An electrochemical aptamer-based sensor prepared by utilizing the strong interaction between a DNA aptamer and diamond

An electrochemical biosensor based on DNA tetrahedron nanoprobe for sensitive and selective detection of doxorubicin

Doxorubicin (DOX) is a clinical chemotherapeutic drug and patients usually suffer from dose-dependent cytotoxic and side effects during chemotherapy process with DOX. Therefore, developing a reliable strategy for DOX analysis in biological samples for dosage guidance during chemotherapy process is of great significance. Herein, a sensitive and selective electrochemical biosensor for DOX detection was designed based on gold nanoparticles (AuNPs) and DNA tetrahedron (TDN) nanoprobe bifunctional glassy carbon electrode that could detect DOX in human serum and cell lysate samples. AuNPs not only could enhance electron transfer efficiency and detection sensitivity, but also could improve the biocompatibility of electrode. TDN nanoprobes were employed as specific DOX bind sites that could bind abundant DOX through intercalative characteristics to contribute to sensitive and selective detection. Under the optimal conditions, the proposed TDN nanoprobes-based DOX biosensor exhibited a wide linear range that ranged from 1.0 nM to 50 μM and a low detection limit that was 0.3 nM. Moreover, the proposed DOX biosensor displayed nice selectivity, reproducibility and stability, and was successfully applied for DOX detection in human serum and cell lysate samples. These promising results maybe pave a way for DOX dosage guidance and therapeutic efficacy optimization in clinic.

Constructing a Hydrophilic Microsensor for High-Antifouling Neurotransmitter Dopamine Sensing

Real-time sensing of dopamine is essential for understanding its physiological function and clarifying the pathophysiological mechanism of diseases caused by impaired dopamine systems. However, severe fouling from nonspecific protein adsorption, for a long time, limited conventional neural recording electrodes concerning recording stability. This study reported a high-antifouling nanocrystalline boron-doped diamond microsensor grown on a carbon fiber substrate. The antifouling properties of this diamond sensor were strongly related to the grain size (i.e., nanocrystalline and microcrystalline) and surface terminations (i.e., oxygen and hydrogen terminals). Experimental observations and molecular dynamics calculations demonstrated that the oxygen-terminated nanocrystalline boron-doped diamond microsensor exhibited enhanced antifouling characteristics against protein adsorption, which was attributed to the formation of a strong hydration layer as a physical and energetic barrier that prevents protein adsorption on the surface. This finally allowed for in vivo monitoring of dopamine in rat brains upon potassium chloride stimulation, thus presenting a potential solution for the design of next-generation antifouling neural recording sensors. Experimental observations and molecular dynamics calculations demonstrated that the oxygen-terminated nanocrystalline boron-doped diamond (O-NCBDD) microsensor exhibited ultrahydrophilic properties with a contact angle of 4.9°, which was prone to forming a strong hydration layer as a physical and energetic barrier to withstand the adsorption of proteins. The proposed O-NCBDD microsensor exhibited a high detection sensitivity of 5.14 μA μM-1 cm-2 and a low detection limit of 25.7 nM. This finally allowed for in vivo monitoring of dopamine with an average concentration of 1.3 μM in rat brains upon 2 μL of potassium chloride stimulation, thus presenting a potential solution for the design of next-generation antifouling neural recording sensors.

Computational aptamer design for spike glycoprotein (S) (SARS CoV-2) detection with an electrochemical aptasensor

A new bioinformatic platform (APTERION) was used to design in a short time and with high specificity an aptamer for the detection of the spike protein, a structural protein of SARS-CoV-2 virus, responsible for the COVID-19 pandemic. The aptamer concentration on the carbon electrode surface was optimized using static contact angle and fluorescence method, while specificity was tested using differential pulse voltammetry (DPV) associated to carbon screen-printed electrodes. The data obtained demonstrated the good features of the aptamer which could be used to create a rapid method for the detection of SARS-CoV-2 virus. In fact, it is specific for spike also when tested against bovine serum albumin and lysozyme, competitor proteins if saliva is used as sample to test for the virus presence. Spectrofluorometric characterization allowed to measure the amount of aptamer present on the carbon electrode surface, while DPV measurements proved the affinity of the aptamer towards the spike protein and gave quantitative results. The acquired data allowed to conclude that the APTERION bioinformatic platform is a good method for aptamer design for rapidity and specificity. KEY POINTS: • Spike protein detection using an electrochemical biosensor • Aptamer characterization by contact angle and fluorescent measurements on electrode surface • Computational design of specific aptamers to speed up the aptameric sequence time.

