Real Saliva Samples Research Articles

Composite PEDOT-PSS based highly sensitive electrochemical sensors for sensing glucose from human saliva

Here we report two composites, especially two different 2D materials and Au nanoparticle composite with conducting polymer PEDOT-PSS as electrodes for highly sensitive, cost effective and reliable biosensors. Conducting polymer composite electrodes of AuNP/WS2/PEDOT-PSS and AuNP/GO/PEDOT-PSS were prepared by electrochemical deposition and were studied using various structural and electrochemical techniques. XRD, FTIR and SEM have been used for structural characterization which confirmed the elemental compositions of these composite electrodes. Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV) were used to examine the charge transfer kinetics and electroactive properties of the modified electrodes. Impedance spectra analysis had shown the reduced charge transfer resistance and diffusive property of AuNP/WS2/PEDOT-PSS electrodes compared to AuNP/GO/PEDOT-PSS. To demonstrate biosensing advantages of these electrodes, interaction between covalently immobilized glucose oxidase (GlOx) enzyme and D-glucose was monitored via chronoamperometry and CV. GlOx/AuNP/WS2/PEDOT-PSS/ITO yielded wider linear range from 0.74 to 440.67 µM towards the oxidation of glucose with high selectivity and lower limit of detection (LOD) of 1 µM. AuNP/GO/PEDOT-PSS/ITO composite electrode exhibited linearity in the range 3.84–373.33 µM and LOD 2.33 µM. Better sensitivity and wider linear range of GlOx/AuNP/WS2/PEDOT-PSS/ITO has been assigned to special layered structure as sheets formed by incorporation of WS2 to PEDOT-PSS. Validation of the glucose sensors has shown satisfactory results using real saliva samples. Study suggests use of conducting polymer, 2D layered material and metal nanoparticle composite electrodes based sensors offer wider linearity range and higher sensitivity for stable, reliable, cost- effective sensor electrodes which can be used easily in non-clinical diagnostics.

Fabrication of a salivary amylase electrochemical sensor based on surface confined MWCNTs/β-cyclodextrin/starch architect for dental caries in clinical samples

Salivary α-amylase (α-ALS) has drawn attention as a possible bioindicator for dental caries. Herein, combining the synergistic properties of multi-walled carbon nanotubes (MWCNTs), β-cyclodextrin (β-CD) and starch, an electrochemical sensor is constructed employing ferrocene (FCN) as an electrochemical indicator to oversee the progression of the enzymatic catalysis of α-ALS. The method involves a two-step chemical reaction sequence on a screen-printed carbon electrode (SPCE). X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Field emission scanning electron microscope (FE-SEM), and Dynamic light scattering (DLS) were used to characterize the synthesized material, while Static water Contact angle measurements, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were performed to monitor each step of sensor fabrication. The electrochemical sensor permitted to detect α-ALS within the linear range of 0.5–280 U mL−1, revealing detection (LOD), and quantification (LOQ) values of 0.041 U mL−1, and 0.159 U mL−1, respectively. Remarkably, the sensor demonstrated exceptional specificity and selectivity, effectively discriminating against other interfering substances in saliva. Validation of the method involved analyzing α-ALS levels in artificial saliva with an accuracy range of 97 % to 103 %, as well as in real clinical saliva samples across various age groups.

Combining PDMS Composite and Plasmonic Solid Chemosensors: Dual Determination of Ammonium and Hydrogen Sulfide as Biomarkers in a Saliva Single Test

