Biocompatible molecularly imprinted polynorepinephrine nanoparticles: rational design and one-step reversible immobilization for enhanced protein recognition by surface plasmon resonance

Abstract: Polynorepinephrine nanoparticles (PNE-NPs) are emerging bioinspired nanomaterials with significant potential in diagnostics and therapy, yet their systematic synthesis and functional assessment remain limited. In this work, a Design of Experiments approach was applied to optimize the synthesis of non-imprinted and imprinted PNE-NPs. A green, pH-triggered precipitation/redispersion protocol was introduced for nanoparticle purification, providing fast and reproducible recovery without organic solvents, and surpassing conventional membrane dialysis methods, which are typically long and labor-intensive. Key parameters (pH, temperature, reaction time, stirring, and monomer concentration) were screened in H2O/NaOH and TRIS buffer media. Optimized PNE-NPs displayed hydrodynamic diameters below 200 nm, spherical morphology, and negligible cytotoxicity in HaCaT keratinocytes across a broad concentration range. As a model study, PNE-NPs were imprinted against the Fc portion of human IgG1 and tested as synthetic receptors by surface plasmon resonance (SPR). Two flow-mode immobilization strategies were compared on bare gold chips: covalent grafting on thiol-modified gold and direct adsorption. Both allowed real-time, in-flow monitoring and markedly improved affinity (KD < 10−8 mol L−1) compared to previous imprinted PNE nanofilms. The adsorption protocol stood out for its simplicity, high affinity and selectivity (α > 27.4), and full in situ reconditioning of the SPR gold transducer with NaClO washes, enabling multiple reuse cycles. These results establish PNE-NPs as versatile synthetic receptors, highlighting their promise as next-generation platforms for diagnostics and therapy.