Evaluation of the use of xanthan as vehicle for cationic antifungal peptides.

Oral candidiasis frequently occurs in individuals with dry mouth syndrome (xerostomia), in immunocompromised patients and in denture wearers. The aim of this study was to develop a formulation which will prolong the retention time of antimicrobial agents at the site of application. The activity against Candida albicans of a synthetic cationic peptide dhvar 1, based on the human fungicidal salivary peptide histatin 5, was tested either in a mixture with the bioadhesive polymer xanthan, or after covalent coupling to this polymer. The presence of xanthan resulted in an increase of the LC50 value of the peptide from 2.6 (S.D.=0.6) to 5.8 (S.D.=4.0). Covalent coupling caused an additional increase of the LC50 value to 18.4 (S. D.=6.7). Coupling caused a reduction of the viscosity and elasticity of the xanthan solution related to the applied concentration of the coupling agent. Incubation of the peptide with clarified human whole saliva resulted in proteolytic degradation of the peptide. In the presence of xanthan the degradation occurred more slowly. It was concluded that xanthan is an appropriate vehicle for antimicrobial peptides in a retention increasing formulation.