A modified Prussian blue biosensor with improved stability based on the use of self-assembled monolayers and polydopamine for quantitative L-glutamate detection

A miniature L-glutamate (L-Glu) biosensor is described based on Prussian blue (PB) modification with improved stability by using self-assembled monolayers (SAMs) technology and polydopamine (PDA). A gold microelectrode (AuME) was immersed in NH2(CH2)6SH-ethanol solution, forming well-defined SAMs via thiol-gold bonding chemistry which increased the number of deposited Prussian blue nanoparticles (PBNPs) and confined them tightly on the AuME surface. Then, dopamine solution was dropped onto the PBNPs surface and self-polymerized into PDA to protect the PB structure from destruction. The PDA/PB/SAMs/AuME showed improved stability through CV measurements in comparison with PB/AuME, PB/SAMs/AuME, and PDA/PB/AuME. The constructed biosensor achieved a high sensitivity of 70.683 nA µM-1 cm-2 in the concentration range 1-476 µM L-Glu with a low LOD of 0.329 µM and performed well in terms of selectivity, reproducibility, and stability. In addition, the developed biosensor was successfully applied to the determination of L-Glu in tomato juice, and the results were in good agreement with that of high-performance liquid chromatography (HPLC). Due to its excellent sensitivity, improved stability, and miniature volume, the developed biosensor not only has a promising potential for application in food sample analysis but also provides a good candidate for monitoring L-Glu level in food production.

Integrating machine learning and electrochemistry to develop a glucose biosensor assembled with Ganoderma applanatum lectin

Fungal lectins have enormous biotechnological potential, but limited knowledge about their biochemical and biophysical features prevents their proper use. Herein, we report an innovative alternative to use Ganoderma applanatum lectin (GAL) as a glucose biorecognition element, after identifying the ideal electroanalytical conditions by machine learning studies performed with a homologous agglutinin from the same macrofungus. The research revealed that GAL has moderate resistance to pH (4-8) and temperature (20-60 °C) variations, but its hemagglutinating activity (376.5 HU mg^-1 GAL at 20 °C) was better conserved under physiological conditions. Integrating electrochemical data and semi-empirical molecular modeling, biocompatible and electrostatically favorable conditions were found to immobilize the lectin on Prussian blue-modified glassy carbon electrode, after thermal activation of the metal-complex film. The glucose dose-response relationship obtained with the developed biosensor, defined as GAL/ta-PB/GCE, showed a typical Hill equation correlation, suggesting electrodic interactions represented by a sigmoidal mathematical function. GAL/ta-PB/GCE achieved remarkable electroanalytical performance, with emphasis on the detection limit (10.2 pM) and sensitivity (0.012 µA µM^-1cm^-2). The biosensor was successfully used to quantify glucose in pharmaceutical formulations, reiterating that the association of theoretical and experimental information drives important advances in bioelectrochemical studies.

Gold Microstructures/Polyaniline/Reduced Graphene Oxide/Prussian Blue Composite as Stable Redox Matrix for Label-free Electrochemical Immunoassay of α-Fetoprotein

Sensitivity amplification strategies in label-free electrochemical immunosensors are mainly limited by redox molecules leaking and degradation of electrical conductivity caused by layers of decoration. Herein, a relatively stable and sensitive label-free electrochemical immunosensor based on a hierarchically flower-like gold microstructures/polyaniline/reduced graphene oxide/prussian blue (HFG/PANI/rGO/PB) composite modified electrode was stepwise fabricated for determination of α-fetoprotein (AFP). In this process, the effect of PANI and rGO on the proposed immunosensor was studied. In detail, PANI/rGO due to the unique electrochemical properties can effectively prevent PB leakage and form a stable sensing platform, which causes sensitive responsiveness and thus a more satisfied detection limit. Meanwhile, the HFG with good biological compatibility can effectively immobilize plenty of antibodies. Under optimal conditions, the HFG/PANI/rGO/PB modified immunosensor exhibited an excellent linearity (0.01 - 30 ng/mL) and a low detection limit (0.003 ng/mL) (S/N = 3), suitable specificity as well as stability and reproducibility towards AFP. The present work offered a promising platform for clinical hepatocellular carcinoma diagnostics.

