Using Au@nano-C60 nanocomposite as an enhanced sensing platform in modeling a TNT aptasensor

A green impedimetric aptasensor for non-invasive and high-selective detection of tramadol validated by molecular dynamic simulation

Although the dosage controlling of tramadol (TRA) as a banned deadly drug in human biofluids is medicolegally important a biocompatible method for its high-selective detection with fewer false interferences has been scarcely reported. Herein, a new impedimetric aptasensor is introduced by utilizing the aptamer (Apt) sequence with high affinity to TRA for the first time to non-invasively measure it. An oriented nanolayer of Au nanoparticles (AuNPs) is easily formed on the surface by the electrodeposition technique to high-densely load the Apt and embed the novel aptasensing interface via a user-friendly methodology. The visual interaction of Apt with its target has been explored using molecular dynamic (MD) simulation to confirm how Apt traps TRA in its arm. The aptasensor measured TRA in a concentration range of 50 pM to 1.3 nM with a limit of detection (LOD) of 16.66 pM in buffer. It also rendered good accuracy and recovery for human salivary and urinary analysis. In addition, the greenness profile of the proposed methodology has been validated with two international common indexes. The developed aptasensor promises a reasonable capability for TRA monitoring in real clinical or street narcotic samples according to green analytical chemistry (GAC).

Green nitrogen and sulfur co-doped carbon dots derived from eggshell as a high performance aptasensing interface for non-invasive detection of metronidazole

BACKGROUND

The concentration monitoring of the banned metronidazole (MTZ) drug as the alarmed carcinogenic agent in human biofluids is medically essential. The electrochemical aptasensors are good candidates to overcome some presence challenges in the detection process.

RESULTS

Herein, an electrochemical aptasensor based on nitrogen and sulfur co-doped carbon dots (NcS-CDs) has been developed for the high-sensitive detection of MTZ for the first time. The N-S-CDs have been synthesized from eggshell waste and the aptasensing interface has been fabricated by the attachment of the N-S-CDs to the glassy carbon electrode surface to fix the high-density aptamer (Apt) sequences via silver nanocubes (AgNCs). The electrochemical signal of the redox probe has changed by trapping the MTZ on the Apt's arm onto the aptasensing interface. The molecular dynamic simulation visually confirmed how the Apt binds to the MTZ. The resulting aptasensor measured MTZ in a wide linear range value from 1 fM to 901.4 nM with a limit of detection value of 333.3 aM and high selectivity regarding some possible interferences.

SIGNIFICANCE

The results reveal that the novel aptasensor has high potential applicability for the non-invasive monitoring of MTZ in human saliva and urine, and also, the tap water analysis. Utilizing waste-derived nanomaterials for the aptasensor fabrication not only less the fabrication costs but also guarantees the greenness of the applied methodology according to sustainable chemistry principles as evaluated by two international index metrics.

Portable label-free electrochemical aptasensor for sensitive detection of paraquat herbicide mediated by oxygen reduction reaction

Paraquat (PQ) is a highly toxic herbicide that has been prohibited in almost 70 countries, but remains in use worldwide. Thus, routine on-site PQ monitoring is a key mechanism to ensure safety and efficiently enforce regulations. Herein, a label-free portable electrochemical aptasensor for the detection of PQ was developed by utilizing aptamer designed to specifically recognize PQ. The aptasensor employs square-wave voltammetry (SWV) to quantify PQ binding on the aptamer-functionalized electrode surface by tracking the downstream oxygen reduction reaction. It provided a detection range spanning from 0.01 to 100.0 μg mL-1 PQ with a limit of detection (LOD) of 8.9 ng mL-1. Validation against spiked tap water, pomegranate juice, and orange juice revealed recovery rate performances of 75 %-130 %. The aptasensor demonstrates promising feasibility for PQ detection in real-world applications, offering remarkable portability and operational simplicity. Notably, it can operate without supplementary redox agents, requiring only sample incubation and subsequent washing steps.

