Determination of guanine and adenine by high-performance liquid chromatography with a self-fabricated wall-jet/thin-layer electrochemical detector at a glassy carbon electrode

A Novel Poly(cytosine)-Based Electrochemical Biosensor for Sensitive and Selective Determination of Guanine in Biological Samples

The novel poly(cytosine)-modified glassy carbon electrode-based electrochemical sensor was fabricated potentiodynamically for the detection of Guanine (G) in clinical and biological samples. The surface of the electrode was successfully activated by electropolymerization, and about a 7.5-fold current improvement due to modification was achieved. From the analysis of the dependence of peak current and peak potential on a scan rate, a higher R 2 for the peak current on the square root of scan rate (R 2 = 0.999) than the dependence of peak current on scan rate (R 2 = 0.982) indicated that the oxidation of G at poly(cytosine)/GCE was predominantly diffusion controlled. The oxidative peak response of the electrode revealed a high linear range of G concentration (0.1-200 μM) under optimized conditions. The detection limit and limit of quantification were 6.10 and 20.13 nM, respectively, associated with the %RSD of under 1%. The validation of the developed electrochemical sensor for the determination of G was investigated by analyzing human urine DNA and serum samples with spike recovery results in the range of 98.20-103.70% with the interferent recovery percentage in the range of 97.86-103.10% containing 50-300% of potential interferents. The newly designed sensor demonstrated the highest level of performance for the G detection in real samples.

Voltammetric Measurement of Antioxidant Activity by Prevention of Cu(II)-Induced Oxidative Damage on DNA Bases Using a Modified Electrode

The protective effect of antioxidants using electrochemical techniques can be evaluated by examining the oxidative changes in deoxyribonucleic acid (DNA) nucleobases. In this study, a gold nanoparticle (AuNP)-decorated and multiwalled carbon nanotube (MWCNT)-Nafion-modified glassy carbon electrode (GCE/AuNP/MWCNT-Nafion) was developed to evaluate the preventive ability of antioxidants on oxidative DNA damage. A modified working electrode was prepared and characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. The developed electrochemical method relies on two phenomena: (i) reactive species (RS) produced by dissolved oxygen in the presence of copper(II) partially damage the DNA immobilized on the electrode surface and (ii) antioxidant compounds prevent this damage by scavenging the formed RS. Changes in guanine, adenine, and cytosine oxidation signals resulting from DNA damage were measured using differential pulse stripping voltammetry before/after the interaction of dsDNA with Cu(II) while antioxidants were absent or present. The DNA protective ability of antioxidants was assessed for a number of antioxidant compounds (i.e., ascorbic acid, gallic acid, epicatechin, catechin, epicatechin gallate, glutathione, chlorogenic acid, N-acetyl cysteine, rosmarinic acid, quercetin, and rutin). Quercetin was found to show the highest antioxidant effect, and its limit of detection was determined as 1 μM. The manufactured biosensor was put in an application for the determination of antioxidant activity of herbal teas.

Selective Fluorescent Sensing of Adenine Via the Emissive Enhancement of a Simple Cobalt Porphyrin

Porphyrins absorb strongly in the visible region and are also excellent fluorophores that emit in the visible region that make them excellent candidates for fluorescence sensing and in vivo imaging. This work describes the fluorescence determination of adenine using cobalt complex of a simple porphyrin. Tetraphenylporphyrin (TPP) and tetraphenylpophyrinatocobalt(II) (CoTPP) were synthesized and characterised. TPP on metallation with cobalt resulted in the red shift of fluorescence emission in the region 652 nm and 716 nm and showed an enhancement in the emission peaks with the addition of the nucleobase, adenine. CoTPP is found to be an efficient fluorescent sensor for adenine in DMF solvent. The fluorescence enhancement is due to the formation of the ground state complex formation between adenine and CoTPP, which is supported by experimental evidences from UV- visible spectra, time resolved fluorescence life time measurements etc. The detection limit of adenine was found to be 4.2 μM using the CoTPP fluorescent probe. The proposed sensor is found to be highly selective for adenine in presence of other nitrogen bases like guanine, cytosine, uracil, thymine, alanine, histidine etc. in 1:1 concentration.

A copper-based metal–organic framework/graphene nanocomposite for the sensitive and stable electrochemical detection of DNA bases

A simple and easy-operation electrode modification strategy was proposed using Cu-MOF/GO nanohybrids for physiologists and pathologists for the feasible and reliable simultaneous electrochemical detections of DNA bases, namely guanine and adenine.

Charge Transfer Platform and Catalytic Amplification of Phenanthroimidazole Derivative: A New Strategy for DNA Bases Recognition

Research about DNA composition has been concentrated on DNA damage in the past few decades. However, it still remains a great challenge to construct a rapid, facile, and accurate approach for simultaneously monitoring four DNA bases, guanine (G), adenine (A), thymine (T), and cytosine (C). Herein, a novel electrochemical sensor based on phenanthroimidazole derivative, 2-(4-bromophenyl)-1-phenyl-1H-phenanthro[9,10-d]-imidazole (PPI), is successfully fabricated by a simple electrochemical method. The bromophenyl group in PI could expand their aromatic plane, induce the π-conjugated extension, and enhance the charge transfer and π-π interaction. The phenyl group at N1 position could regulate the intermolecular interaction, which could promote the possibility of intermolecular connection. The PPI polymer (poly(PPI)) with π-electron enriched conjugation architecture has been applied in simultaneous determination of G, A, T, and C in neutral solution by square wave voltammetry (SWV) method with well-separated peak potentials at 0.714, 1.004, 1.177, and 1.353 V, respectively. The sensor functionalized with poly(PPI) exhibits wide linear response for G, A, T, and C in the concentration ranges of 3-300, 1-300, 30-800, and 20-750 μM, respectively. With favorable selectivity, stability, and reproducibility, the sensor is successfully utilized to monitor four DNA bases in real samples, displaying a promising prospect for electrochemical sensing devices.

