Design of porous S-doped carbon nanostructured electrode sensor for sensitive and selective detection of guanine from DNA samples

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.

Nanomolar Fluorescent Detection of Guanine Using Tin Porphyrin

5,10,15,20-tetramethoxyphenylporphyrinatotin (IV) (SnTMPP) was synthesised. SnTMPP exhibited Soret band at 432 nm and emission peaks at 629 and 682 nm. The fluorescence intensity of SnTMPP was quenched in the presence of guanine linearly in the range 4 × 10-9 M to 7.2 × 10-8 M and the quenching response was found to be stable even in the presence of other nucleosides such as adenine, cytosine, uracil, thymine, alanine, aspartic acid and ascorbic acid. The detection limit was found to be 0.17 nM and the mechanism behind the decrease in the fluorescence intensity of SnTMPP in the presence of guanine is due to dynamic quenching, which was confirmed by cyclic voltammetric studies and life time studies. The CV studies illustrates the possibilty for an electron transfer between the guanine and the electron deficient metal core of SnTMPP.

Using 3D printed magnetic platform as support for screen printed electrode applied for p-toluenediamine detection in biological fluid and water samples

The present work reports the development and application of a new electrochemical sensor for the determination of low concentration levels of p-toluenediamine (PTD) in biological fluids and surface water samples. The proposed sensor was developed using a 3D-printed magnetic device as platform for carbon screen printed electrode (CSPE) modified by magnetic nanoparticles functionalized with carboxylic groups and l-cysteine (MNP-CA-CYS). The results obtained from the morphological and electrochemical characterizations of the sensing platform enabled us to confirm the success of the sensor functionalization with l-cysteine and to have a better understanding of the electrochemical behavior and preconcentration of PTD on the electrode surface. PTD oxidation occurred at 0.24V on MNP-CA-CYS and the mechanism recorded an increase of 51.0% in anodic peak current. Under optimized conditions, the square wave voltammograms obtained for the electrode modified by 40.0 μL MNP-CA-CYS suspension at 1.0 mg mL^-1, with accumulation time of 3 min, presented an analytical curve with linear range of 8.00 × 10^-7 to 8.00 × 10^-5 mol L^-1, represented by the equation Iap = (0.383 ± 0.011)[PTD] - (8.112 ± 0.07) × 10^-8 (R² = 0.9994), and detection and quantification limits of 8.53 × 10^-8 and 2.56 × 10^-7 mol L^-1, respectively. Finally, the proposed method was validated through comparison with high performance liquid chromatography coupled to diode array detector (HPLC-DAD) technique and was successfully applied for PTD determination in samples of surface water, tap water, fetal bovine serum and artificial urine.

Heteroatom-free conjugated tetraphenylethylene polymers for selectively fluorescent detection of tetracycline

The antibiotic tetracycline (Tc) is a major contaminant in food and water, with adverse effects on both ecosystems and human health. The development of novel sensors for tetracycline detection is of great importance. In this work, we develop a novel heteroatom-free conjugated tetraphenylethylene polymer (TPE-CMP) fluorescence sensor for the detection of tetracycline. In the presence of Tc, the emission fluorescence of TPE-CMP was quenched by the photoinduced electron transfer mechanism to achieve high sensitivity. The polymers can detect tetracycline at a concentration of 0-100 μg/mL with a good linear correlation (0.99), and the limit of detection (LOD) is 1.23 μg/mL. Furthermore, TPE-CMP has excellent selectivity in detecting Tc in the presence of various anti-interference analytes, including ions and antibiotics. In addition, the practical feasibilities of TPE-CMP for Tc sensing were further investigated in milk, urine and wastewater samples with satisfactory recoveries (from 94.96% to 112.53% for milk, from 96.41% to 99.31% for urine and from 98.54% to 100.52% for wastewater). We have designed and synthesized TPE-CMP based on heteroatom-free for the specific fluorescence detection of tetracycline, expanding the range of fluorescence detection sensors and offering great promise for practical applications.

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.