Oxidation Of Dopamine Research Articles

Colorimetric Detection of Dopamine Based on Peroxidase-like Activity of β-CD Functionalized AuNPs.

Catalytically active nanomaterials, or nanozymes, have gained significant attention as alternatives to natural enzymes due to their low cost, ease of preparation, and enhanced stability. Because of easy preparation, excellent biocompatibility, and unique optoelectronic properties, gold nanoparticles (AuNPs) have attracted increasing attention in many fields, including nanozymes. In this work, we demonstrated the applicability of beta-cyclodextrin functionalized gold nanoparticles (β-CD-AuNPs) as enzyme mimics for different substances, including TMB and DA. We found that β-CD-AuNPs can catalyze the H2O2-mediated oxidation of DA. The dopamine signal-off sensor was developed by taking advantage of the peroxidase-like activity of β-CD-AuNPs towards TMB and DA, where both 3,3',5,5'-tetramethylbenzidine (TMB) and dopamine (DA) may compete for the binding sites with β-CD-AuNPs. As a result, the presence of dopamine can be detected even through the naked eye (up to the concentration of 3.75 µM) and using a spectrophotometer (up to the concentration of 1.0 µM) by monitoring the disappearance of the blue color of the oxidized form of TMB in the presence of dopamine. Furthermore, no obvious disappearance of color was observed at lower concentrations of interferences including ascorbic and uric acid. Given the versatility of cyclodextrin to host large numbers of analyte molecules, we envision that a similar principle can be applied for the detection of other analyte molecules of biological, medical, and environmental significance.

HDAC4/5 Inhibitor, LMK-235 Improves Animal Voluntary Movement in MPTP-Induced Parkinson's Disease Model.

Oxidation of dopamine can cause various side effects, which ultimately leads to cell death and contributes to Parkinson's disease (PD). To counteract dopamine oxidation, newly synthesized dopamine is quickly transported into vesicles via vesicular monoamine transporter 2 (VMAT2) for storage. VMAT2 expression is reduced in patients with PD, and studies have shown increased accumulation of dopamine oxidation byproducts and α-synuclein in animals with low VMAT2 expression. Conversely, animals that overexpress VMAT2 show better protection for dopamine neurons. Based on these findings, this study used histone deacetylase inhibitors (HDACi) to increase VMAT2 expression, reduce dopamine-induced oxidative stress, and evaluate the resulting behavioral improvements in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD animal model. LMK-235 not only increased VMAT2 expression at various concentrations in the SH-SY5Y cell line differentiated into dopaminergic cells but also demonstrated effective cytoprotective properties in several toxicity assays. It significantly raised VMAT2 expression in both the striatum and the ventral tegmental area of an MPTP-induced PD model, supporting its role in reversing behavioral abnormalities linked to PD. In addition to these results, coadministration of LMK-235 with L-DOPA, a standard therapy for PD, restored typical behavioral patterns, highlighting the potential of HDACi in alleviating PD symptoms. The expression of VMAT2 induced by LMK-235, an inhibitor of Class IIa histone deacetylases primarily found in the nervous system, aids in sequestering dopamine into vesicles, potentially enhancing cell survival by inhibiting dopamine oxidation. Additionally, upregulation of VMAT2 has been shown to offer effective protection against MPTP-induced toxicity and significantly improve behavioral abnormalities associated with PD. Coadministration with L-DOPA produced the most notable improvement in behavioral outcomes. Altogether, these findings suggest that the overexpression of VMAT2 may offer a promising strategy for developing treatments for PD by mitigating dopaminergic neuron death resulting from dopamine oxidation.

Unravelling the Role of Tyrosine and Tyrosine Hydroxylase in Parkinson's Disease: Exploring Nanoparticle-based Gene Therapies.

