Actual Biological Samples Research Articles

Non-Enzymatic Detection of Cardiac Troponin-I with Graphene Oxide Quenched Fluorescent Iron Nanoclusters (FeNCs).

Cardiac troponin I (cTnI) is the most resorted biomarker for the detection of cardiovascular disease (CVD). The means of rapid quantification of cTnI levels in the blood can substantially minimize the risk of acute myocardial infarction and heart failure. A sensor for the non-enzymatic evaluation of cardiac troponin-I has been developed using fluorescent iron nanoclusters via a one-pot synthesis employing (BSA) as the template and reducing agent, and hydrogen peroxide as the additive. The fluorescence of Iron Nanocluster is quenched with graphene oxide (GO) via fluorescence resonance energy transfer (FRET) between conjugate iron nanoclusters and graphene oxide. The sensor shows a low detection limit of 0.011 ng/mL. The benefits of utilizing a non-enzymatic probe for detecting cardiac troponin I is that it avoids the need for enzymes and hence is economical, stable, and less impacted by environmental conditions such as temperature and pH. Non-enzymatic probes are more useful for clinical use since they are more stable and have a longer shelf life. The developed non-enzymatic probes are also highly selective and sensitive to the target analyte, making them suitable for the direct detection of cardiac troponin I in actual biological samples.

Fluorescent sensing platform based on two-dimensional layered double hydroxides and exonuclease I for DNA and microRNA detection

Interfacial and interlayer interactions between layered double hydroxides (LDHs) and nucleic acids offer LDHs great potential to absorb and detect nucleic acids. Herein, we demonstrate a simple, rapid, and versatile fluorescent sensing platform based on two-dimensional LDHs and exonuclease I (Exo I) for the selective analysis of DNA and microRNA. ZnNiAl-LDHs were utilized as quenchers for FAM labelled on single-stranded DNA (ssDNA) probes via dynamic quenching with high fluorescence quenching ability. The quenching mechanism was explored by means of spectral analysis, characterization experiments, DNA adsorption and desorption studies, zeta potential analysis, and molecular dynamics simulations. The driving forces for the adsorption of LDHs toward fluorophore-labelled nucleic acids were confirmed to be electrostatic interaction, van der Waals force, and anion exchange for the first time. In order to distinguish the formed target/probe duplexes from FAM-ssDNA probes, Exo I was introduced to specifically hydrolyze FAM-ssDNA probes. The fabricated fluorescent sensing platform for nucleic acids detection shows a low detection limit of 0.08 nM. Finally, this sensor was effectively utilized for the detection of DNA and microRNA in actual biological and environmental samples, achieving recoveries ranging from 96.4 % to 105 %, indicating high accuracy. This work proposed a promising sensing platform for sequence-specific nucleic acids detection, and provides a new perspective on two-dimensional LDHs as structural supports and biomolecular reservoirs for biomedical applications.

Improving the electrocatalytic activity of the copper (II) metal-organic framework by functionalized imidazolate linker and functionalized carbon nanoparticles for detection of acyclovir

With the aim of expansion of nanocomposite materials in electrochemical sensors, the use of nanostructures as the electrode modifier has been shown to improves the kinetics of the electron transfer reactions and consequently increases the sensitivity of the sensors. So, in this study, a new electrochemical sensor was fabricated by using the nanocomposite of copper (II) metal–organic framework with functionalized imidazolate linker [Cu3(BTC)2-2-MIM] and cationic functionalized carbon nanoparticles (CFCNPs) at the glassy carbon electrode (GCE); Cu3(BTC)2-2-MIM/CFCNPs/GCE. The as prepared nanocomposite; Cu3(BTC)2-2-MIM/CFCNPs was characterized using various instrumental techniques. To identify the capabilities and electrocatalytic activity of the synthesized nanocomposite in analytical chemistry, it was used as an electrochemical modifier along with suitable electrochemical techniques. In this regard, the prepared modified electrode; Cu3(BTC)2-2-MIM/CFCNPs/GCE was utilized to the electrooxidation and determination of the acyclovir (ACR) in NaOH solution. Under optimal experimental conditions, the Cu3(BTC)2-2-MIM/CFCNPs/GCE showed low detection limit (0.24 µM) over the concentration ranges of 2.49–84.28 μM of ACR. On the other hand, the present sensor has robust stability, good reproducibility, high selectivity and sensitivity (5.907 µAµM−1 cm−2) in electrodetermination of ACR. Also, the diffusion coefficient of ACR (DACR = 9.25 × 10−6 cm2 s−1), the transfer coefficient (α = 0.34) and catalytic rate constant (kcat = 10.1 × 105 cm3 mol−1 s−1) of ACR electrooxidation reaction were estimated at the surface of modified electrode in NaOH solution. Finally, the Cu3(BTC)2-2-MIM/CFCNPs/GCE was applied as a promising and low-cost sensor for determination of the ACR in actual pharmaceutical formulations and biological samples.

