Linear Concentration Range Research Articles

Sensitive detection of gallic acid in food by electrochemical sensor fabricated by integrating nanochannel film with nanocarbon nanocomposite

Sensitive detection of gallic acid (GA) in foods is of great significance for assessing the antioxidant properties of products and ensuring consumer health. In this work, a simple electrochemical sensor was conveniently fabricated by integrating vertically-ordered mesoporous silica film (VMSF) with electrochemically reduced graphene oxide (ErGO) and nitrogen graphene quantum dots (NGQDs) nanocomposite, enabling sensitive detection of GA in food sample. A water-soluble mixture of graphene oxide (GO) and NGQDs was drop-cast onto the common carbon electrode, glassy carbon electrode (GCE), followed by rapid growth of VMSF using an electrochemically assisted self-assembly method (EASA). The negative voltage applied during VMSF growth facilitated the in situ reduction of GO to ErGO. The synergistic effects of ErGO, NGQDs, and the nanochannels of VMSF led to nearly a tenfold enhancement of the GA signal compared to that obtained on electrodes modified with either ErGO or NGQDs alone. Sensitive detection of GA was realized with a linear concentration range from 0.1 to 10 μM, and from 10 to 100 μM. The limit of detection (LOD), determined based on a signal-to-noise ratio of three (S/N = 3), was found to be 81 nM. Combined with the size-exclusion property of VMSF, the fabricated sensor demonstrated high selectivity, making it suitable for the sensitive electrochemical detection of gallic acid in food samples.

Development of engineered Zn-MOF/g-C3N4 based photoelectrochemical system for real-time sensors and removal of naproxen in wastewater

Naproxen-contaminated water may lead to the accumulation of the drug in aquatic organisms and can pose high risks to an aquatic environment and human beings. Therefore, this work aimed to develop photoelectrochemical sensing and degradation of naproxen (NPX) using zinc-metal organic framework /graphitic carbon nitride thin film-based fluorine-doped tin oxide (Zn-MOF/g-C3N4/FTO) as anode material for the sensing and degradation of naproxen (NPX). The surface morphology, structure, surface property, surface area, optical property, photocurrent, and charge transfer kinetics abilities were studied using different techniques. The nanocomposites showed a superior photocurrent response (0.815 mA cm-2) compared to the original g-C3N4 (0.328 mA cm-2). The photo-anode made of Zn-MOF@g-C3N4/FTO displayed the highest photocurrent value, indicating that the alignment of the two semiconductor bands prevented the quick recombination of electron-hole pairs. Owing to these attractive features, the Zn-MOF/g-C3N4/FTO electrode was applied for photoelectrochemical detection of NPX using chronoamperometry. Interestingly, the nanocomposites-based FTO ascribed a lower detection limit (2.3 ng l-1) with a wide linear range concentration of NPX (0.5 to 200 µg l-1). Additionally, the analytical assessment of repeatability and reproducibility demonstrated robust performance, with commendable relative standard deviations (RSD%) of 2.54 % and 2.40 %, respectively. On the other hand, a remarkable degradation efficiency of 97.52 % was attained when employing a bias potential of 0.1 V during a 2 h photoelectrocatalytic oxidation of NPX. The degradation process was primarily driven by the active participation of holes and hydroxyl radicals in ring opening and subsequent cleavage of by-products. The notable effectiveness of this degradation can be attributed to the combined and synergistic effects of both electrochemical and photocatalytic degradation techniques. The current state demonstrates its effectiveness in the photoelectrochemical sensing and removal of NPX using MOF/g-C3N4 nanocomposites-based electrode materials in wastewater.

Development and validation of an LC‒MS/MS method for the determination of cyclocreatine phosphate and its related endogenous biomolecules in rat heart tissues

