Design and Evaluation of Molecularly Imprinted Nanoparticles for Oxolinic Acid Photodegradation

Abstract

Molecularly imprinted polymers have evolved into versatile functional platforms that extend far beyond traditional separation science applications. This work reports the development of photoactive molecularly imprinted nanoparticles (MINs) for the capture and photocatalytic degradation of the recalcitrant antibiotic pollutant oxolinic acid (OA) under visible-light irradiation. Molecular dynamics simulations were used to screen eight monomer formulations with varying ratios of (AA), N-isopropylacrylamide (NIPAm), N-tert-butylacrylamide (TBAm), N-(3-aminopropyl)methacrylamide hydrochloride (APMA), and the crosslinker N,N′-methylenebis(acrylamide) (BIS). The computational formulation with the highest affinity to the template (40% AA, 8% NIPAm, 8% TBAm, 39% APMA, and 5% BIS) guided the synthesis of OA-imprinted MINs via high-dilution polymerization in aqueous solution, followed by in situ conjugation with the photosensitizer toluidine blue O (TBO) via EDC/NHS coupling. Dynamic light scattering, zeta potential, and TEM experiments confirmed the nanoscale size and colloidal stability of the synthesized nanoparticles. Photoactive MINs achieved 20% OA binding capacity at 50 μmol L^–1 and sustained singlet oxygen generation under white LED light irradiation (150 mW cm^–2) for 1 h. Immobilized MINs were tested as photocatalysts for OA degradation at 100 and 200 μmol L^–1, achieving 60–80% antibiotic removal after 6 h of irradiation. ¹H-NMR of OA at an early degradation point suggests a possible fragmentation pathway involving dealkylation of the γ-pyridone-β-carboxylic ring. OA degradation at concentrations exceeding the MINs binding capacity confirmed that the photocatalytic removal operates through a cavity-assisted mechanism comprising substrate capture, photochemical degradation, and product release. Despite the long irradiation times required for OA degradation, our results show the potential of integrating molecular imprinting and photosensitization to develop polymeric photocatalysts for antibiotic remediation.