Electrocatalytic and simultaneous determination of isoproterenol, uric acid and folic acid at molybdenum (VI) complex-carbon nanotube paste electrode

Sensitive electrochemical determination of quercetin and folic acid with cobalt nanoparticle functionalized multi-walled carbon nanotube

A nanocomposite of cobalt nanoparticle (CoNP) functionalized carbon nanotube (Co@CNT) was prepared and used to modify a glassy carbon electrode (Co@CNT/GCE). Characterization indicates the morphology of Co@CNT is CoNPs adhering on CNTs. With the nano-interface, Co@CNT provides large surface area, high catalytic activity, and efficient electron transfer, which makes Co@CNT/GCE exhibiting satisfactory electrochemical response toward quercetin (QC) and folic acid (FA). The optimum pH values for the detection of FA and QC are 7.0 and 3.0, respectively. The saturated absorption capacity (Γ*) and catalytic rate constant (kcat) of Co@CNT/GCE for QC and FA are calculated as 1.76 × 10-9, 3.94 × 10-10 mol∙cm-2 and 3.04 × 102, 0.569 × 102 M-1∙s-1. The linear range for both FA and QC is estimated to be 5.0 nM-10 μM, and the LODs (3σ/s) were 2.30 nM and 2.50 nM, respectively. The contents of FA and QC in real samples determined by Co@CNT/GCE are comparable with the results determined by HPLC. The recoveries were in the range 90.5 ~ 114% and the total RSD was lower than 8.67%, which further confirms the reliability of the proposed electrode for practical use.

KLİNİKTE ÖNEMLİ OLAN KATEKOLAMİN VE TÜREVLERİNİN YAPILARININ İNCELENMESİ

Amaç: Katekolaminler olarak adlandırılan monoamin yapısındaki 3,4-dihidroksifeniletilamin türevi dopamin, epinefrin ve norepinefrin, çok önemli biyolojik rolleri olan endojen bileşiklerdir. Katekol yapısı taşıyan bu biyomoleküllerin, kendine özgü reseptörleri uyararak, organizmadaki pek çok sistemi kontrol ettiği bilinmektedir. Özellikle bu endojen bileşiklerin, adrenerjik ve dopaminerjik sistem üzerinden uyarıcı etkilerinin olduğu görülmektedir. Pek çok biyolojik süreçte hormon veya nörotransmitter olarak yer alan bu bileşikler, terapötik önemleri nedeniyle sentetik olarak da elde edilerek klinikte kullanılmaktadır. Ayrıca, endojen katekolaminlerin farmakolojik ve farmasötik özelliklerini iyileştirmek amacıyla, kimyasal modifikasyonlar ile yeni pek çok türevi geliştirilmiştir. Klinikteki kullanımlarının geniş ve önemli olması, bu bileşikleri araştırmacılar için değerli kılmaktadır. Katekolamin ve türevi bileşiklerin aktivitelerinin incelenmesi kadar kimyasal yapılarının anlaşılması ve sentez yöntemlerinin araştırılması da yeni türevlerin geliştirilmesi açısından çok önemlidir. Sonuç ve Tartışma: Bu nedenle bu çalışmada klinik önemleri olan katekolamin türevlerinin yapıları ve özellikleri araştırılmıştır. Çalışma sonucunda katekolaminlerin kimyasal özellikleri, biyosentezleri ve sentetik olarak elde edilme yöntemleri ile biyolojik aktiviteleri ve klinikteki kullanımları ortaya konulmuştur.

Nano optical and electrochemical sensors and biosensors for detection of narrow therapeutic index drugs

For the first time, a comprehensive review is presented on the quantitative determination of narrow therapeutic index drugs (NTIDs) by nano optical and electrochemical sensors and biosensors. NTIDs have a narrow index between their effective doses and those at which they produce adverse toxic effects. Therefore, accurate determination of these drugs is very important for clinicians to provide a clear judgment about drug therapy for patients. Routine analytical techniques have limitations such as being expensive, laborious, and time-consuming, and need a skilled user and therefore  the nano/(bio)sensing technology leads to high interest.