The cardioprotective drug cyclocreatine phosphate has been awarded Food and Drug Administration-orphan drug designation for the prevention of ischemic injury to enhance cardiac graft recovery and survival in heart transplantation. Cyclocreatine phosphate is the water-soluble derivative of cyclocreatine. Estimating the levels of Cyclocreatine phosphate, Adenosine triphosphate, Creatine Phosphate, Creatine and Cyclocreatine helps us in understanding the energy state as well as evaluating the heart cells’ function. The quantification of endogenous compounds imposes a challenging task for analysts because of the absence of a true blank matrix, whose use is required according to international guidelines. Recently, the International Council for Harmonization issued a new guideline that contains guidance on the validation of methods used to quantify endogenous components, such as the background subtraction approach that was employed in our current study. Specifically, we developed and validated a sensitive, reliable and accurate liquid chromatography-tandem mass spectrometry assay to determine simultaneously the levels of mentioned endogenous compounds in rat heart tissue. Tissue samples were prepared by protein precipitation extraction using water: methanol (1:1). Using Ultra Performance Liquid Chromatography, Chromatographic separation was achieved with ZORBAX Eclipse Plus C18 4.6 × 100 mm,3.5 μm column and conditions as following: ammonium acetate (pH 8.5): acetonitrile, 70:30 mobile phase, 0.7 mL/min flow rate and 25 °C temperature. Electrospray ionization mass detector with Multiple reaction monitoring mode was then employed, using both positive and negative modes, Analysis was carried out using 5.00–2000.00 ng/mL linear concentration range within 2 min for each analyte. According to Food and Drug Administration guidelines for bioanalytical methods, validation was carried out. We investigated the matrix effect, recovery efficiency and process efficiency for the analyte in neat solvent, postextraction matrix and tissue. The results stated mean percentage recoveries higher than 99%, accuracy 93.32–111.99%, and Relative Standard Deviation (RSD) below 15% within the concentration range of our study which indicated that target analytes’ stability in their real matrix is sufficient under the employed experimental conditions.

Indirect determination of free chlorine in seawater by cyclic voltammetry using graphite–epoxy composite electrode: Hydrogen adsorption capacity of graphite–epoxy composite is one–third of that of platinum

A new possibility of indirect determination of free chlorine using a graphite–epoxy composite(GEC) electrode instead of Pt disk electrode was suggested by interpreting the relationship between the peak current of the oxidation peak for hydrogen generated through water electrolysis in CV and the amount of the free chlorine. The linear response range of concentration was 0.06–0.2 mg∙L−1 with correlation coefficient of 0.9951 (n = 5) and the sensitivity of 1225 μA cm−2 mg−1 L. The limit of detection (LOD) calculated from the 3σ IUPAC criteria was 1.2 × 10−2 mg L−1. The relative standard deviation (RSD) to 0.06 mg L−1 was 4.65 %(n = 10). The results show that the amount of free chlorine in the disinfected seawater can be indirectly determined by using a GEC electrode without influence of interferences unlike a Pt disk electrode. On the other hand, in this paper, a new method is proposed to evaluate the relative hydrogen adsorption capacity by the sensitivity of GEC electrode compared with that of Pt disk electrode. During the investigation of the hydrogen adsorption on the surface of the working electrode, we obtained the result that the hydrogen adsorption capacity of GEC is one-third of that of platinum.

Photothermal modulated hotspot for accurate and sensitive SERS detection of pesticides in complicated media

Designing smart surface-enhanced Raman scattering (SERS) nanosensors with superior sensibility, stabilities and repeatability is a challenging and intriguing goal in chemical measurement. Herein, we develop a photothermal modulated SERS platform (PM-SERS) for sensitive and stable analysis of targets by exploiting a stimuli-responsive gold nanoparticles (GNPs) decorated polyvinyl alcohol hydrogel (GPH). Importantly, the proposed GPH facilitates exactly controlling 3D hot-spot regions by modulating surrounding temperature and humidity. The adjustable GPH could not only act as a stable matrix for installing of high-density GNPs, but also as a sorption domain for preconcentration of targeted analyte in hot-spots sites, thus permitting simultaneously modulating 3D nanostructures and seizing targeted analytes in plasmonic regions. Crucially, because of the reversible nanostructures and nanoplasmonic features, GPH can eradicate adsorbates after being exposed to bromide solutions, thereby allowing renewable and reliable on-site SERS detection of complex media. The GPH-based PM-SERS platform exhibits excellent sensitivities and reproducibility for on-demand detection of multiplexed pesticide over a wide linear concentration range (2 × 10-6 to 103 μM), with detection limits as low as hundreds of fM. The GPH-based analytical platform provides tremendous potentials for credible quantification of complicated matrices and on-line process screening.

