Highly selective BSA imprinted polyacrylamide hydrogels facilitated by a metal-coding MIP approach

Synthesis and Characterization of Cassava Gum Hydrogel Associated with Chlorhexidine and Evaluation of Release and Antimicrobial Activity

Hydrogels from natural sources are attracting increasing interest due to their ability to protect biologically active molecules. Starch extracted from cassava tubers is a promising material for synthesizing these hydrogels. Copolymerization of cassava gum and incorporation of chlorhexidine digluconate (CLX) into the hydrogels is confirmed by changes in the crystallographic profile, as observed through X-ray diffraction, and a shift in the 1000 cm-1 band in the Fourier-transform infrared spectroscopy spectrum. The differential scanning calorimetry reveals changes in the decomposition temperature of the synthesized hydrogels related to CLX volatility. Micrographs illustrate the material's porosity. Release tests indicate a constant linear release over 72 h, while antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Candida albicans is satisfactory, with 100% effectiveness from 0.5% CLX and the formation of inhibition halos. Toxicity and biocompatibility studies show no cytotoxicity. The continuous release of chlorhexidine is promising for components of biomedical implants and applications as it can ensure antimicrobial action according to specific therapeutic needs.

Molecularly imprinted polymer hydrogel sheets with metalloporphyrin-incorporated molecular recognition sites for protein capture

Metalloporphyrins are often found in nature as coordination recognition sites within biological process, and synthetically offer the potential for use in therapeutic, catalytic and diagnostic applications. While porphyrin containing biological recognition elements have stability limitations, molecularly imprinted polymers bearing these structures offer an alternative with excellent robustness and the ability to work in extreme conditions. In this work, we synthesised a polymerizable porphyrin and metalloporphyrin and have incorporated these as co-monomers within a hydrogel thin-sheet MIP for the specific recognition of bovine haemoglobin (BHb). The hydrogels were evaluated using Scatchard analysis, with Kd values of 10.13 × 10-7, 5.30 × 10-7, and 3.40 × 10-7 M, for the control MIP, porphyrin incorporated MIP and the iron-porphyrin incorporated MIP, respectively. The MIPs also observed good selectivity towards the target protein with 73.8%, 77.4%, and 81.2% rebinding of the BHb target for the control MIP, porphyrin incorporated MIP and the iron-porphyrin incorporated MIP, respectively, compared with the non-imprinted (NIP) counterparts. Specificity was determined against a non-target protein, Bovine Serum Albumin (BSA). The results indicate that the introduction of the metalloporphyrin as a functional co-monomer is significantly beneficial to the recognition of a MIP, further enhancing MIP capabilities at targeting proteins.

Application of thymine-based nucleobase-modified acrylamide as a functional co-monomer in electropolymerised thin-film molecularly imprinted polymer (MIP) for selective protein (haemoglobin) binding

Molecularly imprinted polymers (MIPs) are fast becoming alternatives to biological recognition materials, offering robustness and the ability to work in extreme environments. Here, a modified thymine-based nucleobase, with acrylamide at the 5-postion (AA-dT) was used as a co-monomer in the synthesis of a thin-film electropolymerised MIP system for the molecular recognition of the protein haemoglobin. The AA-dT co-monomer incorporated into a N-hydroxymethylacrylamide (NHMAm) MIP offered a two-fold superior binding affinity of the NHMAm only MIP, with K_D values of 0.72 μM and 1.67 μM, respectively. A unique AA-dT:NHMAm MIP bilayer was created in an attempt to increase the amount AA-dT incorporated into the film, and this obtained a respectable K_D value of 7.03 μM. All MIPs produced excellent selectivity for the target protein and when applied to a sensor platform (Surface Plasma Resonance), the limit of detection for the MIPs is in the nM range (3.87, 3.47, and 3.87 nM, for the NHMAm MIP, AA-dT:NHMAm MIP, and AA-dT:NHMAm MIP bilayer, respectively). The introduction of the modified thymine-based nucleobase offers a promising strategy for improving the properties of a MIP, allowing these MIPs to potentially be a highly robust and selective material for molecular recognition.

