Fabrication of an electrochemical biodevice for ractopamine detection under a strategy of a double recognition of the aptamer/molecular imprinting polymer

Molecular dynamic simulation-empowered detection of digoxin by a green aptasensing interface based on pseudo-gold nanobones@rice husk-derived nanosilica

Screening digoxin (DIG) dosage in human biofluids is medicolegally important to control its overdose and prevent its severe side effects. In this study, the advanced aptasensing interface has been constructed using a novel nanocomposite as a biocompatible scaffold to anchor Apt strings specific to DIG on the surface under a green methodology. The high-performance nanocomposite consisting of the rice husk (RH)-derived nanosilica and pseudo-gold nanobones (pseudo-AuNBs@RH-derived nanosilica) has been utilized for aptasensor fabrication. Each modification step of the surface has been characterized by the signal change of the ferro/ferri cyanide as the electrochemical probe. The molecular dynamic (MD) computational method has been applied to simulate a visual interaction of Apt with DIG through a conformation-switching assay format from a molecular view to validate DIG binding to Apt. The resulting aptasensor is able to measure DIG quantitatively from 100 fM to 0.85 μM with a limit of detection (LOD) value of 33.33 fM. The satisfactory results with a minimum nonspecific adsorption effect of the aptasensor in analyzing some real samples of human blood serum, saliva and urine containing DIG not only promise DIG diagnosis in real clinical trials but also pave the way for its non-invasive measurement. The greenness of the applied strategy has been evaluated with a high score according to two international metrics, which is another achievement of this study. The synthesis of porous nanosilica from RH waste as value-added nanomaterials with outstanding features not only decreases the amount of unused RH waste piled up in nature but also, manages the synthesis costs that may be a path-breaker for more investigations.

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.

A high-performance aptasensing interface based on pseudo-AuNBs@Ti3C2Tx MXene nanocomposite for non-invasive measurement of carbamazepine in human biofluids

For the first time, a novel aptasensing interface based on smart integration of pseudo-gold nanobons (AuNBs) and Ti3C2Tx MXene is introduced for high selective detection of carbamazepine (CBZ). The large specific surface area achieved from the proposed nanocomposite increases the targeted immobilization of the Apt sequence on the surface via AuNBs as the linkage. It embeds a high-performance grafting platform for trapping CBZ with high sensitivity and accuracy in human biofluids and pharmaceutical formulations. The molecular dynamic (MD) simulation method that exhibits how the Apt binds to CBZ in a conformation-switching assay format from a molecular view is a valid certification for the interaction of CBZ on the developed aptasensing interface. The aptasensor measured CBZ from 1 fM to 100 nM with a superior detection limit (LOD) value of 330 aM compared with other reported CBZ sensors. Due to using biocompatible and non-toxic compounds, consuming low energy and chemicals the greenness of the proposed strategy has been certified by the international scoring system.

A novel label-free impedance biosensor for KRAS G12C mutations detection based on PET-RAFT and ROP synergistic signal amplification

The KRAS G12C mutations, as crucial biomarkers, are closely associated with non-small cell lung cancer. Here, a novel label-free electrochemical biosensor with synergistic signal amplification of photocell energy transfer-reversible addition fragmentation chain transfer (PET-RAFT) and ring-opening polymerization (ROP) was developed for the first time for sensitive detection of KRAS G12C mutations. Specifically, hairpin DNA (hDNA), which act as biomolecular probe, was self-assembled on Au electrode surface by Au-S bond. 4-cyano-4-[(dodecylsulfanylthiocarbonyl) sulfanyl] pentanoic acid (CDTPA), the chain transfer agent of PET-RAFT reaction, was then attached to hDNA via amide bond. After that, the target DNA (tDNA) was captured on the electrode surface by complementary base pairing with hDNA. Subsequently, large numbers of electro-active monomers N-acryloxysuccinimide (NAS) were successfully grafted to the electrode surface via PET-RAFT reaction, which provided plenty of junction sites for doxorubicin-polycaprolactone (Dox-PCL) synthesized by ROP. Finally, the Dox-PCL was connected to the electrode surface by ester bond, significantly amplifying the electrochemical signal. Under optimized conditions, the biosensor has a wide linear detection range of 0.1 pM to 1 μM, with a detection limit of 86.9 fM. Attribute to its high sensitivity, specificity, reproducibility and stability, this biosensor possesses considerable potential in early diagnosis of disease and biomedical research.