Development and validation of ultra-performance liquid chromatography tandem mass spectrometry methods for the quantitative analysis of the antiparasitic drug DNDI-6148 in human plasma and various mouse biomatrices

DNDI-6148 is a promising new oral drug for the treatment of cutaneous leishmaniasis (CL), a parasitic neglected tropical disease that affects impoverished populations worldwide. Preclinical target site pharmacokinetics (PK) studies are necessary to evaluate the actual exposure to DNDI-6148 of Leishmania parasites in the skin. To facilitate these investigations, we have developed and validated a reversed phase ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) method to quantify DNDI-6148 in relevant target site PK samples, adhering to the relevant International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) M10 guideline on bioanalytical method validation. Full validation was performed for the surrogate biomatrices human K2EDTA plasma, enzymatic digestion buffer and skin microdialysate. Partial validation was conducted for mouse K2EDTA plasma and tissues. The tissue samples, including mouse skin, liver and spleen, were homogenized using a collagenase A-based enzymatic homogenization workflow. This method was found to be 2.9-fold more effective in extracting DNDI-6148 from skin than the commonly used mechanical homogenization. Protein precipitation was subsequently carried out for all biomatrices. A surrogate biomatrix was used for each method and the range was specifically developed for its intended application, resulting in a linear concentration range of 5.00–2,000 ng/mL, 2.00–1,000 ng/mL, and 3.00–600 ng/mL for human K2EDTA plasma, enzymatic digestion buffer and microdialysate, respectively. Each biomatrix had intra- and inter-run accuracy and precision within 15 % for all concentration levels. Matrix effects did not affect the determination of DNDI-6148, since the stable isotopically-labelled internal standard for DNDI-6148 effectively compensated for these matrix effects. Total recovery across all methods was between 73.5 % and 81.3 % (CV ≤4.5 %). DNDI-6148 was stable under various conditions in all the tested biomatrices. However, a decrease in its concentration was observed during homogenization, for which the internal standard corrected adequately. The suitability of the method for use in future preclinical research involving DNDI-6148 was demonstrated in a preclinical target site PK study using a CL-infected murine model.

Development and Validation of a Method for Detecting and Quantifying Mitragynine in Kratom Samples Using HPLC-PDA

Kratom (Mitragyna speciosa Korth) has been identified as a New Psychoactive Substance (NPS) by the United Nations Office on Drugs and Crime (UNODC) and included in the list of prohibited ingredients in food supplements and traditional medicine by Indonesian FDA. Therefore, a rapid, easy, and reliable analytical method is necessary to detect and quantify this plant and its products. This study developed a method for the detection and quantification of kratom products based on a unique compound, mitragynine, as a biomarker. A previous survey of determining mitragynine in Kratom using GC-MS, LC-MS/MS, UPLC, and HPLC-PDA. Previously, the HPLC-PDA method used a C8 column. Yet, for efficiency, it is also necessary to develop a test method using a C18 column. Analysis was performed using an HPLC - PDA system with Waters Atlantis T3-C18 (250 x 4.6 mm, 5 µm) column. The mobile phase comprises acetonitrile and formic acid 0.05%, pH 5.0 (75:25 v/v), delivered at a 1.0 mL/min flow rate. Detection was carried out at a wavelength of 225 nm. The analytical method was validated with test parameters of selectivity, system suitability, accuracy, precision, linearity, detection limit, and quantification limit. The validation study demonstrated an excellent linear concentration range of 1.96 - 6.01 µg/mL with a correlation coefficient of 0.9996; the detection limit is 0.14 µg/mL, while the limit of quantification is 0.45 µg/mL—accuracy method of 98.88 - 101.44% and a bias of 0.27%. The percent relative standard deviation for six independent assay determinations was 0.67%, and the intermediate precision was 1.56% on two days. The mitragynine amounts in these materials ranged from 6.01 to 6.31 mg/g of dried leaf material. Based on the research results, it can be concluded that the method developed provides quick, simple, reliable, accurate, and valid, and has an advantage over existing methods in terms of simplicity of sample preparation, short analysis time, and cost-effectiveness compared to GCMS and LCMS/MS and can be applied for future analysis in Kratom samples.

