Distribution and visualisation of chlorhexidine within the skin using ToF-SIMS: a potential platform for the design of more efficacious skin antiseptic formulations.

Purpose: In order to increase the efficacy of a topically applied antimicrobial compound the permeation profile, localisation and mechanism of action within the skin must first be investigated.
Methods: Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to visualise the distribution of a conventional antimicrobial compound, chlorhexidine digluconate, within porcine skin without the need for laborious preparation, radio-labels or fluorescent tags.
Results: High mass resolution and high spatial resolution mass spectra and chemical images were achieved when analysing chlorhexidine digluconate treated cryo-sectioned porcine skin sections by ToF-SIMS. The distribution of chlorhexidine digluconate was mapped throughout the skin sections and our studies indicate that the compound appears to be localised within the stratum corneum. In parallel, tape strips taken from chlorhexidine digluconate treated porcine skin were analysed by ToF-SIMS to support the distribution profile obtained from the skin sections.
Conclusions: ToF-SIMS can act as a powerful complementary technique to map the distribution of topically applied compounds within the skin.