Development and evaluation of a novel artificial saliva for xerostomia: physicochemical, microbial, and safety profiles

Xerostomia significantly impairs oral function and quality of life. Existing artificial saliva formulations often exhibit acidic pH or rely on synthetic preservatives such as parabens, which may limit their suitability for long-term use. This study aimed to develop a pH-neutral artificial saliva using a natural preservative (nisin) and to evaluate its stability, microbiological safety, and biocompatibility. An artificial saliva formulation was prepared using sodium carboxymethylcellulose and physiological electrolytes. Stability was assessed over 6 months at 4 °C, 25 °C, 35 °C, and 45 °C. Physicochemical properties (pH, viscosity, density, and osmolality) were measured monthly. Microbiological quality was evaluated according to USP < 61 > and < 62>, including tests for Escherichia coli , Pseudomonas aeruginosa , Staphylococcus aureus , and Candida albicans . In vitro cytotoxicity and irritation were assessed using human oral epithelial cells and reconstructed human oral mucosa models. The formulation remained stable under all tested storage conditions, maintaining a neutral pH (7.00 ± 0.05), viscosity (14,880 cP), and density (1.179 g/mL), with no significant changes in the evaluated physicochemical parameters during the six-month study period ( p > 0.05). No specified microorganisms were detected during storage, and microbial counts remained within the predefined acceptance criteria. In the MTT assay, human gingival keratinocyte metabolic activity remained high across all tested concentrations (0.015625–2.0% v/v), ranging from 96.83 ± 5.94% to 101.36 ± 5.67% relative to the untreated control. In the reconstructed human oral mucosa model, tissue viability was 95.2 ± 4.3% relative to the negative control, with no apparent gross morphological evidence of epithelial disruption or irritation. These findings provide preliminary evidence of cytocompatibility and low irritation potential under the tested in vitro conditions. The developed formulation is stable, microbiologically safe, and biocompatible. Its neutral pH and natural preservative system address limitations of existing products and support its potential for long-term xerostomia management.