A Detailed Study on the Fabrication of Surface Plasmon Sensor Chips: Optimization of Dextran Molecular Weight

The present work discusses a detailed study of the fabrication steps of carboxymethyl-dextran SPR sensor chips with specal focus on the effect of dextran molecular weight (40, 200, and 500 kDa) both on the chip physical characteristics after each fabrication step and on toxin detection performance. Physical characterization was performed using ATR-FTIR, AFM, profilometry, and surface plasmon resonance (SPR) as analytical methods. Based on ATR-FTIR spectroscopy analysis, it is demonstrated that NaOH concentration plays a critical role in the epichlorohydrin (ECH) activation step for subsequent dextran molecules covalent bonding and should be less than 0.4 M, preferably 0.2 M. This is in contrast to the concentration of 0.4 M used in conventional protocols. After covalent binding of the monoclonal anti-staphylococcal enterotoxin B (anti-SEB) to the carboxyl groups of dextran matrix, the detection of enterotoxin B as a function of dextran molecular weight has been assessed. Dextran with a molecular weight of 200 kDa results in a distinct larger SPR angle shift of the final chip with respect to 40 and 500 kDa molecular weights. This observation is explained based on the SPR theory and the physico-chemical characteristics of the antibody/dextran layers measured throughout this study. The SPR sensor chip with the dextran molecular weight of 200 kDa may be considered as an appropriate candidate for the detection of proteins with the same molecular weight as enterotoxin B.