Fast Molecular Recognition of Docosahexaenoic Acid Ethyl Ester in the Liver and Meat of Stingray Using a Miniplatform Based on a 3D Stochastic Microsensor

Docosahexaenoic acid ethyl ester has an important role in the prevention of the neuropsychiatric and neurodegenerative diseases. Its extraction from fish such as the stingray as anoil creates a pharmaceutical formulation. Therefore it is essential to develop fast molecular recognition methods able to perform both qualitative and quantitative determination of docosahexaenoic in stingray meat and liver. A miniplatform incorporating a 3D stochastic microsensor was designed and validated for the molecular recognition of docosahexaenoic acid ethyl ester. The design of the microsensor was based on the modification of a graphene decorated with nitrogen and boron paste (NB-graphene paste) with 10−3mol L−1 alpha-cyclodextrin. A wide linear concentration range (5.0 × 10−14 − 5.0 × 10−7 g mL−1) and a low limit of quantitation (5.0 × 10−14 g mL−1) were obtained. High recovery values were determined when the miniplatform was used for the assay of docosahexaenoic acid ethyl ester from stingray liver and meat with recoveries higher than 99.20%. The relative standard deviation values were less than 0.05 (N = 10).

Novel Electrochemical Sensor Based on One-Step Encapsulation of Metal-Organic Framework (MOF) for Simultaneous Detection of SARS-CoV and SARS-CoV-2.

This study investigates three metal-organic frameworks (MOFs) with distinct Brunauer-Emmett-Teller (BET) surface areas and pore sizes: MOFZr (1274 m2/g, <0.7 nm), MOFAl (371 m2/g, 1.5 nm), and MOFCr (1917 m2/g, 2 nm). Methylene blue (MB, 1.4 × 0.7 × 0.2 nm3) and triferrocene (tri-FC, 1.2 × 0.9 × 0.3 nm3) were adsorbed onto these MOFs. Specific DNA segments targeting SARS-CoV-2 (PR and PO) were employed to block the pores of the MOFs, leading to the formation of DNA-gated MOFs: MOFX/MB/PR and MOFX/tri-FC/PO. These constructs were subsequently integrated with four-arm poly(ethylene glycol) amine (4-arm-PEG-NH2)-modified gold electrodes to create the corresponding sensors (MOFX/MB/PR+MOFX/tri-FC/PO@4-arm-PEG-NH2@Au NPs@GCE). The DNA-gated MOFAl system exhibited the highest loading capacity and a 3-fold increase in sensing efficiency following the introduction of SARS-CoV-2 target DNA, surpassing the performance of the other systems. This study highlights the enhancement of the DNA-gated MOFs when the three-dimensional structures of the guest molecules closely align with the pore sizes of the MOFs. It emphasizes a critical aspect of the traditional design approach for electrochemical sensors based on MOF encapsulation, which often prioritizes BET surface areas while neglecting the compatibility between the sizes of guest molecules and MOF pore diameters. Moreover, the sensor effectively discriminated between SARS-CoV-2 and SARS-CoV by precisely aligning the SARS-CoV-2 target DNA with PR and PO. In contrast, the specific genetic targets (SR) from SARS-CoV showed complete mismatches with PO and a three-base deviation with PR. This differentiation was achieved in a simple one-step assay, even in 5% serum, across a linear concentration range of 10-9 to 10-14 M. This range signifies an expansion of 2 to 3 orders of magnitude compared to sensors that inaccurately selected MOFs.

Aggregation induced emission “Turn on” ultra-low detection of anti-inflammatory drug flufenamic acid in human urine samples by carbon dots derived from bamboo stem waste

