Detection In Biological Samples Research Articles

Electrochemical detection of regorafenib using a graphite sheet electrode modified with nitrogen-doped reduced graphene oxide nanocomposite

Regorafenib (RGF) is a multi-kinase inhibitor drug used for treating various cancers, posing challenges for detection in biological samples due to low solubility and stability. This paper presents a novel electrochemical sensor based on a monolith reduced graphene oxide (M-RGO) nanocomposite modified graphite sheet electrode. M-RGO was synthesized via a hydrothermal method and characterized extensively. The electrochemical performance was assessed using cyclic voltammetry and differential pulse voltammetry. The sensor demonstrated exceptional electrocatalytic activity for RGF oxidation, featuring two linear response ranges (31 nM to 600 nM and 600 nM to 920 nM) with a detection limit of 1.7 nM. The sensor exhibited good selectivity, stability, and reproducibility. Successful application in determining RGF in human serum and urine samples demonstrated the potential of M-RGO nanocomposite as a promising material for the development of electrochemical sensors for pharmaceutical analysis.

Chitosan lecithin nanocomposite based electrochemical biosensor for glycine detection in biological matrices

Increased glycine concentrations are associated with altered metabolism of cancer cells and is reflected in the bodily fluids of the brain cancer patients. Various studies have been conducted in past to detect glycine as an imaging biomarker via NMR Spectroscopy tools. However, the use is limited because of the low concentration and different in vivo detection due to overlapping of peaks with myo-inositol in same spectral position. Alongside, little is known about the electrochemical potential of Glycine as a biomarker for brain cancer. The prime impetus of this study was to check the feasibility of glycine as non-invasive biomarker for brain cancer. A divergent approach to detect glycine “non-enzymatically” via unique chitosan lecithin nanocomposite has been utilised during this study. The electrochemical inactivity at provided potential that prevented glycine to get oxidized or reduced without mediator was compensated utilising the chitosan-lecithin nanocomposite. Thus, a redox mediator (Prussian blue) was used for high sensitivity and indirect detection of glycine. The chitosan nanoparticles-lecithin nanocomposite is used as a matrix. The electrochemical analysis of the onco-metabolomic biomarker (glycine) utilizing cyclic voltammetry in glycine spiked multi-Purpose artificial urine was performed to check distribution of glycine over physiological range of glycine. A wide linear range of response varying over the physiological range from 7- 240μM with a LOD 8.5μM was obtained, showing potential of detection in biological samples. We have further evaluated our results via simulating the interaction of mediator and matrix with Glycine by HOMO-LUMO band fluctuations.

Construction of an autofluorescence interference-free phosphorescence biosensor for the specific detection of TK1 mRNA

The anti-interference ability of biosensors is critical for detection in biological samples. Fluorescence-based sensors are subject to interference from self-luminescent substances in biological matrices. Therefore, phosphorescent sensors stand out among biosensors due to their lack of self-luminescence background. In this study, a phosphorescent sensor was constructed, which can accurately detect thymidine kinase 1 (TK1) mRNA in biological samples and avoid autofluorescence interference. When there is no target, polydopamine (PDA) is used as the phosphorescence resonance energy transfer (PRET) acceptor to quench the phosphorescence of the persistently luminescent (PL) nanomaterial. When there is a target, the DNA modified by the PL nanomaterial is replaced by the hairpin H and removed away from the PDA, resulting in a rebound in phosphorescence. The phosphorescent sensor exhibits a good linear relationship in the TK1 mRNA concentration range of 0–200 nM, and the detection limit was 1.74 nM. The sensor fabricated in this study can effectively avoid interference from spontaneous fluorescence in complex biological samples, and sensitively and precisely detect TK1 mRNA in serum samples, providing a powerful tool to more accurately detect biomarkers in biological samples.

Simultaneous Determination of One-Carbon Folate Metabolites and One-Carbon-Related Amino Acids in Biological Samples Using a UHPLC-MS/MS Method.

