Development of a combined setup for simultaneous detection of total and glycated haemoglobin content in blood samples

AI powered electrochemical multi-component detection of insulin and glucose in serum

Multi-component detection of insulin and glucose in serum is of great importance and urgently needed in clinical diagnosis and treatment due to its economy and practicability. However, insulin and glucose can hardly be determined by traditional electrochemical detection methods. Their mixed oxidation currents and rare involvement in the reaction process make it difficult to decouple them. In this study, AI algorithms are introduced to power the electrochemical method to conquer this problem. First, the current curves of insulin, glucose, and their mixed solution are obtained using cyclic voltammetry. Then, seven features of the cyclic voltammetry curve are extracted as characteristic values for detecting the concentrations of insulin and glucose. Finally, after training using machine learning algorithms, insulin and glucose concentrations are decoupled and regressed accurately. The entire detection process only takes three minutes. It can detect insulin at the pmol level and glucose at the mmol level, which meets the basic clinical requirements. The average relative error in predicting insulin concentrations is around 6.515%, and that in predicting glucose concentrations is around 4.36%. To verify the performance and effectiveness of the proposed method, it is used to determine the concentrations of insulin and glucose in fetal bovine serum and real clinical serum samples. The results are satisfactory, demonstrating that the method can meet basic clinical needs. This multi-component testing system delivers acceptable detect limit and accuracy and has the merits of low cost and high efficiency, holding great potential for use in clinical diagnosis.

New Titanium Dioxide-Based Heterojunction Nanohybrid for Highly Selective Photoelectrochemical-Electrochemical Dual-Mode Sensors

A new titanium dioxide (TiO₂)-based heterojunction nanohybrid (HJNH) composed of TiO₂, graphene (G), poly[3-aminophenylboronic acid] (PAPBA), and gold nanoparticles (Au NPs) was synthesized and designated as TiO₂(G) NW@PAPBA-Au HJNH. The TiO₂(G) NW@PAPBA-Au HJNH possesses dual-mode signal photoelectrochemical (PEC) and electrochemical transduction capabilities to sense glucose and glycated hemoglobin (HbA1c) independently. The synthesis of the HJNH material involved two sequential stages: (i) simple electrospinning synthesis of G-embedded TiO₂ nanowires [TiO₂(G) NWs] and (ii) one-step synthesis of Au NP-dispersed PAPBA nanocomposite (NC) in the presence of TiO₂(G) NWs. The as-synthesized TiO₂(G) NW@PAPBA-Au HJNH was characterized by field emission scanning electron microscopy, field emission transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared, thermogravimetric analysis, and UV-visible diffuse reflectance spectroscopy. A PEC platform was developed with TiO₂(G) NW@PAPBA-Au HJNH for the selective detection of glucose without any enzyme auxiliary. The PEC glucose sensor presents an acceptable linear range (from 0.5 to 28 mM), good sensitivity (549.58 μA mM^-1 cm^-2), and low detection limit (0.11 mM), which are suited for diabetes glucose monitoring. Besides, the boronic acid groups in PAPBA were utilized as a host to capture HbA1c. We fabricated the electrochemical HbA1c sensor based on monitoring the electrocatalytic reduction current of hydrogen peroxide produced by HbA1c tethered to the sensor probe. The amperometric electrochemical sensor for HbA1c exhibited linear responses to HbA1c levels from 2.0 to 10% (with a detection limit of 0.17%). Notably, the performances of the fabricated glucose and HbA1c sensors are superior in the dual-signal transduction modes as compared to the literature, suggesting the significance of the newly designed bifunctional TiO₂(G) NW@PAPBA-Au HJNH.

Current Status of HbA1c Biosensors

Glycated hemoglobin (HbA1c) is formed via non-enzymatic glycosylation reactions at the α–amino group of βVal1 residues in the tetrameric Hb, and it can reflect the ambient glycemic level over the past two to three months. A variety of HbA1c detection methods, including chromatography, immunoassay, enzymatic measurement, electrochemical sensor and capillary electrophoresis have been developed and used in research laboratories and in clinics as well. In this review, we summarize the current status of HbA1c biosensors based on the recognition of the sugar moiety on the protein and also their applications in the whole blood sample measurements.

