Biosensor based on hydrogel optical waveguide spectroscopy for the detection of 17β-estradiol

► A new method - hydrogel optical waveguide spectroscopy (HOWS) - is reported. ► It provides an order of magnitude higher FOM than SPR. ► It is compatible with SPR biosensor instrumentation and improves its sensitivity. ► HOWS is applied for immunoassay-based detection of estradiol.