A novel method for the preparation of nanoaggregates of methoxy polyethyleneglycol linked chitosan.

In the study, methoxy polyethyleneglycol (MPEG) linked chitosan (PLC) with a different degrees of substitution were prepared using a novel yet simple method in the presence of formaldehyde in a solvent of formic acid and dimethylsulfoxide (DMSO). The obtained PLC was verified by the Fourier transformed infrared (FT-IR) and carbon nuclear magnetic resonance (13C-NMR) spectroscopy and by the gel permeation chromatography (GPC). The aqueous solubility of chitosan increased after chemically linking with MPEG and was found to depend on its degree of substitution. With a proper degree of substitution of MPEG on chitosan, PLC may undergo inter- and/or intra-molecular entanglements to produce nanoaggregates. The critical aggregation concentration (CAC) of PLC was determined by the fluorescence emission spectra of pyrene and was found to be 0.003 mg/ml. Measurements of the size distribution and zeta potential of the prepared nanoaggregates were carried out using a Zetasizer. The results suggested that as the degree of MPEG substitution increased, the size and polydispersity index of the prepared nanoaggregates decreased. The prepared nanoaggregates showed a pH-sensitive property and thus may be suitable for the development of drug delivery devices for tumors.