Two Are Better than One: Halloysite Nanotubes-Supported Surface Imprinted Nanoparticles Using Synergy of Metal Chelating and Low pKa Boronic Acid Monomers for Highly Specific Luteolin Binding under Neutral Condition

Surface-imprinted nanoparticles with double recognition (DM-MIPs) are fabricated onto halloysite-nanotubes (HNTs) for highly specific separation of natural flavone luteolin (LTL) under neutral condition. Specifically, a two-step strategy via consecutive surface-initiated atom transfer radical polymerization (SIATRP) is employed to introduce inherent recognition of molecular imprinting and reversible covalent affinity of boronic acid ligands and immobilized Zn2+ into DMMIPs. First, Zn2-immobilized poly(vinyl imidazole) (PVLD) shell based on the HNTs via the first SI-ATRP is prepared to capture LTL by metal chelating. Then HNTs-supported surface imprinted nanoparticles are prepared using low pK(a) boronic acid monomer 4-(2-acrylamidoethylcarbamoy1)-3-fluorophenylboronic acid, (AMCFPBA) via the second SI-ATRP. Taking advantage of low apparent plc of AMCFPBA and large high-affinity binding site density, DM-MIPs possess a promiging binding with cis-diol-containing LTL under neutral condition. In static adsorption, DM-MIPs show large LTL loading amount (83.42 mg g(-1)), fast capture kinetics, remarkable selectivity, and excellent recydability at pH = 7.0. More importantly,:by reducing the pH to 4.0, the loaded TLL can be simply released. As a proof of this concept, a commercially available LTL with 85% purity can be easily enriched and further purified, and the product exhibits the similar antibacterial performance with standard-substance.