Intracellular pH (pH i ) plays a critical role in the physiological and pathophysiological processes of cells, and fluorescence imaging using pH-sensitive indicators provides a powerful tool to assess the pH i of intact cells and subcellular compartments. Here we describe a nanoparticlebased ratiometric pH sensor, comprising a bright and photostable semiconductor quantum dot (QD) and pH-sensitive fluorescent proteins (FPs), exhibiting dramatically improved sensitivity and photostability compared to BCECF, the most widely used fluorescent dye for pH imaging.We found that Förster resonance energy transfer between the QD and multiple FPs modulates the FP/QD emission ratio, exhibiting a >12-fold change between pH 6 and 8. The modularity of the probe enables customization to specific biological applications through genetic engineering of the FPs, as illustrated by the altered pH range of the probe through mutagenesis of the fluorescent protein. The QD-FP probes facilitate visualization of the acidification of endosomes in living cells following polyarginine-mediated uptake. These probes have the potential to enjoy a wide range of intracellular pH imaging applications that may not be feasible with fluorescent proteins or organic fluorophores alone.

Commonly used techniques for analyzing gene expression, such as polymerase chain reaction (PCR), microarrays, and in situ hybridization, have proven invaluable in understanding RNA processing and regulation. However, these techniques rely on the use of lysed and/or fixed cells and are therefore limited in their ability to provide important spatial-temporal information. This has led to the development of numerous techniques for imaging RNA in living cells, some of which have already provided important insight into the dynamic role RNA plays in dictating cell behavior. Here we review the fluorescent probes that have allowed for RNA imaging in living cells and discuss their utility and limitations. Common challenges faced by fluorescent probes, such as probe design, delivery, and target accessibility, are also discussed. It is expected that continued advancements in live cell imaging of RNA will open new and exciting opportunities in a wide range of biological and medical applications.

Stem cells and their paracrine factors have emerged as a resource for regenerative medicine. Many studies have shown the beneficial effects of paracrine factors secreted from adult stem cells, such as exosomes, on skin aging. However, to date, few reports have demonstrated the use of exosomes derived from human pluripotent stem cells for the treatment of skin aging. In this study, we collected exosomes from the conditioned medium of human induced pluripotent stem cells (iPSCs) and investigated the effect on aged human dermal fibroblasts (HDFs). Cell proliferation and viability were determined by an MTT assay and cell migration capacity was shown by a scratch wound assay and a transwell migration assay. To induce photoaging and natural senescence, HDFs were irradiated by UVB (315 nm) and subcultured for over 30 passages, respectively. The expression level of certain mRNAs was evaluated by quantitative real-time PCR (qPCR). Senescence-associated-β-galactosidase (SA-β-Gal) activity was assessed as a marker of natural senescence. As a result, we found that exosomes derived from human iPSCs (iPSCs-Exo) stimulated the proliferation and migration of HDFs under normal conditions. Pretreatment with iPSCs-Exo inhibited the damages of HDFs and overexpression of matrix-degrading enzymes (MMP-1/3) caused by UVB irradiation. The iPSCs-Exo also increased the expression level of collagen type I in the photo-aged HDFs. In addition, we demonstrated that iPSCs-Exo significantly reduced the expression level of SA-β-Gal and MMP-1/3 and restored the collagen type I expression in senescent HDFs. Taken together, it is anticipated that these results suggest a therapeutic potential of iPSCs-Exo for the treatment of skin aging.

There are extensive studies on the applications of extracellular vesicles (EVs) produced in cell culture for therapeutic drug development. However, large quantities of EVs are needed for in vivo applications, which requires high production costs and time. Thus, the development of new EV sources is essential to facilitate their use. Accordingly, plant-derived exosome-like nanovesicles are an emerging alternative for culture-derived EVs. Until now, however, few studies have explored their biological functions and uses. Therefore, it is necessary to elucidate biological activities of plant-derived exosome-like nanovesicles and harness vesicles for biomedical applications. Herein, cabbage and red cabbage were used as nanovesicle sources owing to their easy cultivation. First, an efficient method for nanovesicle isolation from cabbage (Cabex) and red cabbage (Rabex) was developed. Furthermore, isolated nanovesicles were characterized, and their biological functions were assessed. Both Cabex and Rabex promoted mammalian cell proliferation and, interestingly, suppressed inflammation in immune cells and apoptosis in human keratinocytes and fibroblasts. Finally, therapeutic drugs were encapsulated in Cabex or Rabex and successfully delivered to human cells, demonstrating the potential of these vesicles as alternative drug delivery vehicles. Overall, the current results provide strong evidence for the wide application of Cabex and Rabex as novel therapeutic biomaterials.

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A 3D cell culture system that mimics the lung cancer microenvironment was used to investigate the effect of exosomes encapsulating miR-497 on tumor growth and angiogenesis, and could be a predictive, cost-efficient translational tool to develop targeted cancer therapy.

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