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Background and purpose: The increase in diabetes cases has become a major concern in the healthcare sector, necessitating the development of efficient and minimal diagnostic methods. This study aims to provide a comprehensive examination of electrochemical biosensors for detecting diabetes mellitus biomarkers, with a special focus on the utilization of carbon-based electrodes. Review approach: A detailed analysis of electrochemical biosensors incorporating various carbon electrodes, including screen-printed carbon electrodes, glassy carbon electrodes, and carbon paste electrodes, is presented. The advantages of carbon-based electrodes in biosensor design are highlighted. The review covers the detection of several key diabetes biomarkers, such as glucose, glycated hemoglobin (HbA1c), glycated human serum albumin (GHSA), insulin, and novel biomarkers. Key results: Recent developments in electrochemical biosensor technology over the last decade are summarized, emphasizing their potential in clinical applications, particularly in point-of-care settings. The utilization of carbon-based electrodes in biosensors is shown to offer significant advantages, including enhanced sensitivity, selectivity, and cost-effectiveness. Conclusion: This review underscores the importance of carbon-based electrodes in the design of electrochemical biosensors and raises awareness for the detection of novel biomarkers for more specific and personalized diabetes mellitus cases. The advancements in this field highlight the potential of these biosensors in future clinical applications, especially in point-of-care diagnostics.

This study investigates the effects of boron concentration on boron-doped diamond (BDD) electrodes for electrochemical sensors of ciprofloxacin. The effects of boron concentration, scan rate, and pH of BDD electrodes with boron concentrations of 0.1, 0.5, and 1% were examined to determine the optimal conditions. Furthermore, square wave voltammetry (SWV) in phosphate buffer pH 7 was used to analyze the electrochemical behavior of ciprofloxacin. The results revealed a linear calibration curve in the concentration range of 30–100 μM with a recovery of 85–110%. Meanwhile, BDD electrode with the highest boron concentration in this experiment (1%) showed a very low limit of detection of 0.17 μM, meaning that 1% BDD gave a highly sensitive and significant measurement result for the electrochemical sensor of ciprofloxacin. With the results given, this study provides new insights for controlling boron concentrations in diamond electrodes for the electrochemical sensors of quinolone antibiotics.

A straightforward electro-conversion of cumene into acetophenone has been reported using boron-doped diamond (BDD) electrodes. This particular conversion is driven by the addition reaction of a cathodically generated hydroperoxide anion to an anodically generated cumyl cation, where the BDD’s wide potential window enables the direct anodic oxidation of cumene into the cumyl cation. Since electricity is directly employed as the oxidizing and reducing reagents, the present protocol is easy to use, suitable for scale-up, and inherently safe.

Levofloxacin (LEV) was known as one of the fluoroquinolone antibiotics that widely used as an antibacterial agent. Monitoring of LEV is important due to its negative side effect on humans. The determination of LEV was studied for the first time on nickel modified on a boron-doped diamond (NiBDD) electrode using the square wave voltammetry (SWV) method to improve the catalytic and sensitivity of the sensor. The response was linear in the range of 30–100 mM LEV. LEV sensor on NiBDD was found to be selective in the presence of urea, glucose, and ascorbic acid interferences. Good reproducibility with % a relative standard deviation of 1.45% (n = 10) was achieved. Therefore, the NiBDD electrode could be potentially applied for the real detection method of LEV.

On-site monitoring of plasma drug concentrations is required for effective therapies. Recently developed handy biosensors are not yet popular owing to insufficient evaluation of accuracy on clinical samples and the necessity of complicated costly fabrication processes. Here, we approached these bottlenecks via a strategy involving engineeringly unmodified boron-doped diamond (BDD), a sustainable electrochemical material. A sensing system based on a ∼1 cm2 BDD chip, when analysing rat plasma spiked with a molecular-targeting anticancer drug, pazopanib, detected clinically relevant concentrations. The response was stable in 60 sequential measurements on the same chip. In a clinical study, data obtained with a BDD chip were consistent with liquid chromatography–mass spectrometry results. Finally, the portable system with a palm-sized sensor containing the chip analysed ∼40 μL of whole blood from dosed rats within ∼10 min. This approach with the ‘reusable’ sensor may improve point-of-monitoring systems and personalised medicine while reducing medical costs.