A ratiometric fluorescent probe with a large Stokes shift for rapid and sensitive detection of Hg2+ in environmental water samples and its applications in living cells and zebrafish

Detection of highly toxic mercury ions (Hg2+) in actual environmental and biological samples is of significant importance for protecting environment and human health. In this paper, a new ratiometric fluorescent probe BTIA was designed and synthesized from 3-pinone based on Internal Charge Transfer (ICT) mechanism. BTIA could selectively recognize Hg2+ over other competitive analytes with short reaction time (5 s), distinct ratiometric response, strong anti-interference ability, large Stokes shift (200 nm), and low detection limit (2.36 × 10−7 M). Furthermore, BTIA was applicable for detecting Hg2+ in actual water samples and it also performed an excellent imaging capability in living RAW264.7 cells, zebrafish and onion tissue.

Artificial nanochannels for highly selective detection of miRNA based on the HCR signal amplification

Artificial solid-state nanochannels have nanoscale spatial confinement and unique ion transport properties that have been widely used in biosensing, nanofluidic devices, and nucleic acid sequencing. However, most of the nanochannel sensors for miRNA detection are grounded on the complementary pairing of bases, lacking signal amplification, which limits its application in many fields. Herein, we proposed a signal amplification strategy for miRNA-182 detection based on introducing hybridization chain reaction (HCR) in artificial nanochannels to improve the detection sensitivity. In this method, the capture DNA (cDNA) was anchored in the nanochannel, and when the target miRNA appeared, the hairpin probes H1, H2, and initiator were introduced to trigger the HCR reaction to form long nucleic acid double strands, which significantly enhanced the negative charge and affected ion transport in nanochannel. The nanochannel sensor performed excellent selectivity to the target miRNA-182, and it can realize the detection of miRNA-182 with an ultra-low concentration of 1.65 aM, which can be further applied to the detection of miRNA-182 in actual biological samples. Moreover, the nanochannel system was proved by using the AND logic gate that cDNA, initiator, H1, H2, and miRNA-182 are indispensable for successfully triggering HCR. This work provides a simple and efficient signal amplification method for miRNA detection, which considerably expands the application of nanochannel sensors and holds great prospects in biomedical and clinical detection.

Gold Nanoparticle-Modified Carbon-Fiber Microelectrodes for the Electrochemical Detection of Cd2+ via Fast-Scan Cyclic Voltammetry.

