Bacterial colonization in the form of biofilms on surfaces causes persistent infections and is an issue of considerable concern to healthcare providers. There is an urgent need for novel antimicrobial or antibiofilm surfaces and biomedical devices that provide protection against biofilm formation and planktonic pathogens, including antibiotic resistant strains. In this context, recent developments in the material science and engineering fields and steady progress in the nanotechnology field have created opportunities to design new biomaterials and surfaces with anti-infective, antifouling, bactericidal, and antibiofilm properties. Here we review a number of the recently developed nanotechnology-based biomaterials and explain underlying strategies used to make antibiofilm surfaces.

Quorum quenching decreases Pseudomonas aeruginosa virulence factors and biofilm formation, alleviating infections in animal models. Nevertheless, it is usually performed in laboratory strains such as PAO1 and PA14, and studies involving clinical or environmental isolates are scarce. In this work, the effects of ZnO nanoparticles, a potent quorum and virulence quencher for the PAO1 strain, were tested in six clinical strains from cystic fibrosis patients, a furanone C‐30 resistant clinical strain from urine, two PA14 gallium resistant mutants, a PA14 C‐30 resistant mutant and four environmental isolates. ZnO nanoparticles effectively decreased elastase, pyocyanin, and biofilm formation for most of the strains; regardless their origin or their resistance against the canonical quorum quencher C‐30 or the novel antimicrobial gallium. The data indicate ZnO nanoparticles may have a broad spectrum for the quorum quenching of relevant strains and that may be an alternative to treat Ps. aeruginosa recalcitrant infections. Significance and Impact of the Study Virulence inhibition by quorum quenchers in Pseudomonas aeruginosa is usually tested in laboratory strains and studies of their effects in relevant clinical and environmental strains are scarce. This study is significant as the effects of ZnO nanoparticles in QS‐dependent virulence factor production were tested in six clinical strains from cystic fibrosis patients, a C‐30 resistant clinical strain from urine, two PA14 gallium resistant mutants, a PA14 C‐30 resistant mutant, and four environmental isolates. ZnO nanoparticles decreased elastase, pyocyanin, and biofilms for most of the strains; indicating they have broad spectrum and may be an alternative to treat Ps. aeruginosa infections.

The objective of this study was to develop a bimetallic nanoparticle with enhanced antibacterial activity that would improve the therapeutic efficacy against bacterial biofilms. Bimetallic gold–silver nanoparticles were bacteriogenically synthesized using γ-proteobacterium, Shewanella oneidensis MR-1. The antibacterial activities of gold–silver nanoparticles were assessed on the planktonic and biofilm phases of individual and mixed multi-cultures of pathogenic Gram negative (Escherichia coli and Pseudomonas aeruginosa) and Gram positive bacteria (Enterococcus faecalis and Staphylococcus aureus), respectively. The minimum inhibitory concentration of gold–silver nanoparticles was 30–50 µM than that of other nanoparticles (>100 µM) for the tested bacteria. Interestingly, gold–silver nanoparticles were more effective in inhibiting bacterial biofilm formation at 10 µM concentration. Both scanning and transmission electron microscopy results further accounted the impact of gold–silver nanoparticles on biocompatibility and bactericidal effect that the small size and bio-organic materials covering on gold–silver nanoparticles improves the internalization and thus caused bacterial inactivation. Thus, bacteriogenically synthesized gold–silver nanoparticles appear to be a promising nanoantibiotic for overcoming the bacterial resistance in the established bacterial biofilms.