Magnetite-Quantum Dot Immunoarray for Plasmon-Coupled-Fluorescence Imaging of Blood Insulin and Glycated Hemoglobin

New microarray chip strategies that are sensitive and selective and that can measure low levels of important biomarkers directly in a blood sample are significant for improving human health by allowing timely diagnosis of an abnormal condition. Herein, we designed an antibody-aptamer immunoarray chip to demonstrate simultaneous measurement of blood insulin and glycated hemoglobin (HbA1c) levels relevant to diabetic and prediabetic disorders using a surface plasmon microarray with validation by fluorescence imaging. To accomplish both surface plasmon and fluorescence imaging on the same sample, we decorated magnetite nanoparticles with quantum dots for covalent immobilization of aptamers for subsequent capture and isolation of the aptamers specific for insulin and HbA1c markers from 20-times diluted whole blood samples. Direct clinically relevant analysis, along with fluorescent imaging of the two markers, was achieved by this new immunoarray platform. The limit of detection was 4 pM for insulin and 1% for HbA1c. Examination of cross-talk using thrombin and platelet-derived growth factor confirmed that the designed immunoarray was highly selective for insulin and HbA1c. Surface plasmon kinetic analysis provided apparent binding constants of 0.24 (±0.08) nM and 37 (±3) μM, respectively, for the binding of insulin and HbA1c onto their surface immobilized monoclonal antibodies. Thus, quantitative imaging of ultralow levels of blood biomarker levels with binding kinetics is uniquely obtained in the designed immunoarray chip. In conclusion, this report demonstrates considerable significance of the developed magnetite-quantum dot-bioconjugate strategy for clinical diagnostics of whole blood biomarkers with characterization of molecular binding interactions.

A disposable amperometric dual-sensor for the detection of hemoglobin and glycated hemoglobin in a finger prick blood sample

A disposable microfluidic amperometric dual-sensor was developed for the detection of glycated hemoglobin (HbA_1C) and total hemoglobin (Hb), separately, in a finger prick blood sample. The accurate level of total Hb was determined through the measurements of the cathodic currents of total Hb catalyzed by a toluidine blue O (TBO)-modified working electrode. Subsequently, after washing unbound Hb in the fluidic channel of dual sensor with PBS, the cathodic current by only HbA_1C captured on aptamer was monitored using another aptamer/TBO-modified working electrode in the channel. To modify the sensor probe, poly(2,2´:5´,5″-terthiophene-3´-p-benzoic acid) and a multi-wall carbon nanotube (MWCNT) composite layer (pTBA@MWCNT) was electropolymerized on a screen printed carbon electrode (SPCE), followed by immobilization of TBO for the total Hb probe and aptamer/TBO for the HbA_1C probe, respectively. The characterization of each sensor surface was performed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), quartz crystal microbalance (QCM), field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The experimental conditions affecting the analytical signal were optimized in terms of the amount of TBO, pH, temperature, binding time, applied potential, and the content ratio of monomer and MWCNT. The dynamic ranges of Hb and HbA_1C were from 0.1 to 10µM and from 0.006 to 0.74µM, with detection limits of 82(±4.2)nM and 3.7(±0.8)nM, respectively. The reliability of the proposed microfluidic dual-sensor for a finger prick blood sample (1µL) was evaluated in parallel with a conventional method (HPLC) for point-of-care analysis.

Glycated hemoglobin biosensing integration formed on Au nanoparticle-dotted tubular TiO2 nanoarray

Excessive glucose present in the blood of diabetic patients binds with the hemoglobin of red blood cells resulting in the formation of glycated hemoglobin (HbA_1c). Measurement of HbA_1c levels may help in identifying the efficacy of the ongoing treatment and hence provide a better control over the disease. In the present study, we have synthesized a sensitive and stable scaffold, which consists of Au nanoparticles (GNPs)-dotted tubular TiO₂, for the construction of an electrochemical HbA_1c biosensor. 12-phosphotungstic acid has been used as a reducer after depositing well-dispersed GNPs on TiO₂ nanotubes (TiO₂ NTs) and an electron mediator by accelerating the electron transfer between the conductor and protein. The fabricated electrode was characterized using scanning electron microscopy (SEM), cyclic voltammetry (CV), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopic analysis (EIS). Biosensor exhibited low detection limit (0.5 μM), fast response time (3 s) and wide linearity (from 0.5 to 2000 μM). The working electrode was used 100 times over 4 months, when stored at 4 °C. The HbA1c biosensor was then effectively used to measure the % of HbA_1c in the blood of apparently healthy persons and diabetic patients.

Optical detection of glucose and glycated hemoglobin using etched fiber Bragg gratings coated with functionalized reduced graphene oxide

An enhanced optical detection of D-glucose and glycated hemoglobin (HbA1c ) has been established in this study using etched fiber Bragg gratings (eFBG) coated with aminophenylboronic acid (APBA)-functionalized reduced graphene oxide (RGO). The read out, namely the shift in Bragg wavelength (ΔλB ) is highly sensitive to changes that occur due to the adsorption of glucose (or HbA1c ) molecules on the eFBG sensor coated with APBA-RGO complex through a five-membered cyclic ester bond formation between glucose and APBA molecules. A limit of detection of 1 nM is achieved with a linear range of detection from 1 nM to 10 mM in the case of D-glucose detection experiments. For HbA1c , a linear range of detection varying from 86 nM to 0.23 mM is achieved. The observation of only 4 pm (picometer) change in ΔλB even for the 10 mM lactose solution confirms the specificity of the APBA-RGO complex coated eFBG sensors to glucose molecules.

