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.

Stem cells offer great potential for regenerative medicine due to their excellent capability to differentiate into a specialized cell type of the human body. Recently, nanomaterial based scaffolds (e.g. graphene), biodegradable polymers (e.g. PLGA: poly-D,L-lactic-co-glycolic acid), and inorganic nanoparticles (NPs, e.g. metallic, magnetic, upconversion) have made considerable advances in controlling the differentiation of stem cells. Some of the notable advances include the development of a variety of NPs such as gold, silica, selenium and graphene quantum dots (QDs) for the controlled differentiation of stem cells – human mesenchymal stem cells (hMSCs), and magnetic core–shell NPs (e.g. ZnFe₂O₄–Au) for the control of neural stem cells (NSCs). Multimodal imaging (MR, optical, ultrasound, photoacoustic) of stem cells provides opportunities for probing the fate of implanted cells, thereby determining the therapeutic efficacy. Novel multifunctional NPs have been developed over the years, and probed using the aforementioned imaging techniques for stem cell research. This review article underscores the recent progress in nanotechnology for stem cell differentiation, labeling, tracking and therapy. Nano/biomaterial assisted stem cell therapies for bone, heart, and liver regeneration are also delineated.