Development, validation and enzyme kinetic evaluation of multi walled carbon nano tubes mediated tyrosinase based electrochemical biosensing platform for the voltammetric monitoring of epinephrine

Lab-on-a-Scalpel: Medical Tool Incorporating a Disposable Fully 3D-Printed Electrochemical Cell Promoting Drop-Volume Chemical Analysis in the Operating Theater

Surgical operations are intricate and invasive procedures that require continuous monitoring of the patient's biochemical profile. Point-of-care testing would allow healthcare professionals to identify abnormalities and make the necessary interventions to minimize the risk of complications and ensure patient safety. To this end, we report the development of a disposable and compact fully 3D-printed electrochemical cell incorporated into a medical scalpel (Lab-on-a-Scalpel), aiming to promote on-site (electro)chemical analysis in the operating theater. This multifunctional device minimizes the number of instruments needed during surgery and can be fabricated on-demand by using a desktop-sized 3D printer at a very low cost. The performance of the Lab-on-a-Scalpel sensing device was evaluated over various electrochemical techniques (cyclic voltammetry, amperometry, and differential pulse voltammetry) and different setups (stirring, drop-volume analysis, polarization potentials, etc.) for the determination of epinephrine. Results showed attractive analytical figures-of-merit, with the limit of detection (LOD) reaching 0.13 μM, and high accuracy in recovery studies conducted on artificial blood samples. Our findings suggest that Lab-on-a-Scalpel is a valuable tool that enables near-patient diagnostics with a minimum sample volume and holds promise to become an essential tool for robotic-assisted surgery.

Biochemical Sensors for Personalized Therapy in Parkinson's Disease: Where We Stand

Since its first introduction, levodopa has remained the cornerstone treatment for Parkinson's disease. However, as the disease advances, the therapeutic window for levodopa narrows, leading to motor complications like fluctuations and dyskinesias. Clinicians face challenges in optimizing daily therapeutic regimens, particularly in advanced stages, due to the lack of quantitative biomarkers for continuous motor monitoring. Biochemical sensing of levodopa offers a promising approach for real-time therapeutic feedback, potentially sustaining an optimal motor state throughout the day. These sensors vary in invasiveness, encompassing techniques like microdialysis, electrochemical non-enzymatic sensing, and enzymatic approaches. Electrochemical sensing, including wearable solutions that utilize reverse iontophoresis and microneedles, is notable for its potential in non-invasive or minimally invasive monitoring. Point-of-care devices and standard electrochemical cells demonstrate superior performance compared to wearable solutions; however, this comes at the cost of wearability. As a result, they are better suited for clinical use. The integration of nanomaterials such as carbon nanotubes, metal-organic frameworks, and graphene has significantly enhanced sensor sensitivity, selectivity, and detection performance. This framework paves the way for accurate, continuous monitoring of levodopa and its metabolites in biofluids such as sweat and interstitial fluid, aiding real-time motor performance assessment in Parkinson's disease. This review highlights recent advancements in biochemical sensing for levodopa and catecholamine monitoring, exploring emerging technologies and their potential role in developing closed-loop therapy for Parkinson's disease.

A novel copper ion enhanced electrochemical DNA biosensor for the determination of epinephrine

A novel electrochemical biosensor was developed for the detection of epinephrine (EP) by immobilizing double-strand DNA (dsDNA) bound with copper ions on a gold electrode (Cu2+/dsDNA/MCH/AuE). The electrochemical behavior of EP at Cu2+/dsDNA/MCH/AuE was examined, and the results demonstrated a significant enhancement in the electrocatalytic oxidation peak current of EP due to the formation of a stable G-Cu(II)-G sandwich structure between Cu2+ and guanine at the modified electrode. The modification process of the electrode was characterized by scanning electron microscopy, infrared spectroscopy, electrochemical impedance spectroscopy, and differential pulse voltammetry. A study on the effect of pH in phosphate buffer solution on the electrochemical oxidation of EP indicated that the catalytic oxidation process was pH-dependent. A plot of catalytic current versus EP concentration exhibited a dual-linear relationship within two ranges: 1.0-12.5 μM and 12.5-1000.0 μM, with correlation coefficients of 0.995 and 0.997, respectively. The limit of detection was determined to be 47 nM (S/N = 3). According to the calculated Hill coefficient (0.99), it can be concluded that the electrocatalytic process followed the Michaelis-Menten kinetic mechanism. The maximum catalytic current Im was 25 μA, while the apparent Michaelis-Menten constant Km was 1.425 mM. These findings indicated excellent electrocatalytic activity of the modified electrode towards oxidation of EP. The developed biosensor successfully detected EP in spiked mouse serum as well as epinephrine hydrochloride injection with high selectivity, sensitivity, stability, and accuracy.

