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Electrospun DOXY-h loaded-poly(acrylic acid) (PAA) nanofiber mats (PAA/DOXY-h nanofiber mats) were prepared by the electrospinning technique and post-spinning sorption method at various doses: PAA/DOXY-h125, PAA/DOXY-h250, PAA/DOXY-h500, and PAA/DOXY-h1000. The morphology, drug content, release characteristics, and antibacterial activities of the PAA/DOXY-h nanofiber mats were investigated with scanning electron microscopy, UV-vis spectrophotometry, and disc diffusion methodology. The PAA/DOXY-h nanofiber mats had a diameter range of 285-340 nm, and a smooth surface without beads. Adsorption isotherms of DOXY-h could be described well with the Freundlich model. The amounts of DOXY-h, after the post-spinning sorption process, in the PAA/DOXY-h nanofiber mats ranged between 27.57 and 101.71 mg/g. All of the PAA/DOXY-h nanofiber mats exhibited an initial burst release characteristic with cumulative releasing percentages between 37.14 and 45.97%, which followed the Fickian diffusion mechanism. Based on the antibacterial investigation, the tested gram-positive bacteria, Staphylococcus aureus and Streptococcus agalactiae, seemed to be more sensitive to PAA/DOXY-h nanofiber mats than the tested gram-negative bacteria, Pseudomonas aeruginosa. These PAA/DOXY-h nanofiber mats could be used as an antibacterial wound dressing.

Silver nanoparticle (nAg)-embedded poly(vinyl pyrrolidone) (PVP) hydrogels, to be used as antibacterial wound dressings, were prepared by γ-irradiation at various doses: 25, 35, and 45 kGy. The formation and characteristics of the silver nanoparticles were investigated with a UV-vis spectrophotometer, transmission electron microscopy, and scanning electron microscopy with energy-dispersive X-ray. The hydrogels were characterized for physical and biological properties. Based on the antibacterial determination, the 1 and 5 mM nAg-embedded PVP hydrogels were effective, with 99.99% bactericidal activity at 12 and 6 h, respectively. The indirect cytotoxicity evaluation based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay indicated that both the neat and the nAg-embedded PVP hydrogels were non-toxic to mouse fibroblasts (L929). The 5 mM nAg-embedded PVP hydrogels not only provided a clean, moist environment for wound healing, but also effectively prevented bacterial infection and enhanced wound recovery.

Neuronal activities play critical roles in both neurogenesis and neural regeneration. In that sense, electrically conductive and biocompatible biomaterial scaffolds can be applied in various applications of neural tissue engineering. In this study, we fabricated a novel biomaterial for neural tissue engineering applications by coating electrospun poly(lactic acid) (PLA) nanofibers with a conducting polymer, polypyrole (PPy), via admicellar polymerization. Optimal conditions for polymerization and preparation of PPy-coated electrospun PLA nanofibers were obtained by comparing results from scanning electron microscopy, X-ray photoelectron spectrometer, and surface conductivity tests. In vitro cell culture experiments showed that PPy-coated electrospun PLA fibrous scaffold is not toxic. The scaffold could support attachment and migration of neural progenitor cells. Neurons derived from progenitor exhibited long neurite outgrowth under electrical stimulation. Our study concluded that PPy-coated electrospun PLA fibers had a good biocompatibility with neural progenitor cells and may serve as a promising material for controlling progenitor cell behaviors and enhancing neural repair.

Polycaprolactone (PCL)/hydroxyapatite (HA) composite scaffolds were prepared by combining solvent casting and salt particulate leaching with a polymer leaching technique. The hydrophilicity of the dual-leached scaffold was improved by alkaline (NaOH) treatment. Well-defined interconnected pores were detected by scanning electron microscopy. The water absorption capacity of the NaOH-treated PCL/HA dual-leached scaffold increased greatly, confirming that the hydrophilicity of the scaffold was improved by NaOH treatment. The compressive modulus of the PCL/HA dual-leached scaffold was greatly increased by the addition of HA particles. An indirect evaluation of the cytotoxicity of all PCL dual-leached scaffolds with mouse fibroblastic cells (L929) and mouse calvaria-derived pre-osteoblastic cells (MC3T3-E1) indicated that the PCL dual-leached scaffolds are non-toxic to cells. The ability of the scaffolds to support mouse calvaria-derived pre-osteoblastic cell (MC3T3-E1) attachment, proliferation, differentiation, and mineralization was also evaluated. Although the viability of cells was lower on the PCL/HA dual-leached scaffold than on the tissue-culture polystyrene plates (TCPS) and on the other substrates at early time points, both the PCL and NaOH-treated PCL/HA dual-leached scaffolds supported the attachment of MC3T3-E1 at significantly higher levels than TCPS. During the proliferation period (days 1-3), all of the PCL dual-leached scaffolds were able to support the proliferation of MC3T3-E1 at higher levels than the TCPS; in addition, the cells grown on NaOH-treated PCL/HA dual-leached scaffolds proliferated more rapidly. The cells cultured on the surfaces of NaOH-treated PCL/HA dual-leached scaffolds had the highest rate of mineral deposition.

Desaminotyrosyl-tyrosine ethyl ester (DTE) and desaminotyrosyl-tyrosine (DT) were used as monomers in the synthesis of two tyrosine-derived polycarbonates: the slow degrading homopolymer poly(DTE carbonate) and the fast degrading co-polymer poly(DTE-co-20%DT carbonate). Ultrafine fibers of these polymers were successfully fabricated using an electrospinning process. The effects of some solution and process parameters (i.e., polymer concentration, electrostatic field strength and solvent system) on morphological appearance and diameters of the obtained fibers were investigated by scanning electron microscopy (SEM). Smooth fibers were obtained at high enough solution concentrations (i.e., 15 and 20% (w/v)). The average fiber diameter was found to increase with increasing polymer concentration and applied electrostatic field strength. The electrospinnability of poly(DTE-co-20%DT carbonate) in dichloromethane was enhanced when methanol was used as the co-solvent. In all of the conditions investigated, the average diameter of the obtained smooth fibers ranged between 1.9 and 5.8 microm. A qualitative assessment of an as-spun mat of poly(DTE carbonate) fibers as a tissue scaffolding material showed that three different cultured cell lines appeared to adhere and propagate well within the scaffold. For poly(DTE carbonate) exceptionally high cell densities could be achieved after 10 days of cell culture.

The electrospinning of hexanoyl chitosan (H-chitosan), polylactide (PLA) and their blends was performed using chloroform, dichloromethane or tetrahydrofuran as a spinning solvent. The as-spun PLA fibers appeared to be cross-sectionally round, with rough surface morphology, while the as-spun H-chitosan fibers were flat with smooth surface morphology. Electrospinning of the H-chitosan/PLA blend solutions in chloroform with the H-chitosan solution content of less than or equal to 50% (w/w) produced continuous fibers without the presence of beads, while that of the blend solutions in dichloromethane produced beaded fibers or even just beads at high H-chitosan solution contents. The size of the as-spun fibers from blend solutions with a H-chitosan solution content of less than or equal to 50% (w/w) was found to decrease with increasing the H-chitosan solution content. Thermal characteristics and crystalline structure of selected as-spun fibers from pure and blend solutions in chloroform were characterized by thermogravimetric analysis, differential scanning calorimetry and wide-angle X-ray diffraction (WAXD) techniques.