The purpose of this study was to develop and characterize chitosan (Ch)-based films incorporated with varying molecular weight (Mw) and acetylation degree (AD) chitosan-depolymerization-products ...(CDP), to be applied as drug delivery materials. As compared to Ch-film, optical and antioxidant potentials of Ch/CDP-based films were improved, particularly using low Mw and AD-CDP. Whereas, films water resistance, mechanical and antibacterial properties increased as CDP-Mw increased and AD decreased. For the thermal and swelling behaviors, better values were obtained using higher Mw and AD-CDP. Further, to assess their in vitro ciprofloxacin (CFX)-release behavior, loaded-CFX Ch/CDP-based films, crosslinked using glutaraldehyde, were prepared. Expect of elongation at break, crosslinked CFX-loaded films showed increased optical, water resistance, tensile strength and thermal properties, as compared to unloaded films. The CFX-release profiles indicated that a slower and sustained release was observed, particularly when using lower Mw and AD-CDP, and mainly for the crosslinked films during 48 h. These films can release CFX for up to 54% in 6 and 24 h, at pH 1.2 and 7.4, respectively. Through this study, novel biodegradable, swellable and pH-sensitive crosslinked Ch/CDP-based films may be considered as suitable and promising drug delivery systems.
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•Chitosan/chitosan-depolymerization-products (Ch/CDP)-based films were prepared and characterized.•CDP molecular weight (Mw) and acetylation degree (AD) highly influenced films physicochemical and biological properties.•Films crosslinking with glutaraldehyde improved their swelling and ciprofloxacin release behavior.•Low Mw and AD CDP-loaded-films showed lower swelling and a controlled ciprofloxacin release.
A novel and facile route to prepare acrylic-based conetworks consisting of polymethacrylate and polyacrylamide chains is described. This method uses amine-succinimide coupling chemistry and ...sequential polymerization, and it is described using NIPA and MMA monomers as model components. The thermosensitivity in water, related to the NIPA component, has been found to be very different among the conetwork and the reference network of the crosslinked random copolymer.
A facile and gentle route to prepare conetworks with singular thermosensitivity composed of pure polyMMA and polyNIPA chains crosslinked in knots statistically distributed along the chains is described.
The aim of this paper is to study the catalytic behaviour of silver nanoparticles (AgNps) produced using low molecular weight chitosan (LMWC) samples depolymerized by an enzymatic method, using ...either lysozyme or chitosanase. The ability of four sets of silver nanoparticles to reduce Toluidine Blue (TBO) was used as test reaction, and the effect of both catalyst concentration and reaction temperature on the effectiveness of the catalytic reduction was assessed. Generally speaking, AgNps produced through chitosan depolymerization with lysozyme showed better performance than those ones produced using chitosanase. On the other hand, colloidal silver nanoparticles stabilized with LMWC were mixed with medium molecular weight chitosan (MMWC) sample, in order to generate different scaffolds by using beta-glycerol phosphate. These scaffolds were analyzed by microscopy, XRD, ATR-FTIR, and their swelling capacity was evaluated. Their catalytic ability for reducing TBO, as well as their reusability, was assessed. Our results showed that the catalytic properties of the colloidal AgNps were remarkably affected by the properties of the LMWC used for their synthesis. Once again, AgNps-chitosan scaffolds produced with chitosan depolymerized with lysozyme were more effective.
In this study, a digestive chitosanase from blue crab (Portunus segnis) viscera was extracted, characterized and applied. The crude chitosanase showed optimum activity at pH 4.0 and 60 °C and ...retained >80% of its activity over a pH range from 3.0 to 10.0. Subsequently, the crude chitosanase was applied to produce bioactive varying molecular weight (Mw) and acetylation degree chitosan-depolymerization products (CDP) with specially sequences composition determined by MALDI-TOF MS owing to an endo-cleavage mode. This hydrolysis process allowed to the preparation, after 24 h of incubation at 40 °C, of a low Mw water soluble CDP (H 24h, <4.4 kDa) with DP up to 6 and a high Mw CDP (C 24h, 142.19 kDa). Following their physicochemical characterization, the functional properties, antioxidant and antimicrobial activities of CDP were investigated. Interestingly, as compared to the native chitosan, CDP, especially low Mw derivatives (H 24h) exhibited potent antioxidant activities, while high Mw derivatives, especially C 24h, markedly inhibited the growth of all tested bacteria and fungi. These results may provide novel insights into the efficiency of chitosan depolymerisation using the Portunus segnis digestive crude chitosanase as a simple, inexpensive and easily method to produce bioactive chitosan-derivatives and that this bioactivity depends highly on their attractive characteristics.
•Chitosanase from blue crab viscera was extracted and characterized for the first time.•Enzymatic depolymerization of chitosan was investigated to produce varying Mw-CDP.•The physicochemical characterization of CDP was performed.•Antimicrobial and antioxidant activities of CDP were evaluated.