Detection of epinephrine using a K2Fe4O7 modified glassy carbon electrode

Iron-based electrochemical catalysts used to modify electrodes for biosensing have received more attention from biosensor manufacturers because of their excellent biocompatibility and low cost. In this work, a fast-ion conductor potassium ferrite (K2Fe4O7) modified glassy carbon electrode (GCE) was prepared for detecting epinephrine (EP) by electrochemical techniques. The obtained K2Fe4O7/GCE electrode exhibited not only a wide linear range over EP concentration from 2 μM to 260 μM with a detection limit of 0.27 μM (S/N = 3) but also high selectivity toward EP in the presence of common interferents ascorbic acid (AA) and uric acid (UA), as well as good reproducibility and stability.

Development of an Innovative Biosensor Based on Graphene/PEDOT/Tyrosinase for the Detection of Phenolic Compounds in River Waters

Phenolic compounds, originating from industrial, agricultural, and urban sources, can leach into flowing waters, adversely affecting aquatic life, biodiversity, and compromising the quality of drinking water, posing potential health hazards to humans. Thus, monitoring and mitigating the presence of phenolic compounds in flowing waters are essential for preserving ecosystem integrity and safeguarding public health. This study explores the development and performance of an innovative sensor based on screen-printed electrode (SPE) modified with graphene (GPH), poly(3,4-ethylenedioxythiophene) (PEDOT), and tyrosinase (Ty), designed for water analysis, focusing on the manufacturing process and the obtained electroanalytical results. The proposed biosensor (SPE/GPH/PEDOT/Ty) was designed to achieve a high level of precision and sensitivity, as well as to allow efficient analytical recoveries. Special attention was given to the manufacturing process and optimization of the modifying elements' composition. This study highlights the potential of the biosensor as an efficient and reliable solution for water analysis. Modification with graphene, the synthesis and electropolymerization deposition of the PEDOT polymer, and tyrosinase immobilization contributed to obtaining a high-performance and robust biosensor, presenting promising perspectives in monitoring the quality of the aquatic environment. Regarding the electroanalytical experimental results, the detection limits (LODs) obtained with this biosensor are extremely low for all phenolic compounds (8.63 × 10-10 M for catechol, 7.72 × 10-10 M for 3-methoxycatechol, and 9.56 × 10-10 M for 4-methylcatechol), emphasizing its ability to accurately measure even subtle variations in the trace compound parameters. The enhanced sensitivity of the biosensor facilitates detection and quantification in river water samples. Analytical recovery is also an essential aspect, and the biosensor presents consistent and reproducible results. This feature significantly improves the reliability and usefulness of the biosensor in practical applications, making it suitable for monitoring industrial or river water.

The Use of Crystalline Carbon-Based Nanomaterials (CBNs) in Various Biomedical Applications

This review study aims to present, in a condensed manner, the significance of the use of crystalline carbon-based nanomaterials in biomedical applications. Crystalline carbon-based nanomaterials, encompassing graphene, graphene oxide, reduced graphene oxide, carbon nanotubes, and graphene quantum dots, have emerged as promising materials for the development of medical devices in various biomedical applications. These materials possess inorganic semiconducting attributes combined with organic π-π stacking features, allowing them to efficiently interact with biomolecules and present enhanced light responses. By harnessing these unique properties, carbon-based nanomaterials offer promising opportunities for future advancements in biomedicine. Recent studies have focused on the development of these nanomaterials for targeted drug delivery, cancer treatment, and biosensors. The conjugation and modification of carbon-based nanomaterials have led to significant advancements in a plethora of therapies and have addressed limitations in preclinical biomedical applications. Furthermore, the wide-ranging therapeutic advantages of carbon nanotubes have been thoroughly examined in the context of biomedical applications.