Neurotoxic heavy metals, such as Cd2+, pose a significant global health concern due to their increased environmental contamination and subsequent detrimental health hazards they pose to human beings. These metal ions can breach the blood-brain barrierblood-brain barrier, leading to severe and often irreversible damage to the central nervous system and other vital organs. Therefore, developing a highly sensitive, robust, and rapid in vivo detection method for these hazardous heavy metal ions is of the utmost importance for early detection, thus initiating timely therapeutics. Detecting ultra-low levels of toxic metal ions in vivo and obtaining accurate speciation information remains a challenge with conventional analytical techniques. In this study, we fabricated a novel carbon carbon-fiber microelectrode (CFM)-based sensor that can detect Cd2+ ions using fast-scan cyclic voltammetry by electrodepositing gold nanoparticles (AuNP). We optimized electrochemical parameters that generate a unique cyclic voltammogram (CV) of Cd2+ at a temporal resolution of 100 ms with our novel sensor. All our experiments were performed in tris buffer that mimics the artificial cerebellum fluid. We established a calibration curve resulting in a limit of detection (LOD) of 0.01 µM with a corresponding sensitivity of 418.02 nA/ µM. The sensor's selectivity was evaluated in the presence of other metal ions, and it was noteworthy to observe that the sensor retained its ability to produce the distinctive Cd2+ CV, even when the concentration of other metal ions was 200 times higher than that of Cd2+. We also found that our sensor could detect free Cd2+ ions in the presence of complexing agents. Furthermore, we analyzed the solution chemistry of each of those Cd2+-ligand solutions using a geochemical model, PHREEQC. The concentrations of free Cd2+ ions determined through our electrochemical data align well with geochemical modeling data, thus validating the response of our novel sensor. Furthermore, we reassessed our sensor's LOD in tris buffer based on the concentration of free Cd2+ ions determined through PHREEQC analysis, revealing an LOD of 0.00132 µM. We also demonstrated the capability of our sensor to detect Cd2+ ions in artificial urine samples, showcasing its potential for application in actual biological samples. To the best of our knowledge, this is the first AuNP-modified, CFM-based Cd2+ sensor capable of detecting ultra-low concentrations of free Cd2+ ions in different complex matrices, including artificial urine at a temporal resolution of 100 ms, making it an excellent analytical tool for future real-time, in vivo detection, particularly in the brain.

The simultaneous measurement of atomoxetine, venlafaxine, and duloxetine in actual water and biological samples requires the creation of a unique magnetic dispersive micro solid phase extraction sorbent based on MOF-on-MOF

ABSTRACT Atomoxetine, venlafaxine, and duloxetine are three antidepressant drugs widely prescribed to treat this disorder. Determining these drugs is a major challenge due to their low concentration and high matrix effects on biological samples. Dispersive micro solid phase extraction was developed as a sample preparation strategy to extract these drugs in real water and biological samples. A novel sorbent containing a magnetic MOF-on-MOF was prepared to extract these drugs using Fe3O4 nanoparticle and Sol-gel technique. The microextraction procedure was optimised under two steps using experimental design. Three factors, including pH, sorbent amount, and desorption solvent volume, significantly affected the extraction of analytes and optimised using a central composite design. The optimum value of pH, sorbent amount, and desorption solvent volume was 29 mg, 6.5, and 150 µL. Under optimum conditions, the linear ranges for measuring atomoxetine, venlafaxine, and duloxetine in water samples were 1.42–496, 0.43–472, and 0.73–459 ng mL−1, respectively. The detection limits of atomoxetine, venlafaxine, and duloxetine were 0.4, 0.1, and 0.2 ng mL−1. High and proper preconcentration factors ranged from 462.4–511.4 in distiled water samples and 450.7–489.8 in urine samples were obtained to determine atomoxetine, venlafaxine, and duloxetine with three concentrations of 5.0, 20.0, and 100.0 ng mL−1, respectively. Inter-day and intra-day RSD% were calculated by triplicate determination of atomoxetine, venlafaxine, and duloxetine at three concentrations of 10.0, 50.0 and 100.0 ng mL−1 and were between 3.2–4.3% and 3.8–4.6% in distiled water samples, and 4.8–5.7% and 5.0–5.8% in urine samples, respectively. Analysis of tap, river water, and two urine samples as real water and biological samples under optimum conditions exhibited recovery and standard deviation in the ranges of 90.2–96.9% and 3.84–5.74%, respectively, confirmed the proper ability of the method to determine atomoxetine, venlafaxine, and duloxetine in natural water and biological samples.