Carbon dot-based fluorescence sensors have attracted research interest for the selective determination of anti-inflammatory drugs in biological fluids and environments. The overdose and accumulation of anti-inflammatory drugs in tissues can cause chronic side effects including abdominal pain, and renal damage. Herein, we report a new fluorescent probe, bamboo stem waste-derived carbon dots (BS-CDs) for highly sensitive detection of Flufenamic acid (FA), a hazardous anti-inflammatory drug. The UV–vis absorption spectra of BS-CDs show a redshifted absorption peak at 283 nm upon the addition of FA suggesting strong binding interaction between BS-CDs and FA molecule. The BS-CDs showed a fluorescence enhancement (∼2-fold) detection for FA (400 μM) in the linear concentration range (0.40 → 0.65 μM) with a limit of detection (LoD; 17 nM) and binding constant (Ka = 1.33 × 10−3 M−1). The time-resolved fluorescence decay analysis showed that the average lifetime of BS-CDs has slightly changed (4.42 → 4.67 ns) by the interaction with FA through the aggregation-induced emission (AIE) process. The interference, pH, and effect of time results suggest that BS-CDs are highly selective probes for FA detection and do not show any interference involvement during FA detection. The confirmation of the structure and morphology changes of BS-CDs after interaction with FA was carried out by XRD, FESEM, HRTEM, FTIR, and Raman spectroscopy. The practicability of the BS-CDs probe was proved by the detection of FA in human urine samples with recovery of 103–109 %. This suggests that the proposed BS-CDs-based ‘turn-on’ sensor could be used to determine the FA in biological fluids.

Enhanced sensitivity in tobramycin monitoring using a surfactant-aligned liquid crystal aptasensor with a ternary hybrid aptamer

Determining pharmaceutical residues in foodstuffs is of great importance worldwide. The improper use of tobramycin (TOB) with abroad spectrum antibacterial activity results in its accumulation in the food chain and human body. Given its detrimental effects on human health, the careful surveillance of TOB concentrations is essential to ensure food safety. Presented here is a highly sensitive aptasensing array designed to measure the TOB concentration by disrupting the alignment of liquid crystal (LC) molecules induced by surfactants. For the first time, a ternary hybrid of the aptamer strands was incorporated onto the surfactant-designed LC-aqueous interface instead of a single strand of aptamer, causing a significant disruption in the customary orientation of LCs. This changed the brightness quantity from 35.06 to 69.54, due to higher interaction with the positively charged section of the surfactant than that for one aptamer strand. The presence of TOB caused the ternary aptamer hybrid to break apart by creating the complex between the aptamer and TOB, separating the aptamer strands from the LC-aqueous interface. Subsequently, the TOB presence was specified by inducing a color change in the polarized vision of the aptasensor platform, resulting in a shift from colorful to murky. The aptasensor could monitor TOB in the linear concentration range of 1 fM-10 nM, with an impressively low detection limit of 0.217 fM. With the capability to determine TOB in beef, chicken egg, and low-fat milk, the LC-decorated aptasensor is proficient in food quality control. The aptasensor possesses characteristics such as simplicity, high sensitivity, ease of use, and affordability. As a result, it has the potential to be marketed as a portable testing kit that is convenient and cost-effective.

B-069 Characterization of a panel of antibodies as diagnostics for NASH and NAFL

Abstract Background Nonalcoholic fatty liver disease (NAFLD) is on the rise in Western industrialized countries and associated comorbidities like e.g. cirrhosis are a major cause of liver transplantations in the USA. In NAFLD, excess fat is accumulated in the liver whereas this build-up is not caused by alcohol. NASH (nonalcoholic steatohepatitis) and NAFL (nonalcoholic fatty liver) are two forms of NAFLD. NAFL represents a stage of the disease in which the liver does not exhibit major signs of inflammation or damage, while NASH does. NAFL does not necessarily progress to cause liver damage. NASH on the other hand may cause fibrosis and lead to cirrhosis with a risk of progression into liver cancer. Since NAFLD shows a prevalence of over 24-25% in both the USA and Europe, diagnosis moves more and more into focus. The current gold standard for NASH diagnosis is liver biopsy, and NAFLD as such can also be diagnosed by ultrasound and MRI, among others. A quest for biomarkers is ongoing to develop blood tests that allow NAFLD diagnosis by immunoassays for example. We have developed high affinity and specificity antibodies against four highly discussed marker proteins for NAFLD: RBP4 (Retinol Binding Protein 4), FGF21 (Fibroblast Growth factor 21), CHI3L1 (Chitinase-3-like protein 1) and PAI-1 (Plasminogen activator inhibitor-1). All four markers are discussed to be elevated in NAFLD patient serum. Methods We characterized the developed anti-RBP4 and anti-FGF21 antibodies via an in-house developed Chemiluminescence Immunoassay (CLIA). Results We have determined the limit of quantification (LoQ), limit of detection (LoD) and linear range of measurable concentrations for our antibody pairs. We further conducted spike and recovery experiments showing the precision of the developed antibodies against RBP4 and FGF21. Conclusions Together, we present antibody pairs for RBP4 and FGF21 suitable as a part of a diagnostic panel that has high potential to be applied in the diagnosis of NAFLD.

