Surface imprinted upconversion nanoparticles for selective albumin recognition

Upconversion nanoparticles (UCNPs) have attracted researchers' attention because these particles transform two or more low-energy infrared (IR) photons into high-energy visible photons via a sequential absorption process. The molecular imprinting method, one of the biomimicking approaches, has remarkable advantages for creating synthetic receptors for molecules of interest. In this study, we have focused our attention on developing novel selective materials simultaneously having upconversion and biorecognition abilities to form a supramolecular complex. We proposed a new approach to synthesize silica-based UCNPs via surface imprinting of albumin that was chosen as a model biomolecule. In the first step, synthesis of surface imprinted upconversion silica nanoparticles and template removal processes were performed. FTIR, SEM, fluorimetry / UV-Vis spectrophotometry, zeta-size / potential measurements and BET (surface area measurements) were performed for the characterization. Biorecognition conditions were optimized and the optimum BSA recognition conditions were determined as BSA initial concentration, interaction time, pH, and temperature as 0.5 mg/mL, 15 min, 4.5, and 25 oC, respectively. The relative selectivity coefficients, designating the selectivity gained by the imprinting process for BSA/hemoglobin, BSA/ovalbumin, and BSA/gamma-globulin pairs were calculated as 4.69, 38.37, and 9.66, respectively. In the second step, the synthesis of the magnetic nanoparticles and antibody immobilization onto these particles were investigated. At the final step, sandwich-like supramolecular complex with magnetic nanoparticles (MNPs) and upconversion silica nanoparticles (UC-SiNPs) were done and characterized with UV-Vis spectroscopy, fluorescent spectrometry, and zeta size and potential measurements. In a conclusion, developed molecular imprinted upconversion supramolecular complex will be an alternative and intriguing approach where sandwichlike recognition, detection, and selective adsorption properties are simultaneously required.