Multicolor detection of glutathione by manganese dioxide nanosheets and gold nanotetrapods based on an anti-etching mechanism

Glutathione (GSH) is a crucial non-protein thiol and an indispensable endogenous antioxidant. The aberrant expression of GSH in plasma and cytosol is closely related to numerous diseases, including cancer. Therefore, establishing a sensitive method for analyzing GSH has important application value for biomedical research and clinical medical detection. Herein, A method for the rapid and simple detection of GSH was proposed, which is based on an anti-etching mechanism by utilizing gold nanotetrapods (Au NTPs) and manganese dioxide nanosheets (MnO2 NSs). In the absence of GSH, Au NTPs solution can cause a distinct color change from gray-green to red through the etching effect of MnO2 NSs. However, in the presence of GSH, the redox reaction between GSH and MnO2 NSs inhibits the etching of Au NTPs by MnO2 NSs, and Au NTPs solution maintains persistent gray-green color. The colorimetric probe exhibited excellent selectivity for GSH. The limits of detection for GSH were 43.5 nM (UV–vis spectrum) and 0.25 μM (naked eyes). The sensing technique exhibited excellent linearity between wavelength shift and GSH concentration within the range of 0.25 μM–1.5 μM. The outcomes of GSH detection in actual biological samples demonstrate that this probe has the potential to be applied to GSH detection in intricate biological samples.

Highly sensitive detection for xanthine by combining single-band red up-conversion nanoparticles and cycle signal amplification strategy based on internal filtration effect

Up-conversion nanoparticles (UCNPs), especially single-band bright red UCNPs, have better penetration of biological tissues, absorb less lost energy, and have higher sensitivity and accuracy in the determination of actual biological samples in the field of biosensing. Here, a novel colorimetric and fluorescent dual-channel method based upon an internal filtration effect (IFE) quenching mechanism was proposed for the quantitative analysis of xanthine (XA) by using red UCNPs as fluorescence indicator and 3,3′,5,5′ -tetramethylbenzidine (TMB) as chromogenic substrate. The sensitivity of the detection system was also enhanced by a cycle signal amplification strategy based on the Fenton reaction. Under the best conditions, the detection limits of XA by fluorescent and colorimetric methods were 0.58 μM and 1.19 μM, respectively. The developed method was applied to the detection of XA in actual serum samples, and the recoveries of the spiked samples by fluorescent and colorimetric methods were in the range of 96.3–104.3 % and 94.3–105.4 %, respectively. In addition, the commercial ELISA method was used to verify the application of the proposed method and the test results of XA were close to those obtained by fluorescent and colorimetric methods, indicating that the accuracy of the developed nanosensing system was acceptable.

A Schiff base fluorescence switch-on probe derived from vitamin B6 cofactor for simultaneous detection of bovine serum albumin and ovalbumin

The abnormal amount of albumin found in serum and urine samples is an important biomarker for a variety of illnesses. It is essential for clinical diagnosis, medicinal research, and preventative medicine to correctly assess the albumin concentration in actual biological samples. Herein, vitamin B6 cofactors derived Schiff bases obtained by condensing pyridoxal 5′-phosphate (PLP) with 2-aminophenol (L), pyridoxal with 2-aminophenol (L1) and PLP with aniline (L2) were employed for the detection of albumins. Schiff base L is non-fluorescent due to conformational flexibility and free intramolecular rotation, but becomes fluorescent upon protein–ligand complex formation with bovine serum albumin (BSA) and ovalbumin (OVA). Other Schiff bases L1 and L2 failed to response the presence of BSA and OVA. The intensity of fluorescence of L increases linearly with the increasing concentration of BSA and OVA, and the detection limits for BSA and OVA were estimated to be 0.18 µM and 0.13 µM, respectively. The molecular docking and molecular dynamics simulations were done to investigate the binding affinity and modes between the albumins (BSA and OVA) and L. The developed detection method was applied for the detection of BSA and OVA in real biological samples of milk, serum, egg white and urine, with satisfactory recovery.

Truncated total variation in fractional B-spline wavelet transform for micro-CT image denoising.

