Quantum dot monolayer for surface plasmon resonance signal enhancement and DNA hybridization detection

We report results of studies relating to the fabrication of a surface plasmon resonance (SPR)-based nucleic acid sensor for quantification of DNA sequence specific to chronic myelogeneous leukemia (CML). The SPR disk surface has been modified with octadecanethiol self-assembled monolayer followed by deposition of the tri-n-octylphosphine oxide capped cadmium selenide quantum dots (QD) Langmuir monolayer. The deposition is performed via Langmuir-Blodgett (LB) technique. For the sensor chip preparation, covalent immobilization of the thiol-terminated DNA probe sequence (pDNA) using displacement reaction is accomplished. This integrated SPR chip has been used to detect target complementary DNA concentration by monitoring the change in coupling angle via hybridization. It is revealed that this biosensor exhibits high sensitivity (0.7859 m0 pM−1) towards complementary DNA and can be used to detect it in the concentration range, 180 pM to 5 pM with detection limit as 4.21 pM. The results of kinetic studies yield the values of hybridization and dissociation rate constants as 9.6×104 M−1 s−1 and 2.3×10−2 s−1, respectively, with the equilibrium constant for hybridization as 4.2×106 M−1.