Preparation of Electrospun Small Intestinal Submucosa/Poly(caprolactone-co-Lactide-co-glycolide) Nanofiber Sheet as a Potential Drug Carrier

In this work, we chose small intestine submucosa (SIS) as a drug carrier because SIS possesses good biocompatibility, non-immunogenic property and bio-resorbability, and performed electrospinning for preparation of nanofiber sheets (NS). For the preparation of drug-loaded electrospun SIS nanofiber sheets as a drug carrier, we used poly(ε-caprolactone-ran-l-lactide) (PCLA) copolymers to improve the electrospinning performance of SIS. The electrospinning of SIS and PCLA provided the electrospun SIS/PCLA (S/P)-nanofiber sheet (S/P-NS) with adjustable thickness and areas. The electrospun S/P-NS showed different porosities, pore sizes, diameters and tensile strengths depending on the ratios between SIS and PCLA. The electrospun S/P-NS was used as a drug carrier of the dexamethasone (Dex) and silver sulfadiazine (AgS) drug related to anti-inflammation. Dex-loaded S/P-NS and AgS-loaded S/P-NS was successfully fabricated by the electrospinning. In the in vitro and in vivo release, we successfully confirmed the possibility for the sustained release of Dex and AgS from the Dex-S/P-NS and AgS-S/P-NS for three weeks. In addition, the sustained Dex and AgS release suppressed the macrophage infiltration. Collectively, we achieved feasible development of SIS nanofiber sheets for a sustained Dex and AgS delivery system.

Bacterial cellulose as a carbon nano-fiber precursor: Enhancement of thermal stability and electrical conductivity

Bacterial cellulose was selected as a potential precursor for the production of carbon nanofiber because of its high purity and crystallinity. Diammonium phosphate ((NH4)2HPO4) as a flame retardant was used to impregnate the cellulosic nanofiber sheet precursor in order to increase its thermal stability during the thermal processing. Also, the effect of heating rate on the stabilization and carbonization processes of cellulosic nanofiber samples was investigated. The precursor and resulted carbon nanofiber sheets were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and electrical characteristics. The results showed that the simultaneous usage of flame retardant (diammonium phosphate) and low heating rate in the stabilization process (2 °C min-1) increases thermal stability of cellulosic nanofiber sheets and the carbon yield. The presence of a flame retardant acts like a low heating rate effect but does not significantly affect the high heating rate of the stabilization process. As carbonization temperature increased, electrical conductivity and crystallite size were increased for impregnated samples. The carbonization process at 1200 °C, with a heating rate of 2 °C min-1, makes bacterial cellulose precursor an appropriate candidate for producing carbon nanofiber sheets with proper electrical characteristics.