Spatially hierarchical nano-architecture for real time detection of Interleukin-8 cancer biomarker.

In the present work we have developed two hierarchical nano-architectures based electrochemical immunosensors for the detection of interleukin-8 (IL-8) cytokine tumor biomarker. A comparative study has been performed for spatial nano-architectures and their relative sensing to establish the model for real time monitoring. With the first platform, the recognition layer consisted with immobilised IL-8 on aminothiol modified gold electrodes. In the second approach, the activated multi walled carbon nanotubes (MWCNT-COOH) were added in the functionalisation process by covalent attachment between the functionalities NH2 of aminothiol and the functionalities COOH of carbon nanotubes. The surface topology of the recognition layer has been characterised by atomic force spectroscopy (AFM) and contact angle (CA) measurements. The electrochemical response of the developed sensor was measured by electrochemical impedance spectroscopy (EIS). A side-by-side comparison showed that aminothiol/activated MWCNTs/anti-IL-8 based impedimetric immunosensor exhibits high reproducibility (The relative standard deviation (R.S.D) = 3.2%, n = 3) with high stability. The present sensor allows evaluating a lower detection limit of 0.1 pg mL-1 with a large dynamic sensitivity range from 1 pg mL-1to 1000 pg mL-1 covering the entire clinical therapeutic window. The developed MWCNTs based immunosensor has been calibrated by determining IL-8 in artificial plasma and showed a selective response to IL-8 even in the interfering environment of other cytokines such as Interleukin-1 (IL-1) and Interleukin-6 (IL-6).

Development of an Efficient Voltammetric Sensor for the Monitoring of 4-Aminophenol Based on Flexible Laser Induced Graphene Electrodes Modified with MWCNT-PANI.

Sensitive electrodes are of a great importance for the realization of highly performant electrochemical sensors for field application. In the present work, a laser-induced carbon (LIC) electrode is proposed for 4-Aminophenol (4-AP) electrochemical sensors. The electrode is patterned on a commercial low-cost polyimide (Kapton) sheet and functionalized with a multi-walled carbon nanotubes polyaniline (MWCNT-PANI) composite, realized by an in-situ-polymerization in an acidic medium. The LIC electrode modified with MWCNT-PAPNI nanocomposite was investigated by SEM, AFM, and electrochemically in the presence of ferri-ferrocyanide [Fe(CN)6]3-/4- by cyclic voltammetry and impedance spectroscopy. The results show a significant improvement of the electron transfer rate after the electrode functionalization in the presence of the redox mediators [Fe(CN)6]3-/4-, related directly to the active surface, which itself increased by about 18.13% compared with the bare LIG. The novel electrode shows a good reproducibility and a stability for 20 cycles and more. It has a significantly enhanced electro-catalytic activity towards electrooxidation reaction of 4-AP inferring positive synergistic effects between carbon nanotubes and polyaniline PANI. The presented electrode combination LIC/MWCNT-PANI exhibits a detection limit of 0.006 µM for the determination of 4-AP at concentrations ranging from 0.1 µM to 55 µM and was successfully applied for the monitoring in real samples with good recoveries.

A Review of Nanocomposite-Modified Electrochemical Sensors for Water Quality Monitoring.

Electrochemical sensors play a significant role in detecting chemical ions, molecules, and pathogens in water and other applications. These sensors are sensitive, portable, fast, inexpensive, and suitable for online and in-situ measurements compared to other methods. They can provide the detection for any compound that can undergo certain transformations within a potential window. It enables applications in multiple ion detection, mainly since these sensors are primarily non-specific. In this paper, we provide a survey of electrochemical sensors for the detection of water contaminants, i.e., pesticides, nitrate, nitrite, phosphorus, water hardeners, disinfectant, and other emergent contaminants (phenol, estrogen, gallic acid etc.). We focus on the influence of surface modification of the working electrodes by carbon nanomaterials, metallic nanostructures, imprinted polymers and evaluate the corresponding sensing performance. Especially for pesticides, which are challenging and need special care, we highlight biosensors, such as enzymatic sensors, immunobiosensor, aptasensors, and biomimetic sensors. We discuss the sensors' overall performance, especially concerning real-sample performance and the capability for actual field application.

Simultaneous determination of ascorbic acid, uric acid and dopamine using silver nanoparticles and copper monoamino-phthalocyanine functionalised acrylate polymer.