Parkinson's disease (PD) is a neurodegenerative disorder that results from the progressive loss of neurons in the brain followed by symptoms such as slowness and rigidity in movement, sleep disorders, dementia and many more. The different mechanisms due to which the neuronal degeneration occurs have been discussed, such as mutation in PD related genes, formation of Lewy bodies, oxidation of dopamine. This review discusses current surgical treatment and gene therapies with novel developments proposed for PD. Gene therapy based on novel approaches will possess more potential advantages over the conventional methods. Currently, gene therapy for such disorders is still under the process of clinical trials and approval. The pathogenesis comes from the breakdown of dopaminergic neurons within substantia nigra (SN) by the action of tyrosinase enzyme and subsequent accumulation of α-synuclein within the neurons. These dopaminergic neurons are the main source of dopamine, the decline of which is responsible for the symptoms. So, gene therapy can possibly provide more stable supplementation and regulate the expression of tyrosinase enzyme, providing better symptomatic relief and lesser side effects. Dopamine replacement therapy is a wellstudied gene therapy method for PD. Another approach involves introducing functional genes for enzymes such as tyrosine hydroxylase, cyclohydrolases, and decarboxylases with the help of engineered vectors such as AAV and LV. Further, the potential application of nanoparticles in gene therapy as an efficient gene delivery and imaging system has been discussed. Among these, lipidbased nanoparticles such as PILs offer important benefits in terms of enhanced bioavailability, permeability to the cells, and solubility. So, this review paper summarizes some of the advanced gene therapy approaches for PD and the current status of clinical research in the development of gene therapy using nanoparticles.

F-p-d Orbital Hybridization Promotes Hydroxyl Intermediate Adsorption for Electrochemical Biomolecular Oxidation and Identification.

The rational design of efficient hydroxyl intermediate (*OH) adsorption catalysts for dopamine electrooxidation still faces a major challenge. To address this challenge, a CeO2-loaded CuO catalyst inspired by the f-p-d orbital hybridization strategy is designed to achieve efficient *OH adsorption and improve dopamine oxidation. The experimental results and theoretical calculations demonstrate that the f-p-d orbital hybridization regulates the electron distribution at the Ce-O-Cu interface, which facilitates electron transfer and optimizes the adsorption of *OH, thereby promoting dopamine oxidation. The designed electrochemical sensor exhibits excellent catalytic activity and sensitivity, reaching a limit of detection of 3.22 nM. This work provides a promising approach for designing highly active electrocatalysts with orbital hybridization for dopamine oxidation.

G6PD deficiency triggers dopamine loss and the initiation of Parkinson's disease pathogenesis.

Loss of dopaminergic neurons in Parkinson's disease (PD) is preceded by loss of synaptic dopamine (DA) and accumulation of proteinaceous aggregates. Linking these deficits is critical to restoring DA signaling in PD. Using murine and human pluripotent stem cell (hPSC) models of PD coupled with human postmortem tissue, we show that accumulation of α-syn micro-aggregates impairs metabolic flux through the pentose phosphate pathway (PPP). This leads to decreased nicotinamide adenine dinucleotide phosphate (NADP/H) and glutathione (GSH) levels, resulting in DA oxidation and decreased total DA levels. We find that α-syn anchors the PPP enzyme G6PD to synaptic vesicles via the α-syn C terminus and that this interaction is lost in PD. Furthermore, G6PD clinical mutations are associated with PD diagnosis, and G6PD deletion phenocopies PD pathology. Finally, we show that restoring NADPH or GSH levels through genetic and pharmacological intervention blocks DA oxidation and rescues steady-state DA levels, identifying G6PD as a pharmacological target against PD.

A surface modified laser-induced graphene based flexible biosensor for multiplexed sweat analysis.