One-carbon folate metabolites and one-carbon-related amino acids play an important role in human physiology, and their detection in biological samples is essential. However, poor stability as well as low concentrations and occurrence in different species in various biological samples make their quantification very challenging. The aim of this study was to develop a simple, fast, and sensitive ultra-high-performance liquid chromatography MS/MS (UHPLC-MS/MS) method for the simultaneous quantification of various one-carbon folate metabolites (folic acid (FA), tetrahydrofolic acid (THF), p-aminobenzoyl-L-glutamic acid (pABG), 5-formyltetrahydrofolic acid (5-CHOTHF), 5-methyltetrahydrofolic acid (5-CH3THF), 10-formylfolic acid (10-CHOFA), 5,10-methenyl-5,6,7,8-tetrahydrofolic acid (5,10-CH+-THF), and 4-α-hydroxy-5-methyltetrahydrofolate (hmTHF)) and one-carbon-related amino acids (homocysteine (Hcy), methionine (Met), S-ade-L-homocysteine (SAH), and S-ade-L-methionine (SAM)). The method was standardized and validated by determining the selectivity, carryover, limits of detection, limits of quantitation, linearity, precision, accuracy, recovery, and matrix effects. The extraction methods were optimized with respect to several factors: protease-amylase treatment on embryos, deconjugation time, methanol precipitation, and proteins' isoelectric point precipitation on the folate recovery. Ten one-carbon folate metabolites and four one-carbon-related amino acids were detected using the UHPLC-MS/MS technique in various biological samples. The measured values of folate in human plasma, serum, and whole blood (WB) lay within the concentration range for normal donors. The contents of each analyte in mouse plasma were as follows: pABG (864.0 nmol/L), 5-CH3THF (202.2 nmol/L), hmTHF (122.2 nmol/L), Met (8.63 μmol/L), and SAH (0.06 μmol/L). The concentration of each analyte in mouse embryos were as follows: SAM (1.09 μg/g), SAH (0.13 μg/g), Met (16.5 μg/g), 5,10-CH+THF (74.3 ng/g), pABG (20.6 ng/g), and 5-CH3THF (185.4 ng/g). A simple and rapid sample preparation and UHPLC-MS/MS method was developed and validated for the simultaneous determination of the one-carbon-related folate metabolites and one-carbon-related amino acids in different biological samples.

Fabricating NiCoFe2O4 decorated PANI nanostructures for high-performance electrochemical detection of 3-Nitro-L-tyrosine biomarkers for rapid diagnosis

A recent development in novel catalytic nanostructures offers numerous opportunities to perform the electrochemical operations towards sensing applications. The organic material PANI has been endorsed as a conducting polymer as it has controlled electrical properties and low density which will be beneficial over the metallic nanostructures. Herein, Nickel Cobalt Ferrite (NiCoFe2O4 (NCF)) nanostructures were anchored on the surface of PANI and engineered for electrochemical sensing applications. 3-nitro-L-tyrosine (3-NT) is an important compound for diagnosing oxidizing biomarkers that plays a vital role in therapy and diagnosing pathogenesis. Due to NCF/PANI’s conductivity, and superior surface area. It was probed for electrochemical sensing of 3-NT. The NCF/PANI displayed an excellent LOD, broad linear range, better sensitivity, selectivity, and stability. Furthermore, the proposed sensor exhibits sensitive 3-NT detection in biological samples with satisfactory recovery rates.

An innovative aluminium foil electrode modified with Al nanoparticles and EDTA for lead detection in biological samples

This study presents a novel Aluminium foil-based electrode characterized by its affordability, flexibility, and ease of modification with carboxylic moiety-containing organic molecules. Upon foil modification with Aluminium nanoparticles and EDTA (AlNP-EDTA/AlE), the modified electrode exhibits remarkable activity in the oxidation of lead at potentials around −0.4 V. The lead signal is derived from the oxidation of lead deposited on the electrode surface using anodic stripping voltammetry (ASV). The addition of EDTA to AlNP/AlE increased the anodic peak current of lead by more than 500 %. The surface characterization of the electrode was performed by scanning electron microscopy (SEM) and infrared spectroscopy (IR), while its electroactive properties were evaluated by cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS). Optimal operating parameters include pH 2.1, square-wave voltammetry (SWV) with an accumulation time of 60 s and an accumulation potential of −0.8 V. A low detection limit of 0.20 µmol/L and a relative standard deviation (RSD) of 3.0 % were achieved using five different electrodes. The effectiveness of AlNP-EDTA/AlE was further demonstrated with consistent results in biological samples spiked with Pb.

