OFM uses probes with macroscopic openings to exchange substances in a liquid pathway that is based on convection rather than diffusion so that the exchange can occur non-selectively in either direction.
The direct liquid pathway between the probe’s perfusate and the surrounding interstitial fluid (ISF) provides a diluted but otherwise unchanged ISF sample, since no dialysis or filtering occurs. OFM provides unfiltered, merely diluted interstitial fluid from the investigated target tissues (skin, adipose, brain tissue). Endogenous and exogenous substances present in the interstitial fluid of targeted tissues can thus be quantified without the risk of investigating an altered sample.
The distinct advantage of OFM lies in the direct access to the interstitial fluid of different tissues by using membrane-free probes. Membrane-based sampling is often limited to sampling low molecular weight or hydrophilic substances. Membrane-free OFM probes feature an exchange area with no diffusion barrier, hence sampling is not restricted by the size or lipophilicity of substances or protein binding effects.
OFM enables the investigation of disease biomarkers directly in the affected tissue and can be used to continuously monitor therapeutic effects on tissue level. Resulting OFM data are barely influenced by other metabolic processes in the body contrary to standard blood sampling. Time-resolved profiles over longer time periods allow the assessment of treatment effects and can be performed at multiple test sites in one subject.
Study materials
Complementary methods
Study materials