Pressure-Induced Binding Sites in Molecularly Imprinted Network Polymers

Elucidating doxycycline loading and release performance of imprinted hydrogels with different cross-linker concentrations: a computational and experimental study

Effective non-covalent molecular imprinting on a polymer depends on the extent of non-bonded interactions between the template and other molecules before polymerization. Here, we first determine functional monomers that can yield a doxycycline-imprinted hydrogel based on the hydrogen bond interactions at the prepolymerization step, revealed by molecular dynamics (MD) simulations, molecular docking, and simulated annealing methods. Then, acrylic acid (AA)-based doxycycline (DOX) imprinted (MIP) and non-imprinted (NIP) hydrogels are synthesized in cross-linker ethylene glycol dimethacrylate (EGDMA) ratios of 1.0, 1.5, 2.0, and 3.0 mol%. Here, molecularly imprinted polymer with 3.0 mol% EGDMA has the highest imprinting factor (1.58) and best controlled drug release performance. At this point, full-atom MD simulations of DOX–AA solutions at different EGDMA concentrations reveal that AA and EGDMA compete to interact with DOX. However, at 3.0 mol% EGDMA, AA attains numerous stable hydrogen bond interactions with the drug. This study demonstrates that the concentration of the cross-linker and functional monomer can be adjusted to increase the success of imprinting, where the interplay between these two parameters can be successfully revealed by MD simulations.

Synthesis and characterization of a novel molecularly imprinted polymer for the controlled release of rivastigmine tartrate

To develop novel imprinted poly (methacrylic acid) nanoparticles for the controlled release of Rivastigmine Tartrate (RVS), the amalgamation of molecular imprinting techniques and polymerization of precipitates were applied in this work. By permuting different concentrations of pentaerythritol triacrylate (PETA) or trimethylolpropane triacrylate (TMPTA) as cross-linkers, ten different samples were synthesized, and their abilities assessed for RVS absorption. Among them, uniform mono-disperse nanoparticles were synthesized in an RVS/PMAA/PETA mole ratio of 1:6:12, named molecularly imprinted polymers 2 (MIP2), which showed the highest RVS absorption. Analytical procedures involving the Fourier transform infrared (FT-IR), Thermogeometric analysis (TGA), Field emission scanning electron microscopy (FE-SEM), Dynamic light scattering (DLS), and absorption/desorption porosimetry (BET) measurements were applied to characterize the morphology and physicochemical properties of the MIP2. In addition, the cytotoxicity of the MIP2 sample was measured by MTT assay on an L929 cell line. Studies pertaining to the in-vitro release of RVS from MIP2 samples showed that the prepared sample had a controlled and sustained release compared, which differed from the results obtained from the non-imprinted polymer (NIP) with the same formulization. Results obtained further reinforced the feasibility of prepared MIPs as a prime candidature for RVS drug delivery to alleviate Alzheimer's and other diseases.

A star-shaped molecularly imprinted polymer derived from polyhedral oligomeric silsesquioxanes with improved site accessibility and capacity for enantiomeric separation via capillary electrochromatography

A star-shaped molecularly imprinted coating was prepared starting from octavinyl-modified polyhedral oligomeric silsesquioxanes (Ov-POSS). It possesses a relatively open structure and has good site accessibility and a larger capacity even at lower cross-linking. The imprinted coating was prepared from S-amlodipine (S-AML) as the template and analyte, Ov-POSS as the cross-linker, and methacrylic acid as the functional monomer. The preparation and chromatographic parameters were optimized, including ratio of template to functional monomer, apparent cross-linking degree, pH value, ACN content and salt concentration in the mobile phase. The best resolution in enantiomer separation by means of capillary electrochromatography reaches a value of 33. A good recognition ability (α = 2.60) was obtained and the column efficiency for S-AML was 54,000 plates m^-1. The use of Ov-POSS as a cross-linker significantly improves the column capacity and thus the detection sensitivity. The results show that Ov-POSS is an effective cross-linker for the preparation of imprinted polymers with good accessibility and large capacity. Graphical abstract Schematic presentation of the preparation of star-shaped imprinted polymer using octavinyl-modified polyhedral oligomeric silsesquioxanes (Ov-POSS) and by using methacrylic acid (MAA) as functional monomer. The best enantiometric resolution (33) for amlodipine (AML) can be achieved in capillary chromatography (CEC).

Preparation and characterization of core/shell SiOx/PAM nanospheres with ‘graft from’ method

The core/shell SiO(2) encapsulated with polyacrylamide (SiO(x)/PAM) nanospheres were successfully prepared by the radical copolymerization of acrylamide (AM) and a macromonomer, methacryloxypropyl SiO(x) (MP-SiO(x)) nanoparticles, initiated with AIBN via a facile precipitation polymerization method in ethanol. The percentage of encapsulating (PE%) and the conversion of the AM (C%) of 327.5% and 93%, respectively, were achieved after a polymerizing time of 3 h. The formation mechanism of the core/shell SiO(x)/PAM nanospheres was explained. The nanospheres were characterized by elemental analysis (EA), Fourier transform infrared (FTIR), X-ray photoelectron spectrometer (XPS) and transmission electron microscope (TEM).

