Improvement of the homogeneity of protein-imprinted polymer films by orientated immobilization of the template

Thickness Determination and Control in Protein-Based Biomaterial Thin Films

Controlling the thickness and uniformity of biomaterial films is crucial for their application in various fields including sensing and bioelectronics. In this work, we investigated film assemblies of an engineered repeat protein─specifically, the consensus tetratricopeptide repeat (CTPR) protein ─a system with unique robustness and tunability. We propose the use of microreflectance spectroscopy and apparent color inspection for the quick assessment of the thickness and uniformity of protein-based biomaterial films deposited on oxidized silicon substrates. Initially, we characterized the thickness of large, uniform, spin-coated protein films and compared the values obtained from microreflectance spectroscopy with those obtained from other typical methods, such as ellipsometry and atomic force microscopy. The excellent agreement between the results obtained from the different techniques validates the effectiveness of microreflectance as a fast, noninvasive, and affordable technique for determining the thickness of biomaterial films. Subsequently, we applied microreflectance spectroscopy to determine the thickness of drop-casted CTPR-based films prepared from small protein solution volumes, which present a smaller surface area and are less uniform compared to spin-coated samples. Additionally, we demonstrate the utility of apparent color inspection as a tool for assessing film uniformity. Finally, based on these results, we provide a calibration of film thickness as a function of the protein length and concentration for both spin-coated and drop-casted films, serving as a guide for the preparation of CTPR films with a specific thickness. Our results demonstrate the remarkable reproducibility of the CTPR film assembly, enabling the simple preparation of biomaterial films with precise thickness.

Electric Field-Assisted Molecularly Imprinted Polymer-Modified QCM Sensor for Enhanced Detection of Immunoglobulin

In this study, an electric-field-assisted molecularly imprinted polymer (EFAMIP) as an enhanced form of MIP was developed to improve the MIP-modified quartz crystal microbalance (QCM) biosensors. While exerting a vertical electric field, polymerization of methacrylic acid in the presence of immunoglobulin G (IgG) as the template was initiated, and later, after the template removal process, the EFAMIPs were obtained. The polymer surface characterization was conducted by using a scanning electron microscope. The impact of electric field direction on IgG binding sites, forming either EFAMIP-Fab or EFAMIP-Fc, was assessed. Next, the static measurement results in liquid for EFAMIP-modified QCM and MIP-modified QCM were compared. While encompassing IgG, EFAMIP-modified QCMs exhibited up to a 113.5% higher frequency shift than typical MIP in time-limited detection. The final frequency shift of EFAMIP, which determines the detection limit of IgG, was improved up to 12.5% compared to typical MIP. Moreover, the EFAMIP-Fab performance was promising for the selective detection of IgG in a solution containing different types of immunoglobulins.

A strategy of utilizing Cu2+-mediating interaction to prepare magnetic imprinted polymers for the selective detection of celastrol in traditional Chinese medicines

In this work, a novel strategy to prepare molecularly imprinted polymers (MIPs) functionalized magnetic carbon nanotubes (MCNTs) via a facile sol-gel polymerization by adopting Cu²⁺-mediating interaction was presented for selective recognition of celastrol (Cel), in the traditional Chinese medicines (TCM). Firstly, template Cel, 3-aminopropyltriethoxysilane (APTES) as monomer and Cu²⁺ (co-monomer) were mixed to form a self-assembled pre-complex, in which Cu²⁺ could coordinate with Cel. Meanwhile, APTES plays a role of bridge between APTES and Cel. Secondly, carboxyl modified MCNTs as substrate was added into the pre-complex solution. After that, a multi-step sol-gel polymerization process was occurred in the presence of tetraethylorthosilicate as cross-linker and acetic acid as catalyst. Finally, MIPs layer was formed on the surface of the MCNTs (Cel-MIPs@MCNTs) after the removal of template with methanol/acetic. The morphology and structure of Cel-MIPs@MCNTs was investigated by various characterization techniques. The adsorption performance of Cel-MIPs@MCNTs to Cel was illustrated by kinetic, isothermal and selective binding experiments. The results displayed that the Cel-MIPs@MCNTs possessed fast kinetic equilibrium time (40 s), high adsorption capacity (13.35 μg mg^-1), good imprinting factor of 3.41, and high magnetic responsivity (44.38 emu·g^-1), which can be used as an ideal adsorbent for rapid isolation and enrichment of target analytes. A selective and sensitive method based on Cel-MIPs@MCNTs coupling with HPLC was developed for Cel determination including a wide linear range (0.15-200 μg mL^-1) with correlation coefficient of 0.9998, a low limit of detection (0.05 μg mL^-1). Furthermore, the applicability of Cel-MIPs@MCNTs was demonstrated to isolate and determine Cel in TCM samples with satisfactory recoveries ranged from 84.47% to 91.5% (RSD<5.35%). The results revealed that Cel-MIPs@MCNTs offer great potential as an adsorbent for selective and efficient isolation of Cel from complex TCM samples.

