A Novel Ulcer Fluid Collection Method for Use in Metabonomic Profiling Analysis

Venous leg ulcers (VLUs) are a major cause of morbidity with up to 30% failing to heal at 6-months. To allow for treatment personalisation, understanding of the pathophysiological mechanisms underlying this failure to heal is vital. Ulcer fluid has previously been employed to study the metabolic phenotype of VLU patients but has yielded inconsistent results. Newer ambient mass spectrometry (MS) techniques such as desorption electrospray ionisation MS (DESI-MS) allow for rapid analysis of surface metabolites, which may be used to topographically map the metabolites found in the ulcer, representing a novel method for assessment of the VLU microenvironment. This study aims to determine if non-adherent silicone dressings (NASD) which are routinely used in VLU management can adsorb metabolites from VLUs and act as a novel fluid collection method for analysis using DESI-MS platforms.

Methods:

NASD were applied to porcine tissues and feasibility of metabolite acquisition determined by acquiring spectral data using DESI-MS. After confirmation of feasibility, NASD were applied to VLUs of patients for varying durations ranging from five seconds to one hour. These dressings were analysed using DESI-MS platforms and topical spectral data was acquired to determine if detectable quantities of metabolites were obtained using this novel method of VLU fluid collection.

Results:

NASDs that were applied to porcine liver and kidney tissues revealed spectral patterns that correspond to known tissue metabolites, including a phospholipid in the 885-887 mass/charge (m/z) region that is found in all mammalian tissue (Figure 1). The feasibility experiments also showed the potential for discriminating between tissue types, identifying a metabolite in the 723-725 m/z region in kidney tissue that was not found in liver. The mammalian phospholipid was also present on NASDs applied to patient VLUs for only five seconds. This signal was also shown to be present in NASDs applied for longer durations of 30 minutes and one hour (Figure 2).

Conclusions:

This study has shown non-adherent silicone dressings to be a feasible and promising method for VLU fluid collection for metabolomic studies. These dressings can adsorb metabolites in detectable quantities when applied to VLU surfaces even after just 5 seconds. Further experiments using imaging DESI-MS platforms that have finer resolution may allow for topographical mapping of specific metabolites within the imprinted VLU field.