Molecularly imprinted polymer for glutathione by modified precipitation polymerization and its application to determination of glutathione in supplements

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.

Retention and molecular-recognition mechanisms of molecularly imprinted polymers for warfarin derivatives and their application for the determination of warfarin in human serum

Monodisperse molecularly imprinted polymers (MIPs) for warfarin (WF), 4'-chlorowarfarin (CWF), 4'-bromowarfarin (BWF), 4'-nitrowarfarin (NWF) and 4'-methylwarfarin (MWF) (MIP_WF, MIP_CWF, MIP_BWF, MIP_NWF and MIP_MWF, respectively) were prepared using 4-vinylpyridine (4-VPY) and ethylene glycol dimethacrylate as a functional monomer and crosslinker, respectively, by multi-step swelling and polymerization. The retention and molecular-recognition properties of those MIPs were evaluated in HILIC, and reversed- and normal-phase modes. According to ¹H NMR studies, one-to-three complex formation of one WF or CWF molecule with three 4-VPY molecules occurred. Via computational approaches, the intermolecular interaction modes and energies between WF derivatives and 4-VPYs were evaluated by semi-empirical quantum chemistry methods and density functional theory calculations. Three major possible hydrogen bonding interaction modes were identified: the interactions between the 4-hydroxy group, α-proton (methylene C-H) and α-proton (methyl C-H) of the WF derivative and the nitrogen atoms of 4-VPYs. In HILIC and normal-phase modes, the interaction energies showed satisfactory correlations with the retention factors of the WF derivatives. In reversed-phase mode, the retention factors of the WF derivatives were described by the hydrophobicity and the acidity of the 4-hydroxy groups of the WF derivatives. These results demonstrate that three hydrogen bonding interactions in HILIC and normal-phase modes, and hydrogen bonding or ionic interactions and hydrophobic interactions in reversed-phase mode play important roles in the retention and molecular-recognition of the WF derivatives on MIPs. Furthermore, MIP_BWF was successfully applied to the determination of WF in human serum by column-switching LC with high accuracy, precision and selectivity and without template-leakage problems.

Fluorescence assay for the determination of glutathione based on a ring-fused 2-pyridone derivative in dietary supplements

Herein, a novel fluorescent method for the determination of GSH levels in aqueous solutions involving the utilization of citric acid as a derivatization reagent was developed. Therefore, the crucial parameters of the derivatization process were established from what has resulted in the development of a sensitive, reproducible, and accurate GSH assay. The method was validated, and its applicability in the characterization of the GSH concentration in dietary supplements concerning the selectivity in the determination of GSH over GSSG was both confirmed. The chemical structure of the new fluorophore 3-[(carboxymethyl)carbamoyl]-5-oxo-2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyridine-7-carboxylic acid - CTPC was elucidated using detailed NMR: one-dimensional (¹H, ¹³C), as well as two-dimensional NMR spectra (¹H-¹H COSY, ¹H-¹³C HSQC, ¹H-¹³C HMBC, ¹H-¹⁵N HSQC, ¹H-¹⁵N HMBC) experiments. Besides, the essential optical, biological and antioxidative properties of CTPC were investigated.

Microsphere Polymers in Molecular Imprinting: Current and Future Perspectives

Molecularly imprinted polymers (MIPs) are specific crosslinked polymers that exhibit binding sites for template molecules. MIPs have been developed in various application areas of biology and chemistry; however, MIPs have some problems, including an irregular material shape. In recent years, studies have been conducted to overcome this drawback, with the synthesis of uniform microsphere MIPs or molecularly imprinted microspheres (MIMs). The polymer microsphere is limited to a minimum size of 5 nm and a molecular weight of 10,000 Da. This review describes the methods used to produce MIMs, such as precipitation polymerisation, controlled/'Living' radical precipitation polymerisation (CRPP), Pickering emulsion polymerisation and suspension polymerisation. In addition, some green chemistry aspects and future perspectives will also be given.

