Highly-Sensitive SPR Urea Biosensor Based on Urease Immobilized in Metal-Organic Zeolite Framework

A highly-sensitive multi-mode thin-core multi-mode (MTM) surface plasmon resonance (SPR) structure is proposed and applied in urea sensing. The thin-core fiber is sputtered with gold film to excite SPR, and then the probe is coated with enzyme coating that is formed by embedding urease in zeolitic imidazolate framework (ZIF -8/Urease) to realize a highly specific urea biosensor. The bind of urea and urease in the zeolitic imidazolate framework will cause the change of refractive index of the SPR probe, which will then induce the wavelength shift of SPR resonance spectrum. Experimental results demonstrated that the resonance wavelength has a good linear relationship with the urea concentration in the range of 1–10 mM, and the sensitivity can reach to 4 nm/mM.