Although oxidation of benzylic C(sp3)−H bonds is an important process for synthesizing biologically active compounds, the reactions generically require hazardous reagents, catalysts, and harsh conditions. Since electro-organic synthesis utilizes electricity itself as a reagent, reactions can proceed well even under ambient conditions. Herein, we report a selective oxidation of cumene in an electrochemical flow reactor. Cumyl alcohol was selectively obtained under optimum amount of charge and current density. The selective oxidation of cumene to cumyl alcohol was achieved because overoxidation of cumyl alcohol into acetophenone was suppressed by the electrochemical flow reactor.

The rising concentration of carbon dioxide (CO2) as one of the greenhouse gases in the atmosphere is a major source of worry. Electrochemical reduction of CO2 is one of many ways to convert CO2 gas into usable compounds. An electrochemical technique was applied in this study to reduce CO2 using a boron-doped diamond (BDD) working electrode modified with MXene (Ti3C2Tx) material to improve electrode performance. MXene concentrations of 0.5 mg/mL (MXene-BDD 0.5), 1.0 mg/mL (MXene-BDD 1.0), and 2.0 mg/mL (MXene-BDD 2.0) were drop-casted onto the BDD surface. MXene was effectively deposited on top of the BDD surface, with Ti weight loads of 0.12%, 4.06%, and 7.14% on MXene-BDD 0.5, MXene-BDD 1.0, and MXene-BDD 2.0, respectively. The modified working electrode was employed for CO2 electroreduction with optimal CO2 gas aeration. The existence of the MXene substance in BDD reduced the electroreduction overpotential of CO2. For the final result, we found that the MXene-BDD 2.0 electrode effectively generated the most formic acid product with a maximum reduction potential as low as −1.3 V (vs. Ag/AgCl).

Electrogenerated chemiluminescence (ECL) has recently become one of the most prominent and well-established transducers for immunoassay techniques. ECL relates a luminophore concentration in solution with the emission of light triggered by an electrochemical stimulus. ECL immunoassay (ECLIA) performance depends on the parameters of its light generation, including the luminophore, the species that emit light called labels in ECLIA; co-reactants, which are added reagents that support the luminophore to undergo the excited state; electrodes, which are the place for the ECL reactions to take place; and the format of the immunoassay. This review discusses the behaviour of ECLIA parameters, the required instrumentations, and some important examples of detections based on ECLIA.

A micro-band boron-doped diamond (BDD) electrode was prepared by sealing a piece of BDD film with an area of 1.11´10-7 m2 between two insulating plates, one Teflon and one silicon rubber, to form sandwich-like layers, so the surface area could be investigated. The micro-band BDD was combined with capillary zone electrophoresis as an electrode for the simultaneous detection of adenosine monophosphate (AMP), adenosine diphosphate (ADP), and adenosine triphosphate (ATP) in a solution. These adenosine phosphates can be separated with a 0.3 m-long fused silica capillary using Britton–Robinson buffers at pH 2.0. Current in the concentration range of 0.1 to 2.0 mM were linear with the limits of detection of 0.004 ?M, 0.006 ?M, and 0.011 ?M for AMP, ADP, and ATP, respectively. A comparison with an unmodified BDD as the detector in the same electrophoresis system showed that the micro-band generated better limits of detection (LODs) than the macroelectrode. This method was successfully applied to human urine samples injected with three adenosine phosphates, as well as adenine and guanine, which can be well-separated with recovery percentages of adenine, guanine, AMP, ADP, and ATP of 99.2%, 102.5%, 107.4%, 107.7%, and 105.4%, respectively.

CO2 electrochemical reduction (CO2ER) activity is known to be influenced by electrode materials. In this study, we report the fabrication of a copper-nickel-modified boron-doped diamond (CuNi-BDD) electrode using wet chemical seeding and electrodeposition. Annealing was performed to improve the stability of the modified electrode during elec-trolysis. Characterization of the modified BDD electrodes shows successful deposition without damage to the surface of the BDD support material. CO2ER was conducted with the CuNi-BDD electrode, which produces various important products including methanol, formic acid, CO, and CH4. Additionally, a different applied potential affected the product distribution. CO2ER was also conducted on the surfaces of Cu-BDD and Ni-BDD electrodes for comparison.