In recent years, in the field of bioanalysis, the use of saliva as a biological fluid for the determination of biomarkers has been proposed. Saliva analysis stands out for its simplicity and non-invasive sampling. This paper proposes a method for the dual determination of ammonium and hydrogen sulfur in saliva using two colorimetric chemosensors. The ammonia reacts with 1,2-Naftoquinone 4 sulphonic acid (NQS) entrapped in polydimethylsiloxane (PDMS) and the hydrogen sulfide with AgNPs retained in a nylon membrane. The color changed from orange to brown in the case of ammonia chemosensors and from yellow to brown in the H2S. The experimental conditions to be tested have been established. Both analytes have been determined from their gaseous form; these are ammonia from ammonium and hydrogen sulfur from hydrogen sulfur. Good figures of merit have been obtained by using both measuring strategies (reflectance diffuse and digitalized images). The acquired results show that both sensors can be used and provide good selectivity and sensitivity for the determination of these biomarkers in saliva. Both measurement strategies have provided satisfactory results for the real saliva samples (n = 15). Recoveries on spiked samples were between 70 and 100%. This methodology can lead to possible in situ diagnosis and monitoring of certain diseases and pathologies related with NH4+ and/or H2S, in a fast, simple, cheap and non-invasive way.

Polyvinyl chloride coated paper postmodified by nucleophilic substitution with diphenylamine to enhance cation-π interactions with opioids in saliva samples

This article evaluates the potential of cellulose paper as a substrate for preparing a polyvinylchloride (PVC)-diphenylamine sorptive phase that can be used under the thin film microextraction (TFME) format. This phase was easily synthesized using the dip-coating technique to coat the filter paper with PVC, followed by the covalent bonding of diphenylamine. As a result, aromatics rings are available on paper surface to isolate the target analytes by a mixed-mode interaction at physiological pH. The resulting material was characterized by infrared spectroscopy, UV–Vis diffuse reflection spectroscopy, and scanning electron microscopy. As analytical problem, three opioids (methadone, codeine, and tramadol) were determined in saliva samples by direct infusion mass spectrometry. Different variables involved in the extraction procedure have been optimized (e.g. sample pH, extraction time, and sample dilution). The proposed method provides good linearity (R2 > 0.9817) and sensitivity (detection limits in the range from 1.5 µg L−1 to 15 µg L−1). The intra-day and inter-day precision, expressed as relative standard deviation, were better than 16.4 % and 18.5 % respectively. The accuracy, expressed as relative recovery, provides values in the interval from 82 % to 105 %. Finally, the proposed approach has been successfully applied to real saliva samples of patients under codeine and tramadol medical prescription.

Impedimetric sensor based on molecularly imprinted polythionine from deep eutectic solvent for epinephrine determination

Deep eutectic solvents have obtained growing interest in analytical chemistry due to opportunities related the green chemistry paradigm, i.e., substitution of organic solvents, application of nontoxic ingredients and minimal quantities of wastes formed in their synthesis and usage. In this work, the advantages of deep eutectic solvents were shown in the development of electrochemical sensor for epinephrine determination. Polythionine molecularly imprinted with epinephrine (PTNMIP) was electrodeposited from natural deep eutectic solvent (NADES) consisted of citric acid, glucose, and water in 1:1:6 molar ratio and tested with standard solutions of epinephrine, pharmaceutical preparations, and artificial samples of biological liquids. Only one drop (100 µL) of the monomer dissolved in NADES was applied for sensor preparation on the platform of screen-printed carbon electrode. Electropolymerization was performed by multiple scanning of the potential. The formation of molecular imprints was confirmed by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). After the template removal, the charge transfer resistance of the surface layer depended on the epinephrine concentration in the range from 100 nM to 316 µM (limit of detection 50 nM). Selectivity of the signal was confirmed against serotonin and norepinephrine commonly present in biological liquids. Sensor was successfully tested for the determination of epinephrine in spiked solutions mimicking influence of the plasma electrolytes, serum proteins, and in real saliva samples. The recoveries calculated for 10 μM epinephrine ranged from 98.3 to 102.6%. Insignificant influence of the additives and stabilizers present in medications was eliminated by sample dilution. Impedimetric sensor developed showed good opportunities for further application in clinical diagnostics, pharmacokinetics studies and medication manufacture control.

