Compared with traditional conjugates 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS), 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMTMM) is an emerging biological coupling reagent and has been used in the amidation of hyaluronic acid. In this paper, DMTMM was used to achieve the amidation of chitosan (CS) with glucuronic acid (GA) in an aqueous medium to generate a GA-CS derivative. The grafting efficacy was preliminarily compared with the EDC/NHS-mediated reaction. As a result, the substitution degree of 17.6% for DMTMM-mediated grafting and 13.1% for EDC/NHS chemistry indicated that DMTMM-mediated synthesis of GA-CS appeared to be more efficient. The reaction kinetics experiments showed that GA-CS derivative with a degree of substitution up to about 26.1% was obtained using equal molar ratios of DMTMM and GA exceeding CS at room temperature. These results indicate that employing DMTMM as a coupling agent is a feasible and promising strategy for the amidation modification of chitosan.
Yanru Ren,Xiaoyan Qin,Mike Barbeck,Yi Hou,Haijun Xu,Luo Liu,Chaoyong Liu
Infection-related titanium implant failure rates remain exceedingly high in the clinic. Functional surface coating represents a very promising strategy to improve the antibacterial and bioactive properties of titanium alloy implants. Here, we describe a novel bioactive surface coating that consists of a mussel-inspired carboxymethyl chitosan hydrogel loaded with silver nanoparticles (AgNPs) to enhance the bioactive properties of the titanium alloy. The preparation of hydrogel is based on gallic acid grafted carboxymethyl chitosan (CMCS-GA) catalyzed by DMTMM (4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride). To build a firm bonding between the hydrogel and titanium alloy plate, a polydopamine layer was introduced onto the surface of the titanium alloy. With HRP/H2O2catalysis, CMCS-GA can simply form a firm gel layer on the titanium alloy plate through the catechol groups. The surface properties of titanium alloy were characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and water contact angle. Silver nanoparticles were loaded into the gel layer by in situ reduction to enhance the antibacterial properties. In vitro antibacterial and cell viability experiments showed that the AgNPs-loaded Ti-gel possesses excellent antibacterial properties and did not affect the proliferation of rabbit mesenchymal stem cells (MSCs).Keywords:carboxymethyl chitosan;gallic acid;titanium alloy;DMTMM;HRP/H2O2;catechol group;hydrogel coating;antibacterial
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