Recent Advances in Electrochemical and Optical Sensors for Detecting Tryptophan and Melatonin

Tryptophan and melatonin are pleiotropic molecules, each capable of influencing several cellular, biochemical, and physiological responses. Therefore, sensitive detection of tryptophan and melatonin in pharmaceutical and human samples is crucial for human well-being. Mass spectrometry, high-performance liquid chromatography, and capillary electrophoresis are common methods for both tryptophan and melatonin analysis; however, these methods require copious amounts of time, money, and manpower. Novel electrochemical and optical detection tools have been subjects of intensive research due to their ability to offer a better signal-to-noise ratio, high specificity, ultra-sensitivity, and wide dynamic range. Recently, researchers have designed sensitive and selective electrochemical and optical platforms by using new surface modifications, microfabrication techniques, and the decoration of diverse nanomaterials with unique properties for the detection of tryptophan and melatonin. However, there is a scarcity of review articles addressing the recent developments in the electrochemical and optical detection of tryptophan and melatonin. Here, we provide a critical and objective review of high-sensitivity tryptophan and melatonin sensors that have been developed over the past six years (2015 onwards). We review the principles, performance, and limitations of these sensors. We also address critical aspects of sensitivity and selectivity, limit and range of detection, fabrication process and time, durability, and biocompatibility. Finally, we discuss challenges related to tryptophan and melatonin detection and present future outlooks.

Simultaneous determination of ascorbic acid, acetaminophen and codeine based on multi-walled carbon nanotubes modified with magnetic nanoparticles paste electrode

Based on incorporating ZnCrFeO4 into multi-walled carbon nanotubes paste matrix (MWCNTs/ZnCrFeO4/CPE), a chemically modified electrode was prepared for the simultaneous determination of ascorbic acid (AA), acetaminophen (AC) and codeine (CO). The prepared electrode, MWCNTs/ZnCrFeO4/CPE, was characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The MWCNTs/ZnCrFeO4/CPE showed an efficient electrocatalytic activity for the oxidation of AA, AC, and CO. The separations of the oxidation peak potentials for AA-AC and AC-CO were about 250mV and 630mV, respectively. The calibration curves obtained for AA, AC, and CO were in the ranges of 0.4-730.0μmolL(-1), 0.1-368.0μmolL(-1), and 0.3-250.0μmolL(-1), respectively. The detection limits (S/N=3) were 0.03μmolL(-1), 0.009μmolL(-1), and 0.01μmolL(-1) for AA, AC, and CO, respectively. The method was also successfully employed as a selective, simple, and precise method to determinate AA, AC, and CO in pharmaceutical and biological samples.

A composite material based on nanoparticles of yttrium (III) oxide for the selective and sensitive electrochemical determination of acetaminophen

An electrochemical sensor was prepared by modifying a glassy carbon electrode (GCE) with a composite of yttrium (III) oxide nanoparticles (Y2O3NPs) and carbon nanotubes (CNTs) for the determination of acetaminophen (ACT). Compared with a bare GCE and CNTs/GCE, the Y2O3NPs/CNTs/GCE exhibited a well-defined redox couple for ACT and highly enhanced the current response. The separations in the anodic and cathodic peak potentials (ΔEp) for ACT were 552mV, 24mV and 10mV at ba4re GCE, CNTs/GCE and Y2O3NPs/CNTs/GCE, respectively. The observation of only 10mV of ΔEp for ACT at Y2O3NPs/CNTs/GCE was a clear indication of a great acceleration of the electrode process compared to bare GCE and GCE modified with CNTs. Also, l-ascorbic acid (l-AA) and l-tyrosine (l-TRY) did not interfere with the selective determination of ACT. Square wave voltammetry (SWV) was performed for the quantification of ACT. A linear plot was obtained for current responses versus the concentrations of ACT over the range from 1.0×10(-10) to 1.8×10(-8)M with a detection limit of 3.0×10(-11)M (based on 3Sb/m). The proposed composite material provided high electrocatalytic activity, improved voltammetric behavior, good selectivity and good reproducibility. The accurate quantification of ACT makes the proposed electrode of great interest for the public health.