An investigation of the potential application of chitosan/aloe-based membranes for regenerative medicine

A significant number of therapeutics derived from natural polymers and plants have been developed to replace or to be used in conjunction with existing dressing products. The use of the therapeutic properties of aloe vera could be very useful in the creation of active wound dressing materials. The present work was undertaken to examine issues concerning structural features, topography, enzymatic degradation behavior, antibacterial activity and cellular response of chitosan/aloe vera-based membranes. The chitosan/aloe vera-based membranes that were developed displayed satisfactory degradation, roughness, wettability and mechanical properties. A higher antibacterial potency was displayed by the blended membranes. Moreover, in vitro assays demonstrated that these blended membranes have good cell compatibility with primary human dermal fibroblasts. The chitosan/aloe vera-based membranes might be promising wound dressing materials.The authors acknowledge financial support from the Portuguese Foundation for Science and Technology (grants SFRH/BPD/45307/2008 and SFRH/BD/64601/2009), the "Fundo Social Europeu", and the "Programa Diferencial de Potencial Humano". This work was partially supported by the FEDER through POCTEP 0330_IBEROMARE_1_P

Potential use of cellulose soybean hulls as a source of carboxymethyl cellulose for coating bean seeds.

Implementing sustainable practices for using agricultural waste is urgent in the face of the challenges of climate change. This study aimed to investigate the application of carboxymethyl cellulose (CMC) derived from soybean hulls as a bioinput in the seed coat of beans. CMC was obtained after bleaching the pulp, alkalizing and etherifying it varying the chloroacetic acid concentration and the reaction time. The properties of CMC were compared to those of soybean hulls and bleached pulp. The CMC with the highest degree of substitution (DS) was chosen as bioinput. In addition to the control treatment, concentrations of 1%, 2%, and 3% CMC were used for coating, and the impact on the physiological quality of seeds was evaluated. CMC proved suitable as a coating agent for seeds, with a DS of 1.56 obtained with 1.2 g chloroacetic acid per gram of bleached pulp during 192 min at 63 °C. The 2% CMC solution proved to be effective, resulting in 93%, 94%, and 43.5% of germinated seeds at 5 days, 8 days, and after accelerated aging, respectively. Seedlings reached 34.2 cm in length and a dry mass of 0.05 g. Our results indicate that soybean hulls can be successfully used in the production of CMC as a coating material, improving the physiological quality of bean seeds and contributing to more sustainable agricultural practices

Fabrication of endothelial cell-laden carrageenan microfibers for microvascularized bone tissue engineering applications

ecent achievements in the area of tissue engineering (TE) have enabled the development of three-dimensional (3D) cell-laden hydrogels as in vitro platforms that closely mimic the 3D scenario found in native tissues. These platforms are extensively used to evaluate cellular behavior, cell-cell interactions, and tissue-like formation in highly defined settings. In this study, we propose a scalable and flexible 3D system based on microsized hydrogel fibers that might be used as building blocks for the establishment of 3D hydrogel constructs for vascularized bone TE applications. For this purpose, chitosan (CHT) coated κ-carrageenan (κ-CA) microfibers were developed using a two-step procedure involving ionotropic gelation (for the fiber formation) of κ-CA and its polyelectrolyte complexation with CHT (for the enhancement of fiber stability). The performance of the obtained fibers was assessed regarding their swelling and stability profiles, as well as their ability to carry and, subsequently, promote the outward release of microvascular-like endothelial cells (ECs), without compromising their viability and phenotype. Finally, the possibility of assembling and integrating these cell-laden fibers within a 3D hydrogel matrix containing osteoblast-like cells was evaluated. Overall, the obtained results demonstrate the suitability of the microsized κ-CA fibers to carry and deliver phenotypically apt microvascular-like ECs. Furthermore, it is shown that it is possible to assemble these cell-laden microsized fibers into 3D heterotypic hydrogels constructs. This in vitro 3D platform provides a versatile approach to investigate the interactions between multiple cell types in controlled settings, which may open up novel 3D in vitro culture techniques to better mimic the complexity of tissues.Authors thank the Portuguese Foundation for Science and Technology (FCT) for the personal grants SFRH/BD/42968/2008 through the MIT-Portugal Program (SMM) and SFRH/BD/64070/2009 (EGP). The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement no REGPOT-CT2012-316331-POLARIS and MIT/ECE/0047/2009 project