ATP induced alteration in the peroxidase-like properties of hollow Prussian blue nanocubes: a platform for alkaline phosphatase detection

Breaking the pH limitation of the enzyme-like activity of nanomaterials is of great importance for extending their applications in environmental and biomedical fields. Herein, to mimic the role of histidine residues in horseradish peroxidase (HRP), adenosine 5'-triphosphate (ATP) is reported to improve the peroxidase-like activity of hollow Prussian blue nanocubes (hPBNCs). Due to the inherited porous structures, hPBNCs can expose all the binding sites as far as possible to ATP to significantly amplify their catalytic activity and broaden their applicable pH range up to pH 12. Introduction of ATP provides the possibility of realizing efficient catalytic reactions under alkaline conditions. Upon binding with hPBNCs, ATP can enhance the stability of hPBNCs, increase the affinities of the catalysts towards substrates and improve the conductivity of hPBNCs as well as change the decomposed product from H₂O₂. Moreover, on the basis of the different catalytic activities of hPBNCs towards ATP, adenosine 5'-diphosphate and adenosine 5'-monophosphate, hPBNCs-ATP is utilized to construct a novel colorimetric sensor for the detection of alkaline phosphatase (ALP) activity in biological fluids, which is significantly important for the clinical diagnosis of ALP-related diseases.

Enhancing the electrochromic stability of Prussian blue based on TiO2 nanorod arrays

The cyclic stability and optical modulation of Prussian blue (PB) via TiO₂ nanorod arrays are enhanced.

3D Printed Graphene Electrodes Modified with Prussian Blue: Emerging Electrochemical Sensing Platform for Peroxide Detection

3D printing technologies have been considered an important technology due to the ease manufacturing of objects, freedom of design, waste minimization, and fast prototyping. In chemistry, this technology potentializes the fabrication of conductive electrodes in large scale for sensing applications. Herein, we reported the modification of a 3D printed graphene electrode with Prussian blue. The modified electrode (3DGrE/PB) was characterized by microscopy (SEM and AFM) and spectroscopic techniques, and its electrochemical properties were compared to the traditional electrodes: glassy carbon, gold, and platinum. The 3DGrE/PB was used in the sensing of hydrogen peroxide in real-world samples of milk and mouthwash, and the results obtained according to the technique of batch-injection analysis were satisfactory for the concentration range typically found in such samples. Thus, 3DGrE/PB can be used as a new platform for sensing of molecular targets.

Current Innovations of Metal Hexacyanoferrates-Based Nanocomposites toward Electrochemical Sensing: Materials Selection and Synthesis Methods

Mixed valence transition metal hexacyanoferrates (MeHCF)-Prussian blue and its analogs receive enormous research interest in the electrochemical sensing field. In recent years, conducting materials such as conducting polymer, carbon nanomaterial, and noble metals have been used to form nanocomposites with MeHCF. The scope of this review offers the reasons behind the preparation of various MeHCF based nanocomposite toward electrochemical detection. We primarily focus on the current progress of the development of MEHCF-based nanocomposites. The synthesis methods for these nanocomposites are also reviewed and discussed.

Improving Electrochromic Cycle Life of Prussian Blue by Acid Addition to the Electrolyte

In this study, we examined the cyclic stability of Prussian blue (PB) films in electrolytes with acid. The cyclic stabilities of the PB films were investigated in K⁺ based electrolytes with different values of solution pH. The acidified KCl solution can significantly improve the durability of the film. Among the three pH values tested, the KCl solutions (pH = 2.15 and pH = 3.03) showed better performance. Furthermore, we investigated the cyclic stabilities of the PB films in LiClO₄/PC electrolyte containing different acids. We found that the cyclic stability of PB film was significantly improved when a small amount of acetic acid was dissolved in LiClO₄/PC electrolyte. The PB film exhibited stable optical modulation after up to 20,000 cycles in LiClO₄/PC electrolyte containing acetic acid—a much higher result than those of some literatures. This suggests that the addition of acetic acid to LiClO₄/PC electrolyte can promote the development of PB-based devices with improved stability.

