Stable oral lubrication enhancer obtained from thiolated polyethylene glycol and mucin

Mucins are vital components contributing to the unique lubrication properties of human whole saliva. For patients receiving medication and or treatment such as diabetes or radiotherapy, xerostomia (dry mouth) is a common with numerous and deleterious side effects. Although products exist on the market to relive the symptoms of Xerostomia there remains a drive to formulate a biocompatible lubricant that replicate the functionality offered by the natural biological environment. Herein, a combination of mucin and thiolated polyethylene glycol (PEG-SH) was proposed as a new saliva substitute. Mucin and PEG-SH molecules could form hydrated layers immediately by chemisorption. Meanwhile, the chemical interactions between mucin and PEG-SH molecules also promoted the formation of a mixed layer. All the pre-formed layers could decrease friction and had the potential to decrease wear, especially mucin and PEG-SH mixed layer when compared to mucin only solutions. Further investigations of tribological mechanism implied that the excellent lubrication performance of mixed layer with long effectiveness was contributed to the friction-reducing effect of PEG/mucin molecules and the mucoadhesive property of mucin. The study provides a guide for using mucin as a mucoadhesive agent to stable lubricative polymers with low molecular weight as novel salivary substitutes for lubrication.