(W1230-08-49) Influence of Excipients on Interaction of Actives with the TR146 Model

Purpose: The interaction of oral care actives with the oral mucosa is poorly understood. Tin fluoride (SnF2) and Vitamin E Acetate (VEA) are oral care actives that are useful for supporting oral healthcare. The purpose of this work was to investigate the interaction of these actives with an optimised TR146 buccal model. Additionally, the impact of various oral care excipients on these interactions was studied.

Methods: TR146 cells were seeded on ThinCert plates (2 × 10⁴ cells/well) for 27-31 days. This model was optimised to attain transepithelial electrical resistance (TEER) values of ~ 350 Ω·cm². Once a plateau around this TEER value was achieved, the cells were utilized for 6 h transport studies. The active, SnF₂ or VEA, was dissolved in DMEM and applied to the apical layer of cells. Samples of media were taken from the basal layer to determine any Sn permeation. At the end of the study, a mass balance study was conducted to account for the recovery of the total active. The experiments were then repeated in the presence of various excipients, namely, sorbitol, polypropylene glycol (PPG), glycerol, propylene glycol (PG), polyethylene glycol (PEG) 200, and PEG 400. SnF₂ samples were analysed with inductively coupled plasma mass spectrometry (ICP-MS) and VEA samples were analysed using LC-MS.

Results: The results showed that there was no permeation of Sn or VEA over the study period, irrespective of the excipient used. However, the excipient used significantly affected the uptake of the actives into the cell layers (p < 0.05). The uptake of VEA into the cell layers was 0.86% of the applied dose in the absence of excipients. The inclusion of sorbitol, glycerol, and PG reduced cellular uptake of VEA to 0.43%, 0.51%, and 0.44% of the applied dose, respectively, compared with the control (n=3, p < 0.05). The uptake of Sn into the cell layers was 56.4% of the applied dose in the absence of excipients. The presence of glycerol, PEG 200, PEG 400, and sorbitol reduced the uptake of Sn to 47.34%, 34.51%, 49.0%, and 48.2% of the applied dose, respectively, compared with the control (n=3, p < 0.05). While PEG 200 and PEG 400 significantly reduced Sn uptake, they had no significant impact on VEA uptake. In contrast, PG reduced VEA uptake but did not significantly affect Sn uptake – this suggests that the effect is active specific. Notably, glycerol and sorbitol reduced the uptake of both the actives significantly. VEA uptake decreased by approximately 41% with glycerol and 50% with sorbitol compared to the control, while Sn uptake was reduced by about 15% and 16%, respectively (n=3, p < 0.05). This indicates that these polyols may affect membrane dynamics or transport processes to be able to affect the uptake of two physicochemically different actives. Polyols have been shown to affect membrane permeability through osmotic effects and interaction with lipid bilayers. Studies in other cell lines have also shown that mannitol increases tight junction-mediated barrier function, and erythritol has an inhibitory effect on the permeation of certain actives (1,2)

Conclusion: This work has shown that Sn and VEA are taken up by the TR146 model to different extents without permeation. Additionally, these interactions with the buccal mucosa are modulated by the excipients present in the formulation. The interaction of these excipients is nuanced; they can be active-specific but also have a general effect on membrane integrity and permeability. These findings highlight the importance of excipient selection when formulating oral care products.

References: 1. Canuto LP, Collares-Buzato CB. Increased osmolality enhances the tight junction-mediated barrier function in a cultured renal epithelial cell line. Cell Biology International. 2019;43(1):73–82.
2. Chen L, Yao F, Xue S, Yao K, Huang Y, Zhao H, et al. Dynamic membrane changes and osmotic effects by sugar alcohols. NPJ Sci Food. 2025 Mar 30;9:46.

Acknowledgements: This project was funded by UK Research and Innovation (UKRI).

Percentage of applied Sn detected inside the cells in the presence of different excipients and DMEM. Statistical significance between control (no excipient) and conditions is indicated (*p < 0.05, ****p < 0.0001). (n=3, mean ± SD)

Percentage of applied VEA detected inside the cells in the presence of different excipients and DMEM. Statistical significance between control (no excipient) and conditions is indicated (***p < 0.001, ****p < 0.0001). (n=3, mean ± SD)