Boron-doped diamond (BDD) electrodes are next generation electrode materials and their electrochemical applications have been actively developed in recent years. They are expected to be useful electrode materials for improving the environment and for bio-medical applications. Here, examples of practical applications as electrochemical sensors, the development of in vivo real time measurements, and electrochemical organic synthesis using BDD electrodes are briefly introduced. In the second part, our recent work on the production of useful chemicals by means of the electrochemical reduction of CO2 using BDD electrodes is described. The work has attracted particular attention for its potential contribution to carbon neutrality and carbon recycling.

An anodic stripping voltammetry detection method with lateral flow immunochromatographic assay for determining aflatoxin M1 was developed. Cadmium sulfide nanoparticles (CdSNPs) were employed as a label for aflatoxin antibody. Conjugation between the CdSNPs and aflatoxin antibody was performed as the first step. The CdSNP-antibody conjugate was then immobilized on a test strip on a conjugate pad. When the conjugate interacted with the sample containing aflatoxin, it was captured by the aflatoxin in the test zone. The CdSNPs retained in the test zone were then measured by anodic stripping voltammetry using a boron-doped diamond electrode. A linear concentration range of 0–70 ppb aflatoxin, with a sensitivity of 20 µA/mM and a detection limit of 30 ppb, was achieved by this method.

Hearing loss affects >5% of the global population and therefore, has a great social and clinical impact. Sensorineural hearing loss, which can be caused by different factors, such as acoustic trauma, aging, and administration of certain classes of drugs, stems primarily from a dysfunction of the cochlea in the inner ear. Few therapeutic strategies against sensorineural hearing loss are available. To develop effective treatments for this disease, it is crucial to precisely determine the behavior of ototoxic and therapeutic agents in the microenvironment of the cochlea in live animals. Since the 1980s, a number of studies have addressed this issue by different methodologies. However, there is much less information on pharmacokinetics in the cochlea than that in other organs; the delay in ontological pharmacology is likely due to technical difficulties with accessing the cochlea, a tiny organ that is encased with a bony wall and has a fine and complicated internal structure. In this review, we not only summarize the observations and insights obtained in classic and recent studies on pharmacokinetics in the cochlea but also describe relevant analytical techniques, with their strengths, limitations, and prospects.

The effect of sp2 carbon within a boron-doped diamond (BDD) electrode on the electrochemical reduction of CO2 is investigated for the first time. With increasing sp2 content, the Faradaic efficiency for the production of hydrogen (H2) under constant current density increases while that for the production of formic acid (HCOOH) decreases. Moreover, favorable electrolysis conditions for producing HCOOH shift in the negative potential direction with increasing sp2 content. This phenomenon is ascribed to the presence of adsorption sites on the sp2 carbon. This work provides guidance for selectively controlling the reduction of CO2 by adjusting the distribution of carbonaceous species in the BDD electrode.

Neuraminidase sensors have been developed using platinum (Pt) and platinum-modified boron-doped diamond (PtBDD) electrodes based on the difference of electrochemical responses of zanamivir in the absence and in presence of neuraminidase. Cyclic voltammetry of zanamivir showed that the presence of zanamivir decreases the oxidation reduction peak currents of Pt. The responses were found to be linear in the zanamivir concentration range of 7.5-150 µM. Comparison between Pt-BDD and Pt bulk electrodes showed that Pt-BDD offers approximately two times higher sensitivity of zanamivir responses than Pt bulk. Further comparison to gold-based electrodes showed that Pt-based electrodes provided about one order higher sensitivity of zanamivir responses. In the presence of neuraminidase, the oxidation-reduction currents of Pt again increase. Observation on the oxidation currents in the system with 2 x 10-5 M zanamivir showed that the responses were linear in the neuraminidase concentration range of 5-20 mU. Good reproducibility with an RSD < 3 (n = 10) was achieved even when the measurements were performed in a mucin matrix, suggesting that Pt-based electrodes are suitable to be applied for the detection method of neuraminidase