Development of a highly sensitive and selective electrochemical aptasensor for the detection of Staphylococcus aureus in various samples

Food poisoning caused by toxins produced by Staphylococcus aureus (S. aureus) is a significant global public health concern, impacting both developing and developed countries. One effective method for detecting S. aureus is the use of electrochemical aptasensors. This study introduces a highly sensitive and selective electrochemical aptasensor designed for detecting of S. aureus bacteria. The aptasensor incorporates ferrocene (Fc) as an electrochemical signal tag, which is covalently bonded to a zeolitic imidazolate framework-8 (ZIF-8). To enhance the performance of the working electrode, a nanocomposite of three-dimensional reduced graphene oxide and chitosan is used to create a nanomaterial film with a large surface area and excellent conductivity. The S. aureus-specific aptamer sequence is immobilized as the bio-recognition element, and cDNA-ZIF-8-Fc is hybridized with the immobilized aptamer. Differential pulse voltammograms of the modified electrode are recorded before and after the interaction between the immobilized aptamer and S. aureus. The changes in peak current serve as the analytical signal for the quantitative measurement of S. aureus. The designed aptasensor can detect S. aureus within a linear concentration range of 15.0 to 1.5 × 107 CFU mL−1, with a limit of detection (LOD) of 5.3 CFU mL−1. The results demonstrate that the aptasensor effectively quantifies S. aureus selectively in the presence of other bacterial species. Additionally, satisfactory results are obtained when measuring S. aureus in tap water and milk samples.

Fe/Cl/N triply-doped bamboo-like structure wrapped with Fe3C nanoparticles for electrochemical selective nitrite detection

Nitrite is commonly found in the natural environment and in everyday human activities. However, excessive nitrite consumption can potentially harm human health. Consequently, it is crucial to develop a reliable and sensitive method for nitrite detection. In this work, trichloroacetic acid functionalized Cl-Fe-MIL-88B metal-organic framework is obtained through nucleophilic reaction between animated Fe-MIL-88B and trichloroacetic acid, which is then annealed with melamine in an N2 atmosphere to produce the Fe/Cl/N triply-doped bamboo-like carbon nanotubes (CNTs) wrapped with Fe3C nanoparticles. Owing to the effective doping of Fe/Cl/N elements, the charge distribution and chemical activity of the bamboo-like structure are tailored, greatly improving the conductivity and facilitating electron transfer of the composite for potential electrocatalytic reaction. The Fe3C nanoparticles wrapped inside the CNTs contribute to expose more active sites and provide effective surface area. Accordingly, the Fe/Cl/N doped bamboo-like structure modified glassy carbon electrode shows excellent electrochemical nitrite sensing properties with a high sensitivity of 1060µAcm-2 mM-1, a low detection limit of 0.61µM in a wide linear concentration range of 5-5000μM, as well as good anti-interference and long-term stability. Also, the electrochemical sensor has a satisfactory recovery rate for detecting nitrite ions in spiked milk samples. This work proposes a simple precursor chlorination and pyrolysis strategy to obtain metal-filled bamboo-like structure with high electrical conductivity and electrocatalytic properties, endowing great potential in food safety and environment monitoring.

Amplification‐free sub-femtomolar monitoring of SARS-CoV-2-RNA in serum samples using cDNA-modified MoS2 field-effect transistor

The rapid spread of infectious diseases, exemplified by the well-known case of COVID-19, which has led to a global pandemic, has garnered increasing attention toward the development of simple and efficient biosensors for diagnosis. In this study, a field-effect transistor (FET)-based biosensor offers an alternative and promising solution for the diagnosis of clinical COVID-19. Molybdenum disulfide (MoS2) in a channel FET modified with a probe complementary DNA (cDNA) can sensitively detect selected specific sequences from SARS-CoV-2 through hybridization. MoS2 was modified with probe cDNA and exhibited a linear concentration range of 1 fM to 0.1 nM in both phosphate-buffered saline (PBS) and serum samples, with low limits of detection (LOD) of 0.21 and 0.73 fM, respectively. In addition, it demonstrated a rapid response time of 3 min in clinical samples. The developed biosensor is capable of analyzing RNA from 19 clinical samples. These results indicate that the biosensor successfully distinguished between healthy and infected samples, which is consistent with the RT-PCR results (kappa coefficient = 1). Additionally, a notable difference was observed between the RdRp samples of SARS-CoV-2 and SARS-CoV. Therefore, we believe that this study offers a reliable and appealing option for the diagnosis of COVID-19.

