Human Blood Serum Research Articles

#749 Components in blood collection tubes interfere with the spectral signatures of patients with kidney disease: analysis by infrared microspectroscopy

Abstract Background and Aims Kidney disease is a worldwide public health problem, affecting between 8%-16% of the global population. Chronic Kidney Disease (CKD) is a silent disease and its detection is often late, making the treatment difficult. Considering the emerging Fourier-Transform Infrared spectroscopy (FTIR) as a biophotonic resource for the biomedical sciences, we aimed to identify spectral signatures related to biomarkers of CKD in human blood serum using the microscopy FTIR option. Method Blood serum samples from 17 healthy in comparison to 33 CKD patients were analyzed by micro-reflectance FTIR spectroscopy. The first aspect to be addressed refers to the possible influence of components present in the container tube. Here we showed that separator gel in VACUETTE® tubes is a relevant source of spectral interference which could decrease the accuracy of discrimination from 85% to 65%. Acquiring a diluted gel signal as a background would improve the discrimination performance in spite of some gel bands still present in sample data. Results In this case, our results indicated that vibrations associated with galactose-4-sulfate, CH2 bending of the methylene chains, C=C in lipids and fatty acids, C=N stretching, CH bending vibration from the phenyl rings, N-H bending vibration coupled to C-N stretching and β-sheet of Amide II and ring base are modulated in blood serum samples of chronic kidney disease patients compared to healthy patients. Urinary trypsin inhibitors, fatty acids, phenolic derivatives, tryptophan, and plasminogen were the biomolecules related to these assignments were the biomolecules related to these assignments. Conclusion In conclusion, FTIR is a viable option for fast diagnosis of chronic kidney disease being also a powerful tool for monitoring the disease. Due to its capability of large batch analysis, the micro-FTIR would be an eligible technology for clinical laboratories in healthcare facilities. However, for direct clinical applications, ATR-FTIR would be the option of choice.

Electrodeposited Phosphorous-Doped Graphitic Carbon Nitride as A Versatile Metal Free Interface for Tryptophan Detection in Dietary, Nutritional, and Clinical Samples

Tryptophan (TRP) is an essential amino acid that is crucial for human growth and must be obtained through a dietary source or nutritional supplements. Both, the overconsumption or deficiency induces clinical symptoms. Therefore, a sensitive and selective method for quantifying TRP in dietary products, nutritional supplements, and clinical samples is essential. In this work, we have electrodeposited phosphorous doped graphitic carbon nitride (P-gCN) for developing a TRP voltammetric sensor. Outlining the benefits of electrodeposition over drop-casting, the developed P-gCN | GCE sensor demonstrated 7.83 times more sensitivity and a negative shift of ∼0.10 V for TRP electro-oxidation compared to unmodified electrode implying its remarkable electrocatalytic activity. The sensor featured a detection-limit of 7.1 nM and showcased excellent stability, repeatability and reproducibility. The practical utility of the sensor was manifested by estimating TRP in over 12 real samples including, food products, nutritional supplements and clinical samples (urine and human blood serum).

CeO2·ZnO@biomass-derived carbon nanocomposite-based electrochemical sensor for efficient detection of ascorbic acid

Ascorbic acid (AA), a prominent antioxidant commonly found in human blood serum, serves as a biomarker for assessing oxidative stress levels. Therefore, precise detection of AA is crucial for swiftly diagnosing conditions arising from abnormal AA levels. Consequently, the primary aim of this research is to develop a sensitive and selective electrochemical sensor for accurate AA determination. To accomplish this aim, we used a novel nanocomposite comprised of CeO2-doped ZnO adorned on biomass-derived carbon (CeO2·ZnO@BC) as the active nanomaterial, effectively fabricating a glassy carbon electrode (GCE). Various analytical techniques were employed to scrutinize the structure and morphology features of the CeO2·ZnO@BC nanocomposite, ensuring its suitability as the sensing nanomaterial. This innovative sensor is capable of quantifying a wide range of AA concentrations, spanning from 0.5 to 1925 μM in a neutral phosphate buffer solution. It exhibits a remarkable sensitivity of 0.2267 μA μM−1cm−2 and a practical detection limit of 0.022 μM. Thanks to its exceptional sensitivity and selectivity, this sensor enables highly accurate determination of AA concentrations in real samples. Moreover, its superior reproducibility, repeatability, and stability underscore its reliability and robustness for AA quantification.