Electrochemical Biosensing of L-DOPA Using Tyrosinase Immobilized on Carboxymethyl Starch-Graft-Polyaniline@MWCNTs Nanocomposite

The electrochemical behavior of the immobilized tyrosinase (Tyrase) on a modified glassy carbon electrode with carboxymethyl starch-graft-polyaniline/multi-walled carbon nanotubes nanocomposite (CMS-g-PANI@MWCNTs) was investigated. The molecular properties of CMS-g-PANI@MWCNTs nanocomposite and its morphological characterization were examined by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). A simple drop-casting method was employed to immobilize Tyrase on the CMS-g-PANI@MWCNTs nanocomposite. In the cyclic voltammogram (CV), a pair of redox peaks were observed at the potentials of +0.25 to -0.1 V and E°' was equal to 0.1 V and the apparent rate constant of electron transfer (K_s) was calculated at 0.4 s^-1. Using differential pulse voltammetry (DPV), the sensitivity and selectivity of the biosensor were investigated. The biosensor exhibits linearity towards catechol and L-dopa in the concentration range of 5-100 and 10-300 μM with a sensitivity of 2.4 and 1.11 μA μΜ^-1 cm^-2 and limit of detection (LOD) 25 and 30 μM, respectively. The Michaelis-Menten constant (K_m) was calculated at 42 μΜ for catechol and 86 μΜ for L-dopa. After 28 working days, the biosensor provided good repeatability and selectivity, and maintained 67% of its stability. The existence of -COO^- and -OH groups in carboxymethyl starch, -NH₂ groups in polyaniline, and high surface-to-volume ratio and electrical conductivity of multi-walled carbon nanotubes in the CMS-g-PANI@MWCNTs nanocomposite cause good Tyrase immobilization on the surface of the electrode.

Tyrosinase Immobilization Strategies for the Development of Electrochemical Biosensors-A Review

The development of enzyme biosensors has successfully overcome various challenges such as enzyme instability, loss of enzyme activity or long response time. In the electroanalytical field, tyrosinase is used to develop biosensors that exploit its ability to catalyze the oxidation of numerous types of phenolic compounds with antioxidant and neurotransmitter roles. This review critically examines the main tyrosinase immobilization techniques for the development of sensitive electrochemical biosensors. Immobilization strategies are mainly classified according to the degree of reversibility/irreversibility of enzyme binding to the support material. Each tyrosinase immobilization method has advantages and limitations, and its selection depends mainly on the type of support electrode, electrode-modifying nanomaterials, cross-linking agent or surfactants used. Tyrosinase immobilization by cross-linking is characterized by very frequent use with outstanding performance of the developed biosensors. Additionally, research in recent years has focused on new immobilization strategies involving cross-linking, such as cross-linked enzyme aggregates (CLEAs) and magnetic cross-linked enzyme aggregates (mCLEAs). Therefore, it can be considered that cross-linking immobilization is the most feasible and economical approach, also providing the possibility of selecting the reagents used and the order of the immobilization steps, which favor the enhancement of biosensor performance characteristics.

Advanced Nanomaterials-Based Electrochemical Biosensors for Catecholamines Detection: Challenges and Trends

Catecholamines, including dopamine, epinephrine, and norepinephrine, are considered one of the most crucial subgroups of neurotransmitters in the central nervous system (CNS), in which they act at the brain's highest levels of mental function and play key roles in neurological disorders. Accordingly, the analysis of such catecholamines in biological samples has shown a great interest in clinical and pharmaceutical importance toward the early diagnosis of neurological diseases such as Epilepsy, Parkinson, and Alzheimer diseases. As promising routes for the real-time monitoring of catecholamine neurotransmitters, optical and electrochemical biosensors have been widely adopted and perceived as a dramatically accelerating development in the last decade. Therefore, this review aims to provide a comprehensive overview on the recent advances and main challenges in catecholamines biosensors. Particular emphasis is given to electrochemical biosensors, reviewing their sensing mechanism and the unique characteristics brought by the emergence of nanotechnology. Based on specific biosensors' performance metrics, multiple perspectives on the therapeutic use of nanomaterial for catecholamines analysis and future development trends are also summarized.