Electrochemical Biosensors based on Novel Receptors for Diabetes Management

Abstract

To address the challenge of accurate, low cost and robust biosensors for diabetes management and early detection of diabetes complications, we have developed novel, robust sensing chemistry (or receptors) for electrochemical POC biosensors. The biosensors have been developed for the bio-markers associated with diabetes management such as glycated haemoglobin (HbA1c), glycated albumin, glucose, biomarkers associated with diabetes complications such as microalbuminuria, urine creatinine and albumin-to-creatinine ratio (ACR) and biomarkers associated with anaemia and malnutrition conditions such as haemoglobin and serum albumin. For haemoglobin detection, a new POC bio sensing technique has been developed based on Aza-heterocyclic chemicals. The repeatability and accuracy of the biosensor have been tested on real pathology samples. The glycated form of haemoglobin, called glycated haemoglobin or HbA1c, is the gold standard test in diabetes management as it gives the 90-days average blood glucose value. We demonstrate a simple method for electrochemical detection of HbA1c by combining bosonic affinity principle along with aza-heterocyclic receptors. The technique has been verified on the real clinical patient samples. Albumin is the most abundant protein in the human blood. Human serum albumin (HSA) is either alone or an associative biomarker in several chronic diseases like necrosis, nephrosis, hepatitis, malnutrition, arthritis, immune disorders, cancer, diabetes and in some severe infections. In pathology laboratories, the serum albumin is usually tested on serum samples and not in whole blood samples. Since albumin is not a metalloproteinase, it is very difficult to develop electrochemical POC biosensor. We have developed a novel technique for the electrochemical detection of serum albumin in whole blood samples, by exploiting its binding property with redox active copper salts. The accuracy of technique has been verified on both real human blood plasma as well as whole blood samples. Glycated albumin, which is the glycated form of serum albumin, is emerging as a novel biomarker for diabetes management, as it gives the average blood glucose value of 15-20 days. It is also extremely useful in chronic kidney disease patients and patients with hemoglobinopathies where HbA1c can give the erroneous results. By combining the copper chemistry along with bosonic affinity principle, we present the first ever demonstration of glycated albumin sensing. Instant blood glucose monitoring is an integral part of diabetes management. Most of the glucometers available in the market are based on glucose oxidase enzyme. We have demonstrated a low cost non-enzymatic electrochemical technique for blood glucose detection using alkaline methylene blue chemistry. The accuracy of the technique has been verified on real human blood plasma samples. Glucometer is one of the most easily available POC biosensor and a useful tool for diabetes population. India has second largest diabetes population in the world. To analyse the accuracy of the POC glucometers which are available in Indian market, a comprehensive study was conducted. The results were compared with clinical accuracy guidelines using exhaustive statistical analysis techniques. The shortcomings of the commercial glucometers are elucidated, regarding different international standards. Diabetic nephropathy is one of the major diabetes complications and is the primary cause of chronic kidney disease (CKD). The presence of albumin in urine is a well-established biomarker for the early detection of diabetic nephropathy. We have developed a technique for electrochemical detection of microalbuminuria for point of care applications by exploring the binding property of human albumin with electrochemically active molecules like copper and hemin. Methylene blue mediated sensing technique has also been proposed. Urine Albumin-to creatinine ratio (ACR) is another variant of the microalbumuria test that can be done any time and does not suffer from the dilution factor of urine. Iron binding property of creatinine is exploited to develop creatinine biosensor, thus enabling POC ACR tests.