Selective monitoring of ultra-trace guanine and adenine from hydrolyzed DNA using boron-doped carbon electrode surfaces

Tailored portable electrochemical sensor for dopamine detection in human fluids using heteroatom-doped three-dimensional g-C3N4 hornet nest structure

BACKGROUND

There is widespread interest in the design of portable electrochemical sensors for the selective monitoring of biomolecules. Dopamine (DA) is one of the neurotransmitter molecules that play a key role in the monitoring of some neuronal disorders such as Alzheimer's and Parkinson's diseases. Facile synthesis of the highly active surface interface to design a portable electrochemical sensor for the sensitive and selective monitoring of biomolecules (i.e., DA) in its resources such as human fluids is highly required.

RESULTS

The designed sensor is based on a three-dimensional phosphorous and sulfur resembling a g-C3N4 hornet's nest (3D-PS-doped CNHN). The morphological structure of 3D-PS-doped CNHN features multi-open gates and numerous vacant voids, presenting a novel design reminiscent of a hornet's nest. The outer surface exhibits a heterogeneous structure with a wave orientation and rough surface texture. Each gate structure takes on a hexagonal shape with a wall size of approximately 100 nm. These structural characteristics, including high surface area and hierarchical design, facilitate the diffusion of electrolytes and enhance the binding and high loading of DA molecules on both inner and outer surfaces. The multifunctional nature of g-C3N4, incorporating phosphorous and sulfur atoms, contributes to a versatile surface that improves DA binding. Additionally, the phosphate and sulfate groups' functionalities enhance sensing properties, thereby outlining selectivity. The resulting portable 3D-PS-doped CNHN sensor demonstrates high sensitivity with a low limit of detection (7.8 nM) and a broad linear range spanning from 10 to 500 nM.

SIGNIFICANCE

The portable DA sensor based on the 3D-PS-doped CNHN/SPCE exhibits excellent recovery of DA molecules in human fluids, such as human serum and urine samples, demonstrating high stability and good reproducibility. The designed portable DA sensor could find utility in the detection of DA in clinical samples, showcasing its potential for practical applications in medical settings.

Development and characterization of a non-enzymatic electrochemical biosensor for rapid determination of sorbent-based extracted trazodone and doxepin in complicated samples

BACKGROUND

Given the importance of achieving optimal therapeutical concentration in patients treated with antidepressants, this study investigates a novel technique for the simultaneous determination of trazodone (TRZ) and doxepin (DOX) in human plasma and serum samples for the first time.

RESULTS

To achieve simultaneous determination of two antidepressants, TRZ and DOX, a novel detection system was designed: a non-enzymatic voltammetric biosensor based on boron-reduced graphene oxide/manganese oxide nanoparticles (GCE/B-rGO/MnO NPs). The detection was accomplished after pre-concentration and extraction trace amounts of the analytes using the thin film-solid phase microextraction (TF-SPME) technique, which employed polyvinyl alcohol/polyvinyl acetate/copper oxide nanoparticles (PVA/PVAc/CuO NPs) electrospun nanofibers. The successful preparation of composite nanofibers and modified electrodes was confirmed using the evaluation of field emission-scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDX). Also, the composite nanofibers were characterized with attenuated total reflectance-Fourier transform-infrared (ATR-FT-IR) and X-ray diffraction (XRD). In the solution of TRZ and DOX, under optimum experimental conditions, the linear dynamic ranges (LDRs) were 0.1-20.0 μmol L-1 and 0.5-27.0 μmol L-1, respectively. Also, the limit of detection (LOD) values of TRZ and DOX were 0.032 and 0.150 μmol L-1.

SIGNIFICANCE

PVAc acts as a cross-linking agent for PVA, and their mixture is effective for sample preparation and pre-concentration of analytes in complex matrices. Also, adding CuO NPs to this polymeric mixture enhanced the adsorption efficiency. Taking advantage of the high surface area of MnO NPs and the high electrical conductivity of B-rGO, and considering the superiority of their simultaneous utilization, the constructed electrochemical biosensor is both cost-effective and rapid. It demonstrates excellent stability, repeatability, and sensitivity for the simultaneous determination of TRZ and DOX under optimal conditions. This biosensor, the first of its kind, is specifically designed for the simultaneous determination of TRZ and DOX in human plasma and serum samples, representing a significant advancement in biosensing technology.

An electrochemical sensor for purine base detection with ZIF-8-derived hollow N-doped carbon dodecahedron and AuNPs as electrocatalysts

In this paper, a novel electrochemical sensor was constructed for the detection of purine bases. Ultrafine carbide nanocrystals confined within porous nitrogen-doped carbon dodecahedrons (PNCD) were synthesized by adding molybdate to ZIF-8 followed by annealing. With MoC-based PNCDs (MC-PNCDs) as the carrier, gold nanoparticles (AuNPs) were deposited on the electrode surface via potentiostatic deposition as the promoter of electron transfer, forming a AuNPs/MC-PNCDs/activated glassy carbon electrode (AGCE) sensor. MC-PNCDs had a large specific surface area, which combined with the excellent electrocatalytic activity of AuNPs, synergistically improved the electrocatalytic activity. The morphology and structure of the electrode surface modifier were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray photoelectron spectroscopy, infrared spectroscopy, X-ray diffraction, nitrogen adsorption-desorption analysis, and electrochemical characterization. Under the optimal conditions, the linear detection range of guanine (G) and adenine (A) was 0.5-160.0 μM, and the detection limits (S/N=3) were 72.1 and 69.6 nM, respectively. AuNPs/MC-PNCDs/AGCE was successfully constructed, and was used to simultaneously detect G and A with high sensitivity and selectivity. Moreover, the sensor was successfully used to detect G and A in herring sperm DNA samples.

