Recent Advances in Impedimetric Biosensors Focusing on Myocardial Infarction Diagnosis

Acute myocardial infarction is the most common cardiovascular disease and 85% of cardiovascular disease-related deaths are associated with it. The variation in the cardiac troponin concentration is considered as the most significant judge index for acute myocardial infarction diagnosis. Here, a comprehensive insights is given about the impedimetric methods as powerful electrochemical biosensing platforms for cardiac troponin evaluation. Focusing on nano materials, various impedimetric techniques including faradaic and non-faradaic techniques and different transducer modification techniques are addressed. The steps taken by each of the studied platforms to solve the existing problems are discussed and their advantages and drawbacks are highlighted. A glance at the provided table is given a mind into the features of each impedimetric sensors and their comparison are provided.

Ferroelectric bismuth-titanate nanoplatelets and nanowires with a new crystal structure

Two different morphologies of ferroelectric bismuth titanate (Bi₄Ti₃O₁₂) nanoparticles, i.e., nanoplatelets and nanowires, were synthesized by changing the concentration of NaOH during a hydrothermal treatment of precipitated Ti⁴⁺ and Bi³⁺ ions. The nanoparticles' crystal structures were characterized using atomic-resolution imaging with a C_S-probe-corrected scanning-transmission electron microscope in combination with X-ray diffractometry and Raman spectroscopy. The nanoplatelets (10 nm thick and from 50 nm to 200 nm wide) exhibit the Aurivillius-type layered-perovskite crystal structure that is characteristic of Bi₄Ti₃O₁₂, whereas the nanowires (from 15 nm to 35 nm wide and from several hundreds of nm to several μm long) exhibit an entirely new structure with an orthorhombic unit cell (a = 3.804(1) Å, b = 11.816(3) Å, and c = 9.704(1) Å). The nanowire structure is composed of two structural layers alternating along the orthorhombic c-direction: a structural layer composed of two parallel layers of Bi atoms that resembles the (Bi₂O₂)²⁺ layer of the Aurivillius structure, and a structural layer composed of two parallel layers of Ti atoms, where every sixth Ti is replaced with Bi. Observations of the ferroelectric domains with transmission electron and piezo-response force microscopy indicated the ferroelectric nature of both nanostructures. The nanowire structure is a metastable polymorph of the bismuth titanate stabilized at the nanoscale. With annealing at temperatures above 500 °C the nanowire structure topotactically transforms into the Aurivillius structure.

Hydrothermal formation of bismuth-titanate nanoplatelets and nanowires: the role of metastable polymorphs

Understanding the processes involved in the formation of nanoparticles is a prerequisite for the control of their morphology. In this investigation we reveal the processes leading to the formation of...

Sensitive Molybdenum Disulfide Based Field Effect Transistor Sensor for Real-time Monitoring of Hydrogen Peroxide

A reliable and highly sensitive hydrogen peroxide (H₂O₂) field effect transistor (FET) sensor is reported, which was constructed by using molybdenum disulfide (MoS₂)/reduced graphene oxide (RGO). In this work, we prepared MoS₂ nanosheets by a simple liquid ultrasonication exfoliation method. After the RGO-based FET device was fabricated, MoS₂ was assembled onto the RGO surface for constructing MoS₂/RGO FET sensor. The as-prepared FET sensor showed an ultrahigh sensitivity and fast response toward H₂O₂ in a real-time monitoring manner with a limit of detection down to 1 pM. In addition, the constructed sensor also exhibited a high specificity toward H₂O₂ in complex biological matrix. More importantly, this novel biosensor was capable of monitoring of H₂O₂ released from HeLa cells in real-time. So far, this is the first report of MoS₂/RGO based FET sensor for electrical detection of signal molecules directly from cancer cells. Hence it is promising as a new platform for the clinical diagnosis of H₂O₂-related diseases.

Fabrication of SrTiO₃ Layer on Pt Electrode for Label-Free Capacitive Biosensors

Due to their interesting ferroelectric, conductive and dielectric properties, in recent years, perovskite-structured materials have begun to attract increasing interest in the biosensing field. In this study, a strontium titanate perovskite layer (SrTiO₃) has been synthesized on a platinum electrode and exploited for the development of an impedimetric label-free immunosensor for Escherichia coli O157:H7 detection. The electrochemical characterization of the perovskite-modified electrode during the construction of the immunosensor, as well as after the interaction with different E. coli O157:H7 concentrations, showed a reproducible decrease of the total capacitance of the system that was used for the analytical characterization of the immunosensor. Under optimized conditions, the capacitive immunosensor showed a linear relationship from to 1 to 7 log cfu/mL with a low detection limit of 1 log cfu/mL. Moreover, the atomic force microscopy (AFM) technique underlined the increase in roughness of the SrTiO₃-modified electrode surface after antibody immobilization, as well as the effective presence of cells with the typical size of E. coli.

