Chitosan Membranes Containing Plant Extracts: Preparation, Characterization and Antimicrobial Properties.

The main strategy of this study was to combine the traditional perspective of using medicinal extracts with polymeric scaffolds manufactured by an engineering approach to fabricate a potential dressing product with antimicrobial properties. Thus, chitosan-based membranes containing S. officinalis and H. perforatum extracts were developed and their suitability as novel dressing materials was investigated. The morphology of the chitosan-based films was assessed by scanning electron microscopy (SEM) and the chemical structure characterization was performed via Fourier transform infrared spectroscopy (FTIR). The addition of the plant extracts increased the sorption capacity of the studied fluids, mainly at the membrane with S. officinalis extract. The membranes with 4% chitosan embedded with both plant extracts maintained their integrity after being immersed for 14 days in incubation media, especially in PBS. The antibacterial activities were determined by the modified Kirby-Bauer disk diffusion method for Gram-positive (S. aureus ATCC 25923, MRSA ATCC 43300) and Gram-negative (E. coli ATCC 25922, P. aeruginosa ATCC 27853) microorganisms. The antibacterial property was enhanced by incorporating the plant extracts into chitosan films. The outcome of the study reveals that the obtained chitosan-based membranes are promising candidates to be used as a wound dressing due to their good physico-chemical and antimicrobial properties.

Multifunctional Membranes Based on ß-Glucans and Chitosan Useful in Wound Treatment.

In this work, bio-based membranes prepared using a crosslinked ß-glucans-chitosan dispersed in the chitosan matrix useful in promoting wound healing were studied for the first-time. Wound healing is a process that includes sequential steps designed to restore the structure and function of damaged cells and tissue. To minimize damage and the risk of infection during the healing process and to promote restoration of the integrity of damaged tissue, the wound should be dressed. Generally, according to their function in the wound, dressings are classified on the basis of type of material and physical form. The substances used to make a dressing are generally natural polymers such as hydrocolloids, alginates, polyurethane, collagen, chitosan, pectin and hyaluronic acid. The combination of polymeric substances, with antibacterial and antioxidant properties, could be exploited in the biomedical field for the development of biocompatible materials able to act as a barrier between the wound and the external environment, protecting the site from bacterial contamination and promoting healing. To this aim, bio-based membranes were prepared by the phase inversion induced by solvent evaporation, using the crosslinked ß-glucans-chitosan obtained by esterification reactions as a functional additive in the chitosan membrane. The reaction intermediates and the final products were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) while the morphological properties of membranes were analyzed using electronic scanning microscopy (SEM). The chemical bonding between chitosan and ß-glucans allowed for the obtainment of a better dispersion of the combined new material into the membrane's matrix and as a consequence, an enhanced antibacterial property evaluated through in vitro tests, with respect to the starting materials.

Ionotropic Gelation of Chitosan Flat Structures and Potential Applications.

The capability of some polymers, such as chitosan, to form low cost gels under mild conditions is of great application interest. Ionotropic gelation of chitosan has been used predominantly for the preparation of gel beads for biomedical application. Only in the last few years has the use of this method been extended to the fabrication of chitosan-based flat structures. Herein, after an initial analysis of the major applications of chitosan flat membranes and films and their usual methods of synthesis, the process of ionotropic gelation of chitosan and some recently proposed novel procedures for the synthesis of flat structures are presented.

Tannery Effluent Treatment by Nanofiltration, Reverse Osmosis and Chitosan Modified Membranes.