Design of high-performance electrochemical sensor based on SnS2 nanoplates and ionic liquid-modified carbon paste electrode for determination of hydrazine in water samples

Designing effective and accurate analytical techniques to determine hydrazine is essential for preserving the environment. Herein, an electrochemical sensor based on a carbon paste electrode (CPE) modified with SnS2 nanoplates (SnS2NPs) and ionic liquid (IL) was presented for determination of hydrazine in water samples. The SnS2NPs were synthesized using the hydrothermal method and characterized through field emission scanning electron microscope, Fourier transform infrared spectrometer and energy dispersive spectroscopy. The use of cyclic voltammetry in electrochemical investigations has shown that incorporating IL and SnS2NPs in an electrochemical sensor significantly improves its efficiency. These results in a considerable increase in the oxidation peak current and a decrease in the oxidation peak potential of hydrazine compared to an unmodified CPE. The method of differential pulse voltammetry was utilized to accurately measure the quantity of hydrazine. The SnS2NPs/ILCPE showed improved sensing capabilities, resulting in a noticeable sensitivity of 0.0747 µA/µM and a low limit of detection of 0.05 µM for a broad linear range of hydrazine concentration from 0.08 µM to 450.0 µM. In addition, the SnS2NPs/ILCPE sensor was successfully utilized to measure the amount of hydrazine present in water samples, with a recovery range of 96.0 to 104.4 %. The relative standard deviation was found to be lower than 3.6 % (n = 5), indicating that the developed sensor is suitable for accurately determining hydrazine in water samples with high sensitivity.

DIAGNOSTIK PAPER ANALYTICAL DEVICE (PAD) MENGGUNAKAN EKSTRAK UBI JALAR UNGU UNTUK DETEKSI BORAKS DALAM MAKANAN

Consuming foods containing borax (tetraborate) will cause health problems. However, in reality, borax is often added to foods such as crackers, meatballs, wet noodles, dumplings. These foods are usually produced by unregistered public members, so their quality is less controlled, so routine monitoring of borax levels in food is needed so that the food quality circulating in the community is maintained and safe for consumption. This research aimed to develop simple method that does not use special instruments to diagnose borax using a Paper Analytical Device (PAD) based on digital imaging using natural reagents from purple sweet potato extract. The research design was laboratory research and development (RnD). The research was conducted at Poltekkes Kemenkes Bandung in January-June 2022. The samples used were borax samples at concentrations of 100, 300, and 500 ppm. The research method was PAD based on digital imaging using Image J. This research was carried out by extracting anthocyanins from purple sweet potatoes, then optimizing the anthocyanin concentration extract; pH; measurement time, determining measurement linearity, and validation by determining % recovery. The research results include that the optimum pH is 9. Optimized measurement time is 3 minutes and is stable until the 5th minute, the linear concentration range of tetraborate is 100-500 ppm tetraborate. In the validation test of the PAD method, a recovery percentage of 87.58-87.95% was obtained for 200 and 300 ppm tetraborate samples. The research result will be able to diagnose and monitor borax in food.

Ultra high-performance liquid chromatography tandem mass spectrometry: Development and validation of an analytical method for N2-Ethyl-2’-deoxyguanosine in dried blood spot

