Jinghong Han

A micro-potentiometric hemoglobin immunosensor based on electropolymerized polypyrrole-gold nanoparticles composite

We report a novel micro-potentiometric hemoglobin (Hb) immunosensor based on electrochemically synthesized polypyrrole (PPy)-gold nanoparticles (AuNPs) composite. PPy-AuNPs film with AuNPs uniformly distributed in it was deposited on gold electrode surface by a simple and direct procedure, without the addition of any nanoparticles or reducing agent. And this generic method makes it possible to deposite different polymers on miniaturized electrodes. With the existence of AuNPs, the antibody immobilization onto the electrode surface was facilitated. Morphology study by field emission scanning electron microscope (FE-SEM) confirms the presence of AuNPs in PPy. Based on an ion-sensitive field-effect transistors (ISFETs) integrated chip, a micro-potentiometric immunosensor for Hb and hemoglobin-A1c (HbA1c) has been constructed. The sensor response was linear over the concentration range 60-180 microg/ml Hb and 4-18 microg/ml HbA1c. The Hb concentration in whole blood samples has also been analysed, with a linear dose-response behavior between 125 and 197 microg/ml and a sensitivity of 0.20 mV microg(-1)ml. The measuring ranges of the developed Hb and HbA1c immunosensors meet the clinical demand for measuring the HbA1c/Hb ratio of 5-20%. This sensor results in simple and rapid differential measurement of Hb and HbA1c, and has great potential to become an inexpensive and portable device for monitoring of diabetes.

A gastroesophageal tract pH sensor based on the H+-ISFET and the monitoring system for 24 h

Abstract This paper presents a gastroesophageal tract pH sensor based on the H+-ISFET and its monitoring system for 24 h. This pH sensor consists of an H+-ISFET, an Ag/AgCl reference electrode and a temperature sensor. The monitoring system consists of two parts: one is a portable dynamically monitor with a microprocessor and a memory. The another is a PC system that analyses the data transmitted from the dynamic monitor, and diagnoses the sickness. The specification of the pH sensor and the monitor, and the measurement results in clinic are reported in this paper.

A silicon-based bulk micro-machined microelectrode biosensor with SU-8 micro reaction pool

A new silicon-based amperometric microelectrode biosensor made with bulk micromachining technology is provided. We designed this new biosensor and fabricated it with anisotropic silicon wet etching technique. P-type silicon wafers, Au and SU-8 are used for making substrate, microelectrode and micro reaction pool respectively. To our knowledge, consecutive platinization and polymerization of pyrrole is firstly used consecutively for microelectrode surface modification. The sensor aims for low unit cost, small dimensions and compatibility with CMOS technology. SU-8 micro reaction pools are made to contain detection solution to reduce reagent volume and unit cost. Bulk micromachining, platinization and polymerization of pyrrole enhance sensitive coefficient, thus helping to miniaturize its dimensions and to reduce unit cost. Using p-type silicon wafers as substrates make compatibility with CMOS technology possible. Successful experimental results have been achieved for glucose detection. Compared to conventional amperometric biosensors and amperometric microelectrode biosensors made with surface micromachining technology, it has several advantages, such as smaller sensing surface area (1 mm /spl times/ 1 mm), lower detection limit (1/spl times/10/sup -4/ M), larger sensitive coefficient (39.640 nA mM/sup -1/ mm/sup -2/), broader linear range (1/spl times/10/sup -4/-1/spl times//sup -2/ M), better replicability (3.2% RSD for five respective detections) and stability (enzyme efficiency remains well above 95% after being stored for a month), easier to be made into arrays and to be integrated with processing circuitry, etc.

Lipid LB films for room temperature ethanol gas assay

Various phospholipids and one fatty acid can be transferred on quartz crystal microbalance (QCM) with vertical lifting method; the transfer of the materials including the subphase solution, surface pressure, speed of dip etc. has been investigated in detail. The response characteristics of QCM deposited with the materials to ethanol gas in room temperature have been analyzed.