Highly sensitive plasmonic-grating PCF biosensor for cancer cell detection

Highly sensitive biosensor based on D-shaped photonic crystal fiber (PCF) with plasmonic grating is introduced and analyzed. The suggested structure is tested using four different grating structures (rectangular, triangular, circular, or elliptical) on the polished surface of the D-shaped PCF. The sensing operation depends on surface plasmon resonance mechanism where the analyte refractive index (RI) is utilized to control the coupling between the core mode and surface plasmon mode via phase matching phenomenon. Rhodium is employed as a plasmonic material to induce the SPMs. The resonance (i.e., phase matching) wavelength is a function of the analyte RI. The geometrical parameters of the proposed structure are optimized using full vectorial finite element method to enhance the sensor sensitivity. The proposed biosensor can be utilized in the detection of different cancerous Basel, Breast and Cervical cells. The performance of the reported biosensor is investigated in terms of sensitivity, linear response, and fabrication tolerance. The reported biosensor has high sensitivities of 19,750 nm/RIU, 20,428 nm/RIU and 20,041 nm/RIU for the detection of Basel, Breast and Cervical cancer cells, respectively. The presented biosensor is a good candidate for biological sample detection and organic chemical sensing.

A ratiometric fluorescence probe based on dual quantum dots for methyl parathion detection in agricultural products

Methyl parathion (MP) is an organic phosphorus pesticide widely used for pest control of various crops, however, the residual MP can enter the human body and damage the nervous system. Therefore, it is necessary to effectively monitor MP residues. Based on dual-fluorescent quantum dots, this study establishes a ratio fluorescence sensing platform for MP detection, wherein the probe is β-cyclodextrin (β-CD) modified molybdenum disulfide quantum dots (MoS2 QDs) called β-CD-MoS2 QDs. Under alkaline conditions, MP is hydrolyzed into p-nitrophenol (p-NP) and enters the hydrophobic cavity of β-CD, quenching the blue fluorescence of MoS2 QDs whose quenching degree of fluorescence intensity (I400) correlates with the concentration of MP, while the fluorescence intensity (I540) of gQDs remains unchanged and is selected as reference signal. The quantitative detection of MP is conducted by calculating the ratio of fluorescence intensities (I540/I400). The probe detected MP in the range of 0.05–25 ppm with a detection limit of 0.032 ppm which is proved to meet the requirements for biological sample detection according to the methodological validation results. The probe has been successfully applied for the detection of MP in apples and vegetables, confirming its applicability for MP detection in crops.

A high-precision and wide-range pH monitoring system based on broadband cavity-enhanced absorption spectrum

A high-precision pH monitoring system over a wide pH range is introduced. The system comprises a cavity-enhancement module constructed by two high-reflectivity mirrors, a microfluidic pH sensing chip based on a binary-indicator membrane of Congo red and m-cresol purple, and a hyperspectral transmission module. This structure extends the effective absorption optical path of the sensing chip, significantly amplifying the spectral differences at various pH values. The spectrum of the transmitted light is recorded by a self-developed hyperspectral module and then converted to broadband cavity-enhanced absorption spectrum (BBCEAS) via the Beer-Lambert law. An artificial neural network (ANN) is employed to predict pH values of the solution. With such a design, this system exhibits a wide detecting range of 2 M [H+] − 2 M [OH–] (corresponding to pH −0.3–14.3) with a response time of about 120 s. The system can achieve a higher detection accuracy with root mean square error (RMSE) of 0.073, as compared to 0.137 without the cavity enhancement. The system also possesses good properties of repeatability, long-term stability, ion resistance, and organic corrosion resistance. These excellent properties make the proposed system a promising candidate technology for harsh environments, such as seawater acidification warning, chemical plant sewage monitoring, and biological sample detection.

