Influence of Polymer Morphology on the Capacity of Molecularly Imprinted Resins to Release or to Retain their Template

Abstract

This paper deals with the specific ability of molecularly imprinted polymers (MIPs) to release and/or to retain their template. MIPs for caffeine with various MIP:porogen volume ratios were prepared by a non-covalent route. Formation of a prepolymerization complex between the template and the functional monomer was confirmed by nuclear magnetic resonance and computer simulation. The MIP monoliths were successively grinded, sieved, and dried under vacuum. The morphology of the imprinted particles was investigated by scanning electron microscopy, swelling experiments and nitrogen adsorption. Typical release patterns of as-synthesised MIP particles in solvents can be decomposed in three fractions: initial release ( 0 ), slow release over several hours (Á Release ), permanent retention/encapsulation within the MIP (Á Reservoir ). The effect of MIP:porogen volume ratio (related to the MIP porosity) on the releasing/retaining profiles of the materials has been investigated. Finally, the results were critically compared with the available literature and the applicability of MIP reservoirs is briefly discussed.KEY WORDS: Molecular Imprinting / Polymer Morphology / Controlled Release / Polymer Reservoir / Self-Assembly / Molecular imprinting is an emerging technology, which allows the molecular design of polymeric materials containing highly specific receptor sites with an affinity for target compounds.1-3 Formation of a self-assembled pre-polymerization complex between a template molecule and functional monomers, followed by polymerization with a cross-linker in a porogenic solvent and the subsequent extraction of the template, produces a molecularly imprinted polymer (MIP) possessing specifically sized and shaped cavities capable of molecular recognition. 4,5 MIPs are generally highly crosslinked thermosets, and therefore porosity is a necessary feature of their morphology to allow permeability and transport of templates molecules to the bulk polymer phase.To date, a number of promising applications have been proposed for MIPs. For instance, imprinted polymers are used in chromatography as the stationary phase for separation and isolation of racemates.6,7 A related area is solid-phase extraction, where imprinted polymers are employed as a selective sorbent to concentrate the molecule of interest.8 MIPs are also used in immunoassays-type analyses as synthetic antibody 9 and in catalysis as enzyme mimics. 10,11 In the emerging field of biosensors, MIPs demonstrate a potential as the recognition element, although their performance and selectivity in aqueous systems is still a limiting factor. 12,13The application of desorption properties of MIPs is a relatively new area.14,15 Chromatographic data have shown that the MIP-template dissociation kinetics can be controlled by varying the local environment (MIP composition, solvent. . .). Therefore, it seems feasible that MIPs could form highly specific rate limiting reservoirs releasing active compounds at well-defined rates. Early studies delivered promising results and showe...

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

“…The integration of MIPs in, or interaction of MIPs with, biological systems is perhaps the area that has drawn most attention from the scientific community at large over recent years. Two themes dominate this sector, namely the use of MIPs for drug delivery and the development of MIPs with biological function . The use of molecular imprinted materials in conjunction with ocular drug delivery is arguably the sector that has come closest to clinical use.…”

Development of an active packaging with molecularly imprinted polymers for beef preservation

“…As we know, MIT is good at forming selective sites in a polymer matrix with the memory of a template and enables the use of stimuli‐responsive molecularly imprinted polymers (MIPs) materials as smart chemicals and drug‐delivery systems . The template release kinetics of MIPs indicates their potential for controlled release drug dosage, and the increase in release rate at higher loadings is attributed to partial drug adsorption to nonspecific non‐specific binding sites with weak attachment, typical release patterns of MIPs morphology were determined, and MIPs particles in solvents can be decomposed in 3 fractions . Although MIPs were not evaluated as components of active agents for food packaging materials, Benito‐Peña et al proposed to develop active packaging materials by using molecularly imprinted hydrogels loaded with natural ferulic acid as the antioxidative agent.…”

FIB and MIP: understanding nanoscale porosity in molecularly imprinted polymers via 3D FIB/SEM tomography

“…In fluids, MIPs and NIPs may swell differentially depending on the solvent and the composition of the imprinted and nonimprinted polymer. [33][34][35] Therefore, in a first-step the swelling behavior of these materials was investigated, as a difference in the resulting overall volume of MIP and NIP may also result in variations of the associated pore space. As Epoxy resin is liquid prior to polymerization, MIP0 and NIP0 particles were soaked in liquid resin.…”