Effects of weightlessness on the cardiovascular system: a systematic review and meta-analysis

Background: The microgravity environment has a direct impact on the cardiovascular system due to the fluid shift and weightlessness that results in cardiac dysfunction, vascular remodeling, and altered Cardiovascular autonomic modulation (CAM), deconditioning and poor performance on space activities, ultimately endangering the health of astronauts.Objective: This study aimed to identify the acute and chronic effects of microgravity and Earth analogues on cardiovascular anatomy and function and CAM.Methods: CINAHL, Cochrane Library, Scopus, Science Direct, PubMed, and Web of Science databases were searched. Outcomes were grouped into cardiovascular anatomic, functional, and autonomic alterations, and vascular remodeling. Studies were categorized as Spaceflight (SF), Chronic Simulation (CS), or Acute Simulation (AS) based on the weightlessness conditions. Meta-analysis was performed for the most frequent outcomes. Weightlessness and control groups were compared.Results: 62 articles were included with a total of 963 participants involved. The meta-analysis showed that heart rate increased in SF [Mean difference (MD) = 3.44; p = 0.01] and in CS (MD = 4.98; p < 0.0001), whereas cardiac output and stroke volume decreased in CS (MD = −0.49; p = 0.03; and MD = −12.95; p < 0.0001, respectively), and systolic arterial pressure decreased in AS (MD = -5.20; p = 0.03). According to the qualitative synthesis, jugular vein cross-sectional area (CSA) and volume were greater in all conditions, and SF had increased carotid artery CSA. Heart rate variability and baroreflex sensitivity, in general, decreased in SF and CS, whereas both increased in AS.Conclusion: This review indicates that weightlessness impairs the health of astronauts during and after spaceflight, similarly to the effects of aging and immobility, potentially increasing the risk of cardiovascular diseases.Systematic Review Registration:https://www.crd.york.ac.uk/prospero/, identifier CRD42020215515

Study of the structure/property relationships of chitin and chitosan

Foi desenvolvido um estudo para melhor compreensão das correlações entre procedimentos de obtenção e purificações de quitosana e suas características. Quitosanas, nas formas neutra e acetato, foram solúveis em ácido diluído e apresentaram-se mais cristalinas e menos hidrofílicas que o cloridrato de quitosana, que foi produto solúvel em água e ácido diluído, além de hidrofílico e amorfo. As desacetilações de quitina foram realizadas em solução de hidróxido de sódio 40%, por 6 horas a 115°C; as de quitosana feitas em solução de hidróxido de sódio 5%, por 3 horas a 100ºC. Em ambas desacetilações foram verificadas influências da ausência/presença de aditivos, boroidreto de sódio ou antraquinona, e de fluxo de gás inerte. Quitosanas obtidas por desacetilação de quitina na presença de boroidreto de sódio, mostraram menor despolimerização. Quitosanas obtidas a partir de desacetilações de quitosana , com menor despolimerização, foram preparadas na presença de aditivos e de fluxo de nitrogênio; na ausência dos quais foi obtida quitosana com menor grau de acetilação. Foram feitas reações de acetilação com variação na metodologia, parâmetros reacionais e quitosana de origem. Os estudos reológicos mostraram que a mudança do regime diluído para o semi-diluído ocorreu quando o produto da concentração da solução pela sua viscosidade intrínseca estava próximo de 1. O estudo da influência da força iônica sobre a viscosidade intrínseca do cloridrato de quitosana e a aplicação dos modelos de Smidsrod e de Odijk foram concordantes, no sentido de classificar a cadeia do cloridrato de quitosana como semi-rígida.A study for a better understanding of the correlations between procedures of preparation and purifications of chitosan and its characteristics has been developed. Chitosan in neutral and acetate forms was soluble in diluted acid and showed more crystalline and less hydrophilic than chitosan hydrochloride, which was hydrophilic , amorphous and soluble in water and diluted acid. The chitin deacetylation was carried out in aqueous sodium hydroxide solution (40%), for 6 hours at 115°C; the reactions of chitosan deacetylation were carried out in aqueous sodium hydroxide solution (5%), for 3 hours at 100ºC. ln both deacetylations the influences of absence/presence of additive, sodium borohydride or anthraquinone, and inert gas flow were verified. Chitosan obtained from chitin deacetylation in presence of sodium borohydride showed smaller depolymerization. Deacetylated chitosan, with smaller depolymerization, was obtained in the presence of additives and flow of nitrogen; in their absence chitosan with smaller acetylation degree was obtained. Chitosan acetylation was carried out varying methodology , parameters of reaction and chitosan of origin. Rheological studies showed that the change from diluted solution regime to semi-diluted solution regime occurred when the product of solution concentration by its intrinsic viscosity was close to 1. The study of the ionic force influence on the intrinsic viscosity of chitosan hydrochlorides and the application of empirical and theoretical models (Smidsrod and Odijk) showed that the chitosan hydrochloride chain is semi-rigid

