title: On/off-switchable LSPR nano-immunoassay for troponin-T.
abstract: Regeneration of immunosensors is a longstanding challenge. We have developed a re-usable troponin-T (TnT) immunoassay based on localised surface plasmon resonance (LSPR) at gold nanorods (GNR). Thermosensitive poly(N-isopropylacrylamide) (PNIPAAM) was functionalised with anti-TnT to control the affinity interaction with TnT. The LSPR was extremely sensitive to the dielectric constant of the surrounding medium as modulated by antigen binding after 20 min incubation at 37 °C. Computational modelling incorporating molecular docking, molecular dynamics and free energy calculations was used to elucidate the interactions between the various subsystems namely, IgG-antibody (c.f., anti-TnT), PNIPAAM and/or TnT. This study demonstrates a remarkable temperature dependent immuno-interaction due to changes in the PNIPAAM secondary structures, i.e., globular and coil, at above or below the lower critical solution temperature (LCST). A series of concentrations of TnT were measured by correlating the λLSPRshift with relative changes in extinction intensity at the distinct plasmonic maximum (i.e., 832 nm). The magnitude of the red shift in λLSPRwas nearly linear with increasing concentration of TnT, over the range 7.6 × 10-15to 9.1 × 10-4g/mL. The LSPR based nano-immunoassay could be simply regenerated by switching the polymer conformation and creating a gradient of microenvironments between the two states with a modest change in temperature.
authors.affiliation: Institute of Advanced Materials, UCS, Teknikringen 4A, Mjärdevi Science Park, SE-58330 Linköping, Sweden.|Biosensors and Bioelectronics Centre, Department of Physics, Chemistry and Biology (IFM), Linköping University, 581 83 Linköping, Sweden.
authors.forename: Md
authors.initials: M
authors.lastname: Ashaduzzaman
authors.affiliation: Institute of Advanced Materials, UCS, Teknikringen 4A, Mjärdevi Science Park, SE-58330 Linköping, Sweden.|Biosensors and Bioelectronics Centre, Department of Physics, Chemistry and Biology (IFM), Linköping University, 581 83 Linköping, Sweden.
authors.forename: Swapneel R
authors.initials: SR
authors.lastname: Deshpande
authors.affiliation: Virtual Laboratory for Molecular Probes, Division of Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, S-106 91 Stockholm, Sweden.
authors.forename: N Arul
authors.initials: NA
authors.lastname: Murugan
authors.affiliation: Functional Nanomaterials, Institute for Materials Science, Kiel University, Kaiserstr. 2, D-24143, Kiel, Germany.
authors.forename: Yogendra Kumar
authors.initials: YK
authors.lastname: Mishra
authors.affiliation: Biosensors and Bioelectronics Centre, Department of Physics, Chemistry and Biology (IFM), Linköping University, 581 83 Linköping, Sweden.
authors.forename: Anthony P F
authors.initials: AP
authors.lastname: Turner
authors.affiliation: Institute of Advanced Materials, UCS, Teknikringen 4A, Mjärdevi Science Park, SE-58330 Linköping, Sweden.|Biosensors and Bioelectronics Centre, Department of Physics, Chemistry and Biology (IFM), Linköping University, 581 83 Linköping, Sweden.|Vinoba Bhave Research Institute, Binda-Dhokri Road, Saidabad, Allahabad 221508, India.
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Tiwari
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D006801:Humans; D007118:Immunoassay / Q000295:instrumentation / Q000379:methods*; D062105:Molecular Docking Simulation; D043942:Nanotubes; D020349:Surface Plasmon Resonance / Q000295:instrumentation / Q000379:methods*; D020107:Troponin T / Q000032:analysis* / Q000276:immunology
chemical_list: D000180:Acrylic Resins; D020107:Troponin T; C052970:poly-N-isopropylacrylamide; D006046:Gold