Hybridization of 2D MnO2 and MoS2 via single-step microwave synthesis for trace-level detection of thrombin in simulated blood serum samples

Thrombin (THMB), a critical enzyme in the coagulation of blood, necessitates rapid and sensitive detection for assessing thrombotic disorders and cardiovascular health. Here, we demonstrate the trace-level detection of thrombin in simulated human blood serum samples by hybridization of 2D materials MnO2 and MoS2 modified nickel Foam (MnO2/MoS2/NF). MnO2/MoS2 hybrid is synthesized by a low-cost, and ultra-fast (within five minutes) solid-phase synthesis via microwave technique. Synthesized MnO2/MoS2 hybrid has been characterized by Transmission electron microscope (TEM) to know the microstructure of the hybrid. The crystalline nature of the material is confirmed by X-ray diffraction (XRD), Chemical fingerprint, and vibrational modes of the as-synthesized MnO2/MoS2 hybrid is examined using Raman spectroscopy (Raman, etc). The MnO2/MoS2/NF sensor demonstrates a wide linear range of detection varying from 10 fM to 50 nM with a superior sensitivity of 3.5 μA/nM/cm2 and a lower detection limit of 3.2 pM (LOD = 3 s/m). It is highly selective over other interfering species (IgG, BSA, Na2+, CA, and Urea). The standard addition method was employed to conduct real-time analysis of simulated blood serum samples using the DPV technique. The sensor demonstrated outstanding recovery percentages of ∼ 98 % to 102 %. The hybrid structure offers a greater number of active sites, employing the distinctive surface characteristics of both MnO2 and MoS2. This facilitates more efficient electrochemical reactions, crucial for sensitive Thrombin detection. Additionally, the 3D highly porous skeletal NF substrate ensures stability and enhances catalytic activity, while enabling rapid electron transfer, further boosting the sensor’s sensitivity. This work provides a rapid, cost-effective, and efficient solid-phase microwave synthesis method for obtaining MnO2/MoS2 hybrid material, thereby expanding its utility in detecting biological samples for clinical diagnosis and biomedical research purposes.

Label-free voltammetric screening of human blood serum

The current study presents a comprehensive voltammetric investigation into the direct analysis of untreated human blood serum in a phosphate buffer at an unmodified, graphite electrode by means of voltammetry. By employing advanced square-wave voltammetry at an edge plane pyrolytic graphite electrode (EPPGE), the basic principles were established for developing a sensitive, fast, simple, and label-free method for the simultaneous screening of uric acid, bilirubin, and albumin analytes that are present in human blood serum and are quite essential for rapid medical diagnostics. The electrochemical protocol utilizes the specific structural patterns of the EPPGE, the inherent redox and adsorption properties of the analysed analytes, and the sensitivity and rapidity of the employed advanced voltammetric technique. The methodology has been successfully applied for quantification of the considered analytes in a series of samples of human blood serum and was compared with the standard methods used in a clinical biochemical laboratory. This novel method represents a significant advancement towards the development of point-of-care devices aimed at swiftly and simultaneously quantifying uric acid, bilirubin, and albumin levels in human serum.

Pentacenequinone-Modulated 2D GdSn-PQ Nanosheets as a Fluorescent Probe for the Detection of Enrofloxacin in Biological and Environmental Samples.

