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In this work, a novel nanocomposite hydrogel based on cellulose nanocrystal (CNC) and chitosan (CS) was fabricated and applied as a carrier for the controlled delivery of theophylline. CNC was firstly periodate-oxidized to obtain dialdehyde nanocellulose (DACNC). Then, chitosan was crosslinked using DACNC as both the matrix and crosslinker in different weight ratios, to fabricate CNC/CS composites. The prepared composites were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction pattern (XRD), scanning electron microscopy (SEM), zeta potential measurement and swelling ratio tests. FT-IR results confirmed the successful reaction between the free amino groups on chitosan and the aldehyde groups on DACNC. With the increase of chitosan percentage in the hydrogel, the isoelectric point was shifted towards an alkaline pH, which was probably caused by the higher content of free amino groups. The swelling ratio of the composite also increased, which may have been due to the decrease of crosslinking density. Because the swelling ratio of the drug-loaded hydrogels differed under varied pH values, the cumulative drug release percentage of the composite hydrogel was achieved to approximately 85% and 23% in the gastric (pH 1.5) and intestinal (pH 7.4) fluids, respectively. Therefore, CNC/CS hydrogel has application potential as a theophylline carrier.

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The selection of non-hazardous solvent systems is an important factor that can significantly influence fiber formation during polymer electrospinning. In this paper, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/polyethylene oxide (PEO) has been electrospun using different solvent systems to investigate the influence of different solution properties on nanofiber morphology and diameter, the thermal and mechanical properties, as well as the degradation kinetics of the electrospun fibers. The morphology, thermal and mechanical properties of PHBV/PEO electrospun fibers were characterized using scanning electron microscopy (SEM), thermogravimetric analysis (TG) and differential scanning calorimetry (DSC), and a universal testing machine, respectively. The results showed that the binary-solvent system (dichloromethane/ethanol DCM/EtOH) gave the finest defect-free fibers, and exhibited the best thermal and mechanical properties of all the single solvents (chloroform (CHL), dichloromethane (DCM)).Therefore, the effect of DCM/EtOH in different ratios on PHBV/PEO electrospun fibers was studied in detail. In brief, the DCM/EtOH solvent system was considered to be the best candidate for PHBV/PEO for electrospinning.

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