Determination of monocrotaline and usaramine in rat plasma by UPLC-MS/MS and their pharmacokinetics

AbstractAn ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of monocrotaline and usaramine in rat plasma, to study the plasma drug concentration and pharmacokinetics, and to calculate the absolute bioavailability. The plasma was treated with acetonitrile and methanol (9:1, v/v) protein precipitation method. The chromatographic column was UPLC HSS T3 (50 mm × 2.1 mm, 1.7 μm), the mobile phase was methanol-water (containing 0.1% formic acid with 10 mM ammonium acetate in water), and the elution time was 4 min at a flow rate of 0.4 mL min−1. Electrospray ionization (ESI) positive ion mode was used for detection and multiple reaction monitoring (MRM) mode was used for quantitative analysis. Monocrotaline and usaramine were administered sublingual intravenously (iv) 1 mg kg−1 and orally (po) 5 mg kg−1, respectively, with 6 rats in each group, for a total of 24 rats. Then the pharmacokinetic differences in rats were evaluated. For the UPLC-MS/MS method, the calibration curve showed good linearity in the range of 2–2,000 ng mL−1, where r was greater than 0.99. The precision, accuracy, recovery, matrix effect and stability results were all consistent with the requirements of biological sample detection methods. to provide scientific experimental basis for the basic research The bioavailability of monocrotaline and usaramine in rat plasma was calculated, which was 43.5 and 19.5%, respectively.

Facile Synthesis of Needle-like Copper Sulfide Structures as an Effective Electrochemical Sensor Material for Neurotransmitter Detection in Biological Samples.

Electrochemical sensors, due to their excellent and unique features, are of high interest nowadays for the detection and monitoring of several biological compounds. In such a case, serotonin (SRN), an important neurotransmitter, was herein studied for its detection in biological fluids since its presence is more crucial to be monitored and detected in clinical and medical applications. Several study strategies have been used to determine the chemical and physical properties. The crystalline size of the constructed copper sulfide (Cu2S) material was measured to be 25.92 nm. The Cu2S was fabricated over the working surface and further analyzed for several sensor parameters to be optimized. The charge transfer resistance of the copper sulfide-modified glassy carbon electrode (Cu2S/GCE) was determined to be about 277.0 Ω. With the linear range from about 0.029 μM to 607.6 μM for SRN, the limit of detection (LOD) was calculated as 3.2 nM, with a good sensitivity of 13.23 μA μM-1 cm2. The sensor experienced excellent repeatability, reproducibility, and long-term stability. The fabricated electrode was selective with the presence of different interfering compounds. The real sample analysis, as determined with the regular addition method with human serum and urine samples, revealed a good recovery percentage. Thus, the employed fabricated electrode material will be highly effective in sensing other analytes of choice.

Graphene and gold nanoparticles integrated terahertz metasurface for improved sensor sensitivity

Terahertz metamaterial technology, as an efficient nondestructive testing method, has shown great development potential in the detection of biological samples. In this study, we have proposed a graphene-integrated gold nanoparticles (AuNPs) terahertz (THz) biosensor and have analyzed the sensing performance of four IC-type resonators (ICSRs) for biosensors: bare ICSRs, ICSRs-integrated AuNPs, ICSRs-integrated graphene, and ICSRs-integrated graphene and AuNPs. The AuNPs generate charge accumulation and induce local electric field enhancement due to the tip effect, and enhance the interaction between the THz wave and the analyte, thus improving the sensitivity of the sensor. The combination of AuNPs and ICSRs-integrated graphene results in sensors with more pronounced amplitude changes and higher sensitivity. Due to the Fermi energy level of graphene being close to the Dirac point, the sensor is ultra-sensitive to external stimuli with a limit of detection of 10.48 fg/ml for aspartic acid solutions. This biosensor has the potential to detect trace amino acids with high sensitivity, contributing to early disease detection and environmental detection for early diagnosis and ecological balance.