Voltammetric Sensor for Doxorubicin Determination Based on Self-Assembled DNA-Polyphenothiazine Composite

A novel voltammetric sensor based on a self-assembled composite formed by native DNA and electropolymerized N-phenyl-3-(phenylimino)-3H-phenothiazin-7-amine has been developed and applied for sensitive determination of doxorubicin, an anthracycline drug applied for cancer therapy. For this purpose, a monomeric phenothiazine derivative has been deposited on the glassy carbon electrode from the 0.4 M H2SO4-acetone mixture (1:1 v/v) by multiple potential cycling. The DNA aliquot was either on the electrode modified with electropolymerized film or added to the reaction medium prior to electropolymerization. The DNA entrapment and its influence on the redox behavior of the underlying layer were studied by scanning electron microscopy and electrochemical impedance spectroscopy. The DNA-doxorubicin interactions affected the charge distribution in the surface layer and, hence, altered the redox equilibrium of the polyphenothiazine coating. The voltametric signal was successfully applied for the determination of doxorubicin in the concentration range from 10 pM to 0.2 mM (limit of detection 5 pM). The DNA sensor was tested on spiked artificial plasma samples and two commercial medications (recovery of 90-95%). After further testing on real clinical samples, the electrochemical DNA sensor developed can find application in monitoring drug release and screening new antitumor drugs able to intercalate DNA.

Molecular Biomarkers and Recent Liquid Biopsy Testing Progress: A Review of the Application of Biosensors for the Diagnosis of Gliomas

Gliomas are the most common primary central nervous system tumors, with a high mortality rate. Early and accurate diagnosis of gliomas is critical for successful treatment. Biosensors are significant in the detection of molecular biomarkers because they are simple to use, portable, and capable of real-time analysis. This review discusses several important molecular biomarkers as well as various biosensors designed for glioma diagnosis, such as electrochemical biosensors and optical biosensors. We present our perspectives on the existing challenges and hope that this review can promote the improvement of biosensors.

Impedimetric DNA Sensor Based on Electropolymerized N-Phenylaminophenothiazine and Thiacalix[4]arene Tetraacids for Doxorubicin Determination

Electrochemical DNA sensors are highly demanded for fast and reliable determination of antitumor drugs and chemotherapy monitoring. In this work, an impedimetric DNA sensor has been developed on the base of a phenylamino derivative of phenothiazine (PhTz). A glassy carbon electrode was covered with electrodeposited product of PhTz oxidation obtained through multiple scans of the potential. The addition of thiacalix[4]arene derivatives bearing four terminal carboxylic groups in the substituents of the lower rim improved the conditions of electropolymerization and affected the performance of the electrochemical sensor depending on the configuration of the macrocyclic core and molar ratio with PhTz molecules in the reaction medium. Following that, the deposition of DNA by physical adsorption was confirmed by atomic force microscopy and electrochemical impedance spectroscopy. The redox properties of the surface layer obtained changed the electron transfer resistance in the presence of doxorubicin due to its intercalating DNA helix and influencing charge distribution on the electrode interface. This made it possible to determine 3 pM-1 nM doxorubicin in 20 min incubation (limit of detection 1.0 pM). The DNA sensor developed was tested on a bovine serum protein solution, Ringer-Locke's solution mimicking plasma electrolytes and commercial medication (doxorubicin-LANS) and showed a satisfactory recovery rate of 90-105%. The sensor could find applications in pharmacy and medical diagnostics for the assessment of drugs able to specifically bind to DNA.