Emerging resistance to antibiotics is a mounting worldwide health concern and increases the need for nonantibiotic strategies to combat infectious diseases caused by bacterial pathogens. In this study, the authors used the antibiofilm activity of the naturally occurring antimicrobial cinnamaldehyde (CNMA) conjugated to the surface of gold nanoparticles (GNPs) to deliver CNMA efficiently and eradicate biofilms of Gram-negative organisms (enterohemorrhagic Escherichia coli O157:H7, and Pseudomonas aeruginosa), Gram positive (methicillin-sensitive Staphylococcus aureus organisms, and methicillin-resistant Staphylococcus aureus) bacteria. CNMA-GNPs containing 0.005% (v/v) of CNMA were found to inhibit biofilm formation efficiently. The distributions of nanoparticles in biofilm cells and their biofilm disruption activities, including distorted cell morphology, were determined by transmission electron microscopy. In addition to their antibiofilm activities, CNMA-GNPs attenuated S. aureus virulence and protected Caenorhabditis elegans (C. elegans) worms. Here, the authors report the antibiofilm effects of CNMA-GNPs and suggest that they could be used to treat pathogenic bacterial infections in vivo.

A new antibacterial gold nanorod (GNR) conjugated magnetic nanoparticle (MNP) composite (GNR–MNP) was synthesized successfully for the eradication of antibiotic resistant nosocomial pathogens in water to improve the water quality. The composite was fabricated via the reaction of nucleophilic amine and epoxide carbon moieties with silanes. Tagging of MNP over GNR was confirmed using electron microscopy. Zeta potential measurements were used to study the fundamental surface chemical states of GNR and MNP (before and after surface modification). The synthesized GNR–MNP composite was directly mixed with a bacterial culture suspension and the photo-thermally induced bactericidal effects were evaluated before and after laser treatment. Optical, spectral and electron microscopy results revealed that laser irradiated GNR–MNP show a more pronounced bactericidal effect than other disinfecting agents. Further, the results indicate that there is a positive correlation between the bacterial cell mortality and nanoparticle concentration and laser energy used. Interestingly, GNR–MNPs are capable of generating a rapid and reiterated photothermal effect for more than three consecutive cycles with enhanced magnetic separation for repeatable bactericidal application. These results suggest that the fabricated GNR–MNPs are a highly efficient photothermal agent against a wide variety of bacteria, suitable for cleaning real samples like water. Importantly, our method showed superior cell lysing results for both Escherichia coli (E. coli) and Enterococcus faecalis (E. faecalis) compared to conventional heat treatment.

Role of surface modification in zinc oxide nanoparticles and its toxicity assessment toward human dermal fibroblast cells Mohankandhasamy Ramasamy,1 Minakshi Das,1 Seong Soo A An,1 Dong Kee Yi2 1Division of Bionanotechnology, Gachon University, Seongnam, 2Department of Chemistry, Myongji University, Yongin, South Korea The wide-scale applications of zinc oxide (ZnO) nanoparticles (NPs) in ­photocatalysts, gas sensors, and cosmetics may cause toxicity to humans and environments. Therefore, the aim of the present study was to reduce the toxicity of ZnO NPs by coating them with a silica (SiO2) layer, which could be used in human applications, such as cosmetic preparations. The sol–gel method was used to synthesize core ZnO with SiO2-shelled NPs (SiO2/ZnO NPs) with varying degrees of coating. Diverse studies were performed to analyze the toxicity of NPs against cells in a dose- and time-dependent manner. To ensure the decreased toxicity of the produced SiO2/ZnO NPs, cytotoxicity in membrane damage and/or intracellular reactive oxygen species (ROS) were assessed by employing 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, lactate dehydrogenase, 2',7'-dichlorofluorescin, and lipid peroxide estimations. The cores of ZnO NPs exhibited cytotoxicity over time, regardless of shell thickness. Nevertheless, the thicker SiO2/ZnO NPs revealed reduced enzyme leakage, decreased peroxide production, and less oxidative stress than their bare ZnO NPs or thinner SiO2/ZnO NPs. Therefore, thicker SiO2/ZnO NPs moderated the toxicity of ZnO NPs by restricting free radical formation and the release of zinc ions, and decreasing surface contact with cells. Keywords: zinc oxide, silica coating, photostability, human dermal fibroblast, membrane damage, oxidative stress