Preparation of molecularly imprinted polymer/Au nanohybrids as an effective biosensing material

Single-Component Electroactive Polymer Architectures for Non-Enzymatic Glucose Sensing

Organic mixed ionic-electronic conductors (OMIECs) have emerged as promising materials for biological sensing, owing to their electrochemical activity, stability in an aqueous environment, and biocompatibility. Yet, OMIEC-based sensors rely predominantly on the use of composite matrices to enable stimuli-responsive functionality, which can exhibit issues with intercomponent interfacing. In this study, an approach is presented for non-enzymatic glucose detection by harnessing a newly synthesized functionalized monomer, EDOT-PBA. This monomer integrates electrically conducting and receptor moieties within a single organic component, obviating the need for complex composite preparation. By engineering the conditions for electrodeposition, two distinct polymer film architectures are developed: pristine PEDOT-PBA and molecularly imprinted PEDOT-PBA. Both architectures demonstrated proficient glucose binding and signal transduction capabilities. Notably, the molecularly imprinted polymer (MIP) architecture demonstrated faster stabilization upon glucose uptake while it also enabled a lower limit of detection, lower standard deviation, and a broader linear range in the sensor output signal compared to its non-imprinted counterpart. This material design not only provides a robust and efficient platform for glucose detection but also offers a blueprint for developing selective sensors for a diverse array of target molecules, by tuning the receptor units correspondingly.

A new copper nanocluster surface molecular imprinted polymethacrylic acid probe for ultratrace trichlorophenol based on in situ-generated nanogold SPR effects

A new coinage metal nanocluster surface molecularly imprinted polymethacrylic acid nanoprobe (NC@MIP) for the selective determination of 2,4,6-trichlorophenol (TCP) was prepared via microwave synthesis using 2,4,6-trichlorophenol as a template molecule, copper nanoclusters (CuNC) as a nanosubstrate, and methacrylic acid as a polymer monomer. It was found that the copper nanocluster MIP (CuNC@MIP) shows the strongest catalytic performance for the reduction of HAuCl4 by hydrazine hydrate for the on-site generation of gold nanoparticles (AuNPs) with the surface plasmon resonance (SPR) effects of resonance surface-enhanced Raman scattering (SERS) and resonance Rayleigh scattering (RRS) as well as absorption (Abs). When TCP was added, the CuNC@MIP nanoprobe and TCP-formed CuNC@MIP-TCP nanoenzyme with stronger catalytic activity generated more AuNPs, and the trimodal analytical signal was enhanced linearly. Therefore, a new SERS/RRS/Abs trimodal sensing platform for TCP was constructed, which was simple, rapid, sensitive, and selective. For each mode, the linear ranges were 0.0075-0.075, 0.010-0.10, and 0.010-0.10 nmol L-1, and the detection limits were 0.0010, 0.021, and 0.043 nmol L-1, respectively. The relative deviation of TCP in different water quality was 0.47%-2.5% and the recovery rate was 94.6%-108.6%.

Molecularly imprinted polymers as effective capturing receptors in a pseudo-ELISA immunoassay for procalcitonin detection in veterinary species

In this study, a new sandwich-type immunoenzymatic assay, based on a molecularly imprinted polymer (MIP) as an artificial antibody (pseudo-ELISA), was developed for the determination of procalcitonin (PCT) in veterinary species. The quantification of PCT in human medicine represents the state of the art for the diagnosis of sepsis; instead the clinical studies on the relevance of PCT as a sepsis predictor in veterinary patients are few, likely due to the total absence of validated assays. MIPs have been widely used as antibody mimics for important applications, and MIP-based sandwich assays have emerged as promising analytical tools for the detection of disease biomarkers. Herein, a polynorepinephrine (PNE)-based imprinted film was directly synthesized on the well surface of a 96-well plate. Subsequently, based on a commercial ELISA kit, the PCT quantification was accomplished via a colorimetric sandwich assay by replacing the capture antibody of the kit with the PNE-based MIP. This method was performed to detect canine and equine PCT in buffer and in plasma samples. Under optimal conditions, the results obtained in plasma samples showed a limit of detection (LOD) of 5.87 ng mL^-1 and a reproducibility (CV_av%) of 10.0% for canine samples, while a LOD = 4.46 ng mL^-1 and CV_av% = 7.61% were obtained for equine samples.

