Thin nanoporous alumina-based SERS platform for single cell sensing

Enhancing Raman signals of living cells has long been a challenge, and so far it has been achieved in most cases through cell labeling with gold nanoparticles. This work demonstrates the feasibility of analytical biosensors capable to detect living cells and assess their operation at the interface with the substrate based on gold-coated nanoporous alumina (APA) as an active SERS surface. Thin films of APA with increasing pore diameter and constant pore pitch were fabricated starting from evaporated Al with ∼500 nm thickness. After coating with a 25 nm-thick gold layer (Au-APA), preliminary characterization with test molecules proved such surfaces to be large area SERS substrates. Raman measurements were then performed on living cells cultured on Au-APA, which confirmed to be biocompatible, yielding Raman peaks related to the different components of the cells. The use of Au-APA allows the enhancement of the Raman scattering signals of those components, which become easily detectable with low laser power and short acquisition times and without the need of additional labels such as metal nanoparticles.