A silver nanoparticle and copper monoamino-phthalocyanine-acrylate (Cu-MAPA) polymer modified glassy carbon electrode was developed for the simultaneous detection of dopamine (DOP), ascorbic acid (AA) and uric acid (UA) using voltammetric techniques. Silver nanoparticles (AgNPs) were synthesised according to the citrate reduction method. Following synthesis and characterisation the copper phthalocyanine polymer was co-deposited with AgNPs realising a surface with enhanced electron transfer which lowered the overpotential required for analyte electro-oxidation. Differential pulse voltammetry (DPV) was employed for the simultaneous determination of dopamine (DOP), ascorbic acid (AA) and uric acid (UA) at AgNP/Cu-MAPA modified surfaces at <µM ranges. The peak potential separations for DOP-AA and DOP-UA were ca. 181 mV and 168 mV respectively. The chemical sensor was also capable of individual quantitation of DOP, UA and AA with detection limits of 0.7, 2.5 and 5.0 nM respectively. Overall, the approach realised a simple and effective electrode modifier for the selective discrimination and quantitation of DOP in the presence of physiological levels of AA and UA.

Yersinia pestis detection using biotinylated dNTPs for signal enhancement in lateral flow assays.

Due to the extreme infectivity of Yersinia pestis it poses a serious threat as a potential biowarfare agent, which can be rapidly and facilely disseminated. A cost-effective and specific method for its rapid detection at extremely low levels is required, in order to facilitate a timely intervention for containment. Here, we report an ultrasensitive method exploiting a combination of isothermal nucleic acid amplification with a tailed forward primer and biotinylated dNTPs, which is performed in less than 30 min. The polymerase chain reaction (PCR) and enzyme linked oligonucleotide assay (ELONA) were used to optimise assay parameters for implementation on the LFA, and achieved detection limits of 45 pM and 940 fM using SA-HRP and SA-polyHRP, respectively. Replacing PCR with isothermal amplification, namely recombinase polymerase amplification, similar signals were obtained (314 fM), with just 15 min of amplification. The lateral flow detection of the isothermally amplified and labelled amplicon was then explored and detection limits of 7 fM and 0.63 fg achieved for synthetic and genomic DNA, respectively. The incorporation of biotinylated dNTPs and their exploitation for the ultrasensitive molecular detection of a nucleic acid target has been demonstrated and this generic platform can be exploited for a multitude of diverse real life applications.

Capacitance electrochemical biosensor based on silicon nitride transducer for TNF-α cytokine detection in artificial human saliva: Heart failure (HF).

In the present study, we have developed a capacitance electrochemical biosensor based on silicon nitride substrate (Si3N4/SiO2/Si[P]/Al) for Tumour Necrosis Factor Alpha (TNF-α) cytokines detection. Micro-contact printing, Fluorescence microscopy characterization and contact angle measurement (CAM) were carried out during the bio-functionalization of the biosensor surface. Mott-Schottky analyses were applied for TNF-α detection within the range of 1 pg/mL to 30 pg/mL in which the immunosensor has exhibited a good linearity, a sensitivity of 4 mV.pM-1 and 4.4 mV.pM-1 in PBS and artificial saliva (AS) respectively. While the LOD was found at 0.38 pg/mL and 1 pg/mL in PBS and AS respectively. The developed immunosensor has also demonstrated a high and good selectivity for TNF-α detection in human AS when compared to other interferences like Cortisol and Interleukin-10. The performances of the developed biosensor are very promising for biomedical application to predict the first sign of inflammation.

Determination of prostate cancer biomarker acid phosphatase at a copper phthalocyanine-modified screen printed gold transducer.

In this work, a novel sensor based on immobilised copper phthalocyanine, 2,9,16,23-tetracarboxylic acid-polyacrylamide (Cu(II)TC Pc-PAA) was developed for determination of acid phosphatase (ACP) levels in nanomolar quantities. Detection was based on the measurement of enzymatically generated phosphate, with initial studies focused on phosphate detection at a Cu(II)TC Pc-PAA modified screen-printed gold transducer. The sensor was characterised in relation to operational performance (pH, response time, stability, linearity, and sensitivity) and common anionic interferents (nitrate, sulphate, chloride, and perchlorate). The functionalised surface also facilitated rapid detection of the enzyme bi-product 2-naphthol over the range 5-3000 µM. Quantitation of ACP was demonstrated, realising a linear response range of 0.5-20 nM and LOD of 0.5 nM, which is within the clinical range for this prostate cancer biomarker.

