Label-free detection of DNA hybridization based on poly(indole-5-carboxylic acid) conducting polymer

Conjugated Polymers for Aptasensing Applications

Rapid and specific assaying of molecules that report on a pathophysiological condition, environmental pollution, or drug concentration is pivotal for establishing efficient and accurate diagnostic systems. One of the main components required for the construction of these systems is the recognition element (receptor) that can identify target analytes. Oligonucleotide switching structures, or aptamers, have been widely studied as selective receptors that can precisely identify targets in different analyzed matrices with minimal interference from other components in an antibody-like recognition process. These aptasensors, especially when integrated into sensing platforms, enable a multitude of sensors that can outperform antibody-based sensors in terms of flexibility of the sensing strategy and ease of deployment to areas with limited resources. Research into compounds that efficiently enhance signal transduction and provide a suitable platform for conjugating aptamers has gained huge momentum over the past decade. The multifaceted nature of conjugated polymers (CPs), notably their versatile electrical and optical properties, endows them with a broad range of potential applications in optical, electrical, and electrochemical signal transduction. Despite the substantial body of research demonstrating the enhanced performance of sensing devices using doped or nanostructure-embedded CPs, few reviews are available that specifically describe the use of conjugated polymers in aptasensing. The purpose of this review is to bridge this gap and provide a comprehensive description of a variety of CPs, from a historical viewpoint, underpinning their specific characteristics and demonstrating the advances in biosensors associated with the use of these conjugated polymers.

Poly(indole-5-carboxylic acid)/reduced graphene oxide/gold nanoparticles/phage-based electrochemical biosensor for highly specific detection of Yersinia pseudotuberculosis

Yersinia pseudotuberculosis is an enteric bacterium causing yersiniosis in humans. The existing Yersinia pseudotuberculosis detection methods are time-consuming, requiring a sample pretreatment step, and are unable to discriminate live/dead cells. The current work reports a phage-based electrochemical biosensor for rapid and specific detection of Yersinia pseudotuberculosis. The conductive poly(indole-5-carboxylic acid), reduced graphene oxide, and gold nanoparticles are applied for surface modification of the electrode. They possess ultra-high redox stability and retain 97.7% of current response after performing 50 consecutive cycles of cyclic voltammetry.The specific bacteriophages vB_YepM_ZN18 we isolated from hospital sewage water were immobilized on modified electrodes by Au-NH₂ bond between gold nanoparticles and phages. The biosensor fabricated with nanomaterials and phages were utilized to detect Yersinia pseudotuberculosis successfully with detection range of 5.30 × 10² to 1.05 × 10⁷ CFU mL^-1, detection limit of 3 CFU mL^-1, and assay time of 35 min. Moreover, the biosensor can specifically detect live Yersinia pseudotuberculosis without responding to phage-non-host bacteria and dead Yersinia pseudotuberculosis cells. These results suggest that the proposed biosensor is a promising tool for the rapid and selective detection of Yersinia pseudotuberculosis in food, water, and clinical samples.

A highly sensitive electrochemiluminescence immunosensor for h-FABP determination based on self-enhanced luminophore coupled with ultrathin 2D nickel metal-organic framework nanosheets

In this work, a novel ECL immunosensor based on self-enhanced luminophore and ultrathin 2D nickel MOF nanosheets was fabricated for sensitive and specific detection of h-FABP. Initially, the porous ultrathin Ni-TCPP (Fe) nanosheets with high specific surface area and plentiful active sites were newly synthesized, which could enhance ECL signal of luminol by the superior peroxidase mimics activity towards H₂O₂ decomposition. Then, PEI and luminol were simultaneously immobilized on Ni-TCPP (Fe) nanosheets to construct self-enhanced solid state luminophore (Ni-TCPP (Fe)-PEI-Lum), possessing desirable stability and high ECL efficiency. Furthermore, poly (indole-5-carboxylic acid) (PICA) worked as substrate with outstanding conductivity and abundant binding sites to improve sensitivity. Under optimal conditions, the designed ECL immunosensor exhibited a wide dynamic range from 100 fg mL^-1 to 100 ng mL^-1 and a low detection limit of 44.5 fg mL^-1. In addition, the ECL immunosensor behaved excellent specificity and was successfully applied to detect target h-FABP protein in complex physiological matrix. Therefore, this work may provide an alternative method for biomarker detection in clinical diagnosis and expand the application potential of 2D MOF nanosheets in ECL technique.

Electrochemical DNA sensors based on spatially distributed redox mediators: challenges and promises

DNA and aptasensors are widely used for fast and reliable detection of disease biomarkers, pharmaceuticals, toxins, metabolites and other species necessary for biomedical diagnostics. In the overview, the concept of spatially distributed redox mediators is considered with particular emphasis to the signal generation and biospecific layer assembling. The application of non-conductive polymers bearing redox labels, supramolecular carriers with attached DNA aptamers and redox active dyes and E-sensor concept are considered as examples of the approach announced.