Electrochemical synthesis of gold nanoparticles in polypyrrole for antibody immobilization

This paper reports a rapid, simple and direct method for the synthesis of gold nanoparticles (AuNPs) in polypyrrole (PPy) film, which provides a biocompatible matrix for the strong adsorption of antibodies. The electrochemical synthesis of AuNPs/PPy composite on gold or carbon electrode occurs within 20 minutes, and does not involve addition of any nanoparticles or reducing agent. This method is compatible to deposit different polymers on miniaturized electrodes selectively. Antibodies were orientedly immobilized on the AuNPs/PPy composite film in the presence of protein A, which provided an adsorption affinity to the Fc fragment of antibodies. Based on an ion-sensitive field-effect transistors (ISFETs) integrated chip, a label-free micro potentiometric HbA1c immunosensor was constructed. The differential voltage response of the sensor changed linearly with the concentration of HbA1c in the range of 0.5–21 µg/ml, with a sensitivity of 0.19 mV µg−1 ml. The response time was less than 1 min. The sensor has potential use as an inexpensive and portable device for monitoring of diabetes. The developed method can also be used to enhance performances of other immunosensors.

A micro hemoglobin-A1c immunosensor based on FET and electrochemical growth of gold nanoparticles

A micro potentiometric hemoglobin-A1c (HbA1c) immunosensor based on field-effect transistor (FET) and electrochemical growth of gold nanoparticles (AuNPs) in polypyrrole (PPy) film is reported. Integrated ion-sensitive field-effect transistors (ISFETs) chips containing two ISFETs, two reference FETs (REFET) and the signal read-out circuits were fabricated. Micro electrodes of the sensor were fabricated by MEMS techniques and electrochemical method, both compatible with electrode miniaturization. The simple and direct procedure to form PPy-AuNPs composite film enhances the sensitivity of the micro sensor. Electrochemical characterization and morphology study by scanning electron microscopy (SEM) confirm the presence of AuNPs in PPy. Simple, rapid and precise differential measurement of HbA1c is achieved. HbA1c in the concentration ranges of 2-20 ng/ml and 4-15 µg/ml can be detected by this sensor with a response time less than 1 min, which meets the needs of clinical detection of HbA1c. The miniaturized electrodes and integrated ISFET chip have the potential to be integrated and to achieve system on chip (SOC).

Characteristics of the PPy Material as pH Sensitive Membrane

A monolithic pH sensor system has been studied and developed, based on standard CMOS technology. The micro system includes an on-chip integration of differential ISFET/REFET sensing devices, metal constructed pseudo reference electrode (PRE) and their relative signal processing circuits. We mainly present the development of PPy(polypyrrole) membrane by the way of electrochemical polymerization, which was grown on the gate of ISFET, as pH sensitive material. With a series of experiments, a high sensitivity of 56mV/pH was achieved within the pH range from 1 to 12. In the end, we discussed the influence of reagents and polymerization parameters on the pH sensor system.

Fabrication of silicon-based bulk micro-machined amperometric microelectrode biosensor

A new silicon-based bulk micro-machined amperometric microelectrode biosensor, especially its fabrication, is provided. We designed the biosensor and fabricated it with anisotropic silicon wet etching. P-type silicon wafers are used as substrates, and Au and SU-8 are used for making electrodes and micro reaction pools, respectively. To our knowledge, consecutive platinization and polymerization of pyrrole is firstly used for surface modification. Successful experimental results have been achieved for glucose detection. It has several advantages, such as smaller sensitive surface area (1 mm/spl times/1 mm), lower detection limit (1/spl times/10/sup 4/ M), broader linear range (1/spl times/10/sup -4/ -1/spl times/10/sup -2/ M), larger sensitive coefficient (39.640 nA/spl middot/mm/sup -2//sub /spl middot//mM/sup -1/), better replicability (RSD 3.2% for five respective detections) and stability (sensitive coefficient remains well above 95% after being stored in a clean container at room temperature for a month), easier to be made into arrays and to be integrated with processing circuitry, etc.

RESEARCH ON BULK MICRO-MACHINED MICROELECTRODE BIOSENSOR

A new silicon-based amperometric microelectrode biosensor produced using bulk micromachining technology is presented here. Bulk micromachining, platinization and polymerization of pyrrole enhance sensitive coefficient, thus helping to miniaturize its dimensions and reduce unit cost. To our knowledge, platinization and polymerization of pyrrole is first used consecutively for microelectrode surface modification. Successful experimental results have been achieved for glucose detection. Compared to conventional amperometric biosensors and amperometric microelectrode biosensors made with surface micromachining technology, it has several advantages, such as smaller sensing surface area (1 mm × 1 mm), lower detection limit (1×10-4M), larger sensitive coefficient (39.640 nAmM-1mm-2), broader linear range (1 × 10-4-1 × 10-2M), better replicability (3.2% RSD for five respective detections) and stability (enzyme efficiency remains well above 95% after being stored for a month), easier to be made into arrays and to be integrated with processing circuitry, etc.