Finding the Lost Dissociation Constant of Electrochemical Aptamer-Based Biosensors

Electrochemical aptamer-based (E-AB) biosensors afford real-time measurements of the concentrations of molecules directly in complex matrices and in the body, offering alternative strategies to develop innovative personalized medicine tools. While different electroanalytical techniques have been used to interrogate E-AB sensors (i.e., cyclic voltammetry, electrochemical impedance spectroscopy, and chronoamperometry) to resolve the change in electron transfer of the aptamer's covalently attached redox reporter, square-wave voltammetry remains a widely used technique due to its ability to maximize the redox reporter's faradic contribution to the measured current. Several E-AB sensors interrogated with this technique, however, show lower aptamer affinity (i.e., μM-mM) even in the face of employing aptamers that have high affinities (i.e., nM-μM) when characterized using solution techniques such as isothermal titration calorimetry (ITC) or fluorescence spectroscopy. Given past reports showing that E-AB sensor's response is dependent on square-wave interrogation parameters (i.e., frequency and amplitude), we hypothesized that the difference in dissociation constants measured with solution techniques stemmed from the electrochemical interrogation technique itself. In response, we decided to compare six dissociation constants of aptamers when characterized in solution with ITC and when interrogated on electrodes with electrochemical impedance spectroscopy, a technique able to, in contrast to square-wave voltammetry, deconvolute and quantify E-AB sensors' contributions to the measured current. In doing so, we found that we were able to measure dissociation constants that were either separated by 2-3-fold or within experimental errors. These results are in contrast with square-wave voltammetry-measured dissociation constants that are at the most separated by 2-3 orders of magnitude from ones measured by ITC. We thus envision that the versatility and time scales covered by electrochemical impedance spectroscopy offer the highest sensitivity to measure target binding in electrochemical biosensors relying on changes in electron-transfer rates.

Recent progress and perspectives of continuous in vivo testing device

Devices for continuous in-vivo testing (CIVT) can detect target substances in real time, thus providing a valuable window into a patient's condition, their response to therapeutics, metabolic activities, and neurotransmitter transmission in the brain. Therefore, CIVT devices have received increased attention because they are expected to greatly assist disease diagnosis and treatment and research on human pathogenesis. However, CIVT has been achieved for only a few markers, and it remains challenging to detect many key markers. Therefore, it is important to summarize the key technologies and methodologies of CIVT, and to examine the direction of future development of CIVT. We review recent progress in the development of CIVT devices, with consideration of the structure of these devices, principles governing continuous detection, and nanomaterials used for electrode modification. This detailed and comprehensive review of CIVT devices serves three purposes: (1) to summarize the advantages and disadvantages of existing devices, (2) to provide a reference for development of CIVT equipment to detect additional important markers, and (3) to discuss future prospects with emphasis on problems that must be overcome for further development of CIVT equipment. This review aims to promote progress in research on CIVT devices and contribute to future innovation in personalized medical treatments.

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A detailed and comprehensive review of continuous in vivo testing device.

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The nanomaterials, delicate structures and detection principles of the works are discussed.

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The achievements and shortcomings of the existing devices are summarized.

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The problems that should be solved in the further development of the devices and the future prospects are put forward.

Electrochemical detection of triamterene in human urine using boron-doped diamond electrodes

Urine is one of the most used biological fluids for screening drug delivery and the resultant metabolites. In sports, the use of diuretics such as triamterene is considered a violation of anti-doping rules and is stipulated to be present at less than 79 nM in urine by the World Anti-Doping Agency (WADA). It is therefore important to develop effective rapid and low-cost tests for this diuretic. Here we apply electrochemical analysis using boron-doped diamond (BDD) electrodes, which have superior properties such as low background current, a wide potential window, and high resistance to deactivation. Since real urine samples show clear oxidation current peaks in the potential range more positive than 0.5 V (vs. Ag/AgCl) due to the presence of bio-components such as protein, uric acid, and ascorbic acid, to detect triamterene effectively, the electrochemical protocol was optimized towards a potential range where the other components have limited effect. Our results show that reduced triamterene exhibits an oxidation peak at 0.1 V (vs. Ag/AgCl) in 0.1 M phosphate buffer (PB) and at 0.2 V (vs. Ag/AgCl) in pooled human urine. The peak current value increased according to the triamterene concentration. The limit of detection (LOD) was 3.15 nM in the PB and 7.80 nM in pooled human urine. Finally, triamterene detection was attempted in individual urine samples. Triamterene was electrochemically detectable in individual urine samples, excluding urine samples containing an excess amount of ascorbic acid. The limit of detection (LOD) in individual urine samples was determined to be 20.8 nM.

