Magnetic Optical Microarray Imager for Diagnosing Type of Diabetes in Clinical Blood Serum Samples

A versatile bioelectronic interface programmed for hormone sensing

Precision medicine requires smart, ultrasensitive, real-time profiling of bio-analytes using interconnected miniaturized devices to achieve individually optimized healthcare. Here, we report a versatile bioelectronic interface (VIBE) that senses signaling-cascade-guided receptor-ligand interactions via an electronic interface. We show that VIBE offers a low detection limit down to sub-nanomolar range characterised by an output current that decreases significantly, leading to precise profiling of these peptide hormones throughout the physiologically relevant concentration ranges. In a proof-of-concept application, we demonstrate that the VIBE platform differentiates insulin and GLP-1 levels in serum samples of wild-type mice from type-1 and type-2 diabetic mice. Evaluation of human serum samples shows that the bioelectronic device can differentiate between samples from different individuals and report differences in their metabolic states. As the target analyte can be changed simply by introducing engineered cells overexpressing the appropriate receptor, the VIBE interface has many potential applications for point-of-care diagnostics and personalized medicine via the internet of things.

Ultrasensitive quantum dot-coupled-surface plasmon microfluidic aptasensor array for serum insulin detection

Monitoring insulin levels in complex clinical matrices such as serum, holds immense importance in diagnosing type of diabetes. The present study reports the development of surface plasmon resonance aptamer based insulin sensor array in a four-channel microfluidic format which utilizes antibody attached to magnetic nanoparticles for capturing insulin from diabetic patient serum samples and surface immobilized plasmon enhancing quantum dots for signal amplification. The aptasensor gives minimal non-specific binding due to the immobilization of high molecular weight dendrimers on a cysteamine monolayer. The aptamer-insulin-antibody sandwich microarray monitors insulin levels in two-fold diluted serum and offers a detection limit 800 fM with a linear dynamic range 0.8-250 pM. Its clinical applicability on measuring serum insulin levels in 24 diabetic patient samples and correlation with ELISA is demonstrated.

Magnetic Particle Bioconjugates: A Versatile Sensor Approach

: Nanomaterial biosensors have revolutionized the entire scientific, technology, biomedical, materials science, and engineering fields. Among all nanomaterials, magnetic nanoparticles, microparticles, and beads are unique in offering facile conjugation of biorecognition probes for selective capturing of any desired analytes from complex real sample matrices (e.g., biofluids such as whole blood, serum, urine and saliva, tissues, food, and environmental samples). In addition, rapid separation of the particle-captured analytes by the simple use of a magnet for subsequent detection on a sensor unit makes the magnetic particle sensor approach very attractive. The easy magnetic isolation feature of target analytes is not possible with other inorganic particles, both metallic (e.g., gold) and non-metallic (e.g., silica), which require difficult centrifugation and separation steps. Magnetic particle biosensors have thus enabled ultra-low detection with ultra-high sensitivity that has traditionally been achieved only by radioactive assays and other tedious optical sources. Moreover, when traditional approaches failed to selectively detect low-concentration analytes in complex matrices (e.g., colorimetric, electrochemistry, and optical methods), magnetic particle-incorporated sensing strategies enabled sample concentration into a defined microvolume of large surface area particles for a straightforward detection. The objective of this article is to highlight the ever-growing applications of magnetic materials for the detection of analytes present in various real sample matrices. The central idea of this paper was to show the versatility and advantages of using magnetic particles for a variety of sample matrices and analyte types and the adaptability of different transducers with the magnetic particle approaches.

