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Near-infrared (NIR) fluorescent probes are attractive tools for bioimaging applications because of their low auto-fluorescence interference, minimal damage to living samples, and deep tissue penetration. H2S is a gaseous signaling molecule that is involved in redox homeostasis and numerous biological processes in vivo. To this end, we have developed a new red shifted fluorescent probe 1 to detect physiological H2S in live cells. The probe 1 is based on a rhodamine derivative as the red shifted fluorophore and the thiolysis of 7-nitro 1,2,3-benzoxadiazole (NBD) amine as the H2S receptor. The probe 1 displays fast fluorescent enhancement at 660 nm (about 10-fold turn-ons, k2 = 29.8 M−1s−1) after reacting with H2S in buffer (pH 7.4), and the fluorescence quantum yield of the activated red shifted product can reach 0.29. The probe 1 also exhibits high selectivity and sensitivity towards H2S. Moreover, 1 is cell-membrane-permeable and mitochondria-targeting, and can be used for imaging of endogenous H2S in living cells. We believe that this red shifted fluorescent probe can be a useful tool for studies of H2S biology.

Designing the “ideal” hydrogel/matrix which can load bone morphogenetic protein-2 (BMP-2) in a low dose and with a sustained release is the key for its successful therapeutic application to enhance osteogenesis. The current use of natural collagen sponges as hydrogel/matrix is limited due to the collagen matrix showing weak mechanical strength and unmanageable biodegradability. Furthermore, the efficiency and safe dose usage of the BMP-2 has never been seriously considered other than purely chasing the lowest dose usage and extended-release time. In this paper, we customized a novel enzymatically cross-linked recombinant human-like collagen (HLC) sponge with low immunogenicity, little risk from hidden viruses, and easy production. We obtained a unique vertical pore structure and the porosity of the HLC, which are beneficial for Mesenchymal stem cells (MSCs) migration into the HLC sponge and angiopoiesis. This HLC sponge loading with low dose BMP-2 (1 µg) possessed high mechanical strength along with a burst and a sustained release profile. These merits overcome previous limitations of HLC in bone repair and are safer and more sensitive than commercial collagens. For the first time, we identified that a 5 µg dose of BMP-2 can bring about the side effect of bone overgrowth through this sensitive delivery system. Osteoinduction of the HLC-BMP sponges was proved by an in vivo mouse ectopic bone model and a rat cranial defect repair model. The method and the HLC-BMP sponge have the potential to release other growth factors and aid other tissue regeneration. Additionally, the ability to mass-produce HLC in our study overcomes the current supply shortage, which limits bone repair in the clinic.