Mucoadhesive interaction of cysteine grafted poly(2-hydroxyethyl aspartamide) with pig mucin layer of surface plasmon resonance biosensor

A new type of thiolated polyaspartamide was synthesized and characterized with a surface plasmon resonance (SPR) biosensor. l-Cysteine grafted poly(2-hydroxyethyl aspartamide) (PHEA)s was obtained by grafting S-(Trityl)-l-cysteine to poly(succinimide) and subsequently deprotecting Trityl groups. The degree of substitution was confirmed by 1H NMR, and elemental analysis. The amount of free thiol groups immobilized on the PHEA was determined by colorimetric reaction of thiols with Ellman's reagent. The stability of thiol groups at different pH levels was also reported. Mucoadhesive interaction was determined by pig mucin immobilized SPR biosensor. It is concluded that cysteine grafted PHEA enhances the interaction with mucin but that the amount of free thiol groups among the grafted thiols determines the mucoadhesive properties.