Surface plasmon resonance characterization of monoclonal and polyclonal antibodies of malaria for biosensor applications.

Surface plasmon resonance (SPR) screening of monoclonal and polyclonal antibodies of Plasmodium falciparum (MoabPf and PoabPf) for recombinant Histidine rich protein-II antigen (Ag) of Pf (rHRP-II Ag) was conducted in a real-time and label-free manner to select an appropriate antibody (Ab) for biosensor applications. In this study 4-mercaptobenzoic acid (4-MBA) modified gold SPR chip was used for immobilizing the Ag and then Ab was interacted. SEM image showed modification of SPR chip with 4-MBA and EDAX confirmed the presence of 4-MBA on the SPR chip. Equilibrium constant (KD) and maximum binding capacity of analyte (Bmax) values for the interaction of MoabPf or PoabPf with the immobilized rHRP-II Ag were calculated and found to be 0.517 nM and 48.61 m° for MoabPf and 2.288 nM and 46.80 m° for PoabPf, respectively. In addition, thermodynamic parameters such as ΔG, ΔH and ΔS were determined for the interaction between rHRP-II Ag and MoabPf or PoabPf and the values revealed that the interaction is spontaneous, exothermic and driven by entropy. The kinetics and thermodymanic results of this study revealed that the interaction between MoabPf and rHRP-II Ag is more effective than that of PoabPf due to the fact that MoabPf was derived from a single epitope (single clone) whereas the PoabPf was from the mixture of a number of epitopes (polyclones). Finally, SPR methodology was developed for the sensing of malarial antibodies. The limit of detection was found to be 5.6 pg with MoabPf which was found to be the best in our study.