Selective Sensing of DNA Nucleobases with Angular Discrimination

The fast and precise selective sensing of DNA nucleobases is a long-pursued method that can lead to huge advances in the field of genomics and have an impact on aspects such as the prevention of diseases, health enhancement, and, in general, all types of medical treatments. We present here a new type of nanoscale sensor based on carbon nanotubes with a specific geometry that can discriminate the type of nucleobase and also its angle of orientation. The proper differentiation of nucleobases is essential to clearly sequence DNA chains, while angular discrimination is key to improving the sensing selectivity. We perform first-principle and quantum transport simulations to calculate the transmission, conductance, and current of the nanotube-based nanoscale sensor in the presence of the four nucleotides (A, C, G, and T), each of them rotated 0, 90, 180, or 270°. Our results show that this system is able to effectively discriminate between the four nucleotides and their angle of orientation. We explain these findings in terms of the interaction between the phosphate group of the nucleotide and the nanotube wall. The phosphate specifically distorts the electronic structure of the nanotube depending on the distance and the orientation and leads to nontrivial changes in the transmission. This work provides a method for finer and more precise sequential DNA chains.

A novel electrochemical aptasensor based on polyaniline and gold nanoparticles for ultrasensitive and selective detection of ascorbic acid

Ascorbic acid (AA) is involved in many physiological activities of the body and plays an important role in maintaining and promoting human health. It is also present in many natural and artificial foods. Therefore, the development of highly sensitive and accurate AA sensors is highly desirable for human health monitoring, as well as other commercial application fields. Herein, an ultrasensitive and selective electrochemical sensor based on an aptamer was developed for the determination of AA for the first time. The aptasensor was fabricated by modifying a composite made of polyaniline (PANI) and gold nanoparticles (AuNPs) on a glassy carbon electrode. The morphologies and electrochemical properties of the resulting electrodes were characterized by various analytical methods. The results indicated relatively good electrical conduction properties of PANI for accelerated electron transfer. The modification with AuNPs provided signal amplification, suitable for applications as novel platforms for the sensitive sensing of AA. Under optimized conditions, the proposed aptasensor displayed a wide linear response toward the detection of AA from 1.0 to 1.0 × 105 ng L-1 coupled with a low detection limit of 0.10 ng L-1. The sensor also exhibited excellent selectivity and high stability, with at least 2000-fold higher sensitivity than similar previously reported methods. Importantly, the aptasensor exhibited promising properties for the determination of AA in real fruits, vegetables, and infant milk powder, thereby showing potential for food analysis.

Incorporating Fullerenes in Nanoscale Metal-Organic Matrixes: An Ultrasensitive Platform for Impedimetric Aptasensing of Tobramycin

The rational design and preparation of available fullerene@metal-organic matrix hybrid materials are of profound significance in electrochemical biosensing applications due to their unique photoelectric properties. In this work, C₆₀@UiO-66-NH₂ nanocomposites serve as greatly promising materials to modify electrodes and fix aptamers, resulting in a remarkable electrochemical aptasensor for impedimetric sensing of tobramycin (TOB). Nanoscale composites have preferable electroactivity and small particle size with more exposed functional sites, such as Zr(IV) and -NH₂, to immobilize aptamers for enhanced detection performance. As we know, most of the electrochemical impedance aptasensors require a long time to complete the detection process, but this prepared biosensor shows the rapid quantitative identification of target TOB within 4 min. This work expands the synthesis of functional fullerene@metal-organic matrix hybrid materials in electrochemical biosensing applications.

Voltammetric determination of pethidine in biofluids at a carbon cloth electrode modified by carbon selenide nanofilm