In-site encapsulating gold "nanowires" into hemin-coupled protein scaffolds through biomimetic assembly towards the nanocomposites with strong catalysis, electrocatalysis, and fluorescence properties

An efficient and green biomimetic assembly protocol was developed for the fabrication of multifunctional nanocomposites by mimicking the configuration of natural protein enzymes. Bovine serum albumin (BSA) as the protein model was first split to produce the disassembled BSA (dBSA) of linear polymer and then coupled with catalytic Hemin (Hem). The yielded dBSA-Hem scaffolds were utilized to in-site encapsulate gold nanoclusters (AuNCs) through biominerization, yielding the dBSA-Hem-AuNCs. It was discovered that the nanocomposites could display the well-defined composition and spheric morphology. In particular, they could exhibit unexpectedly strong catalysis, electrocatalysis, and fluorescence properties, in which the biominerized AuNCs would act as fluorescence sources and "nanowires" for promoting the electron-transfer of the catalytic nanocomposites. Colorimetric investigations show that the developed enzyme mimics could present peroxidase-like catalysis activities comparable to natural horseradish peroxidase. In addition, they could facilitate the direct electrocatalysis for H₂O₂ at concentrations as low as 0.40 μM. Moreover, strong red fluorescence of AuNCs in nanocomposites could be expected for the fluorimetric analysis of H₂O₂ with linear concentrations ranging from 50 nM to 100 μM. Such a biomimetic assembly route may open a new door toward the preparation of diverse nanocomposites with multifunctional catalysis and fluorescence, thus promising extensive applications of catalysis and detection in the chemical, environmental, and biomedical fields.

Cobalt phosphide nanowires: an efficient electrocatalyst for enzymeless hydrogen peroxide detection

In this letter, we demonstrate for the first time that cobalt phosphide nanowires (CoP NWs) exhibit remarkable catalytic activity toward electrochemical detection of hydrogen peroxide (H2O2). As an enzymeless H2O2 sensor, such CoP NWs show a fast amperometric response within 5 s and a low detection limit of 0.48 μM. In addition, this nonenzymatic sensor displays good selectivity, long-term stability and excellent reproducibility.

Highly Sensitive Electrochemical Biosensor for Evaluation of Oxidative Stress Based on the Nanointerface of Graphene Nanocomposites Blended with Gold, Fe3O4, and Platinum Nanoparticles

High levels of H2O2 pertain to high oxidative stress and are associated with cancer, autoimmune, and neurodegenerative disease, and other related diseases. In this study, a sensitive H2O2 biosensor for evaluation of oxidative stress was fabricated on the basis of the reduced graphene oxide (RGO) nanocomposites decorated with Au, Fe3O4, and Pt nanoparticles (RGO/AuFe3O4/Pt) modified glassy carbon electrode (GCE) and used to detect the released H2O2 from cancer cells and assess the oxidative stress elicited from H2O2 in living cells. Electrochemical behavior of RGO/AuFe3O4/Pt nanocomposites exhibits excellent catalytic activity toward the relevant reduction with high selection and sensitivity, low overpotential of 0 V, low detection limit of ∼0.1 μM, large linear range from 0.5 μM to 11.5 mM, and outstanding reproducibility. The as-prepared biosensor was applied in the measurement of efflux of H2O2 from living cells including healthy normal cells and tumor cells under the external stimulation. The results display that this new nanocomposites-based biosensor is a promising candidate of nonenzymatic H2O2 sensor which has the possibility of application in clinical diagnostics to assess oxidative stress of different kinds of living cells.

Electrochemical method assisted immobilization and orientation of myoglobin into biomimetic brij 56 film and its direct electrochemistry study

A simple cyclic voltammetric method was applied to assemble and orient a model protein, namely, myoglobin (Mb), into a biocompatible Brij 56 film. Ultraviolet-visible and circular dichroism spectra indicated that Mb in Brij 56 matrix preserved its secondary structure. Fourier transform infrared spectra confirmed the formation of hydrogen bonds between Mb and Brij 56. These hydrogen bonds acted as the electron tunnel to transfer electrons from Mb's active sites to the underlying glassy carbon electrode. Effective direct electron transfer of Mb was realized with the presence of a couple of quasi-reversible and well-defined redox peaks at -310 mV (vs standard calomel electrode) in the studied potential range. The peaks were attributed to the redox couple of heme Fe(II)/Fe(III) of the well-oriented Mb in Brij 56 matrix. The surface coverage and the electron transfer rate (ks) of Mb immobilized into the Brij 56 film was ∼4.9×10(-11) mol cm(-2) and 72.6±3.0 s(-1), respectively. An excellent electrocatalytic response of the immobilized Mb toward nitrite in the absence of electron transfer mediators was observed. These results emphasized that the biomimetic Brij 56 could be used as an attractive material for immobilizing proteins and constructing biosensors.

Mn-modified Bi2Ti2O7 photocatalysts: bandgap engineered multifunctional photocatalysts for hydrogen generation

The applicability of pyrochlore bismuth titanate as a photocatalyst amenable to additional element inclusion resulting in a bandgap engineered composite oxide nanostructure (BECON) offers significant potential for multifunctional photo-driven applications.