The fate and effects of fluoroquinolone antibacterial (FQ) on the environment are important since there appears to be a surge in FQ resistance like enrofloxacin (ENR) in both environmental and clinical organisms. Numerous reports indicate that the sensing capabilities of these antibiotics need to be improved. Here, we have investigated the interaction of ENR with our synthesized pentacenequinone-modulated gadolinium-tin (GdSn-PQ) nanosheets and the formation of intermolecular interactions that caused the occurrence of aggregation-induced emission enhancement. The concept for designing hybrid metallic nanosheets comes from the unique features inherited from the parent organic precursor. Due to the distinct interaction between ENR and GdSn-PQ, the interstate conversion (ISC) between GdSn-PQ and ENR induces a significant wavelength shift in photoluminescence (PL), improving reliability, selectivity, and visibility compared to quenching- or AIEE-based methods without peak shifts, allowing for highly sensitive and visually detectable analyses. The fluorescence signal of GdSn-PQ exhibited a linear relationship (R2 = 0.9911), with the added ENR concentrations ranging from 5 to 90 nM, with a detection limit of 0.10 nM. We have demonstrated its potential and wide use in the detection of ENR in biological samples (human urine and blood serum) and environmental samples (tap water and seawater) with a recovery rate of 98- 108%. The current approach has demonstrated that the 2D GdSn-PQ nanosheet is a novel and powerful platform for future biological and environmental studies.

Gold nanoparticles assisted colorimetric sensing of paroxetine, duloxetine, and olanzapine in aqueous and micellar systems with improved sensitivity

The present study explored a rapid and facile colorimetric identification of two antidepressants (paroxetine and duloxetine) and one antipsychotic drug (olanzapine) in aqueous and micellar systems using citrate-stabilized gold nanoparticles (Cit-AuNPs). The sensing approach involved hydrogen bonding and electrostatic interactions on the surface of Cit-AuNPs. The attributes of Cit-AuNPs and their interactions with the drugs were probed using characterization techniques like UV–Vis spectroscopy, scanning electron microscopy (SEM), dynamic light scattering (DLS), zeta potential measurement, and Fourier-transform infrared spectroscopy (FT-IR). Various factors including the volume of Cit-AuNPs, pH, reaction time, surfactant concentration, and the sequence of addition of reagents were optimized to inspect their impacts on sensing results. Under optimized conditions, the probe showed good linearity for the three drugs at the nanomolar (nM) range. Consequently, the color of the Cit-AuNP solution transformed from red to royal purple and blue, which was visible to the naked eye and monitored by visible absorption spectra. This label-free optical detection approach could recognize paroxetine (Prx), duloxetine (Dlx), and olanzapine (Olz) in aqueous system at concentrations ranging from 1 to 17 nM with a limit of detection (LOD) of 0.312, 0.258, and 0.418 nM (S/N = 3), respectively. Meanwhile, the sensitivity was improved in the Triton X-100 (TX-100) micellar system with LOD of 0.029, 0.030, and 0.029 nM for Prx, Dlx, and Olz, respectively accompanied by a shift in the absorption bands. The micellar system contributes stability to the Cit-AuNP-drug complex. The devised colorimetric approach was convenient and did not require any complex equipment. It was efficaciously used to detect three drugs in pharmaceutical products, spiked human urine, and blood serum samples with satisfactory recoveries of 99.83–103.45% and RSD < 3.5%. Notably, the sensing assay demonstrated good selectivity for three drugs in the existence of commonly encountered foreign species and certain common drugs with a relative error below 3%. The results of the present study were statistically compared with reference methodology. The results were validated with no significant difference between the devised and reported approaches considering precision and accuracy, respectively.

Zn-CD@Eu Ratiometric Fluorescent Probe for the Detection of Dipicolinic Acid, Uric Acid, and Ex Vivo Uric Acid Imaging.