The conductive and diffusional behavior of electrolytes in media with different dielectric and viscoelastic properties is investigated. A revised model to separate the contribution of dissociated and ...nondissociated species to the diffusion coefficients determined with NMR is proposed. Impedance spectroscopy is used to measure the ionic conductivity of lithium salts in aqueous medium, ionic liquids in aprotic solvents, and hydrogel polyelectrolytes. The diffusion coefficients of the species of interest in those systems are determined with multinuclear pulsed-gradient spin–echo (PGSE) NMR. The results are analyzed using the revised model. It is shown that the degree of ionization could be determined directly from measurements of ionic conductivity and diffusion coefficients in very different types of electrolytes and in a wide range of concentrations. Furthermore, these findings support the original Arrhenius hypothesis about electrolytes and show that the assumption of a complete dissociation is not required to describe their conductive behavior. The reduced conductivity observed in hydrogels, at or near swelling equilibrium, compared to that in solutions could be attributed mainly to the hindered ionic mobility caused by the network structure.
•A variety of chitosan sulfate with different degree of sulfation was prepared.•Chitosan sulfate exhibited strong interaction with protein growth factors.•The effect of chitosan sulfate on neural ...stem cell depends on its chemical structure.
Despite the relevant biological functions of heparan sulfate (HS) glycosaminoglycans, their limited availability and the chemical heterogeneity from natural sources hamper their use for biomedical applications. Chitosan sulfates (ChS) exhibit structural similarity to HSs and may mimic their biological functions. We prepared a variety of ChS with different degree of sulfation to evaluate their ability to mimic HS in protein binding and to promote neural cell division and differentiation. The structure of the products was characterized using various spectroscopic and analytical methods. The study of their interaction with different growth factors showed that ChS bound to the proteins similarly or even better than heparin. In cell cultures, a transition effect on cell number was observed as a function of ChS concentration. Differences in promoting the expression of the differentiation markers were also found depending on the degree of sulfation and modification in the chitosan.
Chitosan sulfates have demonstrated the ability to mimic heparan sulfate (HS) function. In this context, it is crucial to understand how the specific structural properties of HS domains determine ...their functionalities and biological activities. In this study, several HS-mimicking chitosans have been prepared to mimic the structure of HS domains that have proved to be functionally significant in cell processes. The results presented herein are in concordance with the hypothesis that sulfated chitosan-growth factor (GF) interactions are controlled by a combination of two effects: the electrostatic interactions and the conformational adaptation of the polysaccharide. Thus, we found that highly charged
-sulfated
and
polysaccharides with a low degree of contraction interacted more strongly with GFs than
-sulfated
, with a higher degree of contraction and a low charge. Finally, the evidence gathered suggests that
would be able to bind to an allosteric zone and is likely to enhance GF signaling activity. This is because the bound protein remains able to bind to its cognate receptor, promoting an effect on cell proliferation as has been shown for PC12 cells. However,
and
would sequester the protein, decreasing the GF signaling activity by depleting the protein or locally blocking its active site.
•Poly (ɛ-caprolactone) membranes with surface porosity were prepared using supercritical CO2 foaming.•The membranes displayed surface hierarchical macroporosity and pore interconnectivity between ...both sides of the membrane.•The surface hierarchical porosity consists of two pores types, type 1 with an average pore size of 300–500μm and type 2 of 15–50μm.•Hierarchical porosity was achieved by using pressures of >100bars and <300bars, temperatures lower than 45°C and depressurization over several steps.•Membranes showed good biocompatibility in cell culture assays.
This article describes the preparation of porous poly (ɛ-caprolactone), PCL, membranes by supercritical CO2 (SCCO2) foaming, displaying surface hierarchical macroporosity which could be tailored by careful control of the pressure, in the range of 150–250bar, and depressurization processes in several steps, showing also pore interconnectivity between both membrane faces. The membranes exhibited two distinct types of surface macroporosity, the larger with diameter sizes of 300–500μm were surrounded by and also composed of smaller pores of 15–50μm (same size as inner pores). Membranes were prepared by solvent casting and submitted to different SCCO2 foaming. Parameters such as membrane thickness, CO2 flow, foaming time, pressure, temperature and the depressurization processes (rate and profiles), were varied to determine their influence on final porosity and to decipher which parameters were the most critical ones in terms of surface hierarchical pore organization. No remarkable changes in PCL crystallinity were found when membranes were processed under SCCO2. Finally, biological evaluation of the porous membranes was achieved by seeding human skin fibroblasts on the prepared membranes. The results, in terms of cell adhesion, spreading, proliferation and metabolic activity indicate that these membranes could hold promise for the fabrication of meshes with controlled porosity for tissue engineering applications.
En este trabajo se prepararon micropartículas de carboximetil quitosana (CMCS) y alginato (ALG) entrecruzadas con CaCl.sub.2 cargadas con ketoprofeno (KETO), en composiciones (CMCS-ALG: 0:1, 1:2 y ...1:1) para controlar la liberación de este fármaco poco soluble. Se preparó CMCS con grado de sustitución de 1,09 por alquilación directa de la quitosana con ácido monocloroacético en isopropanol. Las micropartículas cargadas con KETO se obtuvieron mediante secado por aspersión. Se caracterizaron por espectroscopia infrarroja, difracción de rayos X y microscopía electrónica de barrido. Las micropartículas se entrecruzaron con CaCl.sub.24 M. La liberación del fármaco se realizó a pH 1,2 y 7,4, siendo mayor a pH 7,4. A este pH, las micropartículas CMCS-ALG 0:1 liberaron casi el 75% de KETO en 20 horas. Las otras formulaciones liberaron aproximadamente el 40% del fármaco. Se concluye que las micropartículas de CMCS-ALG reticuladas con calcio constituyen un sistema prometedor parala liberación prolongada de KETO.
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