Ultrasensitive Immunosensor Array for TNF-α Detection in Artificial Saliva using Polymer-Coated Magnetic Microparticles onto Screen-Printed Gold Electrode.

Tumor necrosis factor-α (TNF-α) is a biomarker of inflammation that occurs in patients suffering from heart failure (HF). Saliva can be sampled in a non-invasive way, and it is currently gaining importance as matrix alternative to blood in diagnostic and therapy monitoring. This work presents the development of an immunosensor array based on eight screen-printed gold electrodes to detect TNF-α in saliva samples. Two different functionalization strategies of electrodes were compared. In the first, anti-TNF-α antibodies were chemically bonded onto the electrode by functionalization with 4-carboxymethylaniline. The other functionalization procedure involved the binding of antibodies onto polymer-coated magnetic microparticles, which were then deposited onto the electrode by pulsed chronoamperometry. Finally, the chronoamperometry technique was applied to characterize the modified SPEAu. The use of a secondary antibody anti-TNF-α (Ab-TNF-α-HRP) labelled with horseradish peroxidase (HRP, 2 µg·mL-1) was investigated using tetramethylbenzidine (TMB, pH = 3.75) as electrochemical substrate containing 0.2 mM of H2O2. A sandwich-type detection strategy with a secondary antibody anti-TNF-α provided chronoamperometric analyses in 10 s for each sample. Linearity, precision, limit of detection, and selectivity of devices were investigated. Interferences were evaluated by analyzing solutions containing other cytokine produced during the acute stage of inflammation. The immunosensor showed good performance within the clinically relevant concentration range, with a precision of 8%, and a limit of detection of 0.3 pg/mL. Therefore, it may represent a promising tool for monitoring HF in a non-invasive way.

A novel amperometric enzyme inhibition biosensor based on xanthine oxidase immobilised onto glassy carbon electrodes for bisphenol A determination.

A novel and simple biosensor for the determination of bisphenol A (BPA) based on xanthine oxidase (XOD) enzymatic inhibition has been developed. The biosensor was prepared from xanthine oxidase immobilised by crosslinking with glutaraldehyde, with hypoxanthine as enzyme substrate, and was successfully applied to the determination of BPA using fixed potential amperometry. Biosensor performance was optimised with respect to the applied potential, influence of pH of the electrolyte solution, XOD loading and the substrate concentration. The enzyme inhibition mechanism was evaluated from Cornish-Bowden plus Dixon plots and was found to be reversible and competitive with an apparent inhibition constant of 8.15 nM. Under optimised conditions, the determination of BPA can be achieved in the linear range up to 41 nM with a detection limit of 1.0 nM, which is equal to the lowest reported in the literature, with very good repeatability and reproducibility. The selectivity of the biosensor was evaluated by performing an interference study and found to be excellent; and stability was investigated. It was successfully applied to the detection of BPA in mineral water and in river water.

A novel amperometric biosensor based on gold nanoparticles anchored on reduced graphene oxide for sensitive detection of l-lactate tumor biomarker.

In this work, a novel amperometric biosensor based on gold nanoparticles anchored on reduced graphene oxide (RGO-AuNPs) and l-lactate dehydrogenase (LDH) was developed for the sensing of l-lactate. Firstly, the RGO-AuNPs modified screen printed electrodes were tested for NADH detection showing a wide dynamic range and a low detection limit. Next, the biosensor was constructed by incorporating both enzyme and RGO-AuNPs in a sol gel matrix derived from tetrametoxysilane and methyltrimetoxysilane. The enzyme loading, working pH, and coenzyme concentration were optimized. The biosensor linearly responded to l-lactate in the range of 10µM-5mM and showed a good specific sensitivity of 154µA/mMcm(2) with a detection limit of 0.13µM. This was accompanied by good reproducibility and operational stability. Tests on artificial serum proved that l-lactate can be determined practically without interferences from commonly interfering compounds such as urate, paracetamol and l-ascorbate. Our LDH/RGO-AuNPs/SPCE based biosensor thus performs as electrochemical device for the detection of l-lactate as a viable early cancer bio-marker.