Upconversion nanoparticle arrays for detecting glycated hemoglobin with high sensitivity and good reusability

Lanthanide-doped upconversion nanoparticles (UCNPs) have attracted extensive interest in bio-applications due to their unique optical properties by converting near infrared excitation to visible emission.

Selective label-free electrochemical impedance measurement of glycated haemoglobin on 3-aminophenylboronic acid-modified eggshell membranes

We propose a novel alternative approach to long-term glycaemic monitoring using eggshell membranes (ESMs) as a new immobilising platform for the selective label-free electrochemical sensing of glycated haemoglobin (HbA1c), a vital clinical index of the glycaemic status in diabetic individuals. Due to the unique features of a novel 3-aminophenylboronic acid-modified ESM, selective binding was obtained via cis-diol interactions. This newly developed device provides clinical applicability as an affinity membrane-based biosensor for the identification of HbA1c over a clinically relevant range (2.3 - 14 %) with a detection limit of 0.19%. The proposed membrane-based biosensor also exhibited good reproducibility. When analysing normal and abnormal HbA1c levels, the within-run coefficients of variation were 1.68 and 1.83%, respectively. The run-to-run coefficients of variation were 1.97 and 2.02%, respectively. These results demonstrated that this method achieved the precise and selective measurement of HbA1c. Compared with a commercial HbA1c kit, the results demonstrated excellent agreement between the techniques (n = 15), demonstrating the clinical applicability of this sensor for monitoring glycaemic control. Thus, this low-cost sensing platform using the proposed membrane-based biosensor is ideal for point-of-care diagnostics.

Recent Progress in Electrochemical HbA1c Sensors: A Review

This article reviews recent progress made in the development of electrochemical glycated hemoglobin (HbA1c) sensors for the diagnosis and management of diabetes mellitus. Electrochemical HbA1c sensors are divided into two categories based on the detection protocol of the sensors. The first type of sensor directly detects HbA1c by binding HbA1c on the surface of an electrode through bio-affinity of antibody and boronic acids, followed by an appropriate mode of signal transduction. In the second type of sensor, HbA1c is indirectly determined by detecting a digestion product of HbA1c, fructosyl valine (FV). Thus, the former sensors rely on the selective binding of HbA1c to the surface of the electrodes followed by electrochemical signaling in amperometric, voltammetric, impedometric, or potentiometric mode. Redox active markers, such as ferrocene derivatives and ferricyanide/ferrocyanide ions, are often used for electrochemical signaling. For the latter sensors, HbA1c must be digested in advance by proteolytic enzymes to produce the FV fragment. FV is electrochemically detected through catalytic oxidation by fructosyl amine oxidase or by selective binding to imprinted polymers. The performance characteristics of HbA1c sensors are discussed in relation to their use in the diagnosis and control of diabetic mellitus.

Bioelectrocatalytic detection of glycated hemoglobin (HbA1c) based on the competitive binding of target and signaling glycoproteins to a boronate-modified surface

We developed an electrochemical glycated hemoglobin (HbA(1c)) biosensor for diagnosing diabetes in whole human blood based on the competitive binding reaction of glycated proteins. Until now, no studies have reported a simple and accurate electrochemical biosensor for the quantification of HbA(1c) in whole blood. This is because it is very difficult to correctly distinguish HbA(1c) from large amounts of hemoglobin and other components in whole blood. To detect glycated hemoglobin, we used electrodes modified with boronic acid, which forms a covalent bond between its diol group and the cis-diol group of the carbohydrate moiety of glycated proteins. For accurate HbA(1c) biosensing, we first removed blood components (except for hemoglobin) such as glycated proteins and blood glucose as they interfere with the boronate-based HbA(1c) competition analysis by reacting with the boronate-modified surface via a cis-diol interaction. After hemoglobin separation, target HbA(1c) and GOx at a predetermined concentration were reacted through a competition onto the boronate-modified electrode, allowing HbA(1c) to be detected linearly within a range of 4.5-15% of the separated hemoglobin sample (HbA(1c)/total hemoglobin). This range covers the required clinical reference range of diabetes mellitus. Hence, the proposed method can be used for measuring %HbA(1c) in whole human blood, and can also be applied to measuring the concentration of various glycated proteins that contain peripheral sugar groups.

