Surface-Enhanced Raman Spectroscopic Investigation of Bacterial Lipolysis in a Skin Pore Phantom

Bacterial lipolysis of triglycerides is followed in a sebum pore phantom by microprobe surface-enhanced Raman scattering (SERS) spectroscopy. The phantom consists of a purpose-built syringe pump operating at physiological flow rates coupled to a 300 μm i.d. capillary. We employ silicon substrate SERS microprobes (50 μm × 700 μm) to monitor the lipolysis products. The silicon support allows some tip flexibility that makes these probes ideal for insertion into small structures. Propionibacterium acnes (P. acnes) are immobilized on the inner surface of the capillary. These bacteria produce a lipase that hydrolyzes the triglycerides in a model sebum emulsion flowing through the capillary. The transformation is followed in vitro as changes in the SERS caused by lipolysis of triglyceride to free fatty acids. The acids adsorb as their carboxylates, and they can be readily identified by their characteristic spectra (carboxylate marker at ∼ 1390 cm⁻¹).