Reconstruction of damaged nerves remains a significant unmet challenge in clinical medicine. To foster improvements, the control of neural stem cell (NSC) behaviors, including migration, proliferation and differentiation are critical factors to consider. Topographical and mechanical stimulation based on the control of biomaterial features is a promising approach, which are usually studied separately. The synergy between topography and mechanical rigidity could offer new insights into the control of neural cell fate if they could be utilized concurrently in studies. To achieve this need, silk fibroin self-assembled nanofibers with a beta-sheet-enriched structure are formed into hydrogels. Stiffness is tuned using different annealing processes to enable mechanical control without impacting the nanofiber topography. Compared with nonannealed nanofibers, NSCs on methanol annealed nanofibers with stiffness similar to nerve tissues differentiate into neurons with the restraint of glial differentiation, without the influence of specific differentiation biochemical factors. These results demonstrate that combining topographic and mechanical cues provides the control of nerve cell behaviors, with potential for neurogenerative repair strategies.

With the rapid development of nanotechnology, the unique rare-earth lanthanide-doped upconversion nanocrystals (UCNs), which can convert tissue-penetrable near-infrared (NIR) photonic irradiation into ultraviolet, visible, and NIR emissions, have a significant potential in bioimaging, diagnosis, and therapy, as well as in photovoltaic systems and optical data storage. Despite the promising achievements made in the past decade, critical challenges associated with low upconversion efficiencies and the overheating effect induced by NIR laser-irradiation still remain in the biomedical fields. In high demand are more well-defined material design and unique structural modifications that are capable of solving these technical concerns and promoting such promising NIR light-mediated upconversion nanocrystals for their further application in the medical sciences. Recent advances in upconversion nanomaterials have witnessed a tremendous development towards enhancing their photon conversion efficiency, which provides great opportunities in expanding the potential of the UCNs in bioimaging diagnosis and anticancer therapy. Hence, this review is mainly focused on summarizing the fundamental principles and strategies that improve upconversion luminescence and the approaches to reduce the local thermal effect on the basis of a rational design of UCNs. In addition, the future perspectives in the development of UCNs for biomedical applications are also proposed.

A simple and unique surface-enhanced Raman spectroscopy (SERS) platform is developed for the precise and sensitive in situ monitoring of nitric oxide (NO) release from an individual bacterium. Using this live bacteria SERS platform, NO release from MRSA under the stress of antibiotics and co-infected bacteria was evaluated.