Graphene oxide (GO) is extensively proposed as an effective antibacterial agent in commercial product packaging and for various biomedical applications. However, the antibacterial mode of action of GO is yet hypothetical and unclear. Here we developed a new and sensitive fingerprint approach to study the antibacterial activity of GO and underlying mechanism, using Raman spectroscopy. Spectroscopic signatures obtained from biomolecules such as Adenine and proteins from bacterial cultures with different concentrations of GO, allowed us to probe the antibacterial activity of GO with its mechanism at the molecular level. Escherichia coli (E. coli) and Enterococcus faecalis (E. faecalis) were used as model micro-organisms for all the experiments performed. The observation of higher intensity Raman peaks from Adenine and proteins in GO treated E. coli and E. faecalis; correlated with induced death, confirmed by Scanning electron Microscopy (SEM) and Biological Atomic Force Microscopy (Bio-AFM). Our findings open the way for future investigations of the antibacterial properties of different nanomaterial/GO composites using Raman spectroscopy.

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.

The synergistic impact of nanomaterials is critical for novel intracellular and/or subcellular drug delivery systems of minimal toxicity. This synergism results in a fundamental bio/nano interface interaction, which is discussed in terms of nanoparticle translocation, outer wrapping, embedding, and interior cellular attachment. The morphology, size, surface area, ligand chemistry and charge of nanoparticles all play a role in translocation. In this review, we suggest a generalized mechanism to characterize the bio/nano interface, as we discuss the synergistic interaction between nanoparticles and cells, tissues, and other biological systems. Novel perceptions are reviewed regarding the ability of nanoparticles to improve hybrid nanocarriers with homogeneous structures to enhance multifunctional biomedical applications, such as bioimaging, tissue engineering, immunotherapy, and phototherapy.