The growing popularity of electrochemical sensors featuring non-invasive biosensing technologies has generated significant enthusiasm for continuous monitoring of bodily fluid biomarkers, potentially aiding in the early detection of health issues in individuals. However, detection of multiple biomarkers in complex biofluids often necessitates a high-density array which creates a challenge in achieving cost-effective fabrication methods. To overcome this constraint, this work reports the fabrication of an electrochemical sensor utilizing a NiO-Ti3C2Tx MXene-modified flexible laser-induced graphene (LIG) electrode for the separate and concurrent analysis of ascorbic acid (AA), dopamine (DA), and uric acid (UA) in human sweat and also addresses the deficiencies in the existing state of the art by offering a cost-efficient and high-performance sensor that mitigates the degrading constraints of conventional LIG electrodes. Cyclic voltammetry and differential pulse voltammetry measurements reveals that the electrochemical properties of the modified electrode, attain a low detection limit and great sensitivity for the target biomarkers. The NiO-Ti3C2Tx/LIG sensor demonstrated enhanced electrocatalytic activity for the oxidation of ascorbic acid, dopamine, and uric acid, and proved useful for analysing these biomarkers in synthetic sweat samples. Under the optimized conditions, the LOD values were estimated to be 16, 1.97 and 0.78 μM for AA, DA and UA, respectively. The developed high-efficiency sensor holds significant promise for applications in flexible and wearable electronics for health monitoring.

A covalent organic frameworks based sensor for adsorptive stripping voltammetric detection of nanomolar dopamine in living mouse brain

Dopamine (DA) is a type of neurotransmitter playing key roles in brain functions, but detection of DA in the brain is challenging because of its nanomolar concentration. Herein we report a strategy using the covalent organic frameworks (COF) modified electrode for highly sensitive and selective detection of DA in the living mouse brain. The unique physiochemical properties and space-confinement effect of ultrasmall nanochannels of COF can regulate the molecular conformation and electrochemical oxidation of DA. In particular, the electrochemically active oxidation intermediates can be stabilized and accumulated in the nanochannels, thus allowing the detection of nanomolar DA by adsorptive stripping analysis with the limit of detection improved by ∼103 fold in comparison with the conventional cyclic voltammetry. Additionally, thanks to the remarkable difference in adsorption energies of other structurally similar neurotransmitters, the COF modified electrode also displays an excellent selectivity to DA. Finally, the modified electrode was combined with microdialysis to successfully quantify DA in the normal and Parkinson’s disease model mice brain. We believe that COF with tunable selectivity will offer enormous promise for detection of different neurotransmitters.

Cysteine-Grafted Cu MOF/ZnO/PANI Nanocomposite for Nonenzymatic Electrochemical Sensing of Dopamine.

Electrochemical sensing has shown great promise in monitoring neurotransmitter levels, particularly dopamine, essential for diagnosing neurological illnesses like Parkinson's disease. Such techniques are easy, cost-effective, and extremely sensitive. The present investigation discusses the synthesis, characterization, and potential use of a cysteine-grafted Cu MOF/ZnO/PANI nanocomposite deposited on the modified glassy carbon electrode surface for nonenzymatic electrochemical sensing of dopamine. The synthesized nanocomposite was confirmed through X-ray diffraction, Fourier transform infrared, Raman, and scanning electron microscopy characterization techniques. Additionally, electrochemical analysis was conducted using cyclic voltammogram, differential pulse voltammetry, and chronoamperometry. The process was determined to be the diffusion-controlled oxidation of dopamine. Dopamine underwent spontaneous adsorption on the electrode surface through an electrochemically reversible mechanism. Despite various biological interfering factors, the nonenzymatic electrochemical sensor demonstrated a remarkable level of selectivity toward dopamine. Cysteine-grafted Cu MOF/ZnO/PANI produced the lowest dopamine detection limit, at 0.39 μM, and the sensitivity was observed as 122.57 μAmM-1 cm-2. Results have demonstrated that enhanced catalytic and conductive properties of MOFs, combined with nanostructured materials, are the primary factors affecting the sensor's performance.

