Versatile Biocompatible Polymer Hydrogels: Scaffolds for Cell Growth

Abstract

Hydrogels have attracted considerable attention as so-called "smart materials" because of the various and often intriguing physical and chemical phenomena that they can display when subjected to a variety of external stimuli, such as changes in pH, temperature, light, and electric fields. [1][2][3][4][5] As a result, hydrogels have been applied as fundamental components in a range of applications such as controlled drug delivery, [6] soft linear actuators, sensors, and energy-transducing devices. [2][3][4][5]7] Many hydrogels exist, as well as methods of their synthesis, which include the cross-linking of linear poly(N-isopropylacrylamide) (PNIPAM), [7] poly(ethylene glycol), [8] polyacrylamide, [9] and poly(acrylic acid) based polymers [10] and their copolymers [11,12] to name but a few. Chitosan and poly(ethylenimine) are two widely used polymers (Figure 1 a). Chitosan is a polysaccharide derived from chitin, and is an attractive material for use in the biomedical field [13] because of its controlled biodegradability [14] and biocompatibility.[15] Chitosan forms so-called "hydrogels" by the neutralization of acidic solutions of chitosan, although the resulting materials are opaque, with a granular crystalline morphology.[16] Poly(ethylenimine) (PEI) is a linear-branch polymer which has been extensively used in the gene delivery field [17] and as a coating material in biosensor applications.[18] Chitosan and PEI have been chemically grafted to give materials with enhanced gene-carrier abilities.[19] Herein we report the preparation of quite remarkable hydrogels that support 3D cell growth by the simple expedient of mixing solutions of these two cationic polymers.Polymer blends were generated by mixing chitosan (partially hydrolyzed, Mw = 250 kDa, 1 % aqueous acetic acid, pH % 4.0) and poly(ethylenimine) (Mw = 300 kDa, 10 % in water, pH % 11) in various molar ratios (90:10 to 10:90). The resulting solutions (pH % 7.5) became, over a period of 5 minutes, gels that were stable to inversion and manipulation. All compositions showed gelation, but these varied from clear (chitosan/PEI 10:90) to more opaque gels (chitosan/PEI 40:60; Figure 1 b).The resulting hydrogels were examined by scanning electron microscopy (SEM), XRD, and IR (see Figure 2 and the Supporting Information). The hydrogel prepared from chitosan/PEI (40:60) displayed a spongelike, microporous morphology, which is radically different to that found in normal chitosan gels prepared by neutralization of solubilized chitosan (see Figure 2) [16] and suggested possible application as a cellular support or scaffold.The mechanical analysis of the gels (see Figure 3 and Figure S4 in the Supporting Information) showed that the storage modulus (G') was significantly greater than the loss modulus (G'') up to 50 % strain, a property typical of a gel network, [20] in which all gels show very similar behavior. G' and G'' were also evaluated for samples exposed to the cell culture conditions (up to 28 days). The results presented in Figure 3 b indicated degradation...

Direct Synthesis of Biodegradable Polysaccharide Derivative Hydrogels Through Aqueous Diels‐Alder Chemistry

“…[1][2][3][4][5][6] Over the past decade, many methods have been employed for preparation of biodegradable hydrogels. [7][8][9][10][11][12][13][14][15] Conventional hydrogel synthesis techniques are limited by operational complexity, involvement of cytotoxic reagents, instability of the functional groups, possible side reactions, and low coupling efficiency. Recent developments have utilized ''click chemistry'' methods to prepare biodegradable hydrogels with specific association mechanisms, the most common example being the copper (I)-catalysed reaction of azides with alkynes.…”

A clinical and radiographic evaluation of the management of periodontal osseous defects with alloplast and platelet rich plasma

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Biodegradable Colour Polymeric Film (Starch-Chitosan) Development: Characterization for Packaging Materials

“…Over the last decade, the interest in biodegradable films and films-made packaging materials from renewable and natural polymers has increased. Recently, scientists have devoted much energy to developing novel biodegradable hydrogels material for drug delivery [5], tissue engineering [6], sensors [7], contact lenses [8], purification [9], etc.…”