Development of reliable methods for the detection of potential biomarkers is of the utmost importance for an early diagnosis of critical diseases and disorders. In this study, a novel lanthanide-functionalized carbon dot-based fluorescent probe Zn-CD@Eu is reported for the ratiometric detection of dipicolinic acid (DPA) and uric acid (UA). The Zn-CD@Eu nanoprobe was obtained from a simple room-temperature reaction of zinc-doped carbon dots (Zn-CD) and the EDTA-Eu lanthanide complex. Under optimal conditions, a good linear response was obtained for DPA in two concentration ranges of 0-55 and 55-100 μM with a limit of detection of 0.53 and 2.2 μM respectively, which is significantly below the infectious dosage of anthrax (∼55 μM). Furthermore, the Zn-CD@Eu/DPA system was employed for the detection of UA with a detection limit of 0.36 μM in the linear range of 0-100 μM. The fluorescent probe was successfully implemented for determining DPA and UA in human blood serum, sweat, and natural water bodies with considerable recovery rates. In addition, the potential of the nanoprobe for ex vivo visualization of UA was demonstrated in fruit fly (Drosophila melanogaster) as a model organism.

A novel potentiometric screen-printed electrode based on crown ethers/nano manganese oxide/Nafion composite for trace level determination of copper ion in biological fluids.

Copper levels in biological fluids are associated with Wilson's, Alzheimer's, Menke's, and Parkinson's diseases, making them good biochemical markers for these diseases. This study introduces a miniaturized screen-printed electrode (SPE) for the potentiometric determination of copper(II) in some biological fluids. Manganese(III) oxide nanoparticles (Mn2O3-NPs), dispersed in Nafion, are drop-casted onto a graphite/PET substrate, serving as the ion-to-electron transducer material. The solid-contact material is then covered by a selective polyvinyl chloride (PVC) membrane incorporated with 18-crown-6 as a neutral ion carrier for the selective determination of copper(II) ions. The proposed electrode exhibits a Nernstian response with a slope of 30.2 ± 0.3mV/decade (R2 = 0.999) over the linear concentration range 5.2 × 10-9 - 6.2 × 10-3mol/l and a detection limit of 1.1 × 10-9mol/l (69.9ng/l). Short-term potential stability is evaluated using constant current chronopotentiometry (CP) and electrochemical impedance spectroscopy (EIS). A significant improvement in the electrode capacitance (91.5 μF) is displayed due to the use of Mn2O3-NPs as a solid contact. The presence of Nafion, with its high hydrophobicity properties, eliminates the formation of the thin water layer, facilitating the ion-to-electron transduction between the sensing membrane and the conducting substrate. Additionally, it enhances the adhesion of the polymeric sensing membrane to the solid-contact material, preventing membrane delamination and increasingthe electrode's lifespan. The high selectivity, sensitivity, and potential stability of the proposed miniaturized electrode suggests its use for the determination of copper(II) ions in human blood serum and milk samples. The results obtained agree fairly well with data obtained by flameless atomic absorption spectrometry.

Comparative analysis of serum titanium level in patient with healthy dental implant and patients with peri-implantitis- A cross sectional prospective study

Objectives: Titanium dental implants can last for more than two decades in the oral environment. Corrosion of the implant surface can release metallic particles or ions into surrounding tissue. The metallic constituents like titanium in human blood serum have not been fully studied. The study compares titanium serum levels before and after dental implant placement and compares levels in patients with healthy implants and those with per-implantitis. Methods: The study comprised 2groups of Group 1 patient observing implant surgery and group 2 patients with diagnosed peri-implantitis. Each group comprised of 60 patients. Serum titanium level was measured from blood obtained from Group 1 at three different intervals (one month prior to implant surgery, 4th and 8th month after successful loading) and from Group 2 during the course of peri-implantitis by inductively coupled plasma–mass spectroscopy. The statistical analysis was done for the obtained data. Results: Analysis showed a raised level of serum titanium at 4th month of post implant placement (2.39 mg/dl) and in patient with peri-implantitis(2.94 mg/dl) and both levels are significantly differ (ANOVA test) from pre-surgical estimation of serum titanium level (1.79 mg/dl). Conclusions: Understanding the correlation between titanium corrosion and peri-implantitis is vital for enhancing the long-term success and safety of dental implants. Additional research is required to investigate these links and potential strategies to protect the well-being of implant patients.