Graphene nanoplatelets-polyaniline composite for the detection of cortisol

In this study, a highly selective Graphene oxide (GO)-Polyaniline (PANI) modified glassy carbon electrode (GCE) was fabricated and its electrocatalytic behaviour towards the electro-reduction of cortisol in human saliva was investigated. The synthesized nanocomposites were characterized using different analytical approaches. The electrochemical study of the PANI-GO modified electrode was analyzed by employing a cyclic Voltammetry (CV) study. The outcomes demonstrated a substantial enhancement in the reduction and oxidation current peaks of the modified GCE as associated to bare GCE, GO/GCE and PANI/GCE. Along with enhanced electronic properties, the biosensor displays the good selectivity and sensitivity, good reproducibility (95 %, n = 8), high stability (maintaining more than 95 % response even after 11 weeks of storage at −20C, 50 cycles), a wide linear range (100μ-10 mM) and small detection limit (30 μM). The utilization of PANI-GO in the electrode modification process may be attributed to these positive outcomes, given some of the amazing characteristics of the composite, such as its larger surface area, outstanding electrical conductivity, and good electrocatalytic behavior. Furthermore, the PANI-GO modified GCE was successfully validated by detecting cortisol in real human saliva samples using cyclic voltammetry, highlighting the effectiveness of the PANI-GO composite for non-invasive electrochemical cortisol detection.

High-Precision Viral Detection Using Electrochemical Kinetic Profiling of Aptamer-Antigen Recognition in Clinical Samples and Machine Learning.

High-precision viral detection at point of need with clinical samples plays a pivotal role in the diagnosis of infectious diseases and the control of a global pandemic. However, the complexity of clinical samples that often contain very low viral concentrations makes it a huge challenge to develop simple diagnostic devices that do not require any sample processing and yet are capable of meeting performance metrics such as very high sensitivity and specificity. Herein we describe a new single-pot and single-step electrochemical method that uses real-time kinetic profiling of the interaction between a high-affinity aptamer and an antigen on a viral surface. This method generates many data points per sample, which when combined with machine learning, can deliver highly accurate test results in a short testing time. We demonstrate this concept using both SARS-CoV-2 and Influenza A viruses as model viruses with specifically engineered high-affinity aptamers. Utilizing this technique to diagnose COVID-19 with 37 real human saliva samples results in a sensitivity and specificity of both 100 % (27 true negatives and 10 true positives, with 0 false negative and 0 false positive), which showcases the superb diagnostic precision of this method.

High‐Precision Viral Detection Using Electrochemical Kinetic Profiling of Aptamer‐Antigen Recognition in Clinical Samples and Machine Learning

AbstractHigh‐precision viral detection at point of need with clinical samples plays a pivotal role in the diagnosis of infectious diseases and the control of a global pandemic. However, the complexity of clinical samples that often contain very low viral concentrations makes it a huge challenge to develop simple diagnostic devices that do not require any sample processing and yet are capable of meeting performance metrics such as very high sensitivity and specificity. Herein we describe a new single‐pot and single‐step electrochemical method that uses real‐time kinetic profiling of the interaction between a high‐affinity aptamer and an antigen on a viral surface. This method generates many data points per sample, which when combined with machine learning, can deliver highly accurate test results in a short testing time. We demonstrate this concept using both SARS‐CoV‐2 and Influenza A viruses as model viruses with specifically engineered high‐affinity aptamers. Utilizing this technique to diagnose COVID‐19 with 37 real human saliva samples results in a sensitivity and specificity of both 100 % (27 true negatives and 10 true positives, with 0 false negative and 0 false positive), which showcases the superb diagnostic precision of this method.

Self-Diagnosis of SARS-CoV-2 from Saliva Samples at Home: Isothermal Amplification Enabled by Do-It-Yourself Portable Incubators and Laminated Poly-ethyl Sulfonate Membranes.