Developing a sensitive portable sensor for the screening of illicit drugs is always challenging. Due to the importance of pethidine (PTD) tracking in addiction diagnosis, many demands have recently increased for a selective and real-time sensor. Herein, a simple electrochemical sensor has been developed based on conductive carbon cloth (CC) modified with carbon selenide nanofilms (CSe₂NF) to provide a CSe₂NF/CC electrode as a novel PTD sensing tool. Profiting from the ingenious design of doping strategy during the synthesis process, Se was doped in the carbonaceous skeleton of the CC. Thus, the active surface area of the CSe₂NF (4.61 cm²) increased respect to the unmodified CC (0.094 cm²) to embed a suitable sensing interface in the fast PTD assay. By optimizing some effective experimental parameters such as pH, supporting electrolyte, Se powder amount, scan rate and accumulation time, the sensor catalyzed efficiently the oxidation reaction of PTD at 0.97 V. Based on peak current variations, the PTD was measured over a broad concentration range from 29 nM up to 181.8 μM with a limit of detection (LOD) as low as 19.3 nM compared to the other reported PTD sensors. The developed flexible sensor recognized the spiked PTD concentrations in some biofluids, including human blood, urine and saliva. The results of PTD analysis in the non-spiked and spiked blood, urine and saliva samples as the real samples by the developed sensor were validated by HPLC analysis as the reference method using t-test statistical method at confidence level of 5%. This sensing strategy based on the binder-free electrode could be promising for designing some sizable wearable sensors at a low cost. The high sensitivity of the sensor, which is a bonus for the rapid and on-site measurement of PTD, may open up a route for noninvasive routine analysis in clinical samples.

Voltammetric measurement of entacapone in the presence of other medicines against Parkinson's disease by a screen-printed electrode modified with sulfur-tin oxide nanoparticles

A screen-printed electrode (SPE) is described modified with sulfur-tin oxide nanoparticles (S@SnO₂NP) for the determination of entacapone (ENT) in the presence of other medicines against Parkinson's disease (PD). The S@SnO₂NP was synthesized through the hydrothermal method and used in the modification of the SPE. The smart utilization of the S@SnO₂NP and the SPE provided excellent properties such as high surface area and current density amplification by embedding an efficient sensing interface for highly selective electrochemical measurement. Under optimized experimental conditions, the anodic peak current related to the ENT oxidation onto the sensor surface at 0.46 V presented a linear response towards different ENT concentration sin the range 100 nM to 75 μM. The limit of detection (LOD) and electrochemical sensitivity were estimated to be 0.010 μM and 2.27 μA·μM^-1·cm^-2, respectively. The applicability of the sensor was evaluated during ENT determination in the presence of other conventional medicines againts, including levodopa (LD), carbidopa (CD), and pramipexole (PPX). The results of the analysis of human urine and pharmaceutical formulation as real samples using the developed sensor were in good agreement withre sults of high-performance liquid chromatography (HPLC) as a standard method. These findings demonstrated that the strategy based on the SPE is a cost-effective platform creating a promising candidate for practical determination of ENT in routine clinical testing.Graphical abstract.

Advances in Electrochemical Aptasensors Based on Carbon Nanomaterials

Carbon nanomaterials offer unique opportunities for the assembling of electrochemical aptasensors due to their high electroconductivity, redox activity, compatibility with biochemical receptors and broad possibilities of functionalization and combination with other auxiliary reagents. In this review, the progress in the development of electrochemical aptasensors based on carbon nanomaterials in 2016–2020 is considered with particular emphasis on the role of carbon materials in aptamer immobilization and signal generation. The synthesis and properties of carbon nanotubes, graphene materials, carbon nitride, carbon black particles and fullerene are described and their implementation in the electrochemical biosensors are summarized. Examples of electrochemical aptasensors are classified in accordance with the content of the surface layer and signal measurement mode. In conclusion, the drawbacks and future prospects of carbon nanomaterials’ application in electrochemical aptasensors are briefly discussed.

Recent Developments in the Field of Explosive Trace Detection

Explosive trace detection (ETD) technologies play a vital role in maintaining national security. ETD remains an active research area with many analytical techniques in operational use. This review details the latest advances in animal olfactory, ion mobility spectrometry (IMS), and Raman and colorimetric detection methods. Developments in optical, biological, electrochemical, mass, and thermal sensors are also covered in addition to the use of nanomaterials technology. Commercially available systems are presented as examples of current detection capabilities and as benchmarks for improvement. Attention is also drawn to recent collaborative projects involving government, academia, and industry to highlight the emergence of multimodal screening approaches and applications. The objective of the review is to provide a comprehensive overview of ETD by highlighting challenges in ETD and providing an understanding of the principles, advantages, and limitations of each technology and relating this to current systems.