Nanosized iron telluride for simultaneous nanomolar voltammetric determination of dopamine, uric acid, guanine and adenine

Herein, an efficient electrochemical sensor based on nano-sized iron telluride material (FeTe₂) have been developed for the first time for simultaneous nanomolar determination of dopamine, uric acid, guanine and adenine molecules.

An efficient electrode for simultaneous determination of guanine and adenine using nano-sized lead telluride with graphene

Herein, lead telluride (PbTe) nanocrystals were chemically synthesized at room temperature via reduction of homogeneous mixtures of tartrate complexes of Pb²⁺ and Te⁴⁺ with sodium borohydride.

Highly sensitive and selective fluorescent assay for guanine based on the Cu(2+)/eosin Y system

A fluorescent probe has been developed for the determination of guanine based on the quenched fluorescence signal of Cu(2+)/eosin Y. Cu(2+) interacted with eosin Y, resulting in fluorescence quenching. Subsequently, with the addition of guanine to the Cu(2+)/eosin Y system, guanine reacted with Cu(2+) to form 1:1 chelate cation, which further combined with eosin Y to form a 1:1 ternary ion-association complex by electrostatic attraction and hydrophobic interaction, resulting in significant decrease of the fluorescence. Hence, a fluorescent system was constructed for rapid, sensitive and selective detection of guanine with a detection limit as low as 1.5 nmol L(-1) and a linear range of 3.3-116 nmol L(-1). The method has been applied satisfactorily to the determination of guanine in DNA and urine samples with the recoveries from 98.7% to 105%. This study significantly expands the realm of application of ternary ion-association complex in fluorescence probe.

Detection and quantification of new psychoactive substances (NPSs) within the evolved "legal high" product, NRG-2, using high performance liquid chromatography-amperometric detection (HPLC-AD)

The global increase in the production and abuse of cathinone-derived New Psychoactive Substances (NPSs) has developed the requirement for rapid, selective and sensitive protocols for their separation and detection. Electrochemical sensing of these compounds has been demonstrated to be an effective method for the in-field detection of these substances, either in their pure form or in the presence of common adulterants, however, the technique is limited in its ability to discriminate between structurally related cathinone-derivatives (for example: (±)-4′-methylmethcathinone (4-MMC, 2a) and (±)-4′-methyl-N-ethylmethcathinone (4-MEC, 2b) when they are both present in a mixture. In this paper we demonstrate, for the first time, the combination of HPLC-UV with amperometric detection (HPLC-AD) for the qualitative and quantitative analysis of 4-MMC and 4-MEC using either a commercially available impinging jet (LC-FC-A) or custom-made iCell channel (LC-FC-B) flow-cell system incorporating embedded graphite screen-printed macroelectrodes. The protocol offers a cost-effective, reproducible and reliable sensor platform for the simultaneous HPLC-UV and amperometric detection of the target analytes. The two systems have similar limits of detection, in terms of amperometric detection [LC-FC-A: 14.66 μg mL(-1) (2a) and 9.35 μg mL(-1) (2b); LC-FC-B: 57.92 μg mL(-1) (2a) and 26.91 μg mL(-1) (2b)], to the previously reported oxidative electrochemical protocol [39.8 μg mL(-1) (2a) and 84.2 μg mL(-1) (2b)], for two synthetic cathinones, prevalent on the recreational drugs market. Though not as sensitive as standard HPLC-UV detection, both flow cells show a good agreement, between the quantitative electroanalytical data, thereby making them suitable for the detection and quantification of 4-MMC and 4-MEC, either in their pure form or within complex mixtures. Additionally, the simultaneous HPLC-UV and amperometric detection protocol detailed herein shows a marked improvement and advantage over previously reported electroanalytical methods, which were either unable to selectively discriminate between structurally related synthetic cathinones (e.g. 4-MMC and 4-MEC) or utilised harmful and restrictive materials in their design.

Facile synthesis of 3D porous nitrogen-doped graphene as an efficient electrocatalyst for adenine sensing

We demonstrate a simple, low-cost and eco-friendly strategy for the convenient preparation of three-dimensional porous nitrogen-doped graphene (3D-N-GN) for the highly sensitive detection of adenine.

Electrochemical sensing of guanine, adenine and 8-hydroxy-2′-deoxyguanosine at glassy carbon modified with single-walled carbon nanotubes covalently functionalized with lysine

Synthesis and characterization of l-lysine covalently functionalized SWCNT and analytical application for the highly sensitive quantification of guanine, adenine and 8-hydroxy-2′-deoxyguanosine.