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.

Multicopper oxidases linked to multiwall carbon nanotubes via the molecular tethering reagent, 1-pyrenebutanoic acid, succinimidyl ester, displayed high bioelectrocatalytic activity for oxygen reduction.

Comamonas sp. strain JS765 can grow with nitrobenzene as the sole source of carbon, nitrogen, and energy. We report here the sequence of the genes encoding nitrobenzene dioxygenase (NBDO), which catalyzes the first step in the degradation of nitrobenzene by strain JS765. The components of NBDO were designated Reductase NBZ , Ferredoxin NBZ , Oxygenase NBZ␣ , and Oxygenase NBZ␤ , with the gene designations nbzAa, nbzAb, nbzAc, and nbzAd, respectively. Sequence analysis showed that the components of NBDO have a high level of homology with the naphthalene family of Rieske nonheme iron oxygenases, in particular, 2-nitrotoluene dioxygenase from Pseudomonas sp. strain JS42. The enzyme oxidizes a wide range of substrates, and relative reaction rates with partially purified Oxygenase NBZ revealed a preference for 3-nitrotoluene, which was shown to be a growth substrate for JS765. NBDO is the first member of the naphthalene family of Rieske nonheme iron oxygenases reported to oxidize all of the isomers of mono-and dinitrotoluenes with the concomitant release of nitrite.Nitroaromatic compounds are used extensively as industrial feedstocks for many manufacturing processes, including the production of pesticides, dyes, and explosives (11). Due to improper storage, use, and disposal, nitroaromatic compounds have been released into the environment, where they are considered environmental pollutants. For example, nitrobenzene and 2,4-and 2,6-dinitrotoluene are included in the U.S. Environmental Protection Agency's list of priority pollutants (14).The biodegradation of aromatic hydrocarbons and related compounds by aerobic bacteria is often initiated by multicomponent dioxygenase systems that catalyze the addition of both atoms of molecular oxygen to the substrate. Nitroaromatic compounds, in general, are resistant to oxidative attack due to the electron-withdrawing nature of the nitro groups and the stability of the benzene ring (29,33). Only recently have aerobic bacteria been isolated that utilize nitroaromatic compounds as growth substrates (19,32). One example is Comamonas sp. strain JS765, which can grow with nitrobenzene as the sole source of carbon, nitrogen, and energy. Previous experiments showed that JS765 uses an oxidative pathway for the degradation of nitrobenzene, with the initial reaction catalyzed by nitrobenzene 1,2-dioxygenase (NBDO; Fig. 1) (18). Other nitroarene dioxygenase genes from aerobic bacteria have been cloned and sequenced; these include genes encoding 2-nitrotoluene dioxygenase from Pseudomonas sp. strain JS42 (20) and 2,4-dinitrotoluene dioxygenases (DNTDOs) from Burkholderia sp. strain DNT (35) and Burkholderia cepacia R34 (G. R. Johnson, B. E. Haigler, R. K. Jain, and J. C. Spain, Abstr. 98th Gen. Meet. Am. Soc. Microbiol., abstr. Q-83, p. 435, 1998). However, strains DNT and R34 are unable to grow with nitrobenzene and we have observed only slight growth of JS42 with nitrobenzene.The majority of nitroaromatic compounds are synthetic, and therefore they have been present in the environment for...

We report a method for the synthesis of antimicrobial coatings on medical instruments that combines the bacteriolytic activity of lysozyme and the biocidal properties of silver nanoparticles. Colloidal suspensions of lysozyme and silver nanoparticles were electrophoretically deposited onto the surface of stainless steel surgical blades and needles. Electrodeposited films firmly adhered to stainless steel surfaces even after extensive washing and retained the hydrolytic properties of lysozyme. The antimicrobial efficacy of coatings was tested by using blades and needles in an in vitro lytic assay designed to mimic the normal application of the instruments. Coated blades and needles were used to make incisions and punctures, respectively, into agarose infused with bacterial cells. Cell lysis was seen at the contact sites, demonstrating that antimicrobial activity is transferred into the media, as well as retained on the surface of the blades and needles. Blade coatings also exhibited antimicrobial activity against a range of bacterial species. In particular, coated blades demonstrated potent bactericidal activity, reducing cell viability by at least 3 log within 1.5 h for Klebsiella pneumoniae, Bacillus anthracis Sterne, and Bacillus subtilis and within 3 h for Staphylococcus aureus and Acinetobacter baylyi. The results confirmed that complex antimicrobial coatings can be created using facile methods for silver nanoparticle synthesis and electrodeposition.

This work demonstrates a new approach for building bioinorganic interfaces by integrating biologically derived silica with single-walled carbon nanotubes to create a conductive matrix for immobilization of enzymes. Such a strategy not only allows simple integration into biodevices but presents an opportunity to intimately interface an enzyme and manifest direct electron transfer features. Biologically synthesized silica/carbon nanotube/enzyme composites are evaluated electrochemically and characterized by means of X-ray photoelectron spectroscopy. Voltammetry of the composites displayed stable oxidation and reduction peaks at an optimal potential close to that of the FAD/FADH(2) cofactor of immobilized glucose oxidase. The immobilized enzyme is stable for a period of one month and retains catalytic activity for the oxidation of glucose. It is demonstrated that the resulting composite can be successfully integrated into functional bioelectrodes for biosensor and biofuel cell applications.