Towards a specific characterisation of components on a cell surface - combined TERS-investigations of lipids and human cells

Supported lipid structures and human cells (human dermal derived keratinocyte, HaCaT) were investigated using tip-enhanced Raman spectroscopy (TERS) to use the high spatial resolution capabilities of TIERS, which is assumed to be less than 10 nm, to determine specific components on the cell surface. As lipids are a main component of cellular membranes, the correlation of spectral properties of pure lipids with respect to the complex biological sample was investigated. Induced by dynamic structural changes as well as nanoscale effects, a particular spectral feature of the lipid TERS spectra is found to vary, and a similar spectral deviation appears among the TIERS spectra measured on the cell. Modifications of the cell surface alone cannot cause such behaviour. In contrast to soft lipid agglomerates, the cells were fixed and therefore hampered for intrinsic structural changes. Hence, the main contribution for the cell TIERS spectra variation results from nanoscale effects, determined by different spectral characteristics compared to conventional Raman spectroscopy. The present results demonstrate the capability of TERS to provide a detailed and fast insight into the composition of the cell surface, even allowing the detection of single components. Copyright (C) 2009 John Wiley & Sons, Ltd.