Enhancement of signal intensity of elements in human blood serum using a metal mesh-enhanced CO2 laser-induced breakdown spectroscopy in ambient He gas

Accurate and reliable identification and analysis of the elemental composition of human blood serum is of utmost importance. The present investigation included the analysis of human blood serums for elemental composition using a metal mesh-supported CO2 laser-induced breakdown spectroscopy under a helium gas environment at atmospheric pressure. In this study, a pulsed transversely excited atmospheric CO2 laser with a wavelength of 10.64 µm and a pulse duration of 200 ns was applied to irradiate the human blood serum film placed on a copper metal to induce a luminous plasma. A significant increment of elemental signal intensity occurs by introducing a metal mesh covering the serum film. Qualitative and quantitative analyses have been conducted on the human blood serum's major, minor, and trace elements. The concentrations of elements in the human blood are estimated to be 9160 parts per million (ppm) for carbon (C), 174 ppm for calcium (Ca), 600 ppm for potassium (K), 1410 ppm for magnesium (Mg), 343 ppm for phosphorus (P), 2180 ppm for sodium (Na), and 48 ppm for iron (Fe). The results of the CO2 LIBS method demonstrate a high level of concurrence with the results obtained by the conventional XRF method.

Copper(II) Driven Fluorescence switch-on Detection of Ovalbumin and GSH Using a Pyridoxal 5'-phosphate Derived Tetradentate Schiff Base and its Applications.

The facile detection of glutathione (GSH) and ovalbumin (OVA) is of great importance in biological research. Herein, a tetradentate Schiff base N, N'-bis(pyridoxal-5-phosphate)-o-phenylenediamine (L) obtained by condensing two moles of pyridoxal 5'-phosphate (PLP) with one mole of 1,2-phenylenediamine was employed for the fluorescence switch-on detection of GSH and OVA. When excited at 389nm, receptor L showed a weak emission at 454nm in an aqueous medium. The addition of GSH to the solution of L caused a significant fluorescence enhancement at 454nm. Amino acids (leucine, glycine, serine, tryptophan, homocysteine, alanine, methionine, arginine and proline) and albumins (bovine serum albumin and OVA) failed to alter the fluorescence profile of L. Receptor L can be applied to detect GSH down to 1.16 µM. However, the fluorescence emission of L was quenched upon the formation of the L-Cu2+ complex. The addition of GSH and OVA to the in-situ formed L-Cu2+ complex restored not only the fluorescence emission of L but also a noticeable fluorescence enhancement observed at 454nm. The decomplexation of L-Cu2+, along with the interaction of L with GSH and OVA is expected to suppress the conformational flexibility of L that enhanced the fluorescent intensity at 454nm. Using L-Cu2+ complex, the concentration of OVA and GSH can be detected down to 0.31 µM and 0.20 µM, respectively. Molecular docking and dynamics simulation were performed to analyze the binding mode, conformational flexibility and dynamic stability of the L-Cu2+-OVA complex. Finally, the analytical novelty of L-Cu2+ was examined by detecting GSH/OVA in real biological samples, such as human blood serum, urine, and egg white.

