MicroRNA (miR) sponges containing miR binding sequences constitute a potentially powerful molecular therapeutic strategy. Recently, naturally occurring circular RNAs (circRNAs) were shown to function as efficient miR sponges in cancer cells. We hypothesized that synthetic circRNA sponges could achieve therapeutic loss-of-function targeted against specific miRs. Linear RNA molecules containing miR-21 binding sites were transcribed in vitro; after dephosphorylation and phosphorylation, circularization was achieved using 5′-3′ end-ligation by T4 RNA ligase 1. circRNA stability was assessed using RNase R and fetal bovine serum. Competitive inhibition of miR-21 activity by a synthetic circRNA sponge was assessed using luciferase reporter, cell proliferation, and cell apoptosis assays in three gastric cancer cell lines. circRNA effects on downstream proteins were also delineated by Tandem Mass Tag (TMT) labeling (data available via ProteomeXchange identifier PRIDE: PXD008584), followed by western blotting. We conclude that artificial circRNA sponges resistant to nuclease digestion can be synthesized using simple enzymatic ligation steps. These sponges inhibit cancer cell proliferation and suppress the activity of miR-21 on downstream protein targets, including the cancer protein DAXX. In summary, synthetic circRNA sponges represent a simple, effective, convenient strategy for achieving targeted loss of miR function in vitro, with potential future therapeutic application in human patients.

Articular cartilage defect repair is challenging for clinics because it is avascular tissue lack of self-regenerative ability. Gelatin-based hydrogels are widely used in the field of tissue engineering because of their good biodegradability, excellent biocompatibility, and cell/tissue affinity. However, gelatin-based hydrogels exhibit poor thermal stability and low mechanical strength, which limits their applications in cartilage repair. In this study, methacrylic anhydride (MA) was employed to modify gelatin to obtain photo-crosslinkable methacrylated gelatin (GelMA). The GelMA-based natural-synthetic polymer biohybrid hydrogel was prepared by co-polymerizing acrylamide (AM) and GelMA under ultraviolet radiation in the presence of a photo-initiator. The GelMA/PAM biohybrid hydrogel simultaneously possessed the advantages of both PAM hydrogels and GelMA hydrogels. The GelMA block provided specific biological functions for cell adhesion and proliferation, while the flexible PAM chains reinforced the brittle gelatin network and sustain load during deformation. Compared with pure PAM hydrogel and GelMA, the GelMA/PAM biohybrid hydrogels showed enhanced compression strength (0.38 MPa) and improved elasticity (storage modulus of 1000 Pa). The GelMA/PAM biohybrid hydrogel showed a favorable degradation rate and sustained protein release. In vitro cell culture showed that the chondrocytes remained viable and proliferated on the biohybrid hydrogel, demonstrating that the biohybrid hydrogels had good cell adhesion and excellent biocompatibility. In a rabbit knee cartilage defect model, we evaluated the cartilage repair ability of the biohybrid hydrogel in vivo. In summary, this study demonstrated that hybridization of synthetic polymers considerably improves the performance and expands the application of the gelatin-based hydrogels. The biohybrid

Biofilm can protect bacteria from immune attacks and antibiotic inhibition, and bacterial biofilm hosted in implanted materials and medical devices is a serious threat for modern medical system. Herein, we report biofilm-responsive caged guanidine nanoparticles (CGNs) to deeply penetrate and accumulate in bacterial biofilm, and then efficient photothermal eradication of bacterial biofilm is achieved upon NIR laser irradiation via the proof-of-concept formulation of photothermal agents in CGNs. In physiological conditions and blood circulation, CGNs are negatively charged by masking the positive charge of guanidine via covalent modification with acid-cleavable moieties, exhibiting high biocompatibility and minimal hemolysis. Whereas upon blood circulation and passive accumulation at infected implant sites, CGNs are self-adaptive in acidic biofilm to release the protective caging group and expose native guanidine moieties, which can promote nanoparticle deep biofilm penetration and bacteria adhesion as well as membrane fusion. After that, remarkable photothermal effect with a high photothermal conversion efficiency of ∼40.9% can eradicate implant biofilm upon NIR laser irradiation. It can efficiently treat S. aureus biofilminfected implant catheters in vivo via only one single treatment in a mouse model, exhibiting ∼99.6% bacteria inhibition ratio. Apart from this proof-of-concept work, current guanidine-caged biofilm responsive polymeric nanoparticles are promising general vectors to treat biofilm and resistant pathogens in medicine and daily healthcare.