Towards Point-of-Care Insulin Detection

Good glucose management through an insulin dose regime based on the metabolism of glucose helps millions of people worldwide manage their diabetes. Since Banting and Best extracted insulin, glucose management has improved due to the introduction of insulin analogues that act from 30 minutes to 28 days, improved insulin dose regimes, and portable glucose meters, with a current focus on alternative sampling sites that are less invasive. However, a piece of the puzzle is still missing-the ability to measure insulin directly in a Point-of-Care device. The ability to measure both glucose and insulin concurrently will enable better glucose control by providing an improved estimate for insulin sensitivity, minimizing variability in control, and maximizing safety from hypoglycaemia. However, direct detection of free insulin has provided a challenge due to the size of the molecule, the low concentration of insulin in blood, and the selectivity against interferants in blood. This review summarizes current insulin detection methods from immunoassays to analytical chemistry, and sensors. We also discuss the challenges and potential of each of the methods towards Point-of-Care insulin detection.

Electrochemical and surface plasmon insulin assays on clinical samples

Diabetes is a complex immune disorder that requires extensive medical care beyond glycemic control. Recently, the prevalence of diabetes, particularly type 1 diabetes (T1D), has significantly increased from 5% to 10%, and this has affected the health-associated complication incidences in children and adults. The 2012 statistics by the American Diabetes Association reported that 29.1 million Americans (9.3% of the population) had diabetes, and 86 million Americans (age ≥20 years, an increase from 79 million in 2010) had prediabetes. Personalized glucometers allow diabetes management by easy monitoring of the high millimolar blood glucose levels. In contrast, non-glucose diabetes biomarkers, which have gained considerable attention for early prediction and provide insights about diabetes metabolic pathways, are difficult to measure because of their ultra-low levels in blood. Similarly, insulin pumps, sensors, and insulin monitoring systems are of considerable biomedical significance due to their ever-increasing need for managing diabetic, prediabetic, and pancreatic disorders. Our laboratory focuses on developing electrochemical immunosensors and surface plasmon microarrays for minimally invasive insulin measurements in clinical sample matrices. By utilizing antibodies or aptamers as the insulin-selective biorecognition elements in combination with nanomaterials, we demonstrated a series of selective and clinically sensitive electrochemical and surface plasmon immunoassays. This review provides an overview of different electrochemical and surface plasmon immunoassays for insulin. Considering the paramount importance of diabetes diagnosis, treatment, and management and insulin pumps and monitoring devices with focus on both T1D (insulin-deficient condition) and type 2 diabetes (insulin-resistant condition), this review on insulin bioassays is timely and significant.

Combined covalent and noncovalent carboxylation of carbon nanotubes for sensitivity enhancement of clinical immunosensors

We report here for the first time with quantitative details that the combination of pi-pi stacking of pyrenecarboxylic acid with chemically carboxylated multiwalled carbon nanotubes (MWNT-COOH) offers superior sensitivity compared to MWNT-COOH alone for serum insulin measurements and that this combination is broadly applicable for biosensors, drug delivery, and catalytic systems.

Epitope-Resolved Detection of Peanut-Specific IgE Antibodies by Surface Plasmon Resonance Imaging

Peanut allergy can be life-threatening and is mediated by allergen-specific immunoglobulin E (IgE) antibodies. Investigation of IgE antibody binding to allergenic epitopes can identify specific interactions underlying the allergic response. Here, we report a surface plasmon resonance imaging (SPRi) immunoassay for differentiating IgE antibodies by epitope-resolved detection. IgE antibodies were first captured by magnetic beads bearing IgE ϵ-chain-specific antibodies and then introduced into an SPRi array immobilized with epitopes from the major peanut allergen glycoprotein Arachis hypogaea h2 (Ara h2). Differential epitope responses were achieved by establishing a binding environment that minimized cross-reactivity while maximizing analytical sensitivity. IgE antibody binding to each Ara h2 epitope was distinguished and quantified from patient serum samples (10 μL each) in a 45 min assay. Excellent correlation of Ara h2-specific IgE values was found between ImmunoCAP assays and the new SPRi method.

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.

Magnetic paper – based ELISA for IgM-dengue detection

“Magnetic Paper – Based ELISA” for IgM-dengue antibodies detection provide a system with improved analytical response.