COVID-19 made explicit the need for rethinking the way in which we conduct testing for epidemic emergencies. During the COVID-19 pandemic, the dependence on centralized lab facilities and resource-intensive methodologies (e.g., RT-qPCR methods) greatly limited the deployment of widespread testing efforts in many developed and underdeveloped countries. Here, we illustrate the development of a simple and portable diagnostic kit that enables self-diagnosis of COVID-19 at home from saliva samples. We describe the development of a do-it-yourself (DIY) incubator for Eppendorf tubes that can be used to conduct SARS-CoV-2 detection with competitive sensitivity and selectivity from saliva at home. In a proof-of-concept experiment, we assembled Eppendorf-tube incubators at our home shop, prepared a single-tube mix of reagents and LAMP primers in our lab, and deployed these COVID-19 detection kits using urban delivery systems (i.e., Rappifavor or Uber) to more than 15 different locations in Monterrey, México. This straightforward strategy enabled rapid and cost-effective at-home molecular diagnostics of SARS-CoV-2 from real saliva samples with a high sensitivity (100%) and high selectivity (87%).

An Enzyme‐Encapsulated Metal‐Organic Frameworks Nanomesh Biosensor for Salivary Glucose Detection

AbstractDiabetes mellitus has become a serious public health problem worldwide. Current home‐based glucose testing, including fingerstick blood testing and continuous glucose monitoring, suffers from low compliance and potential infection. Non‐invasive glucose detection, with the advantages of pain‐free, easy‐to‐operate, and low‐cost, is expected to significantly improve the experience of glucose testing at home for diabetic patients. Here, an enzymatic biosensing platform with high sensitivity and high stability is developed based on a conductive nanomesh composed of interconnected metal‐organic frameworks (MOF). The as‐prepared enzyme‐encapsulated MOF nanomesh exhibits uniform morphology, regular structure, superior catalytic performance, and outstanding electrical conductivity. The glucose sensor modified by enzyme‐encapsulated MOF nanomesh demonstrates a considerably high sensitivity of 86.86 µA mm−1 cm−2 with a limit of detection of 16.57 µm, and remains stable for 16 days of usage. Detection of real saliva samples matches well with the commercial salivary glucose assay kit with an accuracy >93%, and a high correlation with blood glucose with Pearson's r > 0.7. Therefore, the presented enzyme‐encapsulated MOF nanomesh biosensor holds great potential in salivary glucose testing and provides a novel strategy for noan‐invasive glucose detection.

In situ generation of turbostratic nickel hydroxide as a nanozyme for salivary glucose sensor.

Among the 3d-transition metal hydroxide series, nickel hydroxide is a well-studied electroactive catalyst. In particular, nickel hydroxide and its composite materials are well-suited for non-enzymatic glucose sensing. The electrocatalytic efficiency of nickel hydroxide is attributed to the thickness or to be precise, the thinness of the electroactive layer. Herein, we have successfully prepared metallic nickel@nickel hydroxide nanosheets through a straightforward one-pot solvothermal method. We were able to electrochemically generate a highly sensitive α-Ni(OH)2 on the nanosheets. The dynamic generation and synergy between α- and β-Ni(OH)2, imparts a glucose oxidase enzyme-like ability to the catalyst. Our proposed nickel nanozyme exhibits a good sensitivity of 683 μA mM-1 cm-2 for glucose. The sensor operates in the range of 0.001-3.1 mM, with a lower limit of detection (LOD) of 9.1 μM and exhibits a response time of ≈00.1 s. Nickel-nanozyme demonstrated better selectivity for glucose in the presence of interfering compounds. Notably, the sensor does not suffer from an interfering oxygen evolution reaction. This greatly improves sensitivity in glucose detection in lower concentrations making the sensor viable to measure salivary glucose levels. In this study, we demonstrate that our sensor can detect glucose in human saliva. The real sample analysis was carried out with saliva samples from three healthy human volunteers and one prediabetic volunteer. Our proposed sensor measurements show excellent agreement with calculated salivary glucose levels with 98% accuracy in sensing glucose in real saliva samples.

Core-shell niobium(v) oxide@molecularly imprinted polythiophene nanoreceptors for transformative, real-time creatinine analysis.