Self-assembly Pt hollow nanospheres for highly selective and ultrasensitive detection of dopamine

Abnormal concentration of dopamine, one critical neurotransmitter in central nervous system, causes several neurological diseases associated with behavioral responses and brain functions in human beings. Highly sensitive detection of dopamine is of great significance yet challengeable. In this work, Pt hollow nanospheres (Pt HNSs) with a uniform diameter of 30 nm were successfully synthesized in water by self-assembly method under room temperature. The fabricated Pt hollow/Nafion nanospheres modified glassy carbon electrode (Pt HNSS/Nafion/GCE) exhibited superior electrocatalytic performance, with peak currents 2.24 and 4.54 times higher than those of Nafion-modified glassy carbon electrode (Nafion/GCE) and bare glassy carbon electrode (GCE), respectively. Theoretical calculations indicate that dopamine has an adsorption energy of −3.18 eV on the Pt(111) surface, with an electron transfer of + 1.84 |e|, aligning with the 2-electron transfer mechanism. Furthermore, the low energy barrier observed during dopamine oxidation process suggests that the Pt(111) surface is highly favorable for dopamine oxidation. Meanwhile, Pt HNSS/Nafion/GCE electrochemical sensor exhibits highly sensitive and selective response in determination of dopamine ranging from 0.01 to 250 μM with low detection limits of 0.804 nM (S/N = 3). Moreover, the electrochemical sensor shows reliable signals in real test with great anti-interference and stability during the experiments, making it a promising candidate for applications in dopamine sensing.

Hair dyeing based on DNAzyme-catalyzed oxidation of dopamine and natural pigments

Hair dyeing based on DNAzyme-catalyzed oxidation of dopamine and natural pigments

Multi‐walled carbon nanotubes co‐doped with sulfur and nitrogen as sensors for the simultaneous electrochemical determination of biomolecules

AbstractMulti-walled carbon nanotubes co-doped with sulfur and nitrogen (S–N-MWCNTs) were produced onto silicon/silicon oxide by means of chemical vapor deposition (CVD) upon decomposition of dimethyl sulfoxide (DMSO) and acetonitrile (ACN) in the presence of ferrocene (FeCp2). The synthesized S–N-MWCNTs were characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and electrochemical impedance spectroscopy (EIS). The electrochemical response of S–N-MWCNTs towards oxidation of ascorbic acid (AA), dopamine (DA), uric acid (UA), and glucose (GL) was investigated in phosphate buffer solution (PBS) (pH 7.4) by means of cyclic voltammetry (CV). Strong dependence of electrochemical quality of S–N-MWCNTs on the concentration of decomposed DMSO precursor was observed. Namely, upon increasing the percentage of decayed DMSO from 1.0 up to 2.0% wt., the electrocatalytic activity of S–N-MWCNTs tends to improve. The separations of oxidation waves between AA-DA, DA-UA, and AA-UA reached their maximum values on S–N-MWCNTs-3, fabricated upon decomposition of 2.0% wt. DMSO precursor, permitting their individual and simultaneous electrochemical determination. Strong interference of GL in the analysis of DA was observed, and consequently, simultaneous analysis of AA, DA, and UA can be only carried out in the absence of GL. A great influence of concentration of decomposed DMSO precursor on the sensitivity of S–N-MWCNTs was also observed. Specifically, upon increasing the percentage of decayed DMSO from 1.0 up to 2.0% wt., the sensitivity and detection capability of S–N-MWCNTs towards AA, DA, UA, and GL analytes tend to enhance.

Au paste electrode to increase the intensity of cathodic electrochemiluminescence

