Chitosan Nanoparticles Self-Assembled from Electrospun Composite Nanofibers

Abstract

Molecular self-assembly has been intensively investigated for “bottom-up” nanofabrication in recent years. A strategy that offers simple routes to functional nano-scale objects directly from templates through molecular self- assembly may lead to the development of new advanced materials for nanotechnology. Electrospun nanofibers can be good templates for manipulating molecular self-assembly by virtue of their nanometer confinement effect and the formulation of their components into a composite material. One-dimensional nanofiber composites of hydrophilic polyvinylpyrrolidone (PVP) and chitosan (CS) were successfully prepared through an elevated temperature electrospinning process. Scanning electron and transmission electron microscopy observations indicated that the fibers have an average diameter of 77 ± 11 nm with a homogeneous inner structure. Differential scanning calorimetry and X-ray diffraction results demonstrated that PVP and CS were in an amorphous state in the nanofibers, indicating they were mixed on the molecular scale. IR spectra revealed that second-order hydrogen bonding and electrostatic interactions played a fundamental role in promoting the structural homogeneity of the amorphous nanofiber composites. CS nanoparticles of about 10 nm in diameter are spontaneously self-assembled in situ when the nanofibers are added to water. Through a combination of “top-down” electrospinning and a “bottom-up” molecular self-assembly, a brand-new process has been developed for preparing polymer nanoparticles in situ.