Electrospun nanofibers were prepared from mixed solutions of partially hydrolyzed poly(vinyl alcohol) (PVA) and medium molar mass chitosan (CS) at different solution compositions, at 15 and 20 kV. The mats were visualized by scanning electron microscopy (SEM), and the average diameters of nanofibers were determined. Three of these solutions were chosen for further studies, to elucidate the influence of CS on the mats properties. Electrospinning at 15 kV had a higher tendency to produce nanofibers free of defects, in which the diameters (157 to 189 nm) were not affected significantly by the total concentration and solution composition. Polymer interactions between the components were supported by infrared spectroscopy, thermogravimetry and dynamic mechanical analysis (DMA). The effect of CS composition was evidenced by DMA and tensile tests techniques. Immersion in water led to the breakage of nanofibers and flower-like morphologies.

Poly(lactic-co-glycolic acid) (PLGA) has been used in the field of tissue engineering as a scaffold due to its good biocompatibility, biodegradability and mechanical strength. With the aim to explore the degradability of PLGA electrospun nonwoven structures for oral mucosa tissue engineering applications, non-irradiated and gamma irradiated nonwovens were immersed in three different solutions, in which simulated body fluid (SBF) and artificial saliva are important for future oral mucosa tissue engineering. The nonwovens were immersed for 7, 15 and 30 days in SBF, culture media (DMEM) and artificial saliva at 37 °C. Before immersion in the solutions, the dosage of 15 kGy was applied for sterilization in one assay and compared with non-irradiated samples at the same timepoints. Samples were characterized using different techniques such as scanning electron microscopy (SEM), differential scanning calorimetric (DSC) and gel permeation chromatography (GPC) to evaluate the nonwoven degradation and Fourier-transform infrared spectroscopy (FTIR) to evaluate the chain scissions. Our results showed that PLGA nonwovens were constituted by semicrystalline fibers with moderate degradation properties up to thirty days. The non-irradiated samples exhibited slower kinetics of degradation than irradiated nonwovens. For immersion times longer than 7 days in the three different solutions, the mean diameter of irradiated fibers stayed in the same range, but significantly different from the control sample. On non-irradiated samples, the degradation kinetics was slower and the plateau in the diameter value was only attained after 30 days of immersion in the fluids. Plasticization (fluid absorption into the fiber structure) occurred in the bulk material, as confirmed by a decrease in Tg observed by DSC analyses of non-irradiated and irradiated nonwovens, in comparison with the respective controls. In addition, artificial saliva showed a higher capacity of influencing PLGA crystallization than SBF and DMEM. FTIR analyses showed typical PLGA chemical functional groups changes. These results will be important for future application of those PLGA electrospun nonwovens for oral mucosa regeneration.

Random electrospun three-dimensional fiber membranes mimic the extracellular matrix and the interfibrillar spaces promotes the flow of nutrients for cells. Electrospun PLGA membranes were analyzed in vitro and in vivo after being sterilized with gamma radiation and bioactivated with fibronectin or collagen. Madin-Darby Canine Kidney (MDCK) epithelial cells and primary fibroblast-like cells from hamster’s cheek paunch proliferated over time on these membranes, evidencing their good biocompatibility. Cell-free irradiated PLGA membranes implanted on the back of hamsters resulted in a chronic granulomatous inflammatory response, observed after 7, 15, 30 and 90 days. Morphological analysis of implanted PLGA using light microscopy revealed epithelioid cells, Langhans type of multinucleate giant cells (LCs) and multinucleated giant cells (MNGCs) with internalized biomaterial. Lymphocytes increased along time due to undegraded polymer fragments, inducing the accumulation of cells of the phagocytic lineage, and decreased after 90 days post implantation. Myeloperoxidase⁺ cells increased after 15 days and decreased after 90 days. LCs, MNGCs and capillaries decreased after 90 days. Analysis of implanted PLGA after 7, 15, 30 and 90 days using transmission electron microscope (TEM) showed cells exhibiting internalized PLGA fragments and filopodia surrounding PLGA fragments. Over time, TEM analysis showed less PLGA fragments surrounded by cells without fibrous tissue formation. Accordingly, MNGC constituted a granulomatous reaction around the polymer, which resolves with time, probably preventing a fibrous capsule formation. Finally, this study confirms the biocompatibility of electrospun PLGA membranes and their potential to accelerate the healing process of oral ulcerations in hamsters’ model in association with autologous cells.

Effective control of calcium carbonate (CaCO₃) scale formation is crucial to improve the performance and economic efficiency of water systems. This study investigates the impact of various scale inhibitors on the nucleation and crystallization processes of CaCO₃. Calcium carbonate particles were synthesized by mixing CaCl₂·2H₂O and NaHCO₃ solutions, in the presence of various scale inhibitors that had not previously been investigated using the experimental techniques employed in this study. Particle size distribution and zeta potential were analyzed using dynamic light scattering (DLS), while Ca⁺² consumption and pH changes were monitored with ion-selective electrodes. Crystal morphology was evaluated using scanning electron microscopy (SEM) and cryo-transmission electron microscopy (cryo-TEM). We demonstrated that, in all samples, approximately 98% of the CaCO₃ particles (sized between 400 and 840 nm) are formed within the first 30 min of synthesis, and these particles then aggregate to form larger particles (840–1100 nm in size). Due to the solution’s high supersaturation, the inhibitors influence calcium consumption only after 5 min of synthesis. All inhibitors, especially DTPMP, decrease calcium consumption and particle size during synthesis. The zeta potential and morphology of the particles in the samples containing inhibitors differed from those in the control group. Cryo-TEM observations revealed distinct nanometric precursor phases in the calcite crystallization process without inhibitors and different nanostructures when scale inhibitors were used. Moreover, conchoidal fractures were observed in the nanoparticles formed in the presence of DTPMP. This study demonstrates the effectiveness of various inhibitors in reducing calcium consumption in solution and altering the morphology of CaCO₃ crystals, thereby preventing calcium carbonate (CaCO₃) scale formation.