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Research and development in the design, synthesis, modification, evaluation, and characterization of polysaccharide-based bioactive polymeric materials for guiding and promoting new tissue in-growth is reviewed. Emphasis is given in this interdisciplinary field of tissue engineering (TE) with particular reference to bone, cartilage, and skin TE. Current strategies in scaffold-guided TE approaches using polymers of natural origin and their composites are elaborated. Innovative modification techniques in creating functional materials for advanced TE applications are presented. Challenges and possible solutions in the technological innovation in factor molecules incorporation and surface functionalization for improving the fabrication of biomaterials scaffolds for cost-effective TE are also presented.

The engineering of human tissues to cure diseases is an interdisciplinary and a very attractive field of research both in academia and the biotechnology industrial sector. Three-dimensional (3D) biomaterial scaffolds can play a critical role in the development of new tissue morphogenesis via interacting with human cells. Although simple polymeric biomaterials can provide mechanical and physical properties required for tissue development, insufficient biomimetic property and lack of interactions with human progenitor cells remain problematic for the promotion of functional tissue formation. Therefore, the developments of advanced functional biomaterials that respond to stimulus could be the next choice to generate smart 3D biomimetic scaffolds, actively interacting with human stem cells and progenitors along with structural integrity to form functional tissue within a short period. To date, smart biomaterials are designed to interact with biological systems for a wide range of biomedical applications, from the delivery of bioactive molecules and cell adhesion mediators to cellular functioning for the engineering of functional tissues to treat diseases.

Faithfully recapitulating human physiology "in a dish" from a renewable source remains a holy grail for medicine and pharma. Many procedures have been described that, to a limited extent, exhibit human tissue-specific function in vitro. In particular, incomplete cellular differentiation and/or the loss of cell phenotype postdifferentiation play a major part in this void. We have developed an interdisciplinary approach to address this problem, using skill sets in cell biology, materials chemistry, and pharmacology. Pluripotent stem cells were differentiated to hepatocytes before being replated onto a synthetic surface. Our approach yielded metabolically active hepatocyte populations that displayed stable function for more than 2 weeks in vitro. Although metabolic activity was an important indication of cell utility, the accurate prediction of cellular toxicity in response to specific pharmacological compounds represented our goal. Therefore, detailed analysis of hepatocellular toxicity was performed in response to a custom-built and well-defined compound set and compared with primary human hepatocytes. Importantly, stem cell-derived hepatocytes displayed equivalence to primary human material. Moreover, we demonstrated that our approach was capable of modeling metabolic differences observed in the population. In conclusion, we report that pluripotent stem cell-derived hepatocytes will model toxicity predictably and in a manner comparable to current gold standard assays, representing a major advance in the field. STEM CELLS TRANSLATIONAL MEDICINE 2013;2:505-509

Polymeric biomaterials have significant impact in today's health care technology. Polymer hydrogels were the first experimentally designed biomaterials for human use. In this article the design, synthesis and properties of hydrogels, derived from synthetic and natural polymers and their use as biomaterials in tissue engineering are reviewed. The stimuliresponsive hydrogels with controlled degradability and examples of suitable methods for designing such biomaterials, using multidisciplinary approaches from traditional polymer chemistry, materials engineering to molecular biology, have been discussed. Examples of the fabrication of polymer-based biomaterials, utilized for various cells type manipulations for tissue re-generation are also elaborated. Since a highly porous three-dimensional scaffold is crucially important in cellular process, for tissue engineering, recent advances in effective methods of scaffolds fabrication are described. Additionally, the incorporation of factor molecules for the enhancement of tissue formation and their controlled release are also elucidated in this article. Finally, the future challenges in the efficient fabrication of effective polymeric biomaterials in tissue regeneration and medical devices applications.

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gamma-radiation induced effects on the physical and chemical properties of natural lignocellulose (jute) polymer were investigated. Samples were irradiated to required total doses at a particular dose rate. The changes in the parameters such as the tensile strength, elongation at break, and work done at rupture for the lignocellulose samples on irradiation with the gamma-rays from a cobalt-60 source were measured. The mechanical properties were found to have nonlinear relations with the radiation doses. The chemical stability of irradiated fibers was found to degrade progressively with the increase of radiation dose. Additionally, other chemical changes of the samples due to exposure to high-energy radiation were also investigated using fluorescence and infrared spectroscopic analysis. Differential scanning calorimetry and thermogravimetric studies showed a significant reduction in thermal stability. The wide-angle X-ray diffraction study showed that structural changes of cellulose appeared due to the radiation-induced chemical reaction of lignocellulose.

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...