Bioelectrochemical Sensing Using Benchtop Fabricated Nanoroughened Microstructured Electrodes

AbstractCost‐effective miniaturized electrodes that maintain a high electroactive surface area (ESA) are needed for the widespread deployment of point‐of‐care sensors. Cost‐effective methods are recently developed to fabricate nanoroughened microstructured gold electrodes (NR‐MSEs) with ultrahigh ESA. In this work, the effectiveness of NR‐MSEs for bioelectrochemical enzymatic sensors is evaluated. A glucose sensor is constructed by first casting onto NR‐MSEs a solution containing reduced graphene oxide decorated with gold nanoparticles, glucose oxidase, and glutaraldehyde, followed by a solution containing ferrocene, and a layer of chitosan to prevent the leakage of sensor components. A urea biosensor is also fabricated using Nafion as a cationic exchanger for the electropolymerization of polyaniline, followed by the deposition of a composite containing urease, bovine serum albumin, and glutaraldehyde. The limit of quantification for both biosensors is below clinically relevant concentrations of the analytes in biofluids, 0.67 mm for glucose and 1.70 mm for urea. The sensors exhibit excellent performance in complex matrixes (human blood serum and wine for glucose and human blood serum and urine for urea), with recovery for spiked analytes in the range of 92–108%. It is anticipated that NR‐MSEs will expedite the development of highly sensitive bioelectrochemical sensors for use in resource‐limited settings.

In situ anchored ternary hierarchical hybrid nickel@cobaltous sulfide on poly(3,4-ethylenedioxythiophene)-reduced graphene oxide for highly efficient non-enzymatic glucose sensing.

A ternary hierarchical hybrid Ni@CoxSy/poly(3,4-ethylenedioxythiophene)-reduced graphene oxide (Ni@CoxSy/PEDOT-rGO) is rationally designed and in situ facilely synthesized as electrocatalyst to construct a binder-free sensing platform for non-enzymatic glucose monitoring through traditional electrodeposition procedure. The as-prepared Ni@CoxSy/PEDOT-rGO presents unique hierarchical structure and multiple valence states as well as strong and robust adhesion between Ni@CoxSy/PEDOT-rGO and GCE. Profiting from the aforementioned merits, the sensing platform constructed under optimal conditions achieved a wide detection range (0.2μM ~ 2.0mM) with high sensitivity (1546.32 μA cm-2mM-1), a rapid response time (5s), an ultralow detection limit (0.094μM), superior anti-interference performance, excellent reproducibility and considerable stability. Furthermore, the sensor demonstrates an acceptable accuracy and appreciable recoveries ranging from 90.0 to 102.0% with less than 3.98% RSDin human blood serum samples, indicating the prospect of the sensor for the real samples analysis. It will provide a strategy to rationally design and fabricate ternary hierarchical hybrid as nanozyme for glucose assay.

MnO2 nanosheet quenched thulium doped photon-up conversion luminescent immunoprobe for the ‘turn-on’ detection of cardiac troponin T

A “turn-on” photon up conversion nano couple based on NaYF4: Yb, Tm UCNPs quenched with MnO2 nanosheet was developed for the rapid and selective detection of cTnT. Herein, MnO2 nanosheet hold on the surface of Antibody cTnT (Ab-cTnT) conjugated blue emitting up conversion nanoprobe (λem at 475 nm), which leads to quenching of fluorescence due to energy transfer from photon up conversion nanoparticles to MnO2 nanosheets. On introducing cTnT antigen to the system, the energy transfer process is hindered due to strong antigen -antibody interface on the surface. This in turn, influences the nano-couples positions and effectively separates up conversion nanoprobe from MnO2 nanosheets surface resulting in restriction to energy transfer process enabling fluorescence recovery. The developed probe shows a linear response towards cTnT in the range of 0.16–2.77 ng/mL with a Limit of Detection (LoD) of 0.025 ng/mL. The practical feasibility of the nanoprobe is performed with possible coexisting biomolecules. Biological study in human blood serum samples exhibited sufficient recovery percentage in the range of 92–103 % is obtained.

