alpha-Synuclein protein, whose aggregation is associated with Parkinson's disease, is detected using a compact, label-free, localized surface plasmon resonance (LSPR) based optical sensor. U-shaped fiber optic probe immobilized with gold nanoparticles (GNP), and subsequently functionalized using a film of chitosan was used as a sensing platform. The chitosan film acts as a sensitive and selective polysaccharide bioreceptor for detection of alpha-Synuclein. Binding of amyloid proteins to this film causes a localized change of dielectric constant surrounding the nanoparticles, leading to a change in the spectrum at the output end of the fiber. The combination of binding rate kinetics and intensity change was measured to develop a robust sensing platform. The sensor could detect the presence of monomers & amyloid fibrils independently up to 70 nM and could differentiate them in mixtures having fibril to monomer ratio from 0.1 to 10, within 15 min. The present study introduces a new platform for sensitive detection of amyloid fibrils and monomer of alpha-Synuclein (independently as well as in mixtures) for potential applications in inhibition and aggregation based studies. (C) 2017 Elsevier B.V. All rights reserved.