Aptasensors: employing molecular probes for precise medical diagnostics and drug monitoring.

Accurate detection and monitoring of therapeutic drug levels are vital for effective patient care and treatment management. Aptamers, composed of single-stranded DNA or RNA molecules, are integral components of biosensors designed for both qualitative and quantitative detection of biological samples. Aptasensors play crucial roles in target identification, validation, detection of drug-target interactions and screening potential of drug candidates. This review focuses on the pivotal role of aptasensors in early disease detection, particularly in identifying biomarkers associated with various diseases such as cancer, infectious diseases and cardiovascular disorders. Aptasensors have demonstrated exceptional potential in enhancing disease diagnostics and monitoring therapeutic drug levels. Aptamer-based biosensors represent a transformative technology in the field of healthcare, enabling precise diagnostics, drug monitoring and disease detection.

An improved ultra-high performance liquid chromatography-tandem mass spectrometry method determining hispidulin and homoplantaginin in rat plasma and associated pharmacokinetic studies

AbstractFlavonoids are the most abundant components in Salvia plebeia, with significant pharmacological antioxidant and hepatoprotective properties. Hispidulin and homoplantaginin are the main flavonoid components in S. Plebeia. In this study, we established an ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to determine hispidulin and homoplantaginin in rat plasma samples, which were precipitated using acetonitrile-methanol (9:1, v/v). We used a UPLC HSS T3 (100 mm × 2.1 mm, 1.7 μm diameter) chromatographic column, an acetonitrile-water (containing 0.1% formic acid) mobile phase, and a gradient elution flow rate of 0.4 mL min−1 in an elution time of 4 min. We used electrospray ionization (ESI) detection in positive ion mode, and multiple reaction monitoring mode (MRM) for quantitative analysis: m/z 301 → 286 for hispidulin, m/z 463 → 301 for homoplantaginin, and m/z 465 → 303 for internal standard (IS). In pharmacokinetic studies, 24 rats were orally administered hispidulin and homoplantaginin (5 mg kg−1) and received sublingual intravenous injections (1 mg kg−1) at two different doses, four groups with six rats/group. Differences in hispidulin and homoplantaginin pharmacokinetics in rat plasma were evaluated. The calibration curve showed good linearity in the 0.5–1,000 ng mL−1 range, with r > 0.99. Precision, accuracy, recovery, matrix effects, and stability results all met standard biological sample detection requirements. Our pharmacokinetic studies showed hispidulin bioavailability was much higher than homoplantaginin at 17.8% and 0.1%, respectively.

Metasurface-assisted Lab-on-fiber optrode for highly sensitive detection of vitamin D

The increasing demand for vitamin D status assessment has highlighted the need for rapid, sensitive, and user-friendly methods for its detection in biological samples potentially integrated in Point-of-Care (PoC) diagnostic devices. Detection of the major circulating form of vitamin D, 25-hydroxyvitamin D3-25(OH)D3, is particularly challenging due to the laborious procedures for sample preparation and its low molecular weight (∼400 Da), which requires highly sensitive detection methods. In this study, we developed a novel label-free Lab-on-Fiber biosensing platform for highly sensitive detection of 25(OH)D3 based on the integration of plasmonic metasurfaces (MSs) on the tip of a single-mode optical fiber (OF). A dedicated pipeline was carefully designed and developed to optimize the bio-functionalization of the plasmonic sensor tip to specifically detect the target biomolecule. The resulting MS-assisted Lab-on-fiber platform enables direct and highly sensitive detection of 25(OH)D3 in clinically relevant ranges (4–160 ng/mL), both in buffer solution and complex matrix, with limits of detection (LOD) of 1.40 ng/mL in saline buffer and 0.85 ng/mL in complex matrix. Overall, these results demonstrate that our platform can successfully and specifically detect small molecules in label-free configuration, with performances comparable to those of conventional methods used in clinical practice. The high degree of miniaturization combined with its high sensitivity makes our platform an exceptional building block for realizing valid diagnostic alternatives for label-free detection of clinically relevant analytes, which can be transformed into new low-cost, fast, simple, and ready-to-use PoC diagnostic devices with improved processability and performance compared to current methods.