A molecularly imprinted biosensor based on water-compatible and electroactive polymeric nanoparticles for lysozyme detection

A molecularly imprinted biosensor for lysozyme based on the polymer nanoparticles self-assembled from water-soluble and electroactive poly (γ-glutamic acid) modified with 3-aminothiophene copolymer were prepared. The water-soluble copolymer made imprinting of lysozyme in aqueous solution possible and thus facilitated improvement of the activity of LYS. Subsequent electro-polymerization not only locked the recognition site between copolymer and lysozyme but also created a conductive polymer network, which can enhance the electron transfer rate and increase the conductivity of the film. The prepared molecularly imprinted biosensor exhibited a wide linear range from 1 × 10^-10 to 1 × 10^-5 mg mL^-1, and satisfactory selectivity, stability, repeatability for lysozyme detection.

Sensitive 'two-steps' competitive assay for gonadotropin-releasing hormone detection via SPR biosensing and polynorepinephrine-based molecularly imprinted polymer

The work reports an innovative bioassay for the detection of gonadorelin in urine, a gonadotropin-releasing hormone agonist widely used in fertility medicine and to treat hormonal dysfunctions. Gonadorelin is also a synthetic hormone listed by the World Anti-Doping Agency (WADA) and of interest in anti-doping controls. The main novelty relies on the development of a biocompatible, stable, and low-cost biomimetic receptor alternative to classic antibodies. Starting from norepinephrine monomer, a highly selective and sensitive molecularly imprinted polymer (MIP) was developed and optimized for optical real-time and label-free SPR biosensing. The selectivity has been addressed by testing a series of peptides, from high to low similarity, both in terms of molecular weight and primary sequence. Due to the very low molecular weight of gonadorelin (1182 Da), a 'two-steps' competitive assay was developed. Particular attention has been paid to the design of the competitor and its binding affinity constant towards the MIP, being a key step for the success of the competitive strategy. The SPR assay was first optimized in standard conditions and finally applied to untreated urine samples, achieving the sensitivity required by WADA guidelines. The MIP, tested in parallel with a monoclonal antibody, gave comparable results in terms of affinity constants and selectivity towards possible interfering analytes. However, the biomimetic receptor appears clearly superior in terms of sensitivity and reproducibility. This, together with its preparation simplicity, the extremely low-cost of the monomer and its reusability for hundreds of measurements, make polynorepinephrine-based MIPs powerful rivals to immune-based approaches in the near future for similar applications.

Molecular imprinting on PtPd nanoflowers for selective recognition and determination of hydrogen peroxide and glucose

PtPd nanoflowers (PtPd NFs) exhibit intrinsic peroxidase-like activity as nanozymes, but the nanozymes lack substrate specificity and have low catalytic activity. Herein, a molecularly imprinted nanogel on PtPd NFs was prepared by using 3,3',5,5'-tetramethylbenzidine (TMB) as the template through the aqueous precipitation polymerization method. After the TMB was washed out, many substrate binding pockets were retained in the PtPd NFs. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and powder X-ray diffraction (XRD) were employed to characterize the molecularly imprinted polymer (MIP) PtPd nanoflowers (T-MIP-PtPd NFs). The obtained T-MIP-PtPd NFs exhibited enhanced catalytic activity and specific recognition for TMB. Compared with PtPd NFs, T-MIP-PtPd NFs showed a linear range from 0.01-5000 μM and a detection limit of 0.005 μM toward the detection of H2O2. Glucose can also be sensitively detected through cascade reaction by the T-MIP-PtPd NFs and glucose oxidase. Therefore, molecular imprinting on nanozymes technology shows promising application in biocatalysis and sensing fields.

Biosensor Applications of Electrodeposited Nanostructures

The development of biosensors for a range of analytes from small molecules to proteins to oligonucleotides is an intensely active field. Detection methods based on electrochemistry or on localized surface plasmon responses have advanced through using nanostructured electrodes prepared by electrodeposition, which is capable of preparing a wide range of different structures. Supported nanoparticles can be prepared by electrodeposition through applying fixed potentials, cycling potentials, and fixed current methods. Nanoparticle sizes, shapes, and surface densities can be controlled, and regular structures can be prepared by electrodeposition through templates. The incorporation of multiple nanomaterials into composite films can take advantage of the superior and potentially synergistic properties of each component. Nanostructured electrodes can provide supports for enzymes, antibodies, or oligonucleotides for creating sensors against many targets in areas such as genomic analysis, the detection of protein antigens, or the detection of small molecule metabolites. Detection can also be performed using electrochemical methods, and the nanostructured electrodes can greatly enhance electrochemical responses by carefully designed schemes. Biosensors based on electrodeposited nanostructures can contribute to the advancement of many goals in bioanalytical and clinical chemistry.