Obtaining, purification and characterization of chitosan

A proposta deste trabalho é obter, purificar e caracterizar amostras de quitosana comerciais e desacetiladas. Amostras foram obtidas por desacetilação de quitosanas em solução de NaOH (5%) em presença de NaBH4, e por tratamento de ultra-som por tempos variados. As amostras foram purificadas e isoladas em duas formas: neutra e cloridrato. A purificação na forma cloridrato resultou em produtos solúveis em água e em ácido acético diluído, enquanto que a purificação na forma neutra resultou em produtos solúveis apenas em ácido diluído. Em ambas as purificações, as amostras eram de alto grau de pureza e suas soluções isentas de agregados. As amostras purificadas foram caracterizadas quanto ao grau de umidade e teor de cinza por termogravimetria e quanto ao grau de acetilação por titulação condutimétrica e espectroscopia de ressonância magnética nuclear de próton. A partir de medidas de viscosidade intrínseca em solução tampão 0,3M ácido acético/0,2M acetato de sódio, determinou­ se a massa molar média das amostras purificadas na forma neutra e das desacetiladas. Determinou-se a viscosidade intrínseca à várias forças iônicas das amostras purificadas na forma cloridrato. Através desse estudo e do emprego do modelo de Smidsrod determinou-se a rigidez intrínseca da cadeia de quitosana, a qual mostrou ser uma cadeia semi-rígida (B=0,058). O valor de B obtido neste trabalho é muito próximo do relatado para carboximetilcelulose, sugerindo que a rigidez intrínseca da cadeia principal determina a rigidez das cadeias desses polieletrólitos.This work describes the preparation, purification and characterization of commercial and deacetylated chitosan samples. The samples were prepared by deacetylation of chitosan using aqueous sodium hydroxide (5%) with NaBH4 and by ultrasonic treatment for 4,7 and 10 minutes. The purification of the samples was made in two forms: neutral and hydrochloride forms. The purified samples in the hydrochloride form were soluble in water and dilute acetic acid, while the purified samples in neutral form were soluble only in dilute acetic acid. The samples were free of aggregates and they had a high degree of purity. Thermogravimetric analyses and proton nuclear magnetic ressonance spectroscopy were employed for the characterization of the purified samples in terms of water adsorption capacity and degree of acetylation, respectively. The viscosity-average molecular weight of the purified samples were determined by intrinsic viscosity measurements acetic acid 0.3M/sodium acetate 0.2M. The intrinsic viscosity dependence of the ionic strength was evaluated by the empirical approach of Smidsrod. This allowed the determination of B, the stiffness parameter of Smidsrod for the chitosan chain. As judged by the value of B (0.058), the chitosan chain is a semi-rigid one. This is in accord with the literatura and the value of B is also close to that of carboxymethylcellulose , indicating that the stiffness of the main chain determines the stiffness of both polyelectrolytes chains