Preparation of surface-charged chitosan for selective bioresponses

Abstract

Two methods were used to create positive and negative charges on chitosan films. The first method involves the reaction between amino groups (-NH₂) of chitosan with methyl iodide (MeI) to form positively-charged quaternary ammonium salts. The second method is to attach a molecule containing a negatively-charged sulfonate group by reductive alkylation of amino groups using 5-formyl-2-furan sulfonic acid (FFSA). Attenuated total reflectance infrared spectroscopy (ATR-IR), x-ray photoelectron spectroscopy (XPS) and zeta potential measurement confirmed the presence of the designated functional groups on the films and charge formation. Both modified films were more hydrophilic than the non-modified film, as determined by water contact angle measurement. Various proteins having different isoelectric point (pI); albumin, fibrinogen, lysozyme and RNase, were used for studies of protein adsorption, This study has demonstrated that it is conceivable to generate surface charges on chitosan which influence its response to protein adsorption by heterogeneous reactions.