In medical applications, computed tomography (CT) is widely used to evaluate various sample characteristics. However, image quality of CT reconstruction can be degraded due to artifacts. To propose and test a truncated total variation (truncation TV) model to solve the problem of large penalties for the total variation (TV) model. In this study, a truncated TV image denoising model in the fractional B-spline wavelet domain is developed to obtain the best solution. The method is validated by the analysis of CT reconstructed images of actual biological Pigeons samples. For this purpose, several indices including the peak signal-to-noise ratio (PSNR), structural similarity index (SSIM) and mean square error (MSE) are used to evaluate the quality of images. Comparing to the conventional truncated TV model that yields 22.55, 0.688 and 361.17 in PSNR, SSIM and MSE, respectively, using the proposed fractional B-spline-truncated TV model, the computed values of these evaluation indices change to 24.24, 0.898 and 244.98, respectively, indicating substantial reduction of image noise with higher PSNR and SSIM, and lower MSE. Study results demonstrate that compared with many classic image denoising methods, the new denoising algorithm proposed in this study can more effectively suppresses the reconstructed CT image artifacts while maintaining the detailed image structure.

Self-assembly of gold nanoparticles on three-dimensional eggshell biological carbon fiber membranes: Non-enzymatic detection of rutin

A highly selective electrochemical sensing platform based on gold nanoparticles@three-dimensional carbonized eggshell fiber membrane (Au NPs@3D CEFM) was developed for non-enzymatic detection of rutin in the presence of ascorbic acid, dopamine and uric acid. The porous 3D connected-network CEFM with a pore size of ∼5 µm was prepared. Au NPs (∼10 nm) were uniformly anchored on the surface of the 3D CEFM by self-assembly. The porous 3D CEFM acts as a conductive platform and the regular small-sized Au NPs provide more active sites to significantly enhance the catalytic and selective properties of Au NPs@ 3D CEFM. Under the optimal conditions, the Au NPs@ 3D CEFM/ITO electrode exhibits an excellent sensitivity of 3.08 μA·μM−1·cm−2 and a low detection limit of 0.014 µM (S/N = 3) for the detection of rutin in 0–60 µM. Meanwhile, the electrode is also effectively used for the determination of rutin in actual biological samples and the recoveries for spiked samples ranged from 92.3% to 106.8%.

A highly sensitive ratiometric fluorescent probe based on fluorescein coumarin for detecting hydrazine in actual water and biological samples.

Hydrazine (N2 H4 ) is a highly toxic and harmful chemical reagent. Fluorescent probes are simple and efficient tools for sensitive monitoring of N2 H4 enrichment in the environment, humans, animals, and plants. In this work, a ratiometric fluorescent probe (FP-1) containing coumarin was used for hydrazine detection. The proposed FP-1 probe had a linear detection range of 0-250 μM and a limit of detection (LOD) of 0.059 μM (1.89 ppb). A large red Stokes shift was observed in fluorescence and UV-vis absorption spectra due to the hydrolysis of ester bonds between FP-1 and hydrazine. The hydrazine detection mechanism of FP-1 was also investigated using density functional theory (DFT) calculations. Finally, FP-1 could sensitively and selectively monitor hydrazine in actual water samples and BEAS-2B cells. Therefore, it has great application potential in environmental monitoring and disease diagnosis.

A portable electrochemical sensing platform for serotonin detection based on surface-modified carbon fiber microelectrodes.

Serotonin (5-HT) is one of the key neurotransmitters in the human body, regulating numerous physiological functions. A disruption in 5-HT homeostasis could result in serious health problems, including neurodegenerative disorders, depression, and 5-HT syndrome. Detection of 5-HT concentrations in biological fluids, such as urine, is a potential solution for early diagnosis of these diseases. In this study, we developed a novel, simple, and low-cost electrochemical sensing platform consisting of a portable workstation with customized electrodes for 5-HT detection in artificial biological fluids. Nafion/carbon nanotubes (CNTs) and electrochemically modified carbon fiber microelectrodes (Nafion-CNT/EC CFMEs) displayed improved 5-HT sensitivity and selectivity. Together with a customized Ag/AgCl reference electrode and Pt counter electrode, the portable 5-HT sensing platform had a sensitivity of 0.074 μA μM-1 and a limit of detection (LOD) of 140 nM. This system was also assessed to measure 5-HT spiked in artificial urine samples, showing nearly full recovery rates. These satisfactory results demonstrated that the portable system exhibits outstanding performance and confirmed the feasibility of 5-HT detection, which can be used to provide point-of-care analysis in actual biological samples.