Bipolar electrochemical microscopy (BEM) is a novel electrochemical imaging platform using a vertical closed bipolar electrode (cBPE) array as an imaging element. In BEM, the electrochemical reaction generated at one end of the BPE is converted to electrochemiluminescence (ECL) at the other end of the BPE. Unlike the conventional electrode array method, which requires lead wires for each electrode, BEM can operate without wires to each electrode. Therefore, imaging with both high-temporal and high-spatial resolution is possible, from which advantage, BEM is expected to be a tool for the analysis of biological phenomena that occur in a very short period in a local area on the scale of a single cell. As a simple method for fabricating vertical cBPE arrays, Iwama et al. previously proposed a method of filling conducting carbon pastes (CPs) into pores of a glass capillary plate.1 As another direction of BEM development research, we are conducting dopamine (DA) detection using N,N’-dimethyl-3,4,9,10-perylenetetracarboxylicdiimide (PDI-CH3) as a cathodic luminophore for ECL.2 We are currently investigating the use of a PDI-CH3 mixed paste electrodes as BEM detection elements for DA imaging, taking advantage of the flexibility and ease of modification of the paste electrode. In the process, we found a phenomenon in which ECL is enhanced using Au paste (AuP).3 In this study, we compared PDI-CH3 mixed CP and AuP electrode by three-electrode system and cBPE-ECL detection system.CP was prepared by mixing acetylene carbon black (particle size 42 nm), and liquid paraffin at a weight ratio of 1:1. AuRoFUSE (particle size 0.2–0.4 µm) was used for AuP. The PDI-CPs were obtained by wet mixing of PDI-CH3 and CP at weight ratios from 4:1 to 1:20 in an alumina mortar with ethanol. PDI-AuPs were obtained in a similar way by wet mixing of PDI-CH3 and AuP at weight ratios from 1:5 to 1:20. Each paste was filled into a paste electrode holder (1.6 mm in diameter). PDI-CH3/CP 1:1 by weight and PDI-CH3/AuP 1:20 by weight contain the same volume of PDI-CH3 in a given volume of each paste, because the specific gravities of CP and AuP are speculated 0.95 g/cm3 and 19.3 g/cm3, respectively. Measurements using three-electrode system was conducted with 35 mm dish filled with 0.2 M Na2S2O8 (containing phosphate-buffered saline; PBS), a working electrode (WE; 1.6 mm in diameter), a counter electrode (CE; platinum plate), and a reference electrode (RE; Ag/AgCl). Linear sweep voltammograms (LSVs) and ECL intensities were obtained at a scan rate of 50 mV/s with 500 ms exposure time of a CMOS camera. In the cBPE-ECL detection system, two 35 mm dishes filled with 0.2 M Na2S2O8 (containing PBS) and 0 or 1 mM DA (containing PBS) were used as a detection cell and a sample cell, respectively. A paste electrode to be evaluated in the detection cell and a glassy carbon electrode (1.6 mm in diameter) in the sample cell were connected to each other to be a cBPE. As driving electrodes, a platinum plate in the detection cell, an Ag/AgCl electrode and a second platinum plate in the sample cell were connected to the WE, RE, and CE terminals of a potentiostat, respectively. LSVs and ECL intensities were obtained at a scan rate of 20 mV/s with 5 s exposure time of the CMOS camera.At the three-electrode system, LSVs of PDI-CH3/CP 1:1 and PDI-CH3/AuP 1:20 in weight ratio, containing the same volumes of PDI-CH3 in the pastes, produced similar maximum values of the first current peak related to ECL reaction, while the peak ECL intensities were 1.75 times higher in case using PDI-AuP than in case using PDI-CP. This result suggests that the ECL intensity can be enhanced using AuP. This ECL enhancement may be due to the surface plasmon field-enhancement effect by Au particles on the electrode surface, given that the AuRoFUSE particle size is 0.2 to 0.4 µm. The figure shows the images obtained by CMOS camera at 1.2 V using cBPE-ECL detection system. The ECL intensities peaks originating from DA oxidation in the sample cell were 9.5 times higher using PDI-AuP rather than PDI-CP, even though the peak current values obtained using PDI-AuP and PDI-CP were almost the same. By using AuP instead of CP, imaging such as DA is expected be with high sensitivity in BEM system.

Anisotropic gold nanostructure-mediated electrocatalysis on exfoliated GCN: A shape-dependent study

