-carbon fuel in a MFC. The functionalized PHBV electrodes demonstrate stable and reproducible anodic open circuit potentials of -320 ± 20 mV (vs Ag/AgCl) with lactate as the electron donor. Maximum power densities achieved by the hierarchically structured electrodes (~5 mW cm(3)) were significantly higher than previously observed for graphite-felt electrodes. The methodology for fabrication of scalable electrode materials may be amenable to other bioelectrochemical applications, such as enzyme fuel cells and biosensors, and could easily be adapted to various design concepts.

Direct bioelectrocatalysis was demonstrated with pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ–GDH) tethered to a range of carbon nanotube (CNT) materials, as evidenced by the generation of anodic current in the presence of glucose. Physical and electrochemical characterization of CNT paper (buckypaper) reveals marked differences attributed to changes in CNT dimensions, including conductivity, packing density, and electrochemically accessible surface area. By using single-walled CNTs as the electrode material, higher current densities per geometric area and lower electron transfer resistances were achieved. In comparison, electrodes made of oxidized CNTs enhanced in the physical adsorption of PQQ, but displayed voltage drops associated with activation losses. In addition, electrode longevity tests revealed that electrochemical activity was retained for two days but decreased by 50% on the third day. PQQ–GDH enzymatic electrodes show potential application as biological fuel cell anodes and will oxidize a range of mono- and disaccharide substrates.

Amphiphilicity and cationicity are properties shared between antimicrobial peptides and proteins that catalyze biomineralization reactions. Merging these two functionalities, we demonstrate a reaction where a cationic antimicrobial peptide catalyzes self-biomineralization within inorganic matrices. The resultant antimicrobial peptide nanoparticles retain biocidal activity, protect the peptide from proteolytic degradation, and facilitate a continuous release of the antibiotic over time. Taken together, these properties demonstrate the therapeutic potential of selfsynthesizing biomaterials that retain the biocidal properties of antimicrobial peptides.