Study On Thick-Film Based Bio-Chemical Sensor For Blood Analysis

In recent years, micro or small medical devices with high-performance and low-cost have been challenging conventional medical equipments. A new clinical testing mode-the point of care testing (POCT) came into being, because of its portability, easy operation and low cost. POCT is gradually becoming the trend of medical diagnosis. In this thesis, a typical POCT device-- a handheld bio-chemical sensor for blood electrolyte or glucose analysis was studied. It can perform a complete panel of tests, affording facilities for doctors to monitor and diagnose the respiratory status, blood acid-base balance, ion concentration and metabolism of their patients quickly and effectively. The portable blood analyzer has huge social needs and market prospects, particularly suitable for community and rural clinics, field and first aid.Planar all-solid-state sensors based on thick film were developed to measure the concentration of K+, Ca2+, Na+ and pH in human serum. Each sensor consists of an ion-selective electrode and one external reference electrode. Experimentally, the parameters for thick film screen-printing were optimized. Successfully, polyvinyl chloride with neutral carries was formed as solid-state ion selective membrane, after conductive polymer PEDOT(PSS) was coated on the screen-printed carbon electrodes as inner solid-state electrolyte. A structure of external reference electrode similar to the working electrode was innovated to improve the anti-interference performance of the sensors based on the principle of interference potential cancellation. The design also speeded up the sensors to reach steady state. Compared with conventional ion selective electrodes, such planar all-solid-state sensors without liquid part, were easy to store and carry, especially suitable for bedside testing. Lots of clinic trials were carried out to test potassium, calcium, sodium, pH in serum using the sensors developed. The sensitivity, repeatability, reproducibility, stability, and environmental impact of the sensors were explored. The results indicated these four kinds of blood ion. sensors could meet the requirement of clinical diagnosis.Enzyme immobilization is a crucial technology for biosensors using enzymes as sensitive materials. Electrospinning and electropolymerization methods were studied to immobilize glucose oxidase on Pt electrode and screen-printed carbon electrode, respectively. After the processing parameters were optimized, the resulted glucose sensors had low detection limit, good sensitivity and linear detection range, reached the clinical diagnosis requirement. In addition, the effect of carbon nanotubes on sensor response enhancement was studied. Based on PQQ-GDH, a carbon nanotubes modified glucose biosensor was developed. Based on glucose oxidase immobilized by electrospun PANCAA, another carbon nanotubes modified glucose biosensor was developed as well. Based on the experimental results showing that the sensitivity and the electrode reaction rate of the sensors modified by carbon nanotubes are significantly improved, the mechanism of the carbon nanotubes modification was analyzed.