Creatinine, a byproduct of muscle metabolism, is typically filtered by the kidneys. Deviations from normal concentrations of creatinine in human saliva serve as a crucial biomarker for renal diseases. Monitoring these levels becomes particularly essential for individuals undergoing dialysis and those with kidney conditions. This study introduces an innovative disposable point-of-care (PoC) sensor device designed for the prompt detection and continuous monitoring of trace amounts of creatinine. The sensor employs a unique design, featuring a creatinine-imprinted polythiophene matrix combined with niobium oxide nanoparticles. These components are coated onto a screen-printed working electrode. Thorough assessments of creatinine concentrations, spanning from 0 to 1000 nM in a redox solution at pH 7.4 and room temperature, are conducted using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The devised sensor exhibits a sensitivity of 4.614 μA cm-2 nM-1, an impressive trace level limit of detection at 34 pM, and remarkable selectivity for creatinine compared to other analytes found in human saliva, such as glucose, glutamine, urea, tyrosine, etc. Real saliva samples subjected to the sensor reveal a 100% recovery rate. This sensor, characterized by its high sensitivity, cost-effectiveness, selectivity, and reproducibility, holds significant promise for real-time applications in monitoring creatinine levels in individuals with kidney and muscle-related illnesses.

Flexible non-enzymatic glucose strip for direct non-invasive diabetic management

Daily glucose measurements represent the routine practice for monitoring and managing diabetes. Current glucose/sugar analysis is dominated by intrusive finger-prick blood-based methods, which hinder the diabetic community in practical implementations. Nonenzymatic glucose sensors based on transition metals have shown robust glucose analysis performance in non-invasive biofluids. However, transition metals-based nonenzymatic glucose sensors are usually operated in an alkalic medium, thus strictly prohibiting further translational developments. To resolve this issue, we propose a facile strategy to construct flexible nonenzymatic glucose strips (NEGS) for practical, non-invasive glucose analysis. The processed alkaline hydrogel patch was loaded onto the NGS to mimic the electrolyte medium for glucose reaction. The assembled hydrogel patch NEGS could detect glucose levels down to 1 µM, with an excellent linearity response from 10 µM to 3 mM and negligible current responses toward the excessive additions of potential interferences. As a proof of concept, these prepared devices were used for the glucose analysis of real sweat and saliva samples. Additionally, non-invasive biofluids of both healthy and diabetic subjects were synchronously compared, offering new insights into precision diabetic management by directly measuring the glucose levels in the non-invasive biofluidic samples without being cumbersomely correlated to blood glucose.

Deep Learning-Assisted Intelligent Artificial Vision Platform Based on Dual-Luminescence Eu(III)-Functionalized HOF for the Diagnosis of Breast and Ovarian Cancer.

Developing an advanced analytical method to detect spermine (Spm) and N-acetylneuraminic acid (NANA), the biomarkers of breast and ovarian cancers, respectively, is critical for the early diagnosis of the two cancers, which is very meaningful for women's health. Here, a deep learning-assisted artificial vision platform based on a dual-emission ratiometric fluorescence sensor is first constructed to monitor Spm and NANA. The ratiometric fluorescence sensor (Eu@TCBP-HOF, 1) can selectively detect Spm with high sensitivity based on "Turn-on" mode. After adding Spm, the new ratiometric fluorescence sensor (1-Spm, named 2) shows high sensitivity for NANA with "Turn-off" mode. Moreover, the fluorescence sensors can achieve an obvious fluorescence color response to Spm and NANA. Even in real saliva and serum samples, 1 and 2 still show high sensitivity and color responsiveness with limit of detection (LODs) of 0.5 μM for Spm and 0.96 μM for NANA. In virtue of different fluorescence responses, the DenseNet algorithm of deep learning assists the fluorescence sensors, which can simulate the human visual systems to identify fluorescence images and distinguish the concentration of Spm and NANA within 1 s with over 99% recognition accuracy. The intelligent artificial vision platform developed in this work may provide a prospective analytical method for the early diagnosis of female malignant tumors.