A comparative study of Fe (II) doped chiral L/D-methionine carbon dots (MCDs) as a “Turn-on” fluorescent probe for the sensitive detection of L – cysteine

Chiral carbon dots have prominently influenced in the field of chemical, biological, and medicinal research. Comparing to achiral carbon dots, chiral carbon dots exhibit unique characteristics in biosensing application. In this perspective, we have developed bright blue, fluorescent L and d-Methionine Chiral carbon dots (MCDs) using a simple microwave assisted process for effective sensing of l-Cysteine. l-Cysteine plays a vital role in balancing the physiological redox in the body. These MCDs can be complexed with Fe2+ ions to create an energy transfer quenching system due to distinctive N and S functional group distribution on their surface. However, l-Cysteine attaches to Fe2+ ions in a competitive manner, leads to recovery of MCDs fluorescence. As a result, a "turn-on" fluorescent sensing platform based on L and d-Methionine-CDs has been developed for the rapid identification and detection of l-Cysteine. The probe shows good selectivity and sensitivity with coexisting biomolecules and ions. From comparative PL studies, d- MCDs are more responsive than l-Meth CDs towards the detection of l-cysteine with LOD of 0.71 µM and 0.94 µM respectively. The chiroptical properties were evaluated and the probe extends its practical application in paper strip and in biological matrix such as human blood serum with satisfactory recoveries in the range 85–104%.

Smartphone-based device for rapid and single-step detection of piRNA–651 using anti-DNA:RNA hybrid antibody and enzymatic signal amplification

P-element-induced wimpy testis (PIWI)-interacting RNAs (piRNAs/piRs) are a class of small noncoding RNAs that play a crucial role in regulating various biological processes, including carcinogenesis. One specific piRNA, piR–651, has been reported to be overexpressed in both human blood serum and solid cancer tissues, that can be used a viable biomarker in cancer diagnosis. Early diagnosis of cancer can help reduce the burden of the disease and improve survival rates. In the present work, we report for the first time a smartphone-based colorimetric biosensor for highly sensitive and specific detection of piR–651 thanks to an enzymatic signal amplification, which yielded high colorimetric intensities. Indeed, a heteroduplex DNA:RNA was formed in the presence of piR–651 with the capture DNA probe immobilized on the magnetic beads for easy magnetic separation. Then, a HRP tethered to anti-DNA:RNA (S9.6) was used to reveal the DNA-RNA heteroduplex formed by catalyzing the oxidation of TMB substrate into colorimetric TMBox, which absorbs at 630 nm. The absorbance is positively proportional to the piR–651 concentrations. On the other hand, the colorimetric product of the assay can be photographed with a smartphone camera and analyzed using ImageJ software. Using a smartphone and under optimal conditions, the biosensor responded linearly to the logarithm of piRNA–651 from 8 fM to 100 pM with a detection limit of 2.3 fM and discriminates against other piRNAs. It was also successfully applied to the determination of piRNA–651 levels in spiked human serum.

Enhanced cysteine sensor based on modified gold nanoparticles with synergistic role of pH-responsive poly (N,N-dimethylaminoethyl methacrylate)

The development of a highly sensitive and easy-to-prepare sensor for the detection of cysteine (Cys) is of great importance. Gold nanoparticles (AuNPs) have been frequently utilized as a Cys sensor owing to high affinity of the thiol group to gold. However, the presence of additional materials, such as stabilizers, can impact the sensitivity of this sensor. Herein, pH-sensitive gold nanoparticles (Au-PDA) were synthesized using poly (N,N-dimethylaminoethyl methacrylate) (PDMAEMA) for the purpose of Cys detection based on the aggregation size-dependent optical property of gold nanoparticles. Detection of cysteine was also followed by UV–Vis analysis, showing a decrease in intensity of localized surface plasmon resonance (LSPR) peak, a red shift from 525 to 550 nm as well as the appearance of a new peek at 650 nm. To enhance sensor performance, systematic investigations were conducted to optimize sensing conditions, focusing on pH, gold concentration, and ionic strength of the medium. Remarkably, the proposed sensor exhibited excellent selectivity towards Cys compared to other amino acids. The sensitivity of the sensor was evaluated using two methods: changes in the absorption intensity and the LSPR shift. The pH-sensitivity of PDMAEME led to a significant improvement in sensing parameters through a synergistic effect on the Au-Cys interaction, leading to a remarkably low LOD of 0.0004 nM, which is the lowest ever reported LOD for detection of Cys. Finally, practical application of the proposed sensor was validated in human blood serum.