The growth of anisotropic gold nanostructures on exfoliated GCN(E-GCN) surface and the resulting shape dependent electrocatalytic activity towards ascorbic acid (AA), dopamine (DA) and hydrogen peroxide (HP) were investigated in this present study. The SEM images of Au deposited on GC surface shows anisotropic structures after 120 min deposition. On the other hand, Au deposited on E-GCN after 15 min shows flower like structure (GCE/E-GCN-FL-Au) and it remains unchanged up to 60 min. The flower like morphology was changed to distorted hexagonal morphology after 120 min deposition (GCE/E-GCN-DH-Au) Here, citric acid (CA) can act as a reducing agent for the reduction of Au3+ to Au0. The obtained morphological changes of Au on the surface of E-GCN in contrast to GC plate, reveal that the GCN surface can act as a shape directing agent. The electroactive surface area (EAS) of the GCE/E-GCN-DH-Au was greater than the EAS of the GCE/E-GCN-FL-Au. The influence of Au shape on AA and DA oxidation and HP reduction was also investigated. In terms of electrochemical determination towards AA, DA and HP, the GCE/E-GCN-DH-Au outperformed the other modified electrodes. The GCE/E-GCN-DH-Au proved to be a useful tool for sensitive determination of HP with the LOD of 0.75 nM (S/N=3).

L-Theanine Effectively Protects Against Copper-Facilitated Dopamine Oxidation: Implication for Relieving Dopamine Overflow-Associated Neurotoxicities.

Non-physiological disorders release dopamine into extracellular brain fluid to induce neurodegenerative brain diseases. The harmful mechanism of dopamine overflow is attributed to the dopamine-mediated production of hydroxyl radicals, suggesting that transition metal copper which is high in the brain is involved in promoting dopamine oxidation. MPP+ , an intermediate formed from the conversion of MPTP, is one of the most potent dopamine-releasing agents. It has been reported that L-theanine could improve motor dysfunction in MPTP-treated mice, suggesting that L-theanine may restrain copper-mediated oxidation of released dopamine. The present study examined the influences of L-theanine on extracellular dopamine-mediated cytotoxicity in the absence and presence of copper in SH-SY5Y cells. L-theanine significantly but only moderately suppressed cytotoxicity caused by dopamine alone. Surprisingly, dopamine together with copper rapidly and dramatically caused apoptotic responses by massively disrupting redox homeostasis. Nonetheless, L-theanine exhibited an extraordinary protective effect against these devastating events by chelating copper. The above great contrast in terms of copper could be recapitulated in a cell-free system. Though L-theanine reduced dopamine autoxidation as detected by HPLC, the capacity was not impressive, since a molar ratio of 10,000 (L-theanine to dopamine) was required for fully suppressing dopamine decrease. However, HPLC measurement showed that L-theanine was highly efficient in suppressing copper-mediated dopamine oxidation because only a molar ratio of 10 was required for fully suppressing dopamine decrease. Since copper plays a crucial role in promoting extracellular dopamine oxidation, our results suggest that L-theanine by chelating copper is an attractive food-based protective agent against dopamine overflow.

Lanthanide coordination polymers as luminescent laccase mimics for ratiometric sensing of dopamine

Some metal ions, with inner enzyme-like catalytic activity, could be doped into lanthanide coordination polymers (Ln CPs) through coordination, which has been proved as a facile strategy to prepare the luminescent nanozymes. In this study, Cu-doped Ln CPs with laccase-mimic activity and double luminescence were rationally designed and synthesized by self-assembly of guanine monophosphate (GMP), 2-aminoterephthalic acid (ATA), Cu2+ and Tb3+ in buffer solution at room temperature. The obtained probes Tb/Cu-GMP/ATA CPs not only emitted green fluorescence of Tb3+ and blue fluorescence of ATA simultaneously under irradiation at the same wavelength, but also processed enhanced laccase-like activity for catalyzing the oxidation of phenolic substrates. Upon dopamine (DA), the probes catalyzed the oxidation of DA to polydopamine (PDA), which effectively quenched the fluorescence of Tb3+ due to the internal filtration effect. Based on this, a ratiometric fluorescent sensor for DA was constructed accordingly, and the corresponding fluorescence intensity ratio of Tb3+to ATA (F547/F427) was linearly correlated with the DA concentration in the range of 1 to 400 μM, with a detection limit of 0.44 μM. Besides, this sensor could be used to detect DA in human serum samples with good recovery, which results were highly consistent with that of HPLC method. The constituent and luminescence tunability, as well as the extraordinarily facile synthesis, made Ln CPs a potential platform for designing and preparing the integrated multifunctional probe for special target in sensing applications.