Sample treatment based on molecularly imprinted polymers for the analysis of veterinary drugs in food samples: a review

The use of veterinary drugs in medical treatments and in the livestock industry is a recurrent practice. When applied in subtherapeutic doses over prolonged times, they can also act as growth promoters. However, residues of these substances in foods present a risk to human health. Their analysis is thus important and can help guarantee consumer safety. The critical point in each analytical technique is the sample treatment and the analytical matrix complexity. The present manuscript summarizes the development, type of synthesis, characterization, and application of molecularly imprinted polymers in the separation, identification, and quantification techniques for the determination of veterinary drug residues in food samples in extraction, clean-up, isolation, and pre-concentration systems. Synthesized sorbents with specific recognition properties improve the interactions between the analytes and the polymeric sorbents, providing better analysis conditions and advantages in comparison with commercial sorbents in terms of high selectivity, analytical sensitivity, easy performance, and low cost analysis.

Two different states conversion mechanism of the imprinting sites

Bisphenol A molecular imprinted adsorbent (BMIA) was successfully synthesized by a sol-gel process and showed a good specific binding performance in the water. The further studies showed that the mass transfer process was controlled by in-diffusion, and the synthesis conditions would effect on the amount of imprinting sites. Scatchard model analysis evidenced that the high binding affinity sites and the low binding affinity sites were both on BMIA, and the high binding affinity sites played a key role in the specific binding process. Scatchard model analysis of temperature effect experiments and dosage effect experiments proved that the specific binding sites with high binding affinity and the unexpressed specific binding sites with low binding affinity were the two different states of the imprinting binding sites. The conversion between the two different states depended on the reaction driving force, and the increasing reaction driving force would increase the number of specific binding sites. Especially, the temperature showed a linear positive correlation with the amount of specific binding sites. Finally, a possible model was put forward to explain the two different states conversion mechanism of the imprinting sites.

Preparation of metal–organic frameworks with bimetallic linkers and corresponding properties

A series of metal–organic frameworks (MOFs) with bimetallic linkers were synthesized through a facile reflux route.

Novel controllable hydrophilic thermo-responsive molecularly imprinted resin adsorbent prepared in water for selective recognition of alkaloids by thermal-assisted dispersive solid phase extraction

A novel controllable hydrophilic thermo-responsive molecularly imprinted resin (T-MIR) with a switchable zipper-like architecture was synthesized in the aqueous phase and applied to the selective recognition and extraction of alkaloids by positive temperature regulation. In this synthesis process of T-MIR, 2-acrylamide-2- methylpropanesulfonic acid (AMPS) and acrylamide (AAm) were coupled as zipper-like thermo-responsive monomers, resorcinol, and melamine as hydrophilic monomers, formaldehyde as a cross-linker, and berberine chloride (BerbC) as the template. The resulting T-MIR achieved the controlled rebinding and release of BerbC from temperature stimuli (25-45 °C) and the adsorption process followed the Langmuir isotherm (R²>0.99856) and pseudo-second-order kinetic model (R²>0.98138). The highest theory adsorption ability (33.44 mg/g) and recognition ability (imprinting factor: 4.71) of T-MIR was activated between poly(AMPS) and poly(AAm) in the zipper-like architecture at 35 °C. T-MIR was then applied to the selective recognition alkaloids by dispersive solid phase extraction. The limit of detection and limit of quantitation of the method were less than 0.025 mg/L and 0.082 mg/mL, respectively. The recoveries of the proposed method at three spiked levels were 96.8-100.8%, with a relative standard deviation of less than 4.8%. In contrast to previous thermo-responsive materials, this switchable zipper-like hydrophilic T-MIR with good adsorption, specificity recognition, and excellent temperature controllable properties provides a unique alternative to the selective recognition and controlled rebind-release alkaloids by the temperature signal.