Weiqing Kong

Xylan-based temperature/pH sensitive hydrogels for drug controlled release

Xylan-based temperature/pH sensitive hydrogels were prepared by the crosslinking copolymerization of xylan with N-isopropylacrylamide (NIPAm) and acrylic acid (AA) using N,Ń-methylenebis-acrylamide (MBA) as a cross-linker and 2,2-dimethoxy-2-phenylacetophenone as a photoinitiator via ultraviolet irradiation. The influence of the NIPAm, AA and MBA amount on properties of xylan-based hydrogels was discussed. The morphology and interactions of hydrogels were characterized by SEM and FTIR. The lower critical solution temperature (LCST) of hydrogels was investigated by DSC. The results indicated that the LCST of hydrogels emerged at around 34°C and increased with increasing the AA content. The drug encapsulation efficiency of as-prepared hydrogels reached to 97.60% and the cumulative release rate of acetylsalicylic acid was 90.12% and 26.35% in the intestinal and gastric fluid, respectively. Xylan-based hydrogels were proved to be biocompatible with NIH3T3 cell by MTT assay and showed the promising application as drug carriers for the intestinal-targeted oral drug delivery.

Comparative study on temperature/pH sensitive xylan-based hydrogels: their properties and drug controlled release

Temperature/pH dual-responsive hydrogels were prepared by the grafting copolymerization of xylan possessing different functional groups with N-isopropylacrylamide and acrylamide using N,N′-methylenebis-acrylamide as a cross-linker and 2,2-dimethoxy-2-phenylacetophenone as a photoinitiator via ultraviolet irradiation. The influence of xylan and glycidyl methacrylate-modified xylan (GMAX) as the raw materials on the mechanical properties of hydrogels was comparatively investigated. Hydrogels were characterized by SEM, FTIR, TGA and XRD. The prepared hydrogels demonstrated a rapid phase transition temperature around 35 °C. The cumulative release rate of acetylsalicylic acid for xylan-based hydrogels and GMAX-based hydrogels reached to 77.5% and 84.2% in the intestinal fluid, respectively. GMAX-based hydrogels had a drug encapsulation efficiency of 95.21% and low drug release rate in gastric fluid. NIH3T3 cells in GMAX-based hydrogels had the high cell viability by MTT essay. Therefore, GMAX-based hydrogels had the good biocompatibility which make them promising in biomedical applications, especially as intestinal-targeted drug carriers.

Graphene Oxide/Polyacrylamide/Aluminum Ion Cross-Linked Carboxymethyl Hemicellulose Nanocomposite Hydrogels with Very Tough and Elastic Properties.

Development of high-strength hydrogels has recently attracted ever-increasing attention. In this work, a new design strategy has been proposed to prepare graphene oxide (GO)/polyacrylamide (PAM)/aluminum ion (Al(3+) )-cross-linked carboxymethyl hemicellulose (Al-CMH) nanocomposite hydrogels with very tough and elastic properties. GO/PAM/Al-CMH hydrogels were synthesized by introducing graphene oxide (GO) into PAM/CMH hydrogel, followed by ionic cross-linking of Al(3+) . The nanocomposite hydrogels were characterized by means of FTIR, X-ray diffraction (XRD), and scanning electron microscopy/energy-dispersive X-ray analysis (SEM-EDX) along with their swelling and mechanical properties. The maximum compressive strength and the Youngs modulus of GO3.5 /PAM/Al-CMH0.45 hydrogel achieved values of up to 1.12 and 13.27 MPa, increased by approximately 6488 and 18330 % relative to the PAM hydrogel (0.017 and 0.072 MPa). The as-prepared GO/PAM/Al-CMH nanocomposite hydrogels possess high strength and great elasticity giving them potential in bioengineering and drug-delivery system applications.

A promising strategy for preparation of cationic xylan by environment-friendly semi-dry oven process

A semi-dry oven method, being environmental friendly and simple process with the absence of organic solvents, was applied to prepare cationic xylan by quaternization of xylan with 3-chloro-2-hydroxypropyltrimethylammoniumchloride (CHMAC) using sodium hydroxide as a catalyst in this study. The parameters including reaction time (1–9 h), reaction temperature (50–80 °C), the molar ratio of CHMAC to xylan (0.8–3.0), and the molar ratio of NaOH/CHMAC (0.8–1.6) were optimized and the extent of quaternization was measured by degree of substitution (DS). The appropriate DS between 0.10 and 0.41 was achieved by varying the reaction parameters. Compared to the heterogeneous system (ethanol/water), the relatively higher DS could be obtained by the semi-dry oven method. Moreover, results show that a substantial degradation of the xylan polymers occurred during the modification. Therefore, this study provides feasibility of industrial production of cationic xylan.