Water suppression 101 for benchtop NMR–An accessible guide and primer including fully interactive training videos

Benchtop NMR is enjoying a renaissance with numerous manufacturers bringing products to the market over the last decade. The improved accessibility, lower cost of ownership and ease of use (vs high field NMR), is attracting new users into NMR spectroscopy, which is highly beneficial for the field in general. As benchtop NMR systems seldom require deuterated solvents, this allows samples to be analyzed “as is”, without extraction or alteration. However, many interesting samples, be it an organic reaction mixture, beer, or a biofluid, contain one or more solvent/water signals, which often require suppression. Due to the lower spectral dispersion of benchtop NMR's (vs high field) the frequency of solvent/water is much closer to the analytes of interest, making solvent suppression more challenging. As such, there is a conundrum, where novel users wish to analyze unaltered samples but are quickly faced with the challenge of water suppression, and the wealth of options in the high field literature can be overwhelming. It is important to note that all manufacturers offer some sort of automated water suppression that can be performed with a “single click” that are sufficient for “walk-up” applications or occasional users. This primer is aimed as an accessible guide to those wishing to take the next step and is suitable for users who; 1) would like to pick the optimal water suppression approach for their sample type and 2) wish to understand how water suppression works. The guide focuses on water suppression approaches that are easy to apply, namely presaturation based sequences, binomial sequences for aggressive suppression, and WET for multiple signal suppression, across a range of samples including sucrose standards, espresso, human blood serum and wine. The primer finishes with a flow chart that can be used to guide users in choosing the optimal water suppression approach for their specific sample type, with considerations, including exchangeable signals and the preservation of macromolecular signals, amongst others. In addition, the primer includes 3 fully interactive videos based on H5P technology, focusing on how to acquire data using the approaches described here. The videos include quizzes, with a first-person-perspective of the spectrometer software with interactive elements, as if the users were acquiring the data themselves. In summary, the primer is aimed at advanced undergraduates, graduate students, new users, or users wishing to expand their water/solvent suppression skills/knowledge using benchtop NMR.

Aqueous phosphate detection in real samples using NIR-triggered Diamino Bis-Benzimidazoquinoline fluorescence sensor: An experimental and theoretical approach

The present work reports the design, synthesis, and sensing applications of Diamino bis-benzimidazoquinoline (DA-BISQ) derivatives. These compounds were synthesized in appreciable yield and characterized by FT-IR, 1H, and 13C NMR spectral and mass spectrometry. Optical studies revealed intriguing dual excitation properties: single excitations at λex 330-386 nm and double excitations at λex 660-772 nm in 10 % ethanol-water medium. The near-infrared excitation region λex 660-772 nm was particularly focused on the detection of F¯, Cl¯, Br¯, I¯, AcO ̄, ClO4¯, NO3¯, and HPO4¯ anions. Notably, selective fluorescence quenching "OFF" responses were observed for geometric anions like AcO¯, ClO4¯, NO3¯, and HPO4¯. Interestingly, the pyridine spacer-containing derivative 1c exhibited a unique fluorescence "OFF-ON'' response for the phosphate ion. Cyclic voltammetry titration further corroborated the binding affinity towards phosphate. To demonstrate practical applicability, a thin-film strip of receptor 1c was fabricated and tested for effective phosphate sensing in human blood serum samples. Density functional theory calculations were performed to elucidate the sensing mechanism with the phosphate anion. The combined experimental and theoretical results suggest an internal charge transfer process between the receptor and the anion.