Electrosynthesis of Nanostructured, Imprinted Poly(hydroxymethyl 3,4-ethylenedioxythiophene) for the Ultrasensitive Electrochemical Detection of Urinary Progesterone

Sensing of C-Reactive Protein Using an Extended-Gate Field-Effect Transistor with a Tungsten Disulfide-Doped Peptide-Imprinted Conductive Polymer Coating

C-reactive protein (CRP) is a non-specific biomarker of inflammation and may be associated with cardiovascular disease. In recent studies, systemic inflammatory responses have also been observed in cases of coronavirus disease 2019 (COVID-19). Molecularly imprinted polymers (MIPs) have been developed to replace natural antibodies with polymeric materials that have low cost and high stability and could thus be suitable for use in a home-care system. In this work, a MIP-based electrochemical sensing system for measuring CRP was developed. Such a system can be integrated with microfluidics and electronics for lab-on-a-chip technology. MIP composition was optimized using various imprinting template (CRP peptide) concentrations. Tungsten disulfide (WS₂) was doped into the MIPs. Doping not only enhances the electrochemical response accompanying the recognition of the template molecules but also raises the top of the sensing range from 1.0 pg/mL to 1.0 ng/mL of the imprinted peptide. The calibration curve of the WS₂-doped peptide-imprinted polymer-coated electrodes in the extended-gate field-effect transistor platform was obtained and used for the measurement of CRP concentration in real human serum.

MXene/carbon nanohorns decorated with conductive molecularly imprinted poly(hydroxymethyl-3,4-ethylenedioxythiophene) for voltammetric detection of adrenaline

A novel molecularly imprinted sensor was developed for the voltammetric determination of adrenaline (AD). MXene/carbon nanohorn (MXene/CNH) composite with good electric conductivity and enormous accessible active sites was firstly introduced as catalytic substrate. Subsequently, molecularly imprinted polymer (MIP) film was fabricated in mixed solutions containing hydroxymethyl-3,4-ethylenedioxythiophene (functional monomer) and AD (template) through electro-polymerization process. A molecularly imprinted sensor was formed after removing the template. The morphology and elemental composition of the prepared composites were studied by scanning electron microscopy and X-ray photoelectron spectroscopy. Cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical performance of the molecularly imprinted sensors. Under optimized conditions, the designed sensor displays a wide linear range from 1.0 nM to 60.0 μM and a low limit of detection of 0.3 nM. The developed sensor also presents good selectivity, reproducibility and long-term stability, and satisfactory feasibility in practical sample analysis. MXene/carbon nanohorns decorated with conductive molecularly imprinted poly(hydroxymethyl-3,4-ethylenedioxythiophene) was proposed for highly sensitive and selective detection of adrenaline.

Transition metal dichalcogenides to optimize the performance of peptide-imprinted conductive polymers as electrochemical sensors

Molecularly imprinted polymer (MIP)-based electrochemical sensors for the protein α-synuclein (a marker for Parkinson's disease) were developed using a peptide epitope from the protein. MIPs doped with various concentrations and species of transition metal dichalcogenides (TMDs) to enhance conductivity were electropolymerized with and without template molecules. The current during the electropolymerization was compared with that associated with the electrochemical response (at 0.24~0.29 V vs. ref. electrode) to target peptide molecules in the finished sensor. We found that this relationship can aid in the rational design of conductive MIPs for the recognition of biomarkers in biological fluids. The sensing range and limit of detection of TMD-doped imprinted poly(AN-co-MSAN)-coated electrodes were 0.001-100 pg/mL and 0.5 fg/mL (SNR = 3), respectively. To show the potential applicability of the MIP electrochemical sensor, cell culture medium from PD patient-specific midbrain organoids generated from induced pluripotent stem cells was analyzed. α-Synuclein levels were found to be significantly reduced in the organoids from PD patients, compared to those generated from age-matched controls. The relative standard deviation and recovery are less than 5% and 95-115%, respectively. Preparation of TMD-doped α-synuclein (SNCA) peptide-imprinted poly(AN-co-MSAN)-coated electrodes.

Synthesis of MOF525/PEDOT Composites as Microelectrodes for Electrochemical Sensing of Dopamine

Dopamine (DA) is an important neurotransmitter responsible for the functions and activities of multiple systems in human. Electrochemical detection of DA has the advantages of fast analysis and cost-effectiveness, while a regular electrode probe is restricted to laboratory use because the probe size is too large to be suitable for an in vivo or in vitro analysis. In this study, we have developed porphyrin-based metal organic framework (MOF525) and poly(3,4-ethylenedioxythiophene) (PEDOT)-based composites to modify microelectrode for DA detection. Two types of PEDOT monomers with different functional groups were investigated in this study. By varying the monomer ratios, electrolyte concentrations, and electropolymerization temperature, it was found that the PEDOT monomer containing carboxylic group facilitated the formation of regular morphology during the electropolymerization process. The uniform morphology of the PEDOT promoted the electron transmission efficiency in the same direction, while the MOF525 provided a large reactive surface area for electrocatalysis of DA. Thus, the MOF525/PEDOT composite improved the sensitivity-to-noise ratio of DA signaling, where the sensitivity reached 11 nA/μM in a good linear range of 4–100 µM. In addition, porphyrin-based MOF could also increase the selectivity to DA against other common clinical interferences, such as ascorbic acid and uric acid. The as-synthesized microelectrode modified with MOF525/PEDOT in this study exhibited great potential in real time analysis.