Determination of Tenacissoside G, Tenacissoside H, and Tenacissoside I in Rat Plasma by UPLC-MS/MS and Their Pharmacokinetics.

An ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of tenacissoside G, tenacissoside H, and tenacissoside I in rat plasma. The rat plasma was treated with liquid-liquid extraction using ethyl acetate. The determination was performed on the UPLC HSS T3 column (50 mm × 2.1 mm, 1.8 μm) with a mobile phase consisting of acetonitrile-water (containing 0.1% formic acid) and gradient elution at a flow rate of 0.4 mL/min. Electrospray (ESI) positive ion mode detection and multireaction monitoring (MRM) quantitative analysis were performed. A total of 36 rats were given tenacissoside G, tenacissoside H, and tenacissoside I, respectively, orally (5 mg/kg) and intravenously (1 mg/kg), with 6 rats in each group, to evaluate the pharmacokinetic difference of tenacissoside G, tenacissoside H, and tenacissoside I in rats. The calibration curves showed good linearity in the range of 5-2000 ng/mL, where r was greater than 0.99. The results of precision, accuracy, recovery, matrix effect, and stability met the requirements of biological sample detection methods. The established UPLC-MS/MS method was successfully applied to pharmacokinetic studies of tenacissoside G, tenacissoside H, and tenacissoside I, and the bioavailability was 22.9%, 89.8%, and 9.4%, respectively.

Drastic alterations in the loop structure around colchicine upon complex formation with an engineered lipocalin indicate a conformational selection mechanism.

Using Anticalin technology, a lipocalin protein dubbed Colchicalin, with the ability to bind the toxic plant alkaloid colchicine with picomolar affinity, has previously been engineered, thus offering a potential antidote in vivo and also allowing its sensitive detection in biological samples. To further analyze the mode of ligand recognition, the crystal structure of Colchicalin is now reported in its unliganded form and is compared with the colchicine complex. A superposition of the protein structures revealed major rearrangements in the four structurally variable loops of the engineered lipocalin. Notably, the binding pocket in the unbound protein is largely occupied by the inward-bent loop #3, in particular Ile97, as well as by the phenylalanine side chain at position 71 in loop #2. Upon binding of colchicine, a dramatic shift of loop #3 by up to 11.1 Å occurs, in combination with a side-chain flip of Phe71, thus liberating the necessary space within the ligand pocket. Interestingly, the proline residue at the neighboring position 72, which arose during the combinatorial engineering of Colchicalin, remained in a cis configuration in both structures. These findings provide a striking example of a conformational adaptation mechanism, which is a long-known phenomenon for antibodies in immunochemistry, during the recognition of a small ligand by an engineered lipocalin, thus illustrating the general similarity between the mode of antigen/ligand binding by immunoglobulins and lipocalins.

Fabrication of impedimetric sensor based on metallic nanoparticle for the determination of mesna anticancer drug

Electrochemical impedance spectroscopy (EIS) is a highly effective technique for studying the surface of electrodes in great detail. EIS-based electrochemical sensors have been widely reported, which measure the charge transfer resistance (Rct) of redox probes on electrode surfaces to monitor the binding of target molecules. One of the protective drugs against hemorrhagic cystitis caused by oxazaphosphorine chemotherapy drugs such as ifosfamide, cyclophosphamide and trophosphamide is Mesna (sodium salt of 2-mercaptoethanesulfonate). The increase in the use of Mesna due to the high consumption of anti-cancer drugs, the determination of this drug in biological samples is of particular importance. So far, no electrochemical method has been reported to measure Mesna. In this research, a novel impedimetric sensor based on a glassy carbon electrode (GCE) modified with oxidized multiwalled carbon nanotubes (MWCNTs)/gold nanoparticle (AuNPs) (denoted as Au NPs/MWCNTs/GCE) for impedimetric determination of Mesna anticancer drug was developed. The modified electrode materials were characterized by field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX), and EIS. The electrochemical behavior of Mesna at the surface of Au NPs/MWCNTs/GCE was studied by an impedimetric method. The detection mechanism of Mesna using the proposed impedimetric sensor relied on the increase in the Rct value of [Fe (CN)6]3−/4− as an electrochemical probe in the presence of Mesna compared to the absence of Mesna as the analyte. Under the optimum condition, which covered two linear dynamic ranges from 0.06 nmol L−1 to 1.0 nmol L−1 and 1.0 nmol L−1 to 130.0 µmol L−1, respectively. The detection limit was 0.02 nmol L−1. Finally, the performance of the proposed sensor was investigated for Mesna electrochemical detection in biological samples.