A disposable immunosensor for the detection of salivary MMP-8 as biomarker of periodontitis

This work describes the development of a novel voltammetric immunosensor for the detection of salivary MMP-8 at the point-of-care. The electrochemical platform was based on a graphene (GPH) screen-printed electrode (SPE) functionalized by gold-nanospheres (AuNSs) and antibodies against MMP-8 protein (anti-MMP-8). The functionalization with anti-MMP-8 was realized by using 11-mercaptoundecanoic acid (11-MUA), thanks to its ability to give strong sulfur bonds with its –SH end, and to cross-link the –NH2 groups of the antibody molecule with the other –COOH end, using the traditional EDC-NHS method. The voltammetric sensor showed good performances with a linear range of 2.5–300 ng mL−1, a LOD value of 1.0 ± 0.1 ng mL−1 and a sensitivity of 0.05 µA mL cm−2 ng−1. Moreover, the proposed immunosensor was tested in real saliva samples, showing comparable results to those obtained with the conventional ELISA method. The biosensor was single-use and cost-effective and required a small quantity of test medium and a short preparation time, representing a very attractive biosensor for MMP-8 detection in human saliva.

Smart Multiplex Point-of-Care Platform for Simultaneous Drug Monitoring.

Recently, illicit drug use has become more widespread and is linked to problems with crime and public health. These drugs disrupt consciousness, affecting perceptions and feelings. Combining stimulants and depressants to suppress the effect of drugs has become the most common reason for drug overdose deaths. On-site platforms for illicit-drug detection have gained an important role in dealing, without any excess equipment, long process, and training, with drug abuse and drug trafficking. Consequently, the development of rapid, sensitive, noninvasive, and reliable multiplex drug-detecting platforms has become a major necessity. In this study, a multiplex laser-scribed graphene (LSG) sensing platform with one counter, one reference, and three working electrodes was developed for rapid and sensitive electrochemical detection of amphetamine (AMP), cocaine (COC), and benzodiazepine (BZD) simultaneously in saliva samples. The multidetection sensing system was combined with a custom-made potentiostat to achieve a complete point-of-care (POC) platform. Smartphone integration was achieved by a customized application to operate, display, and send data. To the best of our knowledge, this is the first multiplex LSG-based electrochemical platform designed for illicit-drug detection with a custom-made potentiostat device to build a complete POC platform. Each working electrode was optimized with standard solutions of AMP, COC, and BZD in the concentration range of 1.0 pg/mL-500 ng/mL. The detection limit of each illicit drug was calculated as 4.3 ng/mL for AMP, 9.7 ng/mL for BZD, and 9.0 ng/mL for COC. Healthy and MET (methamphetamine) patient saliva samples were used for the clinical study. The multiplex LSG sensor was able to detect target analytes in real saliva samples successfully. This multiplex detection device serves the role of a practical and affordable alternative to conventional drug-detection methods by combining multiple drug detections in one portable platform.

Introduction of graphene oxide-supported multilayer-quantum dots nanofilm into multiplex lateral flow immunoassay: A rapid and ultrasensitive point-of-care testing technique for multiple respiratory viruses.

A lateral flow immunoassay (LFA) biosensor that allows the sensitive and accurate identification of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other common respiratory viruses remains highly desired in the face of the coronavirus disease 2019 pandemic. Here, we propose a multiplex LFA method for the on-site, rapid, and highly sensitive screening of multiple respiratory viruses, using a multilayered film-like fluorescent tag as the performance enhancement and signal amplification tool. This film-like three-dimensional (3D) tag was prepared through the layer-by-layer assembly of highly photostable CdSe@ZnS−COOH quantum dots (QDs) onto the surfaces of monolayer graphene oxide nanosheets, which can provide larger reaction interfaces and specific active surface areas, higher QD loads, and better luminescence and dispersibility than traditional spherical fluorescent microspheres for LFA applications. The constructed fluorescent LFA biosensor can simultaneously and sensitively quantify SARS-CoV-2, influenza A virus, and human adenovirus with low detection limits (8 pg/mL, 488 copies/mL, and 471 copies/mL), short assay time (15 min), good reproducibility, and high accuracy. Moreover, our proposed assay has great potential for the early diagnosis of respiratory virus infections given its robustness when validated in real saliva samples.Electronic Supplementary MaterialSupplementary material (Section S1 Experimental section, Section S2 Calculation of the maximum number of QDs on the GO@TQD nanofilm, Section S3 Optimization of the LFA method, and Figs. S1–S17 mentioned in the main text) is available in the online version of this article at 10.1007/s12274-022-5043-6.