In the body, ethanol is metabolized to acetaldehyde by alcohol dehydrogenase and CYP2E1. Acetaldehyde is the main carcinogen that forms DNA adducts, N2-Ethylidene-2'-deoxyguanosine (N2-Ethylidene-dG), which can cause DNA damage and lead to cancer. However, N2-Ethylidene-dG is an unstable form at the nucleoside level and is difficult to measure. So it needs to be reduced using NaBH4 to become N2-Ethyl-2'-deoxyguanosine (N2-Et-dG). This study aims to obtain a selective, sensitive, and validated analytical method to determine N2-Et-dG using ultra-high-performance liquid chromatography-tandem mass spectrometry with allopurinol as the internal standard. The N2-Et-dG analysis was performed using a C18 Acquity® Bridged Ethylene Hybrid column of (1.7 μm, 100 mm × 2.1 mm). The sample matrix used was dried blood spots, and then the DNA sample was extracted using the QIAamp DNA Mini Kit. The optimum analysis conditions were obtained in a combination eluent of 0.1 % acetic acid and methanol (60:40 v/v) with a flow rate of 0.1 mL/min and eluted isocratically for 5 min. Quantification analysis was performed using triple quadrupole mass spectrometry with electrospray ionization in positive mode, with detection at m/z 296.16 > 180.16 for N2-Et-dG and 137.03 > 110.05 for allopurinol, respectively. The validated analytical method follows the 2018 USA Food and Drug Administration guidelines with a linear concentration range of 5–200 ng/mL.

Development of an Activity-Based Ratiometric Electrochemical Switch for Direct, Real-Time Sensing of Pantetheinase in Live Cells, Blood, and Urine Samples.

Pantetheinase is a key biomarker for the diagnosis of acute kidney injury and the monitoring of malaria progression. Currently, existing methods for sensing pantetheinase, also known as Vanin-1, show considerable potential but come with certain limitations, including their inability to directly sense analytes in turbid biofluid samples without tedious sample pretreatment. Here, we describe the first activity-based electrochemical probe, termed VaninLP, for convenient and specific direct targeting of pantetheinase activity in turbid liquid biopsy samples. The probe was designed such that cleavage of the pantetheinase amide linkage, triggered by a self-immolative reaction, simultaneously ejects an amino ferrocene reporter. Among the distinctive properties of the VaninLP probe for sensing pantetheinase are its high selectivity, sensitivity, and enzyme affinity, a wide linear concentration range (8-300 ng/mL), and low limit of detection (2.47 ng/mL). The designed probe precisely targeted pantetheinase and was free of interference by other electroactive biological species. We further successfully applied the VaninLP probe to monitor and quantify the activity of pantetheinase on the surfaces of HepG2 tumor cells, blood, and urine samples. Collectively, our findings indicate that VaninLP holds significant promise as a point-of-care tool for diagnosing early-stage kidney injury, as well as monitoring the progression of malaria.

Dually-amplified electrochemical aptasensor based on the self-linking AuPt nanoflowers for ultrasensitive determination of hemagglutinin

BackgroundInfluenza virus can spread from person to person and cause epidemics. Therefore, rapid and sensitive diagnosis of virus is essential in controlling influenza outbreaks. Conventional virus diagnostic techniques are time-consuming, labor-intensive and requires large instruments. In this work, a sandwich electrochemical assay by a pair of aptamers was developed for ultrasensitive determination of hemagglutinin (HA) protein, which is one of the two surface glycoproteins of influenza A (H1N1) virus, using dual signal amplification techniques. ResultsHA was captured and magnetically separated by Fe3O4@SiO2–NH2@Au attached to aptamer 1 (Apt1), creating a sandwich structure with AuPt nanoflowers (AuPtNFs) connected to aptamer 2 (Apt2). Herein, AuPtNFs could catalyze H2O2/hydroquinone (HQ) to generate 1,4-benzoquinone (BQ), and achieved amplification of electrochemical signal detection through differential pulse voltammetry (DPV). The constructed aptasensor expressed a wide linear range (10 pg/mL-100 ng/mL) with limit of detection (LOD) of 2.4 pg/mL. Moreover, a novel strategy for dual signal amplification was developed to further enhance sensitivity. The innovative electrochemical aptasensor could achieve secondary amplification of the detection signal with LOD of 0.3 pg/mL and linear concentration range from 0.5 pg/mL to 100 ng/mL. The secondary amplification could be achieved only through the self-linking process, which allowed for the retention of numerous AuPtNFs by simple complementary base pairing to connect more AuPtNFs onto the above-mentioned sandwich structure. SignificanceOverall, the constructed aptasensor exhibited favorable sensitivity and accuracy, indicating the potential expanded application for the clinical detection of numerous viruses.