New hydrogel obtained by chitosan and dextrin-VA co-polymerization

Centro de Engenharia Biológica, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal.
Biotechnology Letters (Impact Factor: 1.59). 09/2006; 28(16):1279-84. DOI: 10.1007/s10529-006-9087-6
Source: PubMed


A novel hydrogel was obtained by reticulation of chitosan with dextrin enzymatically linked to vinyl acrylate (dextrin-VA), without cross-linking agents. The hydrogel had a solid-like behaviour with G' (storage modulus) > G'' (loss modulus). Glucose diffusion coefficients of 3.9 x 10(-6) +/- 1.3 x 10(-6) cm(2)/s and 2.9 x 10(-6) +/- 0.5 x 10(-6) cm(2)/s were obtained for different substitution degrees of the dextrin-VA (20% and 70% respectively). SEM observation revealed a porous structure, with pores ranging from 50 microm to 150 microm.

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    • "Chitosan, the second most abundant natural polymer found in the exoskeleton of marine crustaceans, has gained great interest in immobilization technology [4]. It is also supposed to be very interest substance for diverse applications in biomaterial such as in preparing films [5], beads [6], scaffolds [7], hydrogels [8], nanofibers [9] and nanoparticles [10] in the pharmaceutical field due to its biocompatibility, biodegradability and bioactivity. In this study, we proposed a novel method to immobilize G. oxydans in the chitosan spongy material which was synthesized using NaHCO 3 as the porogen to react with acetic acid producing CO 2 and forming pores in chitosan sponge. "

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    ABSTRACT: a b s t r a c t New dextrin hydrogels with degrees of substitution (DS) from ca. 10% (DS 10) to 70% (DS 70) were pre-pared by radical polymerization of aqueous solutions of vinylacrylate (VA)-derivatized dextrin. A preli-minary analysis on the potential of these hydrogels for the controlled release of bioactive molecules was carried out. The protein (bovine serum albumin) diffusion coefficients on the hydrogels were calcu-lated using the lag-time analysis. Values in range 10 À7 cm 2 /s were obtained for DS 20 and DS 40 and a smaller value of 10 À8 cm 2 /s arised upon DS increasing to 70%, revealing the dependence of the diffusivity on the crosslinking density. The release of BSA from dextrin-VA hydrogels, in the presence of amyloglu-cosidase was shown to be mainly dependent on the diffusion and, to a smaller extent, on the degradation kinetics. The protein release can be tailored from days to months by varying the DS.
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    ABSTRACT: The review describes modern trends in physico-chemical design of responsive hydrogels intended for optical detection of organic compounds such as saccharides, amino acids, alkaloids and alcohols. Optical techniques provide non-destructive and sensitive measurements of concentrations of the above compounds either in aqueous solutions or in physiological fluids, based on registration of the gel swelling, transparency or fluorescence. Fundamentals of equilibrium swelling of neutral and electrically charged hydrogels are considered in respect to the changes in the microstructure of the hydrogels. Kinetic aspects of the solute diffusion through the hydrogel networks are addressed. The devices recently developed for registration of the small volume changes in the gels and generation of optical signals include crystalline colloid arrays, reflections holograms, or densely packed gold nanoparticles. Advantages and limitations of these devices and techniques are discussed in respect to the time of response and the ranges of measurable concentrations of the analytes. A new type of sensors is presented by semi-transparent gels able to change their turbidity in response to the changing concentration of analyte. Optical sensing of sachharides using the new technique is compared with the known sensing techniques. Modern routes to the synthesis of recognition elements within hydrogels include immobilization of group-specific ligands or fluorescent dyes sensitive to the degree and type of hydrogel swelling. Recent studies on molecularly-imprinted hydrogels used in the techniques of optical detection are reviewed.
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