Label-free in vitro visualization and characterization of caveolar bulbs during stimulated re-epithelialization

Tip-enhanced Raman scattering (TERS) was paired with real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) to characterize lipid aggregates during stimulated re-epithelialization using an in vitro wound healing model. In this study, lipid fluctuations in the plasma membrane of epidermal keratinocytes were studied at multiple time points post-wounding. TERS measurements for the first time were also combined with sample analysis after initial wounding and 24 h of wound healing. This enabled simultaneous visualization and characterization of caveolar bulb distribution during wound healing stages, providing noninvasive insight into their associated lipid structure and coating protein, caveolin, in the nanometer range. The combination of Raman spectroscopy and scanning probe microscopy in TERS gives access to topographic and chemical structure information in a single experiment. It is the intrinsic specificity and sensitivity of TERS that enable this discrete detection of cell surface components on the nanometer scale. In contrast with competing biochemical methods, the applied technique does not interfere with the cellular composition, enabling lipid structure analysis without digestion or detergents, and displayed great potential for future biological in vivo studies.