Polyclonal antibodies of aflatoxin B1 were successfully produced from New Zealand White female rabbits after immunization by the hapten of aflatoxin B1-carboxymethyl hydroxylamine hemihydrochloride (AFB1-CMO) conjugated with bovine serum albumin (BSA) as the antigen. The hapten was synthesized using the carbodiimide method with CMO as a linker. Absorption peaks at 362, 264, and 218 nm were observed as a result of characterization with UV-Vis spectroscopy, while IR spectroscopy showed peaks at 3448 cm-1 and 1642 cm-1 attributable to the hydroxyl and nitrile groups, respectively. Furthermore, mass spectrometry showed fragmentation at the m/z of 386, 368.2, and 310, which confirms that the hapten of AFB1-CMO was successfully synthesized. The hapten was then conjugated with BSA to serve as an antigen of AFB1 when it was injected into the rabbits. The specificity of the antigen towards its antibody and the confirmation of hapten-BSA conjugation were characterized using the dot blot immunoassay, which showed a BSA concentration of 1.74 mg/mL. Two weeks after the primary immunization by its antigen, agar gel precipitation testing showed that the rabbit blood serum had positive results for polyclonal antibodiest against AFB1 with the highest concentration of antibodiest of 2.19 mg/mL.

The electroreduction reaction of methyl cinnamate on a boron-doped diamond (BDD) electrode was investigated. The hydrodimer, dimethyl 3,4-diphenylhexanedioate (racemate/meso = 74:26), was obtained in 85% yield as the major product, along with small amounts of cyclic methyl 5-oxo-2,3-diphenylcyclopentane-1-carboxylate. Two new neolignan-type products were synthesized from the hydrodimer.

New Fe(III) compounds from qsal ligand, [Fe(qsal)2](CH3OSO3) (1) and [Fe(qsal)2](CH3SO3)·CH3OH (3), along with known compound, [Fe(qsal)2](CF3SO3) (2), were obtained as large well-shaped crystals (Hqsal = N-(8-quinolyl)salicylaldimine). The compounds 1 and 2 were in the low-spin (LS) state at 300 K and exhibited a cooperative spin crossover (SCO) transition with a thermal hysteresis loop at higher temperatures, whereas 3 was in the high-spin (HS) state below 300 K. The optical conductivity spectra for 1 and 3 were calculated from the single-crystal reflection spectra, which were, to the best of our knowledge, the first optical conductivity spectra of SCO compounds. The absorption bands for the LS and HS [Fe(qsal)2] cations were assigned by time-dependent density functional theory calculations. The crystal structures of 1 and 2 consisted of a common one-dimensional (1D) array of the [Fe(qsal)2] cation, whereas that of 3 had an unusual 1D arrangement by π-stacking interactions which has never been reported. The crystal structures in the high-temperature phases for 1 and 2 indicate that large structural changes were triggered by the motion of counter anions. The comparison of the crystal structures of the known [Fe(qsal)2] compounds suggests the significant role of a large non-spherical counter-anion or solvate molecule for the total lattice energy gain in the crystal of a charged complex.

Modification of carbon, including boron-doped diamond (BDD) and glassy carbon (GC), using gold nanoparticle (AuNP) was developed by self-assembly technique. This technique is based on electrostatic interaction between citratecapped AuNP to amine terminal groups after surface modification of BDD and GC. The fabricated materials, AuNPBDD and AuNP-GC, were then utilized as electrodes for As3+ detection using anodic stripping voltammetry (ASV) technique. Anodic stripping voltammograms of both AuNP-BDD and AuNP-GC electrodes showed similar peak potentials of As° oxidation at ~0.21 V (vs. Ag/AgCl) in optimum conditions of -500 mV, 180 s, and 100 mV/s for deposition potential, deposition time, and scan rate, respectively. AuNP-BDD shows better performances in the case of wide linear concentration range (0-20 mM) and low limit of detection (0.39 μM or 4.64 ppb), whereas those of AuNPGC were linear in the concentration range of 0-10mM with a detection limit of 0.14 μM (13.12 ppb). Excellent reproducibility was shown with RSDs (n=20) of 2.93% and 4.54% at AuNP-BDD and AuNP-GC, respectively. However, decreasing of current responses in 6-concecutive days was found more at AuNP-BDD (~20.1%) than that at AuNP-GC (~2.8%).

The whole molecule of the title compound, C22H28Br2O2, is generated by twofold rotation symmetry. The dihedral angle of the biphenyl moiety is 85.05 (11)°. The hydroxy groups show intramolecular O—H...π interactions without any other hydrogen-bond acceptors. In the crystal, there are no other significant intermolecular interactions present.