Diagnostic Approaches For COVID-19: Lessons Learned and the Path Forward

Coronavirus disease 2019 (COVID-19) is a transmitted respiratory disease caused by the infection of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although humankind has experienced several outbreaks of infectious diseases, the COVID-19 pandemic has the highest rate of infection and has had high levels of social and economic repercussions. The current COVID-19 pandemic has highlighted the limitations of existing virological tests, which have failed to be adopted at a rate to properly slow the rapid spread of SARS-CoV-2. Pandemic preparedness has developed as a focus of many governments around the world in the event of a future outbreak. Despite the largely widespread availability of vaccines, the importance of testing has not diminished to monitor the evolution of the virus and the resulting stages of the pandemic. Therefore, developing diagnostic technology that serves as a line of defense has become imperative. In particular, that test should satisfy three criteria to be widely adopted: simplicity, economic feasibility, and accessibility. At the heart of it all, it must enable early diagnosis in the course of infection to reduce spread. However, diagnostic manufacturers need guidance on the optimal characteristics of a virological test to ensure pandemic preparedness and to aid in the effective treatment of viral infections. Nanomaterials are a decisive element in developing COVID-19 diagnostic kits as well as a key contributor to enhance the performance of existing tests. Our objective is to develop a profile of the criteria that should be available in a platform as the target product. In this work, virus detection tests were evaluated from the perspective of the COVID-19 pandemic, and then we generalized the requirements to develop a target product profile for a platform for virus detection.

Evaluation of the Interaction of Cinacalcet with Calf Thymus dsDNA: Use of Electrochemical, Spectrofluorimetric, and Molecular Docking Methods

The binding of drugs to DNA plays a critical role in new drug discovery and is important for designing better drugs. In this study, the interaction and binding mode of calf-thymus double-stranded deoxyribonucleic acid (ct-dsDNA) with cinacalcet (CIN) from the calcimimetic drug that mimics the action of calcium on tissues group were investigated. The interaction of CIN with ct-dsDNA was observed by the differential pulse voltammetry (DPV) technique by following the decrease in electrochemical oxidation signals to deoxyguanosine and adenosine. A competitive study was performed on an indicator, methylene blue, to investigate the interaction of the drug with ct-dsDNA by fluorescence spectroscopy. Interaction studies have shown that the binding mode for the interaction of CIN with ct-dsDNA could be groove-binding. According to the results obtained, the binding constant values were found to be 6.30 × 10⁴ M⁻¹ and 3.16 × 10⁵ M⁻¹, respectively, at 25 °C as obtained from the cyclic voltammetry (CV) and spectroscopic techniques. Possible molecular interactions of CIN with dsDNA were explored via molecular docking experiments. The docked structure indicated that CIN could fit well into the minor groove of the DNA through H-bonding and π-π stacking contact with CIN.

Real-time monitoring of drug pharmacokinetics within tumor tissue in live animals

The efficacy and safety of a chemotherapy regimen fundamentally depends on its pharmacokinetics. This is currently measured based on blood samples, but the abnormal vasculature and physiological heterogeneity of the tumor microenvironment can produce radically different drug pharmacokinetics relative to the systemic circulation. We have developed an implantable microelectrode array sensor that can collect such tissue-based pharmacokinetic data by simultaneously measuring intratumoral pharmacokinetics from multiple sites. We use gold nanoporous microelectrodes that maintain robust sensor performance even after repeated tissue implantation and extended exposure to the tumor microenvironment. We demonstrate continuous in vivo monitoring of concentrations of the chemotherapy drug doxorubicin at multiple tumor sites in a rodent model and demonstrate clear differences in pharmacokinetics relative to the circulation that could meaningfully affect drug efficacy and safety. This platform could prove valuable for preclinical in vivo characterization of cancer therapeutics and may offer a foundation for future clinical applications.