Homogeneous acylation of xylan with 3,5-dinitrobenzoyl in ionic liquid and the adsorption property

A new xylan ester (xylan 3,5-dinitrobenzoate) as a creatinine adsorbent was prepared by the homogeneous acylation of xylan with 3,5-dinitrobenzoyl chloride in 1-butul-3-methylimidazolium chloride ionic liquid. The influences of reaction conditions on the degree of substitution values of xylan esters were discussed. Results indicated that xylan esters with the degree of substitution range from 1.34 to 1.77 were obtained under the given conditions. The FTIR and (13)C NMR spectroscopies provided the evidence of grafting 3,5-dinitrobenzoyl groups onto the backbone of xylan. Moreover, the adsorption properties of the xylan ester for creatinine were also investigated. Isotherm studies showed that the sorption capacities for creatinine were 2.45, 2.08 and 1.86 mg/g for 23, 30 and 37 °C, respectively. Thermodynamic studies performed indicated the sorption process mainly was controlled by the chemical adsorption. Therefore, xylan 3,5-dinitrobenzoate displayed the promising application in the treatment of chronic renal failure by the creatinine adsorption as the new oral adsorbent.

Xylan-Modified-Based Hydrogels with Temperature/pH Dual Sensitivity and Controllable Drug Delivery Behavior

Among the natural macromolecules potentially used as the scaffold material in hydrogels, xylan has aroused great interest in many fields because of its biocompatibility, low toxicity, and biodegradability. In this work, new pH and thermoresponsive hydrogels were prepared by the cross-linking polymerization of maleic anhydride-modified xylan (MAHX) with N-isopropylacrylamide (NIPAm) and acrylic acid (AA) under UV irradiation to form MAHX-g-P(NIPAm-co-AA) hydrogels. The pore volume, the mechanical properties, and the release rate for drugs of hydrogels could be controlled by the degree of substitution of MAHX. These hydrogels were characterized by swelling ability, lower critical solution temperature (LCST), Fourier-transform infrared (FTIR), and SEM. Furthermore, the cumulative release rate was investigated for acetylsalicylic acid and theophylline, as well as the cytocompatibility MAHX-based hydrogels. Results showed that MAHX-based hydrogels exhibited excellent swelling–deswelling properties, uniform porous structure, and the temperature/pH dual sensitivity. In vitro, the cumulative release rate of acetylsalicylic acid for MAHX-based hydrogels was higher than that for theophylline, and in the gastrointestinal sustained drug release study, the acetylsalicylic acid release rate was extremely slow during the initial 3 h in the gastric fluid (24.26%), and then the cumulative release rate reached to 90.5% after sustained release for 5 h in simulated intestinal fluid. The cytotoxicity experiment demonstrated that MAHX-based hydrogels could promote cell proliferation and had satisfactory biocompatibility with NIH3T3 cells. These results indicated that MAHX-based hydrogels, as new drug carriers, had favorable behavior for intestinal-targeted drug delivery.

Hemicellulose-Based Hydrogels and Their Potential Application

The hydrogels obtained from renewable resources have aroused great interests because they are nontoxic, economical, biodegradable, and biocompatible. Hemicellulose is the second most abundant polysaccharides after cellulose in lignocellulosic biomass. In recent years, hemicellulose-based hydrogels as biomaterials have received ever-increasing attention and they have a wide range of the promising applications in drug delivery and release, waste treatment, dye adsorption, and tissue engineering because of their peculiar physicochemical properties. This paper described the structure of hemicellulose in plant and its physical-chemical prosperities, and summarized the type of hemicellulose-based hydrogels and their potential application, which provide useful information for the utilization of hemicellulose polymers.

Synthesis and Characteristic of Xylan-grafted-polyacrylamide and Application for Improving Pulp Properties

Recently, more attentions have been focused on the exploration of hemicelluloses in the paper industry. In this work, xylan-grafted-polyacrylamide (xylan-g-PAM) biopolymers were synthesized by the graft copolymerization of xylan with acrylamide, and their interaction with fibers was also investigated to improve waste newspaper pulp properties with or without cationic fiber fines. The influences of synthesis conditions were studied on the grafting ratio and the grafting efficiency of biopolymers. Prepared biopolymers were characterized by FTIR, 13C NMR, TGA and rheology. It was found that the grafting of PAM on xylan was conductive to improve xylan properties, such as the solubility in water, rheological features, and thermal stability, and the maximum grafting ratio was achieved to 14.7%. Moreover, xylan-g-PAM could obviously enhance the mechanical properties of waste paper pulps. Xylan-g-PAM also played the dominant role in increasing the strength of paper in the combination with prepared cationic fine fibers. When the amounts of xylan-g-PAM and cationic fiber fines were 1.0 wt % and 0.5 wt %, the mechanical properties such as the tensile index was increased by 49.09%, tear index was increased by 36.54%, and the burst index was increased by 20.67%, when compared with the control handsheets. Therefore, xylan-g-PAM as the new biopolymer could be promising in the application of strength agents for the paper industry as well as cationic fiber fines.