Implanted
medical biomaterials are closely in contact with host
biological systems via biomaterial–cell/tissue interactions,
and these interactions play pivotal roles in regulating cell functions
and tissue regeneration. However, many biomaterials degrade over time,
and these degradation products also have been shown to interact with
host cells/tissue. Therefore, it may prove useful to specifically
design implanted biomaterials with degradation products which greatly
improve the performance of the implant. Herein, we report an injectable,
citrate-containing polyester hydrogel which can release citrate as
a cell regulator via hydrogel degradation and simultaneously show
sustained release of an encapsulated growth factor Mydgf. By coupling
the therapeutic effect of the hydrogel degradation product (citrate)
with encapsulated Mydgf, we observed improved postmyocardial infarction
(MI) heart repair in a rat MI model. Intramyocardial injection of
our Mydgf-loaded citrate-containing hydrogel was shown to significantly
reduce scar formation and infarct size, increase wall thickness and
neovascularization, and improve heart function. This bioactive injectable
hydrogel-mediated combinatorial approach offers myriad advantages
including potential adjustment of delivery rate and duration, improved
therapeutic effect, and minimally invasive administration. Our rational
design combining beneficial degradation product and controlled release
of therapeutics provides inspiration toward the next generation of
biomaterials aiming to revolutionize regenerative medicine.
Photoluminescent hydrogels that function as both injectable scaffolds and fluorescent imaging probes hold great potential for therapeutics delivery and tissue engineering. Current fluorescent hydrogels are fabricated by either conjugating or doping a fluorescent dye, fluorescent protein, lanthanide chelate, or quantum dot into polymeric hydrogel matrix. Their biomedical applications are severely limited due to drawbacks such as photostability, carcinogenesis, and toxicity associated with the above-mentioned dopants. Here, a successful development of dopant-free photoluminescent hydrogels in situ formed by crosslinking of biocompatible polymer precursors is reported, which can be synthesized by incorporating an amino acid to a citric acid based polyester oligomer followed by functionalization of multivalent crosslinking group through a convenient transesterification reaction using Candida Antarctica Lipase B as a catalyst. It is demonstrated that the newly developed hydrogels possess tunable degradation, intrinsic photoluminescence, mechanical properties, and exhibit sustained release of various molecular weight dextrans. In vivo study shows that the hydrogels formed in situ following subcutaneous injection exhibit excellent biocompatibility and emit strong fluorescence under visible light excitation without the need of using any traditional organic dyes. Their in vivo degradation profiles are then depicted by noninvasively monitoring fluorescence intensity of the injected hydrogel implants.
A series of boron-doped graphene-supported Pt (Pt/BG) nanosheets were designed and synthesized using a one-step facile hydrothermal method. ICP, XPS, and TPD results confirmed that boron atoms were successfully embedded into the graphene matrix. The selective catalytic reduction of nitric oxide with hydrogen (H2-SCR) was tested over Pt/BG catalysts. The multi-roles of doped-boron were investigated by Raman, BET, CO-chemisorption, H2-TPD, XPS, and NO-TPD. Boron doping led to a higher dispersion and smaller size of Pt nanoparticles, facilitated hydrogen spillover, promoted more metallic Pt formation, and increased both H2 and NO chemisorption, which were attributed to an enhanced Pt nucleation rate over doped-boron, electron donation from boron to Pt, and extra chemisorption sites. The reaction performances (conversion 94.7%, selectivity 90.3%, and TOF 0.092 s-1) were greatly promoted attributing to a bifunctional catalytic mechanism. This work paves the way to modify the structure and tune the chemisorption ability of graphene-based catalysts, and provides novel insights for designing high performance catalysts.
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