Upconversion Nanoparticles Encapsulated with Molecularly Imprinted Amphiphilic Copolymer as a Fluorescent Probe for Specific Biorecognition

A fluorescent probe for specific biorecognition was prepared by a facile method in which amphiphilic random copolymers were encapsulated with hydrophobic upconversion nanoparticles (UCNPs). This method quickly converted the hydrophobic UCNPs to hydrophilic UNCPs. Moreover, the self-folding ability of the amphiphilic copolymers allowed the formation of molecular imprinting polymers with template-shaped cavities. LiYF4:Yb3+/Tm3+@LiYF4:Yb3+ UCNP with up-conversion emission in the visible light region was prepared; this step was followed by the synthesis of an amphiphilic random copolymer, poly(methacrylate acid-co-octadecene) (poly(MAA-co-OD)). Combining the UCNPs and poly(MAA-co-OD) with the templates afforded a micelle-like structure. After removing the templates, UCNPs encapsulated with the molecularly imprinted polymer (MIP) (UCNPs@MIP) were obtained. The adsorption capacities of UCNPs@MIP bound with albumin and hemoglobin, respectively, were compared. The results showed that albumin was more easily bound to UCNPs@MIP than to hemoglobin because of the effect of protein conformation. The feasibility of using UCNPs@MIP as a fluorescent probe was also studied. The results showed that the fluorescence was quenched when hemoglobin was adsorbed on UCNPs@MIP; however, this was not observed for albumin. This fluorescence quenching is attributed to Förster resonance energy transfer (FRET) and overlap of the absorption spectrum of hemoglobin with the fluorescence spectrum of UCNPs@MIP. To our knowledge, the encapsulation approach for fabricating the UCNPs@MIP nanocomposite, which was further used as a fluorescent probe, might be the first report on specific biorecognition.

Human serum albumin-imprinted polymers with high capacity and selectivity for abundant protein depletion

Depletion of human serum albumin (HSA), the most abundant protein in human plasma, from serum/plasma is a prerequisite before their proteomic analysis. Molecularly imprinted polymers (MIPs) using HSA as a template have been designed for this purpose, but suffer from a low sorption capacity and low selectivity. Here, a new HSA-imprinted polymer was synthesized using N-isopropylacrylamide (NIPAM) as the main monomer; acrylamide (AAm), methacrylic acid (MAA), and dimethylaminoethyl methacrylate (DMAEMA) as functional monomers; and oligoglutamic acid-based peptide crosslinker (PC) as a crosslinker at pH 5.5. When pH is adjusted to 7.4, the peptide chains in the polymer change from a helical conformation to an extended coil conformation, and the polymer swells. Consequently, the template protein is removed completely. When pH is adjusted back to 5.5, the peptide chains fold back precisely to the helical conformation. Both the size and shape of the imprint cavities are restored. Therefore, the polymer rebinds the template protein selectively. Highest imprinting factor (IF) was observed at pH 5.5 at which the polymer was synthesized. The IF increases with the increasing number of glutamic acid residues in the PCs because of their increased degree of helicity at pH 5.5. No improvement in imprinting effect was observed when using a peptide crosslinker containing both L- and D-glutamic acid residues and hence incapable of folding into α-helix, further confirming the key role of the pH-induced helix-coil transition of the peptide chains. The MIP synthesized here presents a much higher affinity to HSA than the nontemplate proteins. It could be used repeatedly without evident decrease in sorption capacity. Because of the mild eluting conditions, the secondary structure of the extracted HSA protein remains unchanged. Finally, the MIP was used to deplete HSA from human serum. Because of its high sorption capacity and high selectivity, HSA was depleted completely and selectively. STATEMENT OF SIGNIFICANCE: A new molecularly imprinted polymer (MIP) using human serum albumin (HSA) as a template was synthesized using N-isopropylacrylamide (NIPAM) as the main monomer; acrylamide (AAm), methacrylic acid (MAA), and dimethylaminoethyl methacrylate (DMAEMA) as functional monomers; and oligoglutamic acid-based peptide crosslinker as a crosslinker. Because of the reversible and precise pH-induced helix-coil transition of the peptide chains, the template protein was removed facilely and completely under mild conditions. Simultaneously, a significant improvement in imprinting efficiency was obtained. The sorption capacity was as high as 648.05 mg/g and the imprinting factor was 7.9. Because of its high selectivity and high binding capacity, the MIP synthesized here is highly promising for the depletion of HSA, the most abundant protein in serum, which is a prerequisite for its proteomic analysis. For the first time, complete and selective depletion of HSA from human serum was achieved using a protein-imprinted polymer.

