A method is provided for biosensing using a photonic crystal fiber having a hollow core. The method includes: designating an analyte of interest; determining a wavelength for an excitation light source which generates a Raman spectrum when incident upon the analyte of interest; selecting a photonic crystal fiber that would guide the light when the fiber is non-selectively filled with a solvent hosting the analyte of interest; non-selectively filling a photonic crystal fiber with the solvent hosting the analyte of interest; interrogating the analyte of interest by coupling light from the light source to the photonic crystal fiber; and analyzing the light output from the photonic crystal fiber for Raman fingerprints.