The biomimetic detection of progesterone by novel bifunctional group monomer based molecularly imprinted polymers prepared in UV light

A novel itaconic acid based progesterone imprinted biosensor was prepared via a reversible addition chain transfer mechanism and surface plasmon resonance.

A multichannel system integrating molecularly imprinted conductive polymers for ultrasensitive voltammetric determination of four steroid hormones in urine

This work reports on a modularized electrochemical method for the determination of the hormones cortisol, progesterone, testosterone and 17β-estradiol in urine. These hormones were employed as templates when generating molecular imprints from aniline and metanilic acid by electropolymerization on the surface of screen-printed electrodes. The electrically conductive imprint was characterized by SEM, AFM and cyclic voltammetry. A four-channel system was then established to enable simultaneous determination of the hormones by cyclic voltammetry. The detection limits for cortisol, progesterone, testosterone and 17β-estradiol are as low as 2, 2.5, 10 and 9 ag·mL^-1 (for S/N = 3). Graphical abstract A four-channel system was established to enable simultaneous determination of 4 steroid hormones by cyclic voltammetry and by using moleculalry imprinted polymers.

Electrochemical SERS for in Situ Monitoring the Redox States of PEDOT and Its Potential Application in Oxidant Detection

In response to recent developments for applying conducting polymers on various biomedical applications, the development of characterization techniques for evaluating the states of conducting polymers in liquids is beneficial to the applications of these materials. In this study, we propose a platform using electrochemical surface-enhanced Raman scattering (EC-SERS) technology, which allows a direct measurement of the redox states of conducing polymers in liquids. A thiophene-based conducting polymer, hydroxymethyl poly(3,4-ethylenedioxythiophene) or poly(EDOT-OH), was used to demonstrate this concept. Poly(EDOT-OH) films were coated on Au nanoparticle-coated ITO glass as SERS-active substrates. Taking the advantage of Raman enhancement, we can in situ and clearly monitor the redox behavior of poly(EDOT-OH) in aqueous solutions. The Raman peak intensity decreases as the poly(EDOT-OH) film is oxidized. Furthermore, we demonstrated our idea to utilize this phenomenon as the sensing mechanism for oxidant detection. The Raman intensity of conducting polymers reduces faster when oxidants exist, and we obtain a quantitative analysis for the detection of oxidants. Moreover, the oxidized poly(EDOT-OH) films can be reused for detection of oxidants simply by applying a reduction potential to activate the poly(EDOT-OH) films. The film stability was also confirmed, and the detection of two other oxidants, namely ammonium persulfate and iron chloride, were also demonstrated. The results show different SERS spectra of poly(EDOT-OH) films oxidized by using different oxidants. Besides, the oxidized films can be easily recovered simply by applying a cathodic potential, which allows repeating usage and makes it possible for continuous monitoring applications. To the best of our knowledge, this is the first time to apply PEDOT's Raman feature for detection purposes.

Molecularly Imprinted Polymers for the Selective Extraction of Bisphenol A and Progesterone from Aqueous Media

This paper describes the development of a novel sorbent for selective extraction of endocrine disruptors (EDs) from aqueous media. The main goal was to obtain sufficient molecularly imprinted polymers (MIPs) for selective detection, preconcentration, and extraction of EDs such as bisphenol A (BPA) and progesterone (PG). Series of MIPs and their analogues, non-molecularly imprinted polymers (NIPs), were synthesised following a non-covalent imprinting strategy based on radical polymerisation. Sets of synthesis were performed in order to optimise variables of the polymerisation including solvent, cross-linker, and template ratio. The retention capacity of MIPs was determined using HPLC in the range of 33.3% to 96.6% and 32.5% to 96% for BPA and PG, respectively. The adsorption mechanism was studied by isothermal and kinetic assays. The kinetic analysis showed a high retention capacity within 15 min of contact. The polymer yield was obtained in the range of 30% to 100%. Additionally, there was no significant cross-reactivity observed upon testing MIPs with structural analogues and other endocrine disruptors instead of target molecules. The results also revealed the high importance of different concentrations of cross-linker and solvent during the polymerisation. Firstly, the pre-organisation of complementary functional groups, which were present in the polymerisation mixture, and secondly, selective cavity formation for target molecules.