In the past decades, Förster resonance energy transfer (FRET) has been used as a powerful tool to provide nanoscale information in many biosensing and bioanalysis applications. The performance of FRET assay is mainly dependent on the design of donor and acceptor pairs. Recently, a series of nanoparticles start to be used in FRET assays including semiconductor quantum dots (QDs), graphene quantum dots (GQDs), upconversion nanoparticles (UCNPs), gold nanoparticles (AuNPs) and graphene oxide (GO). The rapid pace of development in nanoparticles provides a lot of opportunities to revolutionize FRET techniques. Many nanoparticle based FRET assays have also been developed for various biosensing applications with higher sensitivity and better stability compared with traditional organic fluorophore based FRET assays. This article reviews the recent progress of nanoparticle FRET assays and their applications in biosensing area.

Transcriptional activation by c-Myc through specific E box elements is thought to be essential for its biological role. However, c-MycS is unable to activate transcription through these elements and yet retains the ability to stimulate proliferation, induce anchorage-independent growth, and induce apoptosis. In addition, c-MycS retains the ability to repress transcription of several specific promoters. Furthermore, c-MycS can rescue the cmyc null phenotype in fibroblasts with homozygous deletion of c-myc. Taken together, our data argue against the paradigm that all of the biological functions of c-Myc are mediated by transcriptional activation of specific target genes through E box elements.

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The complex pathogenesis of osteoporosis includes excessive bone resorption, insufficient bone formation and inadequate vascularization, a combination which is difficult to completely address with conventional therapies. Engineered exosomes carrying curative molecules show promise as alternative osteoporosis therapies, but depend on specifically-functionalized vesicles and appropriate engineering strategies. Here, we developed an exosome delivery system based on exosomes secreted by mesenchymal stem cells (MSCs) derived from human induced pluripotent stem cells (iPSCs). The engineered exosomes BT-Exo-si Shn3 , took advantage of the intrinsic anti-osteoporosis function of these special MSC-derived exosomes and collaborated with the loaded siRNA of the Shn3 gene to enhance the therapeutic effects. Modification of a bone-targeting peptide endowed the BT-Exo-si Shn3 an ability to deliver siRNA to osteoblasts specifically. Silencing of the osteoblastic Shn3 gene enhanced osteogenic differentiation, decreased autologous RANKL expression and thereby inhibited osteoclast formation. Furthermore, Shn3 gene silencing increased production of SLIT3 and consequently facilitated vascularization, especially formation of type H vessels. Our study demonstrated that BT-Exo-si Shn3 could serve as a promising therapy to kill three birds with one stone and implement comprehensive anti-osteoporosis effects.

Here, we report the one-step in situ detection of targeted miRNAs expression in single living cancer cells via MoS nanosheet-based fluorescence on/off probes. The strategy is based on the folic acid (FA)-poly(ethylene glycol)-functionalized MoS nanosheets with adsorbed dye-labeled single-stranded DNA (ssDNA). Once the nanoprobes are internalized into cancer cells, the hybridization between the probes and target miRNA results in the detachment of dye-labeled ssDNA from MoS nanosheets surface, leading to the green fluorescence recovery. In this nanoprobe, MoS nanosheets offer advantages of high fluorescence quenching efficiency and extremely low toxicity. The FA conjugation could protect the probes and improve cancer cell transfection efficiency. The ability of this nanoprobe for endogenous miRNA detection in single living cancer cells is demonstrated for two types of cancer cells with different miRNA-21 expressions (MCF-7 and Hela cells). This functionalized MoS nanosheet-based nanoprobes could provide a sensitive and real-time detection of intracellular miRNA detection platform.

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