Strategies for Molecular Imprinting and the Evolution of MIP Nanoparticles as Plastic Antibodies-Synthesis and Applications

Materials that can mimic the molecular recognition-based functions found in biology are a significant goal for science and technology. Molecular imprinting is a technology that addresses this challenge by providing polymeric materials with antibody-like recognition characteristics. Recently, significant progress has been achieved in solving many of the practical problems traditionally associated with molecularly imprinted polymers (MIPs), such as difficulties with imprinting of proteins, poor compatibility with aqueous environments, template leakage, and the presence of heterogeneous populations of binding sites in the polymers that contribute to high levels of non-specific binding. This success is closely related to the technology-driven shift in MIP research from traditional bulk polymer formats into the nanomaterial domain. The aim of this article is to throw light on recent developments in this field and to present a critical discussion of the current state of molecular imprinting and its potential in real world applications.

Competitive pseudo-ELISA based on molecularly imprinted nanoparticles for microcystin-LR detection in water

Microcystins (MCs) are dangerous cyanotoxins for the public health, and microcystin-LR (MC-LR) is one of most toxic, dangerous, and frequently found in water bodies. Typically, the detection of MCs is carried out by means of competitive ELISAs which, however, need special precautions for handling and storage, due to the stability of the antibodies used in this test. Molecularly imprinted nanoparticles (nanoMIPs) represents more robust and cost-effective alternative to antibodies. In this work, we developed a competitive pseudo-ELISA based on nanoMIPs (which are used in place of natural antibodies), for the detection of microcystin-LR (MC-LR). This pseudo-ELISA showed a linear response towards MC-LR, showing high affinity and low cross-reactivity against another analogue toxin (microcystin-YR). The analytical recovery of MC-LR in the analysis of water samples by the proposed pseudo-ELISA was 96 %–130 % and the limit of detection was 2.64 × 10−4 nM. The obtained results suggest that this competitive pseudo-ELISA could have high potential in the detection of toxins, due to its rapid, sensitive and accurate detection of toxin in water samples.

Molecular LEGO by domain-imprinting of cytochrome P450 BM3

HYPOTHESIS

Electrosynthesis of the MIP nano-film after binding of the separated domains or holo-cytochrome BM3 via an engineered anchor should result in domain-specific cavities in the polymer layer.

EXPERIMENTS

Both the two domains and the holo P450 BM3 have been bound prior polymer deposition via a N-terminal engineered his6-anchor to the electrode surface. Each step of MIP preparation was characterized by cyclic voltammetry of the redox-marker ferricyanide. Rebinding after template removal was evaluated by quantifying the suppression of the diffusive permeability of the signal for ferricyanide and by the NADH-dependent reduction of cytochrome c by the reductase domain (BMR).

FINDINGS

The working hypothesis is verified by the discrimination of the two domains by the respective MIPs: The holoenzyme P450 BM3 was ca. 5.5 times more effectively recognized by the film imprinted with the oxidase domain (BMO) as compared to the BMR-MIP or the non-imprinted polymer (NIP). Obviously, a cavity is formed during the imprinting process around the his₆-tag-anchored BMR which cannot accommodate the broader BMO or the P450 BM3. The affinity of the MIP towards P450 BM3 is comparable with that to the monomer in solution. The his₆-tagged P450 BM3 binds (30 percent) stronger which shows the additive effect of the interaction with the MIP and the binding to the electrode.

Selective extraction of bioactive glycoprotein in neutral environment through Concanavalin A mediated template immobilization and dopamine surface imprinting

Inspired by the sugar–lectin interaction, Concanavalin A mediated glycoprotein pre-immobilization, combined with dopamine polymerization, is employed to fabricate a glycoprotein imprint that can work in physiological environments.

Precisely controlled molecular imprinting of glutathione-s-transferase by orientated template immobilization using specific interaction with an anchored ligand on a gold substrate

We demonstrate a novel synthetic route for molecularly imprinted polymer (MIP) thin films using a bottom-up approach utilizing protein–ligand specific interactions.

Specific removal of protein using protein imprinted polydopamine shells on modified amino-functionalized magnetic nanoparticles

A simple approach for the specific removal of protein using polydopamine imprinted shells on modified amino-functionalized magnetic nanoparticles was developed.

Solid-Phase Synthesis of Molecularly Imprinted Polymer Nanoparticles with a Reusable Template - "Plastic Antibodies"

Molecularly Imprinted Polymers (MIPs) are generic alternatives to antibodies in sensors, diagnostics and separations. To displace biomolecules without radical changes in infrastructure in device manufacture, MIPs should share their characteristics (solubility, size, specificity and affinity, localized binding domain) whilst maintaining the advantages of MIPs (low-cost, short development time and high stability) hence the interest in MIP nanoparticles. Herein we report a reusable solid-phase template approach (fully compatible with automation) for the synthesis of MIP nanoparticles and their precise manufacture using a prototype automated UV photochemical reactor. Batches of nanoparticles (30-400 nm) with narrow size distributions imprinted with: melamine (d = 60 nm, Kd = 6.3 × 10-8 m), vancomycin (d = 250 nm, Kd = 3.4 × 10-9 m), a peptide (d = 350 nm, Kd = 4.8 × 10-8 m) and proteins have been produced. Our instrument uses a column packed with glass beads, bearing the template. Process parameters are under computer control, requiring minimal manual intervention. For the first time we demonstrate the reliable re-use of molecular templates in the synthesis of MIPs (≥ 30 batches of nanoMIPs without loss of performance). NanoMIPs are produced template-free and the solid-phase acts both as template and affinity separation medium.