The antimicrobial properties of dextrose-encapsulated gold nanoparticles (dGNPs) with average diameters of 25, 60, and 120 nm (± 5) and synthesized by green chemistry principles were investigated against both Gram-negative and Gram-positive bacteria. Studies were performed involving the effect of dGNPs on the growth, morphology, and ultrastructural properties of bacteria. dGNPs were found to have significant dose-dependent antibacterial activity which was also proportional to their size. Experiments revealed the dGNPs to be bacteriostatic as well as bactericidal. The dGNPs exhibited their bactericidal action by disrupting the bacterial cell membrane which leads to the leakage of cytoplasmic content. The overall outcome of this study suggests that green-synthesized dGNPs hold promise as a potent antibacterial agent against a wide range of disease-causing bacteria by preventing and controlling possible infections or diseases.

Need for novel, innovative strategies for developing antibiotics is becoming a necessity due to an increasing number of rapidly evolving micro-organismal threats. Antibiotic encapsulated gold nanoparticles (GNPs) are one such strategy showing promise. We report the development of ampicillin encapsulated gold nanoparticles (Amp-GNPs) that possess highly effective, dose dependant antibacterial activity. In this method, ampicillin molecules have been coated on individual GNPs which can then serve as drug carrier devices. Our method for synthesizing Amp-GNPs is an entirely ecofriendly, single step reaction taking place in an aqueous buffer. Following characterization of Amp-GNPs, we find them to be ~15 nm in diameter and spherical in shape. We have tested the antibacterial activity of Amp-GNPs against multiple strains of bacteria, both Grampositive and Gram-negative, and have found Amp-GNPs to be highly efficient against all tested strains. By examining the mechanism of Amp-GNPs antibacterial activity, it was determined that Amp-GNPs disrupt the bacterial cells membrane when coming into contact with the cells, thus disturbing the cell equilibrium, leading to cell lysis or necrosis. Amp-GNPs have been shown to exhibit significant potential and ability to enter the medical field's arsenal to fight infectious disease.

Xylose is a natural monosaccharide found in biomass such as straw, pecan shells, cottonseed hulls, and corncobs. Using this monosaccharide, we report the facile, green synthesis and characterization of stable xylose encapsulated gold nanoparticles (Xyl-GNPs) with potent antibacterial activity. Xyl-GNPs were synthesized using the reduction property of xylose in an aqueous solution containing choloraurate anions carried out at room temperature and atmospheric pressure. These nanoparticles were stable and near spherical in shape with an average diameter of 15 +/- 5 nm. Microbiological assay results showed the concentration dependent antibacterial activity of these particles against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus epidermidis) bacteria. Thus the facile, environmentally friendly Xyl-GNPs have many potential applications in chemical and biomedical industries, particularly in the development of antibacterial agents in the field of biomedicine.

We report the bactericidal applications of eco-friendly starch encapsulated gold nanoparticles (St-AuNPs). The mechanism of interaction of the properly characterized St-AuNPs with both Gram negative and Gram positive bacteria were investigated using spread plate assay, transmission electron microscopy (TEM), and fluorescent propidium iodide (PI) exclusion assay. The St-AuNPs were found to possess significant dose dependent antibacterial activity against both types of bacteria. St-AuNPs at 1.2 mg/mL caused 98 % eradication of Gram positive bacteria that was exposed over a period of 12 h. Similarly, 4.8 mg/mL St-AuNPs caused 98 % eradication of Gram negative bacteria over a period of 12h. The St-AuNPs are biocompatible and present a useful solid porous carbohydrate-based polymer vehicle with excellent antimicrobial activity against [Frontiers in Bioscience 18, 982-992, June 1, 2013].