Development of magnetic molecularly imprinted polymers for the extraction of salivary pepsin prior to analysis by a novel HPLC-SEC method

Salivary pepsin is a very important and selective biomarker for gastroesophageal reflux disease and high concentrations in the saliva of potential patients can provide a very useful and non-invasive diagnostic tool. Therefore, this study focused on the development of new and highly selective magnetic molecularly imprinted polymers (MIPs) for the extraction of pepsin from human saliva samples. The developed MIPs provide a stable, cost-effective, and reusable synthetic method of extraction for pepsin. Surface imprinting technique was applied for the synthesis of MIPs to provide a wider surface area and faster binding/release of pepsin, since all the binding sites are allocated on the surface of iron oxide nanoparticles. Methacrylic acid was used as functional monomer, ethylene glycol dimethacrylate as cross linker, and deionised water as a porogen. The imprinting procedure was meticulously optimised to reach the highest possible binding indicated by the value of binding capacity Q which reached (190 mg g−1) and an imprinting factor of 1.34, calculated in comparison to non-imprinted polymers (NIPs). Moreover, the surface morphology, thermal stability as well as the binding properties were characterised to ensure validity. The developed MIPs were applied successfully for dispersive solid phase extraction of pepsin from saliva samples. Consequently, a novel, highly sensitive and simple HPLC-SEC method was developed for the quantitation of pepsin fragments extracted using MIPs. The method was optimised and validated according to ICH guidelines where the linearity ranged from 5 to 150 μg mL−1 in saliva samples with LOD reaching down to 0.6 μg mL−1 which is comparable to the low concentrations of pepsin expected to be found in real saliva samples. The developed system enables the accurate extraction and determination of salivary pepsin with recoveries reaching to 98%. Therefore, this system shows potential as an efficient and reliable testing method for pepsin.

A Novel IMFET Biosensor Strategy for Interleukin‐10 Quantification for Early Screening Heart Failure Disease in Saliva

AbstractWe propose a salivary Interleukin‐10 detection strategy as part of an easily integrable Lab‐on‐Chip and Point‐of‐Care IMFET for multi‐detection Heart Failure (HF) biomarkers. Our developed IMFET showed good linearity between increasing IL‐10 concentration and the charge transfer resistance in both standard solutions and real saliva samples with a LOD of 0.02 pg mL−1. Moreover, the cross‐selectivity study showed that the developed IMFET was highly selective towards IL‐10 against other HF biomarkers. The precision of our IMFET was also evaluated, and the difference between the determined IL‐10 concentration using the standard addition method and its expected one is<20 %.

Fluorescent pH sensing and MnO2 nanosphere directed turn-on sensing of glutathione using pyridoxal 5′-phosphate modified polydopamine nanoparticles

The water-soluble fluorescent organic nanoparticles (PDAPLP NPs) was synthesized by the oxidation of dopamine in the presence of vitamin B6 cofactor pyridoxal 5′-phosphate (PLP). The fluorescent intensity of PDAPLP NPs was quenched in the presence of MnO2 nanospheres due to the energy transfer process occurred from the PDAPLP NPs to MnO2 nanospheres. The fluorescence was restored upon addition of GSH to the PDAPLP_MnO2 nanocomposite due to the redox transformation of Mn(IV) to Mn(II). The fluorescence turn-on response allowed to detect GSH down to 0.31 µM. The developed nanoprobing approach was fast (response time < 2 min), simple and highly selective. The practical utility of the PDAPLP_MnO2 nanoprobe was validated by quantifying GSH in real saliva samples. In addition, the PDAPLP NPs was applied for the fluorescence sensing of pH. The cyan-blue fluorescent PDAPLP NPs between pH 2.0 to 7.0 turned to green-fluorescent above pH 7.0 in the basic pH.