A nitrogen-doped hollow carbon nanospheres-based aptasensor for non-invasive salivary detection of progesterone

Developing an easy-to-use and non-invasive sensor for monitoring progesterone (P4) as a multi-functional hormone is highly demanded for point-of-care testing. In this study, an ultrasensitive electrochemical aptasensor is fabricated for monitoring P4 in human biofluids. The sensing interface was designed based on the porous nitrogen-doped hollow carbon spheres (N-HCSs). The N-HCSs covalently immobilized high-dense aptamer (Apt) sequences as the bioreceptor of P4. The electron transfer of the redox probe was hindered by incubating P4 on the aptasensor surface and forming the P4-Apt complexes. Meanwhile, the signaling was decreased under two wide linear dynamic ranges (LDRs) from 10 fM to 5.6 μM with a limit of detection (LOD) value of 3.33 fM. The aptasensor presented satisfactory selectivity in the presence of different off-target species with successful feasibility for P4 detection in some human urine and saliva samples. The aptasensor with high sensitivity, as an advantage for on-site and sensitive measurement of P4, can be considered a non-invasive tool for routine analysis of real-world clinical samples method.

Research progress on preparation methods and sensing applications of molecularly imprinted polymer-aptamer dual recognition elements

The aptamer (Apt) and the molecularly imprinted polymer (MIP), as effective substitutes for antibodies, have received widespread attention from researchers because of their creation. However, the low stability of Apt in harsh detection environment and the poor specificity of MIP have hindered their development. Therefore, some researchers have attempted to combine MIP with Apt to explore whether the effect of "1 + 1 > 2" can be achieved. Since its first report in 2013, MIP-Apt dual recognition elements have become a highly focused research direction in the fields of biology and chemistry. MIP-Apt dual recognition elements not only possess the high specificity of Apt and the high stability of MIP in harsh detection environment, but also have high sensitivity and affinity. They have been successfully applied in medical diagnosis, food safety, and environmental monitoring fields. This article provides a systematic overview of three preparation methods for MIP-Apt dual recognition elements and their application in eight different types of sensors. It also provides effective insights into the problems and development directions faced by MIP-Apt dual recognition elements.

Development of an electrochemical biosensor utilizing a combined aptamer and MIP strategy for the detection of the food allergen lysozyme

This study aims to develop a MIP-Apt-based electrochemical biosensor for the sensitive and selective determination of Lysozyme (Lyz), a food allergen. For the development of the sensor, in the first stage, modifications were made to the screen-printed electrode (SPE) surface with graphene oxide (GO) and gold nanoparticles (AuNPs) to increase conductivity and surface area. The advantages of using aptamer (Apt) and molecularly imprinted polymer (MIP) technology were combined in a single biointerface in the prepared sensing tool. Surface characterization of the biosensor was performed using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectrometry (XPS), contact angle measurements, cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). A wide linear range from 0.001 to 100 pM was obtained under optimized conditions for the determination of Lyz detection using the proposed MIP-Apt sensing strategy. The limit of detection (LOD) and limit of quantification (LOQ) for Lyz were 3.67 fM and 12 fM, respectively. This biosensor displays high selectivity, repeatability, reproducibility, and long storage stability towards Lyz detection. The results show that a sensitive and selective sensor fabrication is achieved compared with existing methods.

Dual recognition elements for selective determination of progesterone based on molecularly imprinted electrochemical aptasensor

A novel molecularly imprinted electrochemical aptasensor (MIEAS) was constructed for selective progesterone (P4) detection based on SnO₂-graphene (SnO₂-Gr) nanomaterial and gold nanoparticles (AuNPs). SnO₂-Gr with a large specific area and excellent conductivity improved the adsorption capacity of P4. Aptamer, as biocompatible monomer, was captured by AuNPs on modified electrode through Au-S bond. An electropolymerized molecularly imprinted polymer (MIP) film consisted of p-aminothiophenol as chemical functional monomer and P4 as template molecule. Due to the synergetic effect of MIP and aptamer towards P4, this MIEAS exhibited better selectivity than the sensor with MIP or aptamer as single recognition element. The prepared sensor had a low detection limit of 1.73 × 10^-15 M in a wide linear range from 10^-14 M to 10^-5 M. Satisfactory recovery obtained in tap water and milk samples proved that this sensor had great potential in environmental and food analysis.

