The aim of this work was to compare the effects induced by two different sterilization methods (exposure to gamma radiation or ethylene oxide) and an antiseptic technique (immersion in 70% ethanol aqueous solution) on the morphology, tensile strength, percentage of strain at break, and in vitro cytotoxicity to Vero cells on chitosan membranes designed for wound healing. Four distinct membrane compositions were evaluated, with chitosan, glycerol, and chitin used as components. Gamma radiation, in spite of being one of the most commonly employed sterilizing agents, negatively affected the morphology of membranes composed solely by chitosan as well as the percentage of strain at break of the chitosan-membranes containing glycerol on their composition. Moreover, its use affected the color of the chitosan membranes. The use of 70% ethanol aqueous solution did not change the chitosan-membrane characteristics significantly, but its use has limitations concerning the process scale up. With ethylene oxide (EtO), chitosan-membrane morphology, percentage of strain at break, and in vitro cytotoxicity to Vero cells were not significantly affected. The tensile strength of the membranes containing chitin were reduced after the treatment with ethylene oxide; however, the obtained values were comprised in the range verified for normal human skin. Therefore, because the final characteristics of the membranes treated with ethylene oxide are appropriate when considering their use as wound healing devices, and because this sterilization process is easily adjusted to use on an industrial scale, EtO can be considered the most adequate sterilizing agent for chitosan membranes. However, it should be considered that this chemical is associated with toxicity, flammability, and environmental risks, as well as with possible material contamination with ethylene oxide residues.

In this work, the preparation and characterization of membranes obtained through chitosan and alginate coacervation and designed for use as wound dressings were evaluated. The influence of different stirring rates and rates of addition of chitosan solution to alginate solution on the final characteristics of the biomaterial was analyzed in detail, aiming at a simple and easily scalable membrane production protocol. The results show that membranes with dry thickness from 66 to 80 lm, wet thickness from 106 to 633 lm, tensile strength varying from 6.86 to 31.14 MPa, elongation at break from 3.97 to 8.42%, and maximum water uptake up to 19 g of water per gram of membrane and that are able to prevent the permeation of bacteria can be obtained in a fairly reproducible way by the procedure established. The membranes prepared at flow ratio of 40 mL/h and stirring equal to 100 rpm showed a high potential for use on highly exuding wounds.

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The purpose of this study was to evaluate the efficacy of chitosan-alginate membrane to accelerate wound healing in experimental cutaneous wounds. Two wounds were performed in Wistar rats by punching (1.5 cm diameter), treated with membranes moistened with saline solution (CAM group) or with saline only (SL group). After 2, 7, 14, and 21 days of surgery, five rats of each group were euthanized and reepithelialization was evaluated. The wounds/scars were harvested for histological, flow cytometry, neutrophil infiltrate, and hydroxyproline analysis. CAM group presented higher inflammatory cells recruitment as compared to SL group on 2(nd) day. On the 7(th) day, CAM group showed higher CD11b(+) level and lower of neutrophils than SL group. The CAM group presented higher CD4(+) cells influx than SL group on 2(nd) day, but it decreased during the follow up and became lower on 14(th) and 21(st) days. Higher fibroplasia was noticed on days 7 and 14 as well as higher collagenesis on 21(st) in the CAM group in comparison to SL group. CAM group showed faster reepithelialization on 7(th) day than SL group, although similar in other days. In conclusion, chitosan-alginate membrane modulated the inflammatory phase, stimulated fibroplasia and collagenesis, accelerating wound healing process in rats.

Three-dimensional (3D) cell culture has tremendous advantages to closely mimic the in vivo architecture and microenvironment of healthy tissue and organs, as well as of solid tumors. Spheroids are currently the most attractive 3D model to produce uniform reproducible cell structures as well as a potential basis for engineering large tissues and complex organs. In this review we discuss, from an engineering perspective, processes to obtain uniform 3D cell spheroids, comparing dynamic and static cultures and considering aspects such as mass transfer and shear stress. In addition, computational and mathematical modeling of complex cell spheroid systems are discussed. The non-cell-adhesive hydrogel-based method and dynamic cell culture in bioreactors are focused in detail and the myriad of developed spheroid characterization techniques is presented. The main bottlenecks and weaknesses are discussed, especially regarding the analysis of morphological parameters, cell quantification and viability, gene expression profiles, metabolic behavior and high-content analysis. Finally, a vast set of applications of spheroids as tools for in vitro study model systems is examined, including drug screening, tissue formation, pathologies development, tissue engineering and biofabrication, 3D bioprinting and microfluidics, together with their use in high-throughput platforms.

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Compacted and porous lamellar membranes of xanthan (Xn) and chitosan (Ch) at mass ratios of 1 : 1 and 1.2 : 0.8 were prepared and tested to verify possible applications in the treatment of skin lesions. All membranes were prepared by complexation of the polysaccharides in solution and subsequent casting. The porous membranes were obtained by adding either Tween 80 or Pluronic F68 to the polysaccharide complexes before casting. Membranes prepared in the absence of surfactants at a mass ratio of Xn to Ch of 1 : 1 proved ideal for use as wound dressings, as they were thin (around 0.10 mm in thickness) and transparent and had low in vitro cytotoxicity to L929 cells, a tensile strength at break of 25 MPa, water absorption after 24 h of around 86 g/g and simulated body fluid absorption of 16% and adequate stability in the presence of the same solutions. Membranes prepared at the mass ratio of Xn to Ch of 1 : 1 in the presence of Pluronic F68 showed the most favorable characteristics for application as scaffolds for tissue engineering. These membranes consisted of a matrix with interconnected pores which were distributed homogeneously throughout the structure and had a thickness of 1.84 mm, high capacity for FBS uptake (around 18 g/g) and cell culture medium uptake (8.6 g/g), a loss of mass in the culture medium of 33% after 144 h, and low in vitro toxicity to L929 cells. In conclusion, membranes of Ch and Xn produced in the presence or absence of the surfactant Pluronic F68 have a high potential for use as scaffolds in tissue engineering or as dermal dressings, respectively, whereas in contrast, membranes prepared in the presence of Tween 80, regardless of the mass ratio of Xn to Ch, were very cytotoxic to L929 cells and therefore were not appropriate for any of the proposed applications. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012