Polymers molecularly imprinted with ergotamine: recognition properties to template and related alkaloids

Abstract Text: Alkaloid toxicities negatively impact livestock health and production. Adsorbent technologies may offer effective means to manage alkaloid toxicities. In this study, molecularly imprinted polymers (MIP) were synthesized and evaluated for specificity of adsorption to various ergot alkaloids. Six different noncovalent copolymers were synthesized from styrene and methyl methacrylate functional monomers with a free radical initiator (2,2'-azobis isobutyronitrile) and three different molar ratios (1x, 2x, 4x) of crosslinker (ethylene glycol dimethacrylate) in toluene. Synthesis was performed in the absence (non-imprinted polymer, NIP) or presence of ergotamine template (MIP), yielding products NIP1x, NIP2x, NIP4x, MIP1x, MIP2x and MIP4x. An isothermal adsorption experiment was conducted in triplicates, with product inclusion of 0.01% w/v, using 5 concentrations (range 65 to 1550 ng/mL) of each of three alkaloids (ergotamine, bromocriptine and methylergonovine) in ammonium citrate buffer (pH 6.7, 37^oC, 90 min). Samples were centrifuged (10,000 g for 10 min) and supernatant was analyzed by UPLC-ESI- MS/MS for quantification of unbound alkaloid. Within each alkaloid, adsorption difference between MIP and NIP interacted (P < 0.05) with alkaloid concentration and crosslinker ratio. For most comparisons at 1x crosslinker ratio, adsorption was greater (P < 0.10) for NIP than MIP. In contrast, for the few differences (P < 0.10) detected for 2x and 4x crosslinker ratios, MIP exceeded NIP adsorption. For both MIP and NIP, adsorption was generally greater for 2x and 4x, as compared with the 1x crosslinker ratio. Differences in adsorption between alkaloids varied with alkaloid concentration and product (alkaloid x concentration x product; P < 0.05). In most cases, adsorption was seen in the order ergotamine > bromocriptine > methylergonovine. Products with 4x crosslinker ratios gave the greatest adsorption, and therefore those means are used for comparison of products and alkaloids.  Averaged across the different alkaloid concentrations, the respective adsorption for MIP and NIP was 91% and 86% for ergotamine, 75% and 69% for bromocriptine, and 26% and 15% for methylergonovine. Differences in adsorption properties among the six products could be explained by differences in functional groups and conformation, which are altered by template or cross linkers. Cross reactivity with related alkaloids exists due to similarities in structure and functional groups. Future in vitro and in vivostudies are required to determine stability of the polymer-alkaloid complexes, and applicability of polymers as adsorbents in livestock to counteract alkaloid toxicoses

Keywords:

Adsorbent, MIP, alkaloid