Molecular Imprinting under Molecular Crowding Conditions: An Aid to the Synthesis of a High-Capacity Polymeric Sorbent for Triazine Herbicides

Molecular crowding, an important feature of the molecular environments in biological cells, was applied to the synthesis of antibody-mimic polymers selective for a group of biologically active compounds, the triazine herbicides. Synthesis of these polymers was conducted using molecular imprinting under molecular crowding conditions, whereby atrazine (a template molecule) was complexed with methacrylic acid (a functional monomer) in the presence of a macromolecular crowding agent (either poly(methyl methacrylate) (PMMA) or polystyrene (PS)) followed by cross-linking with ethylene glycol dimethacrylate. After removal of atrazine from the polymer matrix, the retention properties and selectivity of the resultant polymers were assessed by chromatographic tests. The addition of a crowding-inducing agent resulted in polymers with superior retention properties and excellent selectivity for triazine herbicides, as compared to polymers prepared without addition of a crowding-inducing agent. An imprinted polymer prepared in the presence of PS as a crowding agent exhibited a retention factor for atrazine an order of magnitude larger than that of an imprinted polymer prepared in the absence of a crowding agent. NMR results suggest that the crowding agent is capable of promoting hydrogen bond formation between atrazine and methacrylic acid, which could account for the effect of crowding on molecular imprinting.

Influence of initiator and different polymerisation conditions on performance of molecularly imprinted polymers

A set of polymers was imprinted with (-)-ephedrine using two different initiators. A chemometrics approach was used to optimise experiments aimed at analysis of the interplay of parameters such as polymerisation time, temperature and percentage of initiator. The results presented demonstrate the importance of keeping the right balance between these various parameters of polymerisation conditions. It is shown that enhancing one single parameter such as polymer rigidity does not necessarily improve polymer performance. In general it could be concluded that MIPs should be synthesised over a long period of time using low concentration of initiator and low temperature. The best selectivity was achieved for polymers prepared by photo-initiation with 2,2-dimethoxy-2-phenylacetophenone as initiator.

Non-covalent molecular imprinting with emphasis on its application in separation and drug development

The molecular imprinting technique can be defined as the formation of specific nano-sized cavities by means of template-directed synthesis. The resulting molecularly imprinted polymers (MIPs), which often have an affinity and a selectivity approaching those of antibody-antigen systems, have thus been coined "artificial antibodies." MIPs are characterized by their high specificity, ease of preparation, and their thermal and chemical stability. They have been widely studied in connection with many potential applications, including their use for separation and isolation purposes, as antibody mimics (biomimetic assays and sensors), as enzyme mimics, in organic synthesis, and in drug delivery. The non-covalent imprinting approach, developed mainly in Lund, has proven to be more versatile than the alternative covalent approach because of its preparation being less complicated and of the broad selection of functional monomers and possible target molecules that are available. The paper presents a review of studies of this versatile technique in the areas of separation and drug development, with emphasis being placed on work carried out in our laboratory.

Anatomy of a successful imprint: Analysing the recognition mechanisms of a molecularly imprinted polymer for quercetin

This study comprises a retrospective analysis of a successful molecular imprint for quercetin with the main aim of deriving rational design strategies for more effective molecularly imprinted polymers. Hence, polymers of varying composition were synthesised and chromatographically characterised to examine the effects of monomer-template ratios. (1)H NMR analysis of the pre-polymerisation mixture yielded further information on the nature of the complexes formed prior to the polymerisation step. A direct correlation between the optimum monomer-template ratio derived from the chromatographic studies and the monomer-template ratio providing the most stable pre-polymerisation complexes observed via (1)H NMR T(1) relaxation time measurements, suggests that the formation of particularly stable pre-polymerisation complexes is responsible for an increased formation of selective binding sites during the polymerisation step. Furthermore, physical aspects of the polymerisation, such as the MIP surface area and macroscopic phase partitioning of the mixture during the polymerisation are investigated. The observed effects and their analytical assessment offer insight into the mechanisms governing MIP selectivity at a molecular level.

Molecular imprinting science and technology: a survey of the literature for the years up to and including 2003

Over 1450 references to original papers, reviews and monographs have herein been collected to document the development of molecular imprinting science and technology from the serendipitous discovery of Polyakov in 1931 to recent attempts to implement and understand the principles underlying the technique and its use in a range of application areas. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by papers dealing with fundamental aspects of molecular imprinting and the development of novel polymer formats. Thereafter, literature describing attempts to apply these polymeric materials to a range of application areas is presented.