Research On Portable Grating Coupled Surface Plasmon Resonance Biosensor

Surface plasmon resonance（SPR）sensors have been widely applied in biosensing,medical diagnostics,food safety testing,and environmental monitoring due to their label-free,high sensitivity,low sample requirement,and real-time monitoring of molecular dynamic binding processes.Commercial SPR sensors have become important analytical instruments in pathology research,medical diagnostics,and drug development.However,their non-portability,high cost,and expensive consumables limit their application in field testing.With the increasing concern for health,food safety,and environmental pollution,the demand for portable and low-cost SPR sensors is also increasing.Therefore,in this paper,two portable SPR sensors are designed based on the grating coupled principle,aiming to meet the field detection needs and promote the popularity of SPR sensors.The main works of this article are as follows:（1）Integrating a miniature spectrometer with the SPR sensing optical path can build a portable SPR biosensor with high performance and stability based on the mature spectrometer equipment.The sensor utilizes a gold grating directly stripped from a digital versatile disc（DVD）,significantly reducing the sensing chip’s processing difficulty and cost.Integrated the gold grating and the fluid channel to fabricate the sensing chip,where different liquids to be measured are injected into the channel to achieve dynamic measurement of refractive index changes at the sensing interface.This design concept makes the sensor compatible with most reflective grating sensing chips by controlling the incident angle to adjust the diffraction order and resonance peak position of the excited SPR.Therefore,even if the structural parameters of the DVD grating used in this paper were fixed,we could still find suitable conditions to excite significant SPR phenomena.The performance of the portable SPR sensor was measured using a glucose solution with a refractive index sensitivity of 602.6 nm/RIU and a refractive index resolution of 1.43×10^-4 RIU for 1^st order diffraction and 411.5 nm/RIU and 2.94×10^-4 RIU for-2^nd order diffraction.Dynamic binding measurement of bovine serum albumin（BSA）molecules and quantitative measurement of BSA solution concentration was achieved in biosensing.The limit of detection for the BSA concentration of the sensor was 0.02 mg/m L.Based on the relationship between the fitted protein solution concentration and the resonance wavelength offset,the actual concentration of the unknown BSA solution can be inferred from the resonance wavelength offset under the same measurement conditions.（2）To reduce the manufacturing cost of SPR sensors,we designed a grating coupled SPR sensor using the same grating as a coupler and a disperser based on the diffraction function of the grating and the phenomenon of metal grating SPR excitation.Unlike typical wavelength interrogation SPR sensors,we used a linear charge coupled device（CCD）to measure the diffracted light from the grating.Furthermore,we designed a CCD signal acquisition and analysis software to analyze the excited SPR and then realize the real-time measurement of the SPR diffraction spectrum and resonance wavelength.This low-cost portable SPR sensor has a significant advantage over wavelength interrogation SPR sensors with the same performance in terms of fabrication cost.Moreover,it has vast potential in food safety,environmental monitoring,medical diagnosis,and other SPR sensing application fields.The low cost facilitates the SPR sensors’popularity.The portable SPR sensor designed in this paper is compatible with most metal gratings.It only requires selecting the sensor’s appropriate light source,detector,and structural parameters according to the SPR phenomenon generated by the grating.The designed portable SPR sensor shows good sensing performance,which can be used for on-site detection,personal health monitoring,and point-of-care testing.At the same time,the SPR sensor design and the low-cost metal grating manufacturing method,which is an alternative to the spectrometer,enable the SPR sensor and the sensing chip to be manufactured at a lower cost.The significantly reduced cost of manufacturing and using SPR sensors is an essential factor driving the popularity of SPR sensors.