We present a sensitive and easily regenerated nano-optical sensor based on immobilization of avidin-coated colloidal gold particles on a biotin-modified planar lipid bilayer supported on the walls of a quartz cuvette. The so constructed sensing template, being specific for capturing of biotinylated biomacromolecules, is analyzed using optical spectroscopy combined with Mie theory calculations for quantification of the colorimetric changes induced by biorecognition events in the interfacial region of the particles. By further utilizing de Feiter's formalism, which correlates changes in effective refractive index and thickness with adsorbed mass, a good agreement between the Mie theory and experiments is demonstrated. Furthermore, the template is proven sensitive enough to follow the hybridization kinetics of 15-mer fully complementary DNA strands without the introduction of labels or secondary signal amplification.