Fluorine-Free Water-in-Salt Electrolyte for Green and Low-Cost Aqueous Sodium-Ion Batteries

The highly concentrated "water-in-salt" electrolyte (WiSE) containing sodium acetate and potassium acetate demonstrates surprising performance (specific capacity of 37 mA h^-1  g^-1 at the 5th cycle and average discharge voltage of 0.82 V) in aqueous sodium-ion batteries (SIBs) based on Na₂ MnFe(CN)₆ and NaTi₂ (PO₄ )₃ . The fluorine-free electrolyte offers a wide electrochemical stability window and compatibility with Al current collector. The electrolyte, current collector, and the electrode materials based on abundant elements make the proposed battery chemistry safe, low-cost, and environmentally friendly.

Oxidase-mimicking activity of the nitrogen-doped Fe3C@C composites

The nitrogen-doped Fe₃C@C composites could behave as oxidase-mimics to catalyze the reaction between TMB and molecular oxygen to produce quinonediimine and H₂O.

Electropolymerized phenol derivatives as permselective polymers for biosensor applications

Amperometric biosensors are often coated with a polymeric permselective film to avoid electroactive interference by reducing agents present in the target medium. Phenylenediamine and phenol monomers are commonly used to form these permselective films in the design of microsensors and biosensors. This paper aims to evaluate the permselectivity, stability and lifetime of polymers electrosynthesized using either constant potential amperometry (CPA) or cyclic voltammetry (CV) from naturally occurring phenylpropanoids in monomeric and dimeric forms (eugenol, isoeugenol, dehydrodieugenol and magnolol). Sensors were characterized by scanning electron microscopy and permselectivity analysis. Magnolol formed an electro-deposited polymer with a more defined three-dimensional texture in comparison with the other films. The phenol-derived films showed different permselectivity towards H2O2 over ascorbic acid and dopamine, likely to be related to the thickness and compactness of the polymer. The CV-derived films had a better permselectivity compared to the CPA-corresponding polymers. Based on these results, the permselectivity, stability and lifetime of a biosensor for glucose were studied when a magnolol coating was electro-deposited. The structural principles governing the permselectivity of the magnolol-derived film are suggested to be mainly related to the conformational flexibility of this monomer. Newly designed biosensors, coated with electropolymerized natural phenol derivatives, may represent promising analytical devices for different application fields.

Stabilization of Prussian blue with polyaniline and carbon nanotubes in neutral media for in vivo determination of glucose in rat brains

This study demonstrates a new electrochemical microbiosensor for selectivein vivomonitoring of glucose in rat brains.

A multi-enzyme microreactor-based online electrochemical system for selective and continuous monitoring of acetylcholine

This study demonstrates an online electrochemical system (OECS) for selective and continuous measurements of acetylcholine (ACh) through efficiently integrating in vivo microdialysis, a multi-enzyme microreactor and an electrochemical detector.

A ternary nanocomposite electrode of polyoxometalate/carbon nanotubes/gold nanoparticles for electrochemical detection of hydrogen peroxide

In this work, a nanocomposite film electrode containing polyoxometalate (POM) clusters K₆P₂W₁₈O₆₂ (P₂W₁₈), carbon nanotubes (CNTs) and Au nanoparticles (AuNPs) was fabricated by a layer-by-layer self-assembly technique.

pH-Switchable electroactive composite films of carboxylated multi-walled carbon nanotubes and Prussian blue

Here the combination of carboxylated multi-walled carbon nanotubes (CMWCNTs) and Prussian blue (PB) for fabricating pH-responsive electroactive composite thin films is reported.