RGO-g-C3N4-Co3O4 Composite Modified Platinum Electrode for Electrochemical Detection of Dopamine

A novel RGO-g-C3N4-Co3O4 composite modified platinum electrode with significant sensing performance for dopamine was fabricated. Herein, RGO-g-C3N4-Co3O4 hybrid nanostructure could boost the electrocatalytic performance of nanoparticles by avoiding the clustering of nanoparticles. These spinel-based composites are stable and affordable materials. Electrochemical impedance spectroscopy revealed enhanced electron transfer at the modified electrode, as evidenced by the lowest charge transfer resistance (Rct) for the RGO-g-C₃N₄-Co₃O₄/Pt electrode. An increased electroactive surface area compared to bare and other modified Pt electrodes was obtained. Several experimental parameters were optimized to maximize sensitivity, including the choice of supporting electrolyte and pH. Cyclic voltammetry conducted at varying scan rates confirmed that the oxidation of dopamine followed a diffusion-controlled process. The modified electrode exhibits outstanding electrocatalytic activity, with a detection limit as low as 8.10 × 10−7 M, demonstrating a wide linear range between 2.00 × 10−6 M to 4 × 10−4 M. Selectivity tests indicated that the sensor could reliably detect dopamine in the presence of common interfering substances such as NaCl, KCl, glucose and urea, ascorbic acid, uric acid and L-dopa. This enhanced sensitivity and selectivity were validated in both synthetic blood and urine samples, providing the electrode’s potential for real-world applications in the diagnosis of neurodegenerative diseases.

Neuroprotective Effect of Natural Indole and β-carboline Alkaloids against Parkinson's Disease: An Overview.

Parkinson's disease (PD) is a devastating neurodegenerative condition that mostly damages dopaminergic neurons in the substantia nigra and impairs human motor function. Males are more likely than females to have PD. There are two main pathways associated with PD: one involves the misfolding of α-synuclein, which causes neurodegeneration, and the other is the catalytic oxidation of dopamine via MAO-B, which produces hydrogen peroxide that can cause mitochondrial damage. Parkin (PRKN), α-synuclein (SNCA), heat shock protein (HSP), and leucine-rich repeat kinase-2 (LRRK2) are some of the target areas for genetic alterations that cause neurodegeneration in Parkinson's disease (PD). Under the impact of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which is also important in Parkinson's disease (PD), inhibition of mitochondrial complex 1 results in enhanced ROS generation in neuronal cells. Natural products are still a superior option in the age of synthetic pharmaceuticals because of their lower toxicity and moderate side effects. A promising treatment for PD has been discovered using beta-carboline (also known as " β-carboline") and indole alkaloids. However, there are not many studies done on this particular topic. In the herbs containing β-carbolines and indoles, the secondary metabolites and alkaloids, β-carbolines and indoles, have shown neuroprotective and cognitive-enhancing properties. In this review, we have presented results from 18 years of research on the effects of indole and β-carboline alkaloids against oxidative stress and MAO inhibition, two key targets in PD. In the SAR analysis, the activity has been correlated with their unique structural characteristics. This study will undoubtedly aid researchers in looking for new PD treatment options.

A carboxymethyl chitosan and dextran hydrogel with slow and rapid photothermal conversion for sequential promoting burn wound healing and inhibiting scar proliferation

Facilitating swift burn wound healing while effectively preventing scar formation continues to be a considerable challenge in medical practice. In this study, an injectable carboxymethyl chitosan/oxidized dextran/polyvinylpyrrolidone/dopamine (COPD) hydrogel was designed for the effective sequentially promotion of burn wound healing and inhibition of scar formation. The COPD hydrogel precursor solution was injected into the burn wound via a double-barreled syringe and transformed into an adherent hydrogel within 25 s. The inclusion of dopamine imparted good free radical scavenging properties to the hydrogel. In particular, the gradual oxidation of dopamine to polydopamine enabled a unique heat production pattern—initially slow (photothermal conversion efficiency: 30.3 %) and then rapidly temperature increasing (photothermal conversion efficiency: 42.8 %) —under single laser irradiation. The effect of promoting healing at the initial stage of the wound was evaluated by constructing a male C57BL/6 mice model with deep second-degree burns, observation of the wound area, PCR analysis, and immunohistochemical staining. Furthermore, the scar inhibition was confirmed by observing reduced expression levels of α-SMA and COLI, along with a decreased collagen I/III ratio. With tunable mechanical properties (maximum compressive strength of 966.4 ± 51.7 kPa), the COPD hydrogel holds significant promise as an adjunctive photothermal platform for intelligent burn wound management.