Highly sensitive cholesterol biosensor based on electron mediator thionine and cubic-shaped Cu2O nanomaterials

The preparation of an electrochemical biosensor applicable for the highly sensitive detection of cholesterol content in biological samples in clinical practice is studied in this paper. Commonly used in biosensors, nano-cuprous oxide (Cu2O) contains active electron-hole pairs and a large specific surface area, while thionine (TH) improves the efficiency of electron transfer between the enzyme and the electrode. In this study, a cholesterol biosensor, cholesterol oxidase (ChOx)/thionine/nano-cuprous oxide/ glassy carbon electrode (GCE) (ChOx/TH/Cu2O/GCE), is prepared using cubic-shaped Cu2O as the nanomaterial, TH as an electron mediator, and chitosan (CS) as a cross-linking agent to immobilize cholesterol oxidase. The results show that Cu2O nanoparticles (NPs) are successfully synthesized, and the cholesterol biosensor prepared from synthesized Cu2O NPs exhibits excellent electrochemical characteristics, good linearity (R2 = 0.997) over a substrate concentration range of 10 to 1000 µM, a sensitivity of 70.22 µA µM−1 cm−2, and a low detection limit of 0.0018 µM for the substrate. The ChOx, which immobilizes on the composite electrode, shows a strong affinity for cholesterol due to its low Michaelis–Menten constant (Km) value (25.359 µM). Moreover, with strong anti-interference, good reproducibility, and stability, the cholesterol biosensor can achieve a recovery rate of 99.71 % to 107.75 % according to a recovery test of actual spiked samples. Thus, the prepared nanomaterial-based cholesterol biosensor can be applied to the highly sensitive detection of cholesterol in actual biological samples.

One-Pot Preparation of Hydrophilic Glucose Functionalized Quantum Dots for Diabetic Serum Glycopeptidome Analysis

This paper reports a hydrophilic carbohydrate functionalized quantum dots material (denoted as MnZnS@G6P) synthesized through one-pot strategy and used as hydrophilic materials for the specific enrichment of glycopeptides. MnZnS@G6P had the advantages of worthy stability and low cost, and Mn-doped ZnS quantum dots offer abundant modification sites. To improve the hydrophilicity of the material, glucose-6-phosphate was grafted onto the material through the interaction between phosphate groups and metal ions. Encouraged by the excellent sensitivity (0.05 fmol μL−1) and selectivity (the molar ratio of HRP and BSA is 1:1000), MnZnS@G6P was applied to the capture of glycopeptides in actual biological samples. The outcomes of nano LC-MS/MS indicated that MnZnS@G6P could efficiently capture glycopeptides in the serum. In short, from serum tryptic digests of a healthy human and a diabetic patient, 139 N-glycopeptides corresponding to 76 glycoproteins and 100 N-glycopeptides corresponding to 54 glycoproteins were enriched and identified, respectively.

Post-synthesis of boric acid-functionalized magnetic covalent organic framework as an affinity probe for the enrichment of N-glycopeptides.