The objective of this work is to develop an appropriate technology for environmentally sound membrane-based purification of a tannery effluent assuring, simultaneously, the recovery of chromium, considered as the most hazardous inorganic water pollutant extensively used in leather tanning. A comparison between the permeate fluxes obtained during treatment of a synthetic tannery effluent through nanofiltration (NF270 and NF90 membranes) and reverse osmosis (BW30 and SW30) membranes was first performed. Then, a dedicated polymeric membrane was prepared by coating chitosan (cs) on a polyethersulfone (PES) microfiltration membrane (cs-PES MFO22) support. The resulting membrane was characterized by Fourier Transforms Infrared Spectroscopy Attenuated Total Reflectance (FTIR-ATR), Emission Scanning Electronic Microscopy (SEM) to confirm the process of surface modification and cross-linking of chitosan with glutaraldehyde. This membrane was found to be highly effective for chromium removal (>99%), which was more than eight times higher in reference to monovalent cations (e.g., Na+ and K+) and more than six times higher in reference to the divalent cations (Mg2+ and Ca2+) studied. The reverse osmosis permeate conforms to local Algerian regulations regarding being discharged directly into the natural environment (in this case, Reghaia Lake) or into urban sewers linked to wastewater biological treatment stations. While the SW30 membrane proved to be the most effective for purification of the tannery effluent, the chitosan modified membrane proved to be appropriate for recovery of chromium from the reverse osmosis concentrate.

Behaviour of diferent types of chitosan membranes implanted in horses / Comportamento de diferentes tipos de membranas de quitosana implantadas em equinos

Chitosan has been successfully used as a biomaterial with several purposes in many species. In this study, chitosan membranes were produced with six different types of materials, and their behavior were evaluated upon implantation in the subcutaneous tissue of the flank of twelve healthy horses. We assessed chitosan membranes obtained from commercial chitosan, impregnated or not with silver nanoparticles, sterilized with ethylene oxide (CCEO, n=3; CCSNEO, n=3) or by ultraviolet radiation (CCUR, n=3; CCSNUR, n=3), and chitosan membranes obtained from squid gladius, sterilized with ethylene oxide (SCEO, n=6) or by ultraviolet radiation (SCUR, n=6). The same animals were randomly used in two experimental groups, with a minimum interval of 60 days between procedures, respecting the fact of only one flank side, left or right, be under evaluation by experimental period. After preparation of the membranes and implantation in the flank subcutaneous tissue of the horses, macroscopic and ultrasonographic evaluations of the implant regions were performed, as well as physical examination, blood count and fibrinogen measurement. No clinical or laboratory abnormalities were observed. All animals that received commercial chitosan membranes, regardless of the preparation technique, showed rejection to the biomaterials, considering that 100% of the surgical wounds presented dehiscence of suture and expulsion of the implants. The animals that received squid gladius chitosan membranes showed success in the treatment, with healing by primary intention of the surgical wound. We conclude that squid gladius chitosan membranes are biocompatible and biodegradable when implanted in the subcutaneous tissue of the flank of healthy horses.(AU)

A quitosana tem sido utilizada, com sucesso, como biomaterial para diversas espécies e finalidades. Neste estudo foi avaliada a confecção de membranas de quitosana, produzidas a partir de seis tipos de materiais diferentes e foi estudado seu comportamento quando implantadas no tecido subcutâneo do flanco de doze equinos sadios. Foram avaliadas membranas de quitosana obtidas de quitosana comercial, impregnadas ou não com nanopartículas de prata, esterilizadas com óxido de etileno (QCOE, n=3; QCNPOE, n=3) ou por radiação ultravioleta (QCRU, n=3; QCNPRU, n=3) e membranas de quitosana obtidas do gládio de lula, esterilizadas com óxido de etileno (GLOE, n=6) ou por radiação ultravioleta (GLRU, n=6). Os mesmos animais foram utilizados em dois grupos experimentais, de forma aleatória, com um intervalo mínimo de sessenta dias entre os procedimentos, respeitando-se o fato de apenas um lado do flanco, esquerdo ou direito, estar em avaliação por período experimental. Após preparo das membranas e implantação no tecido subcutâneo do flanco dos equinos, foram realizadas avaliações macroscópicas e ultrassonográficas das regiões de implante, além de exames físicos, hemogramas e fibrinogênio. Não foram observadas alterações clínicas e laboratoriais. Todos os animais que receberam membranas de quitosana comercial, independente da técnica de preparo, demonstraram rejeição dos biomateriais, uma vez que 100% das feridas cirúrgicas apresentaram deiscência da sutura e expulsão dos implantes. Os animais que receberam as membranas de quitosana de gladio de lula demonstraram sucesso no tratamento, com cicatrização das feridas cirúrgicas por primeira intenção. Conclui-se que membranas de quitosana de gládio de lula são biocompatíveis e biodegradáveis, quando implantadas no tecido subcutâneo do flanco de equinos sadios.(AU)

Neuronal Differentiation Modulated by Polymeric Membrane Properties.

