Abstract
Ring resonator-based biosensors have found widespread application as the transducing principle in “lab-on-a-chip” platforms due to their sensitivity, small size and support for multiplexed sensing. Their sensitivity is, however, not inherently selective towards biomarkers, and surface functionalization of the sensors is key in transforming the sensitivity to be specific for a particular biomarker. There is currently no consensus on process parameters for optimized functionalization of these sensors. Moreover, the procedures are typically optimized on flat silicon oxide substrates as test systems prior to applying the procedure to the actual sensor. Here we present what is, to our knowledge, the first comparison of optimization of silanization on flat silicon oxide substrates to results of protein capture on sensors where all parameters of two conjugation protocols are tested on both platforms. The conjugation protocols differed in the chosen silanization solvents and protein immobilization strategy. The data show that selection of acetic acid as the solvent in the silanization step generally yields a higher protein binding capacity for C-reactive protein (CRP) onto anti-CRP functionalized ring resonator sensors than using ethanol as the solvent. Furthermore, using the BS3 linker resulted in more consistent protein binding capacity across the silanization parameters tested. Overall, the data indicate that selection of parameters in the silanization and immobilization protocols harbor potential for improved biosensor binding capacity and should therefore be included as an essential part of the biosensor development process.
Highlights
The basis for diagnosis and monitoring of progression of disease is through quantitative determination of biologically relevant material such as various macromolecules or signaling molecules, possible pathogens, e.g., viruses and bacteria, or cells
The two main points of comparison are atomic force microscopy (AFM) roughness analysis for silanized wafer specimens compared to online monitoring of silanization on the Maverick platform and AFM roughness analysis of immobilized anti-C-reactive protein (CRP) on wafer pieces compared to online monitoring of CRP capture on sensor chips functionalized with anti-CRP following the same parameters as the wafer pieces
The choice of silanization parameters and linker chemistry for antibody immobilization has been shown to impact both the surface roughness of silane and immobilized CPR antibodies on flat silicon test substrates, as well as affecting the binding capacity of CRP on a ring resonator-based setup
Summary
The basis for diagnosis and monitoring of progression of disease is through quantitative determination of biologically relevant material such as various macromolecules or signaling molecules, possible pathogens, e.g., viruses and bacteria, or cells. These molecular parameters have been quantified in centralized laboratories applying processes that depend both on relevant infrastructure as well as personnel. Sensors 2020, 20, 3163 point-of-care settings [1]. Such fast and compact biosensors are often referred to as “lab-on-a-chip”. Various transducing principles are applied in lab on a chip biosensors, such as electrochemical [7] (e.g., amperometric [8], conductometric [9]), based on optical principles [10,11]
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