Label-free impedimetric detection of Listeria monocytogenes based on poly-5-carboxy indole modified ssDNA probe

Listeria monocytogenes is a life threatening pathogenic bacteria concerned with human health. The accurate and rapid detection of L. monocytogenes is required for preventing of listeriosis. In this study, DNA sensing probe based on conducting polymer poly-5-carboxy indole (5C Pin) was developed for the detection of L. monocytogenes hlyA gene responsible for pathogenicity. The probe sequences (24 mer ssDNA) were covalently immobilized on 5C Pin via N-(3-dimethylaminopropyl)-N'-ethylcarbodiimidehydrochloride (EDC) and N-hydroxysuccinimide (NHS). The probe having ssDNA was further hybridized with the target DNA sequence. Electrochemical impedance spectroscopic study was carried out to determine the extent of DNA hybridization over the probe. Significant change was observed in the impedance spectra before and after hybridization of ssDNA immobilized over the probe with the target DNA. RCT (charge transfer resistance) was estimated from the Nyquist plot (impedance plot) for target DNA (hlyA gene) in the solution. RCT vs. logarithmic concentrations of the target (genomic) DNA plot showed a linear range (1 × 10(-4) to 1 × 10(-12)M) in case hybridization was performed under optimized conditions. The method proposed, is simple, free from any label, and highly sensitive for the detection of L. monocytogenes in environmental and clinical samples.

Electrochemical DNA hybridization sensors based on conducting polymers

Conducting polymers (CPs) are a group of polymeric materials that have attracted considerable attention because of their unique electronic, chemical, and biochemical properties. This is reflected in their use in a wide range of potential applications, including light-emitting diodes, anti-static coating, electrochromic materials, solar cells, chemical sensors, biosensors, and drug-release systems. Electrochemical DNA sensors based on CPs can be used in numerous areas related to human health. This review summarizes the recent progress made in the development and use of CP-based electrochemical DNA hybridization sensors. We discuss the distinct properties of CPs with respect to their use in the immobilization of probe DNA on electrode surfaces, and we describe the immobilization techniques used for developing DNA hybridization sensors together with the various transduction methods employed. In the concluding part of this review, we present some of the challenges faced in the use of CP-based DNA hybridization sensors, as well as a future perspective.

Electrochemically reduced graphene oxide supported poly(indole-5-carboxylic acid) nanocomposite for genosensing application

An ultrasensitive DNA electrochemical biosensing interface was developed for rapid determination of BCR/ABL fusion gene by employing ERGNO supported PICA.

Simple Label-Free Femtomolar DNA Detection Based on a Nanostructure Composite Material: MWNT-Doped Poly(indole-6-carboxylic acid)

A nanostructure composite material consisting of poly(indole-6-carboxylic acid) (PICA) and carboxylic groups ended multiwall carbon nanotubes (MWNTs) was directly electrosynthesized from indole-6-carboxylic acid (ICA) monomer and MWNTs in one step, in which MWNTs was also used as supporting electrolytes. And a simple electrochemical sensor for recognition of target DNA related to hepatitis B virus (HBV) was directly fabricated by means of this composite material. The corresponding detection limit is 2.0 fmol L^-1. This interesting conducting polymer with a very large surface area will provide new insights into how a biosensor is designed.

An ionic liquid supported CeO2 nanoshuttles-carbon nanotubes composite as a platform for impedance DNA hybridization sensing

A novel nanocomposite membrane, comprising of nanosized shuttle-shaped cerium oxide (CeO(2)), single-walled carbon nanotubes (SWNTs) and hydrophobic room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF(6)), was developed on the glassy carbon electrode (GCE) for electrochemical sensing of the immobilization and hybridization of DNA. The properties of the CeO(2)-SWNTs-BMIMPF(6)/GCE, the characteristics of the immobilization and hybridization of DNA were studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) using [Fe(CN)(6)](3-/4-) as the redox indicator. The synergistic effect of nano-CeO(2), SWNTs and RTIL could dramatically enhance the sensitivity of DNA hybridization recognition. The electron transfer resistance (R(et)) of the electrode surface increased after the immobilization of probe ssDNA on the CeO(2)-SWNTs-BMIMPF(6) membrane and rose further after the hybridization of the probe ssDNA with its complementary sequence. The remarkable difference between the R(et) value at the probe DNA-immobilized electrode and that at the hybridized electrode could be used for label-free EIS detection of the target DNA. The sequence-specific DNA of phosphoenolpyruvate carboxylase (PEPCase) gene from transgenically modified rape was detected by this DNA electrochemical biosensor. Under optimal conditions, the dynamic range for detecting the sequence-specific DNA of the PEPCase gene was from 1.0x10(-12) mol/L to 1.0x10(-7) mol/L, and the detection limit was 2.3x10(-13) mol/L, suggesting that the CeO(2)-SWNTs-BMIMPF(6) nanocomposite hold great promises for the applications in sensitive electrochemical biosensor.