In this study, different collagen-blend membranes were successfully constructed by blending collagen with chitosan (CHT) or poly(lactic-co-glycolic acid) (PLGA) to enhance their properties and thus create new biofunctional materials with great potential use for neuronal tissue engineering and regeneration. Collagen blending strongly affected membrane properties in the following ways: (i) it improved the surface hydrophilicity of both pure CHT and PLGA membranes, (ii) it reduced the stiffness of CHT membranes, but (iii) it did not modify the good mechanical properties of PLGA membranes. Then, we investigated the effect of the different collagen concentrations on the neuronal behavior of the membranes developed. Morphological observations, immunocytochemistry, and morphometric measures demonstrated that the membranes developed, especially CHT/Col30, PLGA, and PLGA/Col1, provided suitable microenvironments for neuronal growth owing to their enhanced properties. The most consistent neuronal differentiation was obtained in neurons cultured on PLGA-based membranes, where a well-developed neuronal network was achieved due to their improved mechanical properties. Our findings suggest that tensile strength and elongation at break are key material parameters that have potential influence on both axonal elongation and neuronal structure and organization, which are of fundamental importance for the maintenance of efficient neuronal growth. Hence, our study has provided new insights regarding the effects of membrane mechanical properties on neuronal behavior, and thus it may help to design and improve novel instructive biomaterials for neuronal tissue engineering.

Histomorfometría de la regeneración ósea obtenida con sistema liposoma-membrana de quitosano en un modelo experimental

RESUMEN Introducción: desarrollamos un andamiaje a base de quitosano en dos formas físicas, membrana y liposoma como biomateriales para Regeneración ósea guiada no estudiado histológicamente en modelo experimental. Objetivo: determinar histológicamente la eficiencia del quitosano para la regeneración ósea guida en defectos óseos creados en tibias de ratas del linaje Wistar. Materiales y Métodos: esta investigación fue realizada en 25 ratas Wistar machos, adultas con peso entre 350 g - 500 g, a los cuales se les creó un defecto longitudinal en ambas tibias (control y experimental). Los animales fueron divididos al azar en 3 grupos: 9 ratas que fueron evaluadas a las 3 semanas, 8 que fueron valoradas a las 6 semanas y 8 a las 9 semanas. Resultados: los hallazgos histológicos confirmaron que existía mayor actividad osteoinductiva y mayor nivel de madurez ósea en las tibias experimentales a diferencia del grupo control. Conclusiones: el liposoma de quitosano fue eficiente para la regeneración ósea guiada promoviendo mayor regeneración ósea en menor tiempo que en el grupo control.

ABSTRACT Introduction: We developed a chitosan scaffold in two physical forms, membrane and liposome as biomaterials for guided bone regeneration, which has not been studied histologically in an experimental model. Objective: To determine histologically the efficiency of chitosan in the guided bone regeneration in bone defects created in tibias of Wistar rats. This study was performed in 25 male adult Wistar rats with weight between 350 g - 500 g. A longitudinal defect was created in both tibias (control and experimental). The animals were randomly divided into 3 groups: 9 rats were evaluated at 3 weeks, 8 at 6 weeks and 8 at 9 weeks. Results: The histological findings confirmed that there was more osteoinductive activity and a higher level of bone maturity in the experimental tibias than in the control group. Conclusions: The chitosan liposome was efficient in the guided bone regeneration promoting more bone regeneration in less time in the experimental group than in the control group.

Freestanding Artificial Synapses Based on Laterally Proton-Coupled Transistors on Chitosan Membranes.

Freestanding synaptic transistors are fabricated on solution-processed chitosan membranes. A short-term memory to long-term memory transition is observed due to proton-related electrochemical doping under repeated pulse stimulus. Moreover, freestanding artificial synaptic devices with multiple presynaptic inputs are investigated, and spiking logic operation and logic modulation are realized.