Hierarchical engineering of Mn2O3/carbon nanostructured electrodes for sensitive screening of acetylcholine in biological samples

Enzymeless electrochemical sensors have received considerable interest for the direct, sensitive, and selective monitoring of biomolecules in a complex biological environment.

Chipset Nanosensor Based on N‐Doped Carbon Nanobuds for Selective Screening of Epinephrine in Human Samples

Chipset nanosensor design and fabrication are important for healthcare research and development. Herein, a functionalized chipset nanosensor is designed to monitor neurotransmitters (i.e., epinephrine (EP)) in human fluids. An interdigitated electrode array (IDA) is functionalized by N‐doped carbon nanobud (N‐CNB) and N‐doped carbon nanostructure (N‐CNS). The surface morphology of N‐CNB shows the formation of nanotubular‐like branches on sheets and micrometer‐size tubes. The N‐CNS design consists of the formation of aggregated sheets and particles in nanometer size. The irregular shape formation provides surface heterogeneity and numerous free spaces between the stacked nanostructures. N‐atoms ascertain highly active N‐CNS with multifunctional active centers, electron‐rich charged surface, and short distance pathway. The N‐CNB/IDA exhibits the best performance for EP signaling with high sensitivity and selectivity. The N‐CNB/IDA sensing performance for EP detection indicates the successful design of a highly selective and sensitive assay with low detection limit of 0.011 × 10−6 m and a broad linear range of 0.5 × 10−6 to 3 × 10−6 m. The N‐CNB/IDA exhibits a high degree of accuracy and reproducibility with RSD of 2.7% and 3.9%, respectively. Therefore, the chipset nanosensor of N‐CNB/IDA can be used for on‐site monitoring of EP in human serum samples and further used in daily monitoring of neuronal disorders.

Gold Nanorods (AuNRs) and Zeolitic Imidazolate Framework-8 (ZIF-8) Core-Shell Nanostructure-Based Electrochemical Sensor for Detecting Neurotransmitters

The development of novel electrode materials for rapid and sensitive detection of neurotransmitters in the human body is of great significance for early disease diagnosis and personalized therapy. Herein, gold nanorod@zeolitic imidazolate framework-8 (AuNR@ZIF-8) core-shell nanostructures were prepared by controlled encapsulation of gold nanorods within a ZIF-8 assembly. The designed AuNR@ZIF-8 nanostructures have uniform morphology, good dispersion, a large specific surface area, and an average size of roughly 175 nm. Compared with individual ZIF-8 and AuNR-modified electrodes, the obtained core-shell-structured AuNR@ZIF-8 nanocomposite structure-modified electrode shows excellent electrocatalytic performance in the determination of dopamine (DA) and serotonin (ST). The designed AuNR@ZIF-8 exhibited a wide linear range of 0.1-50 μM and low detection limit (LOD, 0.03 μM, S/N = 3) for the determination of DA, as well as a linear range of 0.1-25 μM and low LOD (0.007 μM, S/N = 3) for monitoring ST. The improved performance is attributed to the synergistic effect of the high conductivity of AuNRs and multiple catalytic sites of ZIF-8. The good electroanalytical ability of AuNR@ZIF-8 for detection of DA and ST can provide a guide to efficiently and rapidly monitor other neurotransmitters and construct novel electrochemical sensors.

"ON-OFF-ON" fluorescence switches based on N,S-doped carbon dots: Facile hydrothermal growth, selective detection of Hg2+, and as a reversive probe for guanine

Water contamination due to heavy metal ions has become a major environmental problem worldwide. In this work, "on-off-on" fluorescence switches comprising N,S-doped carbon dots (N,S-CDs) have been developed for selective recognition of Hg²⁺ and as reversive probes for guanine. N,S-CDs were synthesized in a facile one-step hydrothermal approach using citric acid and methionine as precursors. The synthesized N,S-CDs display fluorescence with excitation/emission maxima of 370/440 nm and a quantum yield of 32.5%. Under the variable pH (2-12), the fluorescent N,S-CDs with a linear range from 0.05 to 100 μM displayed selective discrimination for Hg²⁺ with the limit of 6.24 nM over several other cations, anions, and neutral analytes resulting in the quenching of fluorescence response. Furthermore, the addition of guanine at the LOD of 6.4 nM can restore N,S-CDs' fluorescence in a reversible manner. For this kind of fluorescence switch, its purposed applications on environmental samples are employed successfully to detect Hg²⁺ in tap water and river water.

One-dimensional nitrogen doped porous carbon nano-array arranged by carbon nanotubes for electrochemical sensing ascorbic acid, dopamine and uric acid simultaneously

In this work, one-dimensional nitrogen doped porous carbon nano-arrays arranged by carbon nanotube (1D CNTs@NPC) were first constructed, using a coating technology at room temperature and followed by high temperature carbonization. It was expected that the resulting glassy carbon electrodes modified by 1D CNTs@NPC (CNTs@NPC/GCE) could express different electrochemical responses to ascorbic acid (AA), dopamine (DA), uric acid (UA), by virtue of the synergistic-improved effect between CNTs and NPC. Under the optimized conditions, there were excellent analytical parameters for CNTs@NPC/GCE to detect AA, DA and UA, i.e. a wide linear range of 40-2100μM for AA, 0.5-49μM for DA and 3-50μM for AA with low detection limits of 0.36μM, 0.02μmol l^-1and 0.57μM respectively. Importantly, the proposed CNTs@NPC/GCE was efficiently applied to determine AA, DA and UA in some real samples with high stability, reproducibility and selectivity. This work will offer an efficient potential for diagnosing ascorbic acid, dopamine or uric acid-related diseases on clinical testing in future.