New coupling method for anchoring molecularly imprinted polymers onto polymeric transducers: A case study for the detection of the heart failure biomarker Troponin T

Molecularly imprinted polymer nanogels (MIP-NGs) prepared by solid-phase synthesis are attractive as recognition elements in sensors as they offer the advantages of having surface-exposed binding sites, favoring rapid binding kinetics and fast response. On the other hand, transducers like optical fibers meet the needs of contemporary analysis and detection due to their ease of miniaturization, portability and implementation in remote areas. Generally, chemical grafting as opposed to physical coating of the MIP-NGs on the optical fibers is recommended, to ensure sensor stability. To this end, we developed a novel immobilization protocol introducing azido moieties onto polymer microstructures fabricated at the end of a standard telecommunication optical fiber, enabling the anchoring of propargylated MIP-NGs (MIP-ynes) by click chemistry. The set-up was then tested as a proof of concept with MIPs specific for cardiac troponin T (cTnT), a biomarker of myocardial injury. The MIP-NGs were prepared by solid-phase epitope imprinting, whereby the epitope was selected using a rational in silico approach, recently developed in-house. The resultant MIP-NGs were monodisperse and bound recombinant human cTnT with a high affinity and selectivity. MIP-ynes were immobilized on optical fibers using a multi-step process based on initially grafting a visible light trithiocarbonate photoiniferter, followed by surface-initiated photopolymerization of a polymer layer in order to introduce azido moieties on the fiber, followed by MIP attachment by azide-alkyne cycloaddition. The MIP-NGs anchored on the optical fiber recognized a fluorescent epitope peptide of cTnT, opening new horizons for optical fiber sensing with MIPs. Molecularly imprinted polymer nanogels are immobilized onto an acrylic polymer surface by azide-alkyne cycloaddition after photoiniferter coupling and polymer brush synthesis for azide attachment. • Water-soluble MIP-NGs for troponin T were prepared by solid-phase epitope imprinting • A visible light trithiocarbonate photoiniferter was grafted on an optical fiber tip • This enabled surface-initiated grafting of a polymer layer with azido groups • Propargylated MIP-NGs were immobilized on the optical fiber by click chemistry • MIP-NGs binding sites remained accessible after immobilization on the optical fiber