Graphene oxide (GO) has attracted significant interest as a template material for multiple applications due to its two-dimensional nature and established functionalization chemistries. However, for applications toward stem cell culture and differentiation, GO is often reduced to form reduced graphene oxide, resulting in a loss of oxygen content. Here, we induce a phase transformation in GO and demonstrate its benefits for enhanced stem cell culture and differentiation while conserving the oxygen content. The transformation results in the clustering of oxygen atoms on the GO surface, which greatly improves its ability toward substance adherence and results in enhanced differentiation of human mesenchymal stem cells toward the osteogenic lineage. Moreover, the conjugating ability of modified GO strengthened, which was examined by auxiliary osteogenic growth peptide conjugation. Overall, our work demonstrates GO's potential for stem cell applications while maintaining its oxygen content, which could enable further functionalization and fabrication of novel nano-biointerfaces.

Graphene oxide (GO), a derivative of graphene, and its related nanomaterials have attracted much attention in recent years due to the excellent biocompatibility and large surface area of GO with abundant oxygen functional groups, which further enable it to serve as a nano-bio interface. Herein, we demonstrate the induction of blue fluorescence in GO suspensions via a mild thermal annealing procedure. Additionally, this procedure preserves the oxygen functional groups on the graphene plane which enables the conjugation of cancer drugs without obvious cytotoxicity. Consequently, we demonstrate the capability of GO to simultaneously play the dual-role of a: (i) cellular imaging agent and (ii) drug delivery agent in CT26 cancer cells without the need for additional fluorescent protein labeling. Our method offers a simple, controllable strategy to tune and enhance the fluorescence property of GO, which shows potential for biomedical applications and fundamental studies.

Recent developments in epidemiology have confirmed that airborne particulates are directly associated with respiratory pathology and mortality. Although clinical studies have yielded evidence of the effects of many types of fine particulates on human health, it still does not have a complete understanding of how physiological reactions are caused nor to the changes and damages associated with cellular and molecular mechanisms. Currently, most health assessment studies of particulate matter (PM) are conducted through cell culture or animal experiments. The results of such experiments often do not correlate with clinical findings or actual human reactions, and they also cause difficulty when investigating the causes of air pollution and associated human health hazards, the analysis of biomarkers, and the development of future pollution control strategies. Microfluidic-based cell culture technology has considerable potential to expand the capabilities of conventional cell culture by providing high-precision measurement, considerably increasing the potential for the parallelization of cellular assays, ensuring inexpensive automation, and improving the response of the overall cell culture in a more physiologically relevant context. This review paper focuses on integrating the important respiratory health problems caused by air pollution today, as well as the development and application of biomimetic organ-on-a-chip technology. This more precise experimental model is expected to accelerate studies elucidating the effect of PM on the human body and to reveal new opportunities for breakthroughs in disease research and drug development.