Design of DMAP functionalized MoS2-GO hybrid for targeted visual detection of dopamine: a step towards chromogenic substrate free point of care testing

Abnormal release of DA, a crucial neurotransmitter, can cause serious neurological disorders such as Parkinson's and Alzheimer's disease. Thus, sensitive DA detection becomes critical for the investigation of physiological functions and disease diagnosis. Specific DA quantification in real samples is a tedious task due to the presence of analogous neurotransmitters. Therefore, aiming at on-site selective monitoring of DA, a high-performance colorimetric probe has been designed using a DMAP-modified MoS2-GO hybrid for highly selective visual detection of DA, especially for POC testing. The efficient DA recognition can be attributed to the large surface area with potentially active sites for greater electron transport and oxidation ability owing to the synergistic effect of MoS2 and GO. The hybrid has been modified with DMAP, which allows extremely selective and specific DA recognition against potential interferents, especially other neurotransmitters. The proposed mechanism relies on the attachment of DA to the hybrid surface, facilitating the oxidation and complexation processes that induce aggregation causing instant color change. The designed colorimetric method can recognize DA in neutral medium at room temperature without any reagents or supplementary operations. A good linear relationship was observed between the absorbance of the hybrid and DA concentrations in the range 1–100 μM, with a low detection limit of 0.17 μM. Furthermore, the applicability of the present approach was also verified by the analysis of DA in human serum samples and proved to be promising for sequential DA detection in biological samples with good precision and accuracy. From a POC perspective, easy-to-use paper-based test strips were prepared for visual recognition of DA in just 3 min. Results indicate that the designed DA assay provides a powerful, low-cost, convenient, and reagentless colorimetric platform for instant and highly selective DA detection in aqueous solution, strips, and human serum that is predicted to find extended applications in the fields of biosensing, clinical diagnosis, and in-vitro disease monitoring.

LDA enhanced one-bit compressive sensing method for high-throughput mass spectrometry data feature selection

Mass spectrometry (MS) is commonly used for the proteins detection of biological samples. However, it generates high-throughput data, posing huge computational challenges for signal processing. In previous studies, we have proposed a one-bit perturbed block CS (OB-PBCS) method to realize feature selection (FS) and obtain a feature set with reduced dimension for classification. However, its feature selection is realized by solving the reconstruction problem with simple greedy strategies, which fails to consider the final classification objective during reconstruction. Considering such problem, in this paper, we propose a hybrid linear discriminant analysis (LDA) enhanced one-bit CS method, called L-OBPBCS, which selects features by considering the subsequent classification and consists of three parts. The first part roughly filters out the features that do not favor the classification task with the proposed single feature decision coefficient. Then, OB-PBCS obtains significant features from the filtered feature set. Afterwards, LDA algorithm is further used for refining, where the amplitude of the optimal projection vector is gathered as the linear discrimination mapping coefficients to identify important features. To show the efficiency of our proposed L-OBPBCS method, classification based on the selected features for both synthesized dataset and real ovarian cancer MS dataset is evaluated. Results show that the feature set derived by L-OBPBCS ensures excellent classification performance, which surpasses the existing one-bit type FS method, and the computational complexity of L-OBPBCS is obviously reduced compared with the existing OB-PBCS method.