Metal-coded hydrogel magnetic molecularly imprinted polymer for preconcentration and cleanup of sarcosine: Determination in urine; coupled to on-column capillary electrophoresis

In this study, sarcosine metal-coded hydrogel magnetic molecularly imprinted polymer (Hydro-MeC-MMIP) has been fabricated and coupled to on-column derivatization capillary electrophoresis (CE). As a metal-coding approach, sarcosine-Cu²⁺-ligand (Sar-Cu²⁺-L) chelate complex was introduced as a template to overcome the problems associated with the fabrication of MMIP for a small molecule having limited functional groups such as sarcosine. To our best knowledge, it is the first time that methacrylamide (MA) coated Fe₃O₄ (Fe₃O₄@MA) with abounded reactive double-bound on the surface has been used as a magnetic core in the one-pot synthesis of MMIPs. As prepared, Hydro-MeC-MMIP was characterized by different microscopic, spectroscopic, and thermal gravimetric methods. Hydro-MeC-MMIP was used to extract and preconcentrate sarcosine in the urine sample with no treatment and dilution. Sarcosine was quantified by on-column derivatization capillary electrophoresis equipped with a photodiode array detector. A mixture of thirteen amino acids was separated with a total run time of 12 min. Three structural analogs, including alanine, sarcosine, and glycine, were significantly resolved. Under optimal experimental conditions, the method's detection and quantification limits were 9.93 and 33.10 ng mL^-1, respectively. The linear range of 50-2000 ng mL^-1 and 96% recovery, along with the relative standard deviation of 6.07% (n = 6) for the target amino acid, were obtained. This method provides a simple, low-cost, fast, and efficient tool for extracting and quantifying sarcosine in the urine. The present method can address inconsistency in evaluating sarcosine as a candidate biomarker for prostate cancer with a simple CE/UV; no need for a sophisticated detection system such as a mass spectrometer.

Green synthesis as a simple and rapid route to protein modified magnetic nanoparticles for use in the development of a fluorometric molecularly imprinted polymer-based assay for detection of myoglobin

We have developed a low-cost molecularly imprinted polymer (MIP)-based fluorometric assay to directly quantify myoglobin in a biological sample. The assay uses a previously unreported method for the development of microwave-assisted rapid synthesis of aldehyde functionalized magnetic nanoparticles, in just 20 min. The aldehyde functionalized nanoparticles have an average size of 7.5 nm ± 1.8 and saturation magnetizations of 31.8 emu g-1 with near-closed magnetization loops, confirming their superparamagnetic properties. We have subsequently shown that protein tethering was possible to the aldehyde particles, with 0.25 ± 0.013 mg of myoglobin adsorbed to 20 mg of the nanomaterial. Myoglobin-specific fluorescently tagged MIP (F-MIP) particles were synthesized and used within the assay to capture myoglobin from a test sample. Excess F-MIP was removed from the sample using protein functionalized magnetic nanoparticles (Mb-SPION), with the remaining sample analyzed using fluorescence spectroscopy. The obtained calibration plot of myoglobin showed a linear correlation ranging from 60 pg ml-1 to 6 mg ml-1 with the limit of detection of 60 pg ml-1. This method was successfully used to detect myoglobin in spiked fetal calf serum, with a recovery rate of more than 93%.

Synthesis, Characterization, and CO2/N2 Separation Performance of POEM-g-PAcAm Comb Copolymer Membranes

Alcohol-soluble comb copolymers were synthesized from rubbery poly(oxyethylene methacrylate) (POEM) and glassy polyacrylamide (PAcAm) via economical and facile free-radical polymerization. The synthesis of comb copolymers was confirmed by Fourier-transform infrared and proton nuclear magnetic resonance spectroscopic studies. The bicontinuous microphase-separated morphology and amorphous structure of comb copolymers were confirmed by wide-angle X-ray scattering, differential scanning calorimetry, and transmission electron microscopy. With increasing POEM content in the comb copolymer, both CO₂ permeability and CO₂/N₂ selectivity gradually increased. A mechanically strong free-standing membrane was obtained at a POEM:PAcAm ratio of 70:30 wt%, in which the CO₂ permeability and CO₂/N₂ selectivity reached 261.7 Barrer (1 Barrer = 10⁻¹⁰ cm³ (STP) cm cm⁻² s⁻¹ cmHg⁻¹) and 44, respectively. These values are greater than those of commercially available Pebax and among the highest separation performances reported previously for alcohol-soluble, all-polymeric membranes without porous additives. The high performances were attributed to an effective CO₂-philic pathway for the ethylene oxide group in the rubbery POEM segments and prevention of the N₂ permeability by glassy PAcAm chains.