AgNPs/QDs@GQDs nanocomposites developed as an ultrasensitive impedimetric aptasensor for ractopamine detection

Developing easy-to-use and miniaturized sensors for in-field monitoring of targets which is related to human health is necessary. Ractopamine (RAC) is a feed additive with serious side effects that is forbidden in many countries. This study reports the fabrication of an impedimetric aptasensor for ultrasensitive and selective detection of the RAC in human biological fluids. Accordingly, an efficient nanocomposites was synthesized by a beneficial combination of graphene quantum dots (GQDs), quantum dots (QDs) and silver nanoparticles (AgNPs) for modifying a glassy carbon electrode (GCE). This nanocomposite is promising to present a synergistic effect in the increase of the active surface area of the modified electrode to more load the biocapture of the target. Next, the RAC-binding aptamer (Apt) was attached to the AgNPs/QDs@GQDs/GCE surface and a sensitive layer for the RAC detection was embedded. A RAC-Apt complex was formed upon adding the RAC and the changes of the electrochemical behavior were studied by some electrochemical techniques such as electrochemical impedance spectroscopy (EIS). Under optimal conditions, the charge transfer resistance (R_ct) value was increased linearly with increasing of the RAC concentrations in the range of 1 fM to 901.4 nM. Limit of detection (LOD) was calculated to be 330 aM which is superior by other reported electrochemical methods in the RAC sensing. The applicability of the aptasensor was tested in human urine and blood serum as the real samples and satisfactory results of specificity were achieved. It seems that the proposed strategy not only provides a new ultrasensitive strategy for RAC detection but also expands the application of the sensing interface to develop other aptasensors by changing the Apt sequence.

What Electrochemical Biosensors Can Do for Forensic Science? Unique Features and Applications

This article critically discusses the latest advances in the use of voltammetric, amperometric, potentiometric, and impedimetric biosensors for forensic analysis. Highlighted examples that show the advantages of these tools to develop methods capable of detecting very small concentrations of analytes and provide selective determinations through analytical responses, without significant interferences from other components of the samples, are presented and discussed, thus stressing the great versatility and utility of electrochemical biosensors in this growing research field. To illustrate this, the determination of substances with forensic relevance by using electrochemical biosensors reported in the last five years (2015–2019) are reviewed. The different configurations of enzyme or affinity biosensors used to solve analytical problems related to forensic practice, with special attention to applications in complex samples, are considered. Main prospects, challenges to focus, such as the fabrication of devices for rapid analysis of target analytes directly on-site at the crime scene, or their widespread use and successful applications to complex samples of interest in forensic analysis, and future efforts, are also briefly discussed.

Applicability of AuNPs@N-GQDs nanocomposite in the modeling of the amplified electrochemical Ibuprofen aptasensing assay by monitoring of riboflavin

Here, an ultrasensitive and low-cost electrochemical aptasensing assay is developed based on the applicability of a fabricated nanocomposite from nitrogen-doped graphene quantum dots (N-GQDs) and gold nanoparticles (AuNPs). A modified glassy carbon electrode (GCE) with the AuNPs@N-GQDs nanocomposite (AuNPs@N-GQDs/GCE) as an efficient platform has some unique properties such as high surface area and electrical conductivity. Furthermore, the prepared platform is capable of more loading of aptamer (Apt) molecules as a biological recognition element of Ibuprofen (IBP) on the modified electrode surface. It is noteworthy that in this study, riboflavin (RF) as a universal green probe is used for the first time for electrochemical detection of IBP. According to the proposed strategy and under the optimum condition, the unprecedented detection limit (LOD) of this assay (33.33 aM) is lower than previously reported analytical methods. The results demonstrate the ability of the nanocomposite for designing of the aptasensor, integrated within the electrode format, to cheaper and simpler detection of the IBP with a specificity and sensitivity sufficient for analysis in real samples. It seems that the proposed strategy based on the AuNPs@N-GQDs nanocomposite can be expanded to other nanomaterials. So, this is expected to have promising implications in the design of electrochemical sensors or biosensors for the detection of various targets.