Molecularly Imprinted Polymer-Based Sensors for the Detection of Skeletal- and Cardiac-Muscle-Related Analytes

Molecularly imprinted polymers (MIPs) are synthetic polymers with specific binding sites that present high affinity and spatial and chemical complementarities to a targeted analyte. They mimic the molecular recognition seen naturally in the antibody/antigen complementarity. Because of their specificity, MIPs can be included in sensors as a recognition element coupled to a transducer part that converts the interaction of MIP/analyte into a quantifiable signal. Such sensors have important applications in the biomedical field in diagnosis and drug discovery, and are a necessary complement of tissue engineering for analyzing the functionalities of the engineered tissues. Therefore, in this review, we provide an overview of MIP sensors that have been used for the detection of skeletal- and cardiac-muscle-related analytes. We organized this review by targeted analytes in alphabetical order. Thus, after an introduction to the fabrication of MIPs, we highlight different types of MIP sensors with an emphasis on recent works and show their great diversity, their fabrication, their linear range for a given analyte, their limit of detection (LOD), specificity, and reproducibility. We conclude the review with future developments and perspectives.

Au Nanoparticles Functionalized Covalent-Organic-Framework-Based Electrochemical Sensor for Sensitive Detection of Ractopamine

Ractopamine, as a feed additive, has attracted much attention due to its excessive use, leading to the damage of the human nervous system and physiological function. Therefore, it is of great practical significance to establish a rapid and effective method for the detection of ractopamine in food. Electrochemical sensors served as a promising technique for efficiently sensing food contaminants due to their low cost, sensitive response and simple operation. In this study, an electrochemical sensor for ractopamine detection based on Au nanoparticles functionalized covalent organic frameworks (AuNPs@COFs) was constructed. The AuNPs@COF nanocomposite was synthesized by in situ reduction and was characterized by FTIR spectroscopy, transmission electron microscope and electrochemical methods. The electrochemical sensing performance of AuNPs@COF-modified glassy carbon electrode for ractopamine was investigated using the electrochemical method. The proposed sensor exhibited excellent sensing abilities towards ractopamine and was used for the detection of ractopamine in meat samples. The results showed that this method has high sensitivity and good reliability for the detection of ractopamine. The linear range was 1.2-1600 μmol/L, and the limit of detection (LOD) was 0.12 μmol/L. It is expected that the proposed AuNPs@COF nanocomposites hold great promise for food safety sensing and should be extended for application in other related fields.

A molecularly imprinted electrochemical aptasensor based on zinc oxide and co-deposited gold nanoparticles/reduced graphene oxide composite for detection of amoxicillin

The molecularly imprinted electrochemical aptasensor was constructed based on co-deposition of zinc oxide and gold nanoparticles/reduced graphene oxide composite. Aptamer was used as a new kind of functional monomer and the aptamer-amoxicillin complex was formed by hydrogen bond. Then, the complex was fixed on the surface of the modified electrode by Au-S bond. Three-dimensional imprinted polymeric membrane was formed by electropolymerization of dopamine, and the imprinted sites with good specificity and affinity were formed after elution. Combined with the specificity of molecularly imprinted technology and the affinity of aptamer, the selective recognition of amoxicillin can be realized. Under the optimal experimental conditions, the linear range was from 10^-14 to 10^-8 M, and the detection limit was 3.3 × 10^-15 M. The sensor exhibited satisfactory selectivity, repeatability, and stability and was successfully used for 10^-9 M amoxicillin determination in real water and food samples.

(INVITED)Quantitative detection of SARS-CoV-2 virions in aqueous mediums by IoT optical fiber sensors

The COVID-19 pandemic has emphasized the need for portable, small-size, low-cost, simple to use, and highly sensitive sensors able to measure a specific substance, with the capability of the transmission over the Internet of statistical data, such as in this specific case on the spread of the SARS-CoV-2 virions. Moreover, to resolve the COVID-19 emergency, the possibility of making selective SARS-CoV-2 measurements in different aqueous matrices could be advantageous. Thus, the realization of rapid and innovative point-of-care diagnostics tests has become a global priority. In response to the current need for quick, highly sensitive and on-site detection of the SARS-CoV-2 virions in different aqueous solutions, two different nanolayer biorecognition systems separately combined with an adaptable optical fiber sensor have been reported in this work. More specifically, two SARS-CoV-2 sensors have been developed and tested by exploiting a plasmonic plastic optical fiber (POF) sensor coupled with two different receptors, both designed for the specific recognition of the SARS-CoV-2 Spike protein; one is aptamer-based and the other one Molecular Imprinted Polymer-based. The preliminary tests on SARS-CoV-2 virions, performed on samples of nasopharyngeal (NP) swabs in universal transport medium (UTM), were compared with data obtained using reverse-transcription polymerase chain reaction (RT-PCR). According to these preliminary experimental results obtained exploiting both receptors, the sensitivity of the proposed SARS-CoV-2 optical fiber sensors proved to be high enough to detect virions. Furthermore, a relatively fast response time (a few minutes) to detect virions was obtained without additional reagents, with the capability to transmit the data via the Internet automatically.