This work presents the construction and application of boron-doped diamond(BDD) thin film electrode as sensor for the determination of three β-agonists, viz.salbutamol, terbutaline and clenbuterol. Although well-known as a chemically inertmaterial, BDD film however shows fouling in detection of these compounds using fixedpotentialmode amperometry. A suitable waveform for pulsed amperometric detection(PAD) was developed and used to determine the agonist compounds. It was seen that thedeveloped PAD significantly refreshed the BDD surface for long-term detection in flowinjection analysis. Linear working ranges were 0.5-100 μM, 1.0-100 μM and 0.5-50 μM forsalbutamol, terbutaline and clenbuterol, respectively. The developed PAD-BDD system wasapplied to successfully determine salbutamol and terbutaline in commercial pharmaceuticalproducts. The methods were validated with a capillary electrophoresis method.

To develop a new spin-crossover functional material, a magnetic hybrid compound [Fe(qsal)2][Ni(mnt)2] was designed and synthesized (Hqsal = N-(8-quinolyl)salicylaldimine, mnt = maleonitriledithiolate). The temperature dependence of magnetic susceptibility suggested the coexistence of the high-spin (HS) Fe(III) cation and π-radical anion at room temperature and a magnetic transition below 100 K. The thermal variation of crystal structures revealed that strong π-stacking interaction between the π-ligand in the [Fe(qsal)2] cation and [Ni(mnt)2] anion induced the distortion of an Fe(III) coordination structure and the suppression of a dimerization of the [Ni(mnt)2] anion. Transfer integral calculations indicated that the magnetic transition below 100 K originated from a spin-singlet formation transformation in the [Ni(mnt)2] dimer. The magnetic relaxation of Mössbauer spectra and large thermal variation of a g-value in electron paramagnetic resonance spectra below the magnetic transition temperature implied the existence of a magnetic correlation between d-spin and π-spin.

To investigate the π-extension effect on an unusual negative-charged spin crossover (SCO) FeIII complex with a weak N2O4 first coordination sphere, we designed and synthesized a series of anionic FeIII complexes from a π-extended naphthalene derivative ligand. Acetonitrile-solvate tetramethylammonium (TMA) salt 1 exhibited an SCO conversion, while acetone-solvate TMA salt 2 was in a high-spin state. The crystal structural analysis for 2 revealed that two-leg ladder-like cation-anion arrays derived from π-stacking interactions between π-ligands of the FeIII complex anion and Coulomb interactions were found and the solvated acetone molecules were in one-dimensional channels between the cation-anion arrays. A desolvation-induced single-crystal-to-single-crystal transformation to desolvate compound 2’ may be driven by Coulomb energy gain. Furthermore, the structural comparison between quasi-polymorphic compounds 1 and 2 revealed that the synergy between Coulomb and π-stacking interactions induces a significant distortion of coordination structure of 2.

A heterostructure of diamagnetic magnesium‒aluminium layered double hydroxides (Mg‒Al LDHs) and photomag‐ netic cobalt‒iron Prussian Blue analogue (Co‒Fe PBA) was designed, synthesized and then designated as LDH‒PB. The cyanide-bridged Co‒Fe PBA was two-dimensionally intercalated into the Mg‒Al LDH template by the stepwise anion exchange method. LDH‒PB showed ferrimagnetic properties with in-plane antiferromagnetic exchange interactions, as well as small photo-induced magnetization by visible light illumination due to the low dimensional structures and the characteristic photo-induced electronic states of the mixed valence of FeIII(low spin, S = 1/2)‒CN‒ CoII(high spin, S = 3/2)‒NC‒FeII (low spin, S = 0).

Electrochemical detection of Se4+ has been performed by anodic stripping voltammetry on a boron-doped diamond (BDD) electrode modified with gold nanoparticles deposited through chronocoulometry. This method is based on the affinity between the gold nanoparticles and Se0, while the BDD electrode is presented as an ideal material for metal modification due to its unique properties. The resulting anodic stripping voltammograms exhibited a clear peak at 0.9 V versus AgCl related to Se4+, and highly accurate (r2=0.99) calibration curves could be obtained for a selenium concentration range between 10 and 100 μg/L. The influence of Se deposition time and other metals dissolved in solution (Cu, Cd, Pb, Cr, and B) has been investigated as well, and it was found that the Se4+ calibration curves remained unaltered. For all the experiments performed, a detection limit around 10 μg/L was achieved. The high accuracy and reproducibility of the results as well as the excellent stability of the electrode material proves the excellent capabilities of this system for selenium detection.