A field effect transistor (FET)-based immunosensor for detection of HbA1c and Hb

A field effect transistor (FET)-based immunosensor was developed for diabetes monitoring by detecting the concentrations of glycated hemoglobin (HbA1c) and hemoglobin (Hb). This immunosensor consists of a FET-based sensor chip and a disposable extended-gate electrode chip. The sensor chip was fabricated by standard CMOS process and was integrated with signal readout circuit. The disposable electrode chip, fabricated on polyester plastic board by Micro-Electro-Mechanical-Systems (MEMS) technique, was integrated with electrodes array and micro reaction pool. Biomolecules were immobilized on the electrode based on self-assembled monolayer and gold nanoparticles. Experimental results showed that the immunosensor achieved a linear response to HbA1c with the concentration from 4 to 24 μg/ml, and a linear response to Hb with the concentration from 60 to 180 μg/ml.

[Sensor systems for medical application based on hemoproteins and nanocomposite materials]

Recent advances in nanotechnologies stimulate the development of sensor systems based on nanocomposite materials. This review discusses the prospects and challenges of sensors coupled with functionally important for medicine hemoproteins and nanoscale materials. Authors summarized their own experimental results and literature data on hemoprotein-based sensor systems. Mechanisms and the main function principles of electrochemical nanosensors are also discussed.

Method and apparatus using selected superparamagnetic labels for rapid quantification of immunochromatographic tests

A rapid method and instrumentation for quantification of immunochromatographic tests (ICT) are described. The principle and performance of the method was demonstrated by measuring the levels of human chorionic gonadotropin (hCG) present in urine. The test format was a sandwich assay using two distinct monoclonal antibodies directed against hCG. The first anti-hCG antibody was labeled with superparamagnetic particles whereas the second was immobilized as a narrow detection zone on a porous membrane. The human urine sample was mixed with superparamagnetic particles coated with the first anti-hCG antibody, and the mixture was allowed to migrate past the detection zone containing the second anti-hCG antibody. Capillary forces facilitated migration of the immune complexes along the porous membrane. The amount of superparamagnetic particle-labelled monoclonal anti-hCG bound to the detection zone was directly proportional to the amount of hCG present in the sample as detected by measuring magnetization in the detector coil. The method had a practical detection limit of 20 U/l (54 nM) of hCG per 5 μl of human urine and a linear range of three decades from 20 U/l to 10 000 U/l. In addition, the analysis was completed within less than 10 minutes. Thus, the test format should be suitable for fast detection and monitoring of a large variety of clinically important parameters and analytes.

Selective electrochemical sensing of glycated hemoglobin (HbA1c) on thiophene-3-boronic acid self-assembled monolayer covered gold electrodes

We report a novel concept of sensing glycated hemoglobin, HbA 1c, which is now the most important index for a long-term average blood glucose level, by first selectively immobilizing it on the thiophene-3-boronic acid (T3BA) self-assembled monolayer (SAM)-covered gold electrode by a selective chemical reaction with boronic acid. HbA 1c thus immobilized is then detected by the label-free electrochemical impedance spectroscopic (EIS) measurements with a redox probe, an equimolar mixture of K 3Fe(CN) 6 and K 4Fe(CN) 6, present. The rate of charge transfer between the electrode and the redox probe is shown to be modulated by the amount of HbA 1c in the matrix hemoglobin solution due to the blocking effect caused by the binding of HbA 1c with boronic acid. Both the formation of a well-defined T3BA-SAM on the gold surface and the chemical binding of its boronic acid with HbA 1c in solution were confirmed by quartz crystal microbalance, atomic force microscopy, and EIS experiments.

Surface imprinted beads for the recognition of human serum albumin

The synthesis of poly-aminophenylboronic acid (ABPA) imprinted beads for the recognition of the protein human serum albumin (HSA) is reported. In order to create homogeneous recognition sites, covalent immobilisation of the template HSA was exploited. The resulting imprinted beads were selective for HSA. The indirect imprinting factor (IF) calculated from supernatant was 1.6 and the direct IF, evaluated from the protein recovered from the beads, was 1.9. The binding capacity was 1.4 mg/g, which is comparable to commercially available affinity materials. The specificity of the HSA recognition was evaluated with competitive experiments, indicating a molar ratio 4.5/1 of competitor was necessary to displace half of the bound HSA. The recognition and binding of the imprinted beads was also tested with a complex sample, human serum and targeted removal of HSA without a loss of the other protein components was demonstrated. The easy preparation protocol of derivatised beads and a good protein recognition properties make the approach an attractive solution to analytical and bio-analytical problems in the field of biotechnology.