Multifunctional
tissue adhesives with excellent adhesion, antibleeding,
anti-infection, and wound healing properties are desperately needed
in clinical surgery. However, the successful development of multifunctional
tissue adhesives that simultaneously possess all these properties
remains a challenge. We have prepared a novel chitosan-based hydrogel
adhesive by integration of hydrocaffeic acid-modified chitosan (CS-HA)
with hydrophobically modified chitosan lactate (hmCS lactate) and
characterized its gelation time, mechanical properties, and microstructure.
Tissue adhesion properties were evaluated using both pigskin and intestine
models. In situ antibleeding efficacy was demonstrated via the rat
hemorrhaging liver and full-thickness wound closure models. Good antibacterial
activity and anti-infection capability toward S. aureus and P. aeruginosa were confirmed
using in vitro contact-killing assays and an infected pigskin model.
The result of coculturing with 3T3 fibroblast cells indicated that
the hydrogels have no significant cytotoxicity. Most importantly,
the biocompatible and biodegradable CS-HA/hmCS lactate hydrogel was
able to close the wound in a sutureless way and promote wound healing.
Our results demonstrate that this hydrogel has great promise for sutureless
closure of surgical incisions.
There is a lack in clinically-suitable vascular grafts. Biotubes, prepared using in vivo tissue engineering, show potential for vascular regeneration. However, their mechanical strength is typically poor. Inspired by architectural design of steel fiber reinforcement of concrete for tunnel construction, poly(ε-caprolactone) (PCL) fiber skeletons (PSs) were fabricated by melt-spinning and heat treatment. The PSs were subcutaneously embedded to induce the assembly of host cells and extracellular matrix to obtain PS-reinforced biotubes (PBs). Heat-treated medium-fiber-angle PB (hMPB) demonstrated superior performance when evaluated by in vitro mechanical testing and following implantation in rat abdominal artery replacement models. hMPBs were further evaluated in canine peripheral arterial replacement and sheep arteriovenous graft models. Overall, hMPB demonstrated appropriate mechanics, puncture resistance, rapid hemostasis, vascular regeneration, and long-term patency, without incidence of luminal expansion or intimal hyperplasia. These optimized hMPB properties show promise as an alternatives to autologous vessels in clinical applications.
Layered zeolites and their delaminated structures are novel materials that enhance the catalytic performance of catalysts by addressing diffusion limitations of the reactant molecules. n-Hexane catalytic cracking was observed over MCM-22 layered zeolite and its derivative structures over the temperature range of 450–650 °C for the production of olefins. MCM-22, H-MCM-22, and ITQ-2 zeolites were prepared by the hydrothermal method. Oxalic acid was used as a dealuminating reagent to obtain H-MCM-22 with various Si/Al ratios ranging from 09–65. The prepared samples were characterized by XRD, SEM, TGA, and BET. The cracking of n-hexane was carried out by Pyro/GC–MS. It was observed that the selectivity for olefins was improved by increasing the Si/Al ratio. H-MCM-22–10% produced the highest relative olefinic concentration of 68% as compared to other dealuminated structures. Moreover, the product distribution showed that higher reaction temperature is favorable to produce more olefins. Furthermore, a comparison between ITQ-2 and MCM-22 derived structures showed that ITQ-2 is more favorable for olefins production at high temperatures. The concentration of relative olefins was increased up to 80% over ITQ-2 at 650 °C.
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