Interaction of LiYF4:Yb3+/Er3+/Ho3+/Tm3+@LiYF4:Yb3+ upconversion nanoparticles, molecularly imprinted polymers, and templates

In this work, LiYF₄:Yb_0.25³⁺/Er_0.01³⁺/Tm_0.01³⁺/Ho_0.01³⁺@LiYF₄:Yb_0.2³⁺ upconverting nanoparticles (UCNP) were used as luminescent materials for the preparation of molecular imprinting polymer nanocomposites. Three luminescent molecularly imprinted polymer (MIP) nanocomposites were prepared by in situ polymerization. The relationship between the functional monomers, templates, and upconversion nanoparticles was investigated. Two hydrophilic monomers (acrylic acid (AA) and acrylamide (AAm)) and one hydrophobic monomer (N-tert-butylacrylamide (TBAm)) were employed as functional monomers, while one amino acid (cysteine) and two proteins (albumin and hemoglobin) were employed as the templates to investigate the effect of their interaction with LiYF₄:Yb³⁺/Er³⁺/Ho³⁺/Tm³⁺@LiYF₄:Yb³⁺ core/shell UCNPs on the polymerization process, luminescence properties, and adsorption capacity. The results showed that the UCNPs were embedded in the polymeric matrix to form an irregular quasimicrospherical UCNPs@MIP with diameters ranging from several hundred nanometers to several micrometers depending on the functional monomer. The quenching effect was more pronounced for the adsorption of hemoglobin with UCNPs@MIP compared to cysteine and albumin. In addition, the adsorption capacities of the AA- and AAm-made UCNPs@MIP were greater than those of TBAm-made UCNPs@MIP. The rebinding of the templates onto UCNPs@MIP was very fast and approached equilibrium within 30 min, indicating that the synthesized UCNPs@MIP can be employed as fluorescent probes to offer rapid detection of molecules.

In this work, LiYF₄:Yb_0.25³⁺/Er_0.01³⁺/Tm_0.01³⁺/Ho_0.01³⁺@LiYF₄:Yb_0.2³⁺ upconverting nanoparticles (UCNP) were used as luminescent materials for the preparation of molecular imprinting polymer nanocomposites.

A Portable Visual Sensor by Molecularly Imprinted Hydrogels for HRP Recognition

Background:

Molecular imprinting is a technology used to produce artificial receptors that simulate the molecular recognition in the nature and prepare the polymer network structure in the presence of template molecule. Molecularly imprinted visual sensor combines the advantages of specific recognition via molecular imprinting and fast response speed via visualization. The aims of this paper are to prepare a portable visual sensor for Horseradish Peroxidase (HRP) recognition based on molecularly imprinted hydrogel.

Methods:

At first, HRP-imprinted polyacrylamide hydrogels with 1 mm thickness were obtained by one-step synthesis via radical induced in-situ polymerization of acrylamide using acrylamide (AAm) as the functional monomer, N,N'-Methylenebisacrylamide (MBA) as the crosslink agent and HRP as the template molecule.

Results:

Compared with nonimprinted hydrogels, the HRP-imprinted hydrogel sensor showed significant color changes in response to the target HRP. This visual sensor was constructed based on 3, 3', 5, 5'- tetramethyl benzidine (TMB) - H2O2 color reaction system by HRP catalyzing to produce color change through digital photography and image analysis (RGB system). The HRP-imprinted hydrogel showed good response in the range of 0.001-0.5 mg/mL and had a significant specific recognition compared to other proteins via selective test.

Conclusion:

The proposed portable visual sensor could be used for qualitative and semi-quantitative analysis of HRP with high selectivity and reasonable regeneration. The sensor has the advantages of simple operation, low cost, no special equipment, and can be applied to serum sample with less sample consumption and no need of sample preparation. It has wide application prospects in microfluidic devices, biomimetic sensors, flexible biosensor and membrane separation technology.

