Interactions Of A PVM/MA Copolymer With Buccal Mucosa And Enamel Surfaces

Objectives: Gantrez™ S97, a PVM/MA copolymer, is a film-former used for delivery of actives, flavors, and colors from oral care products. It is known as a mucosal adhesive, and interactions with the enamel surface may occur, as well. The objective of this work was to identify interactions of Gantrez™ S97 with buccal mucosa (BM) and enamel surfaces.

Methods: Confocal Raman spectroscopy (CRS) was used to probe the surface of substrates after treatment with artificial saliva followed by Gantrez™ S97 solution. CRS was selected for its functional group specificity, spectral resolution, and sensitivity of individual bands to interactions such as hydrogen bonding. Spectra in the region from 400cm^-1 to 1800cm^-1 were acquired using a RiverD Gen2-SCA confocal Raman spectrometer. The spectral resolution was 4.5 cm^-1. The z-axis resolution (perpendicular to the surface) was 5μm. A video image of the sample was focused at the surface and spectra acquired. One hundred individual exposures, two seconds per exposure, were averaged for each spectrum. Difference spectra were acquired by subtracting substrate spectra treated with artificial saliva only from those subsequently treated with polymer solution. Three spectra each were acquired of either substrate with saliva or polymer solution. Samples were dried prior to data collection.

Results: Spectral bands arising from polymer on the surface were visible upon subtraction. A prominent first-derivative shaped feature centered at the position of the 960 cm^-1 PO₄^3- mode of hydroxyapatite resulted from subtraction. This is due to a shift of the PO₄^3- mode to lower wavenumber, indicative of non-covalent interaction (H-bonding), as is observed broadening of the band of the protein Amide 1 band (1650 cm^-1) of BM.

Conclusions: Surface interactions between Gantrez™ S 97 and BM or enamel were observed with CRS and were manifested by changes in spectral line shape or shifts of the PO₄^3- mode to lower frequency, respectively.