A novel type of boric acid-functionalized magnetic covalent organic framework (mCOF) with polyethyleneimine (PEI) as a linker (denoted as mCOF@PEI@B(OH)2) has beenprepared through a post-synthesis strategy, which points out an achievable path for the construction of boronic acid-functionalized COFs. Based on the boric acid chemistry, the obtained core-shell structured mCOF@PEI@B(OH)2 can selectively isolate glycopeptides through the modified boronic acid groups. The mCOF@PEI@B(OH)2 exhibits excellent performance with good reusability (ten cycles), low detection limit (0.5 fmol·μL-1), size-exclusion effect, and relatively high loading capacity (80μg·mg-1), recovery yield (94.9 ± 2.8%), and selectivity (HRP digests:BSA digests = 1:500). Detection is done bymatrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). In addition, 37 endogenous glycopeptides are captured from human saliva with mCOF@PEI@B(OH)2, providing effective proofs for its capability to capture low-abundance glycopeptides from actual biological samples.

Facile in situ microwave synthesis of Fe3O4@MIL-100(Fe) exhibiting enhanced dual enzyme mimetic activities for colorimetric glutathione sensing

In recent decades, artificial nanozymes with excellent stability, low cost and availability have been gradually explored to avoid the limits of natural enzymes such as poor stability, high cost and difficult preparation. Herein, for the first time, we investigated the capability of nanoscale Fe3O4@MIL-100(Fe) as a nanozyme, which was quickly synthesized in situ by a microwave-assisted method within 20 min using Fe3O4 as the metal precursor. The obtained Fe3O4@MIL-100(Fe) showed satisfactory intrinsic dual enzyme mimetic activities, including peroxidase (POD)- and catalase (CAT)-like activities. Moreover, a simple and effective colorimetric biosensor was fabricated to detect glutathione (GSH) based on its POD-like activity. The proposed measurement had a linear range of 1–45 μM and a limit of detection (LOD) of 0.26 μM (3.3 δ/S). It was proved that the established colorimetric sensing system could be successfully applied to detect GSH in actual biological samples. Importantly, the outstanding reusability and stability made it extremely valuable as a catalyst. The present work implied that Fe3O4@MIL-100(Fe) synthesized in situ by the microwave-assisted method was a very promising candidate for biocatalyst and biosensing.

Decorated graphene oxide flakes with integrated complex of 8-hydroxyquinoline/NiO toward accurate detection of glucose at physiological conditions

Abstract The dramatic increase in the number of diabetic people raised the requirement for developing practical diagnostic setups capable of rapid and precise detection of glucose molecules at physiological conditions through non-enzymatic approaches. To address this requirement, we have developed a highly stable and sensitive non-enzymatic glucose biosensor consisted of decorated graphene oxide (GO) with an integrated platform of nickel oxide, 8-hydroxyquinoline (8H) and N-hydroxysuccinimide (NHS) (GO-NiO-8H-NHS) that enables the detection of glucose at neutral pH values. The optimum platform showed a perfect detection limit (DL) and sensitivity of 41 nM and 712.5 µA.mM−1.cm−2, respectively, via amperometric technique, while these values for voltammetric approaches were measured to be 63 nM and 4911.4 µA.mM−1.cm−2, respectively, at physiological conditions. Correspondingly, the developed platform showed superior sensitivity and accuracy toward detecting glucose within actual blood plasma samples and kept 94% of its initial performance after 30 days. Obtained outcomes revealed the fantastic DL and sensitivity of the developed non-enzymatic biosensors toward detecting glucose in actual biological samples at physiological conditions without using hazardous alkaline solutions.

Matrix-Assisted Laser Desorption/Ionization-Mass Spectrometry Imaging of Lipids in the Ischemic Rat Brain Section: A Practical Approach.

Matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) of lipids is considered one of the shotgun lipidomic techniques that explores the in situ distribution of lipids in tissue sections. To successfully perform this task, knowledge and experience in the conventional cryosection, tissue section collection and handling, and mass spectrometry data analysis and signal processing are needed. A MALDI-MSI protocol covering from the fresh organ collection, cryosection and tissue processing, matrix application, MSI data acquisition, to the final MSI display of lipid distribution in the brain section of an ischemic stroke rat is described to exemplify this technique. Due to the multidisciplinary nature of this approach, plenty of preparation, practice, and familiarization to several critical steps ahead of the engagement with actual biological samples are needed to ensure a successful MALDI-MSI presentation of lipids in situ.