An electrochemical sensor for simultaneous voltammetric detection of ascorbic acid and dopamine enabled by higher electrocatalytic activity of co-modified MCM-41 mesoporous molecular sieve

It is of great value to develop effective methods for accurately and simultaneously detecting ascorbic acid (AA) and dopamine (DA) in the field of biochemistry. This work reports a nonenzymatic electrochemical sensor for the simultaneous detection of AA and DA by employing a Co-modified MCM-41 (CoMCM-41) mesoporous molecular sieve as an efficient electrocatalytic material, which was synthesized by a two-step hydrothermal method. Subsequently, the high structural organization of the CoMCM-41 mesoporous structure was characterized, and the electrocatalytic performance of CoMCM-41 toward AA and DA oxidation was then evidenced by the catalytic effect of different electrodes modified with or without CoMCM-41. By virtue of the superior electrocatalytic activity of the CoMCM-41, a much wider peak potential difference (ΔEpa) of 310 mV was obtained for the oxidation of AA and DA in their mixture solution, and the parameters that influenced the electrochemical signals of the modified electrode were also optimized. Under optimal conditions, a good linear response to AA and DA was observed on the CoMCM-41 modified electrode. For individual detection of AA and DA, the linear ranges were 7 ~ 105 μM and 5 ~ 110 μM respectively, while the linear response range was 20 ~ 100 μM for simultaneous detection of AA and DA. Satisfactory recovery results were obtained when the fabricated sensor was applied to determine AA in orange juice and DA in madopar pill samples.

Copper-Based Electrochemical Sensor Derived from Thiosemicarbazide for Selective Detection of Neurotransmitter Dopamine.

This paper presents the synthesis of the ligand 1-picolinoyl-4-cyclohexyl-3-thiosemicarbazide (H2pctc) and new metal complexes [Ni(Hpctc)2] (1), [Cu(Hpctc)Cl] (2), and [Cd(Hpctc)2] (3). The synthesized metal complexes were precisely characterized using single crystal X-ray diffraction (SC-XRD). In addition, complexes 1-3 were also characterized by UV-vis, fluorescence, and infrared spectroscopy. SC-XRD data confirmed the distorted octahedral geometry around the Ni(II) and Cd(II) centers and the distorted square planar geometry around the Cu(II) center. Data derived from the emission spectra depict that higher fluorescence intensity was exhibited by complexes 1, 2, and 3 in comparison to that of the free ligand H2pctc, and complex 3 showed the maximum intensity. Further, these metal complex-modified GCEs (glassy carbon electrodes) were utilized for electrochemical sensing of dopamine (DPM). The electrochemical studies of these complexes were performed using modified glassy carbon electrodes supported by electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV) methods. In contrast to complexes 1 and 3, complex 2 is a superior electrode material with a high effective surface area for the electrochemical oxidation of DPM, according to the electrochemical response results. The derived sensor had a wide linear detection range of 1 to 1400 μM, an acceptable sensitivity of 0.01531 μA cm-2 μM-1, and a low LOD of 0.38 μM. The proposed approach was free of the interfering effects of ascorbic acid, uric acid, aminophenol, and other substances. During the successive scans, no fouling of the electrode surface was observed. The proposed electrochemical sensor had excellent stability, sensitivity, and a low detection limit making it suitable for the analysis of a variety of real samples. Additionally, it was proven to be useful for analyzing biological fluids.