Effect of Polymerization Time on the Binding Properties of Ciprofloxacin-Imprinted nanoMIPs Prepared by Solid-Phase Synthesis

Abstract

An innovative approach to imprinted nanoparticles (nanoMIPs) is represented by solid-phase synthesis. Since the polymeric chains grow over time and rearrange themselves around the template, the binding properties of nanoMIPs could depend on the polymerization time. Here we present an explorative study about the effect of different polymerization times on the binding properties of ciprofloxacin-imprinted nanoMIPs. The binding properties towards ciprofloxacin were studied by measuring the binding affinity constants (Keq) and the kinetic rate constants (kd, ka). Furthermore, selectivity and nonspecific binding were valued by measuring the rebinding of levofloxacin onto ciprofloxacin-imprinted nanoMIPs and ciprofloxacin onto diclofenac-imprinted nanoMIPs, respectively. The results show that different polymerization times produce nanoMIPs with different binding properties: short polymerization times (15 min) produced nanoMIPs with high binding affinity but low selectivity (Keq > 107 mol L−1, α ≈ 1); medium polymerization times (30 min–2 h) produced nanoMIPs with high binding affinity and selectivity (Keq ≥ 106 mol L−1, α < 1); and long polymerization times (>2 h) produced nanoMIPs with low binding affinity, fast dissociation kinetics and low selectivity (Keq ≤ 106 mol L−1, kdis > 0.2 min−1, α ≈ 1). The results can be explained as the combined effect of rearrangement and progressive stiffening of the polymer chains around the template molecules.

NanoMIP-Based Solid Phase Extraction of Fluoroquinolones from Human Urine: A Proof-of-Concept Study

“…The template molecule, ciprofloxacin hemisuccinamide (CIP-HS), was synthesized according to a modified version of the procedure given by Noël et al [27]. Glass beads (Spheriglass-2429, 70-100 µm average particle size, Potters, UK) were aminated and grafted with the template as previously described [26]. The acrylic acid (AA), chlortetracycline (CTX), ciprofloxacin (CIP), danofloxacin (DAN), enrofloxacin (ENR), N-isopropylacrylamide (NIPAm), levofloxacin (LEV), lomefloxacin (LOM), N,N -methylene-bis-acrylamide (BIS), morpholinoethansulfonic acid (sodium salt, MES), moxifloxacin (MOX), norfloxacin (NOR), sarafloxacin (SAR), N-tert-butylacrylamide (TBAm), ammonium persulphate (APS) and N,N,N ,N -tetramethylethylenediamine (TEMED) that were used in this study were purchased from Merck (Milan, Italy).…”

“…The nanoMIPs were grafted onto aminated glass beads in accordance with the protocol that has been previously reported [26].…”

“…The polymerization mixture that has been previously used [26] to prepare nanoMIPs with molecular ciprofloxacin recognition properties was composed of a cross-linking agent (N,N -methylene-bis-acrylamide) and two functional monomers, which have the task of interacting with the template through either hydrogen bonds/ion pairs (acrylic acid) or hydrophobic interactions (N-tert-butylacrylamide). These monomers constitute 70% molar of the mixture, the remaining 30% of which consists of N-isopropylacrylamide, a thermoresponsive monomer that is useful for the selective detachment of nanoMIPs from the solid phase at the end of the synthesis process.…”

“…As a proof-of-concept, we considered prepared nanoMIPs against ciprofloxacin, a fluoroquinolone of relevant interest as an analytical target in MISPE [22][23][24] on which we have recently published the characterization of the binding properties [25,26]. Several na-noMIPs were prepared with polymerization mixtures of different compositions and the Solid phase synthesis has proved to be very versatile and nanoMIPs that are able to target small molecules [14,15], macrocyclic antibiotics [16,17], toxins [18,19], and peptides [20,21] have been described, and used, for the development of sensors and biomimetic assays.…”

“…As a proof-of-concept, we considered prepared nanoMIPs against ciprofloxacin, a fluoroquinolone of relevant interest as an analytical target in MISPE [22][23][24] on which we have recently published the characterization of the binding properties [25,26]. Several nanoMIPs were prepared with polymerization mixtures of different compositions and the polymer with the highest affinity towards ciprofloxacin was used to set up a method for the extraction of the target analyte from human urine.…”