Comparative Study of One-Step Cross-Linked Electrospun Chitosan-Based Membranes

Chitosan membranes are widely applied for tissue engineering; however, a major drawback is their low resistance in aqueous phases and therefore the structure collapses impeding their long-term use. Although there is extensive research, because of chitosan’s importance as a biomaterial, studies involving chitosan-based membranes are still needed. Herein, a detailed investigation of diverse chemical routes to cross-link fibers in situ by electrospinning process is described. In case of using genipin as cross-linker, a close relationship with the content and the mean diameter values is reported, suggesting a crucial effect over the design of nanostructures. Also, the physical resistance is enhanced for the combination of two types of methods, such as chemical and physical methods. Cross-linked fibers upon exposure to long wave ultraviolet A (UVA light) change their morphology, but not their chemical composition. When they are incubated in aqueous phase for 70 days, they show an extensive improvement of their macrostructural integrity which makes them attractive candidates for tissue engineering application. As a result, the thermal properties of these materials reveal less crystallinity and higher temperature of degradation

Phenylboronic Acid-Installed Polycarbonates for the pH-Dependent Release of Diol-Containing Molecules

Environmental responsiveness is an appealing trait of emerging polymeric materials, as shown for a variety of pH-responsive drug delivery systems. The chemical versatility of the conjugation site and conjugate lability to physiologically relevant changes in pH will largely determine their applicability. Herein, we report on the use of a drug–polymer complex based on boronic acid-functionalized polycarbonates (PPBC) as the substrate for the pH-sensitive delivery of a diol-containing drug, capecitabine (CAPE). Complexation of CAPE with a PEGylated-PPBC block copolymer, via boronic ester formation, resulted in amphiphiles capable of self-assembling into spherical nanoparticles. We examined nanoparticle stability and release kinetics in neutral and acidic media and relate differences in release profiles and particle stability with changes to polymer chemistry. Comparison of complexed nanoparticles with their noncomplex analogues revealed striking differences in release rate and particle stability. Illustrated herein for capecitabine, the pH-sensitive dissociation of boronate esters from PPBCs can be applied in a general manner to diol- or catechol-containing solutes, demonstrating the utility of these polymers for biomedical applications