Preparation and Binding Evaluation of Histamine-Imprinted Microspheres via Conventional Thermal and RAFT-Mediated Free-Radical Polymerization

Abstract

Elevated histamine (HTM) levels are closely linked to food poisoning as well as to pathophysiological allergic diseases. In this study, HTM-imprinted, solution-processable microspheres were prepared via high-dilution conventional thermal polymerization (CTP) and controlled radical polymerization (CRP) using ethylene glycol dimethacrylate (80 or 90 wt %) and methacrylic acid at 60 °C in acetonitrile and evaluated as recognition materials for sensing applications. The polymers were selective to HTM in binding studies, cross-rebinding, and competitive binding assays against the HTM analogues histidine, imidazole, and tryptamine. The selective binding capacity was significantly higher with CTP-80 (on the basis of mass: 21.0 μmol/g and surface area: 8.08 × 10–2 μmol/m2) than that with both CTP-90 (8.47 μmol/g, 4.49 × 10–2 μmol/m2) and CRP-80 (9.00 μmol/g, 1.19 × 10–2 μmol/m2).

Assessment of the binding performance of histamine‐imprinted microspheres by frontal analysis capillary electrophoresis

“…To assess the imprinting effect, both MIM and its nonimprinted equivalent (NIM) were suspended in 1.0 mM of aqueous histamine (adjusted to pH 7 with 25 mM Na‐phosphate buffer) for 30 min before injection. It is worth noting that the buffer concentration (25 mM) employed in this study have previously been optimized . Likewise, rebinding pH tests were also conducted at pH 5, 7, and 9 employing the optimum phosphate buffer concentration of 25 mM (see ESI Supporting Information Fig.…”

Room temperature synthesis and binding studies of solution‐processable histamine‐imprinted microspheres

“…Histamine‐imprinted microspheres were synthesized at RT (30°C) via high dilution photochemical polymerization using AIBN. The monomer MAA and the crosslinker EGDMA were chosen based on previous studies and our study using histamine‐imprinted CTP at 60°C . Whereas, AIBN is both a thermal and photochemical initiator, such that upon exposure to UV, the radicals generated initiate the polymerization process.…”

“…Non‐imprinted microspheres (PCP‐N80 and PCP‐N90), no template added, were also prepared with each corresponding imprinted polymer formulation. The CTPs were synthesized using a procedure described earlier . Briefly, the polymerization solutions were prepared similar to PCP except that the reactions were performed at 60°C for 24 hours.…”

“…Solution‐processable imprinted polymers are highly crosslinked submicron‐sized polymeric particles (ie, microgels, nano‐gels, microspheres, or simple nanoparticles) that form stable dispersions in a given solvent without changing their overall structure including their binding pockets . These polymers also possess more accessible sites providing better binding kinetics .…”

“…Due to these unique properties, these imprinted polymers are ideal for catalysis, for drug delivery or controlled release, and for sensing . These polymers have been prepared via solution polymerization, conventional thermal and controlled radical precipitation polymerization, and mini‐emulsion and micro‐emulsion polymerization, where the resulting processable polymers can be easily characterized as macromolecules both as a solid or in solution form using standard techniques.…”