Affinity capture surface carboxyl-functionalized MoS2 sheets to enhance the sensitivity of surface plasmon resonance immunosensors.

The development of functionalized molybdenum disulfide (MoS2) has led to a new trend in the biosensing field, owing to its high sensitivity and bio-affinity characteristics with regards to the simple synthesis of carboxyl-functionalized MoS2 nanocomposites. In this study, we used monochloroacetic acid (MCA) to successfully modify carboxyl-MoS2. The efficiency of this MCA modification method showed a higher -COOH group content of 30.1%, mainly due to chlorine atoms occupying the MoS2 sulfur vacancy to allow for the formation of a strong bonding effect. This then enhanced the surface area of -COOH and improved the formation of covalent bonds between proteins. We demonstrated that MoS2-COOH-based surface plasmon resonance (SPR) chips can provide excellent sensitivity and high affinity for immunoassay biomolecules detected in a low sample volume of 20 μl. With respect to the shifts of the SPR angles of the chips, the high binding affinity at a BSA concentration of 14.5 nM for a MoS2-COOH chip, a MoS2 chip and a traditional SPR chip are 4.69 m°, 2.49 m° and 1.53 m°, respectively. In addition, the MoS2-COOH chip could amplify the SPR angle response by 3.1 folds and enhance the high association rate of ka by 212 folds compared to MoS2 and traditional SPR chips. The results thus obtained revealed that the overall affinity binding value, KA, of the MoS2-COOH chip can be significantly enhanced by up to ∼ 6.5 folds that of the MoS2 chip. In summary, the excellent binding affinity, biocompatible and high sensitivity suggest the potential of the clinical application of this MoS2-COOH-based SPR chip detection method for in vitro diagnostic and point-of-care testing devices.