Turn-on fluorescence detection of protein by molecularly imprinted hydrogels based on supramolecular assembly of peptide multi-functional blocks

Synthetic receptors for biomacromolecules lack the supramolecular self-assembly behavior typical of biological systems. Here we propose a new method for the preparation of protein imprinted polymers based on the specific interaction of a peptide multi-functional block with a protein target. This peptide block contains a protein-binding peptide domain, a polymerizable moiety at the C-terminus and an environment-sensitive fluorescent molecule at the N-terminus. The method relies on a preliminary step consisting of peptide/protein supramolecular assembly, followed by copolymerization with the most common acrylate monomers (acrylamide, acrylic acid and bis-acrylamide) to produce a protein imprinted hydrogel polymer. Such a peptide block can function as an active assistant recognition element to improve affinity, and guarantees its effective polymerization at the protein/cavity interface, allowing for proper placement of a dye. As a proof of concept, we chose Bovine Serum Albumin (BSA) as the protein target and built the peptide block around a BSA binding dodecapeptide, with an allyl group as the polymerizable moiety and a dansyl molecule as the responsive dye. Compared to conventional approaches these hydrogels showed higher affinity (more than 45%) and imprinted sensitivity (about twenty fold) to the target, with a great BSA selectivity with respect to ovalbumin (α = 1.25) and lysozyme (α = 6.02). Upon protein binding, computational and experimental observations showed a blue shift of the emission peak (down to 440 nm) and an increase of fluorescence emission (twofold) and average lifetime (Δτ = 4.3 ns). Such an approach generates recognition cavities with controlled chemical information and represents an a priori method for self-responsive materials. Provided a specific peptide and minimal optimization conditions are used, such a method could be easily implemented for any protein target.

Generation of ribosome imprinted polymers for sensitive detection of translational responses

Whilst the profiling of the transcriptome and proteome even of single-cells becomes feasible, the analysis of the translatome, which refers to all messenger RNAs (mRNAs) engaged with ribosomes for protein synthesis, is still an elaborate procedure requiring millions of cells. Herein, we report the generation and use of "smart materials", namely molecularly imprinted polymers (MIPs) to facilitate the isolation of ribosomes and translated mRNAs from merely 1,000 cells. In particular, we show that a hydrogel-based ribosome imprinted polymer could recover ribosomes and associated mRNAs from human, simian and mice cellular extracts, but did not selectively enrich yeast ribosomes, thereby demonstrating selectivity. Furthermore, ribosome imprinted polymers enabled the sensitive measurement of an mRNA translational regulatory event, requiring 1,000-fold less cells than current methodologies. These results provide first evidence for the suitability of MIPs to selectively recover ribonucleoprotein complexes such as ribosomes, founding a novel means for sensitive detection of gene regulation.

Imprinting Technology in Electrochemical Biomimetic Sensors

Biosensors are a promising tool offering the possibility of low cost and fast analytical screening in point-of-care diagnostics and for on-site detection in the field. Most biosensors in routine use ensure their selectivity/specificity by including natural receptors as biorecognition element. These materials are however too expensive and hard to obtain for every biochemical molecule of interest in environmental and clinical practice. Molecularly imprinted polymers have emerged through time as an alternative to natural antibodies in biosensors. In theory, these materials are stable and robust, presenting much higher capacity to resist to harsher conditions of pH, temperature, pressure or organic solvents. In addition, these synthetic materials are much cheaper than their natural counterparts while offering equivalent affinity and sensitivity in the molecular recognition of the target analyte. Imprinting technology and biosensors have met quite recently, relying mostly on electrochemical detection and enabling a direct reading of different analytes, while promoting significant advances in various fields of use. Thus, this review encompasses such developments and describes a general overview for building promising biomimetic materials as biorecognition elements in electrochemical sensors. It includes different molecular imprinting strategies such as the choice of polymer material, imprinting methodology and assembly on the transduction platform. Their interface with the most recent nanostructured supports acting as standard conductive materials within electrochemical biomimetic sensors is pointed out.

Limiting the valence: advancements and new perspectives on patchy colloids, soft functionalized nanoparticles and biomolecules

Artistic representation of limited valance units consisting of a soft core (in blue) and a small number of flexible bonding patches (in orange).

Selective extraction of proteins and other macromolecules from biological samples using molecular imprinted polymers

The accurate determination of intact macromolecules in biological samples, such as blood, plasma, serum, urine, tissue and feces is a challenging problem. The increased interest in macromolecules both as candidate drugs and as biomarkers for diagnostic purposes means that new method development approaches are needed. This review charts developments in the use of molecularly imprinted polymers first for small-molecular-mass compounds then for proteins and other macromolecules. Examples of the development of molecularly imprinted polymers for macromolecules are highlighted. The two main application areas to date are sensors and separation science, particularly SPE. Examples include peptides and polypeptides, lysozyme, hemoglobin, ovalbumin, bovine serum albumin and viruses.