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Abstract: This paper presents a micro multichannel immunosensor for hemoglobin-A1c level determination rapidly and conveniently. The micro immunosensor is composed of an integrated FET sensor chip and a disposable microelectrode-array chip based on CMOS and MEMS technique, respectively. Antibody immobilization methods, such as mixed self-assembled monolayers (SAMs), seed mediated growth nano-gold and nano-gold wrapped with mixed SAMs are studied. The immunosensor fabricated by nano-gold wrapped with mixed SAMs immobilization method shows the highest sensitivity due to the uniform distribution of the nano-golds without aggregation, and the increase of biomolecules amount on the sensitive area of the micro electrode chip. Whole blood samples obtained from hospital were examined using this immunosensor. Relative standard deviation of 2.63% and recovery of 102.54% were achieved. [Copyright &y& Elsevier]

Abstract: 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 60–180μg/ml Hb and 4–18μg/ml HbA1c. The Hb concentration in whole blood samples has also been analysed, with a linear dose–response behavior between 125 and 197μg/ml and a sensitivity of 0.20mVμg−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. [Copyright &y& Elsevier]

Biochemical oxygen demand (BOD) is an international regulatory index for evaluating organic water pollution, which requires to be rapidly detected. In this paper, a microbial electrode for rapid BOD sensing has been developed. Carboxyl graphene (GN-COOH) and Au nanoparticles (AuNPs) have been co-electrodeposited on the electrode and microorganisms ( Bacillus subtilis ) have been immobilized onto the modified electrode through covalent bonding. The modification process has been investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), fluorescence microscope and Fourier transform infrared spectroscopy (FT-IR). The AuNPs with an average particle size of 30 nm are dispersed in the GN-COOH film. The co-electrodeposited film not only facilitates the electron transfer between electrode and reagents, but also creates a biocompatible microenvironment and a rough surface with more sites for cell immobilization. Compared with the traditional BOD electrode including immobilized microbial film and oxygen permselective membrane, the B. subtilis /rGN-COOH-AuNPs/Au electrode simplifies the structure for more effective mass transfer. After modification parameters’ optimization, the response time for detection has been shortened to 3 min. The proposed BOD electrode shows a linear range from 2 to 15 mg/L, indicating its potential in BOD rapid detection. [ABSTRACT FROM AUTHOR]

In this paper, a novel biochemical oxygen demand (BOD) sensor based on a single layer of immobilized microorganisms on electrode for fast detection is investigated. Instead of the previous two-layer structure of oxygen permselective membrane and microorganism membrane, a single layer structure using electrodes as the support for microorganism immobilization has been studied. Amino functional groups on the surface of microorganisms have been bonded with carboxyl modified electrodes. Without extra supports for immobilization, mass transfer resistances are reduced, which facilitates fast current response. B acillus subtilis cells with high biodegradation ability are obtained after 12 h cultivation. The immobilization process has been investigated by CV and EIS. B. subtilis cultivation time, response time and linear range have been optimized. The proposed sensor can reach equilibrium in 5 min which has the advantage for real-time BOD determination in the future. The linear range is 5–30 mg/l with correlation coefficient of 0.978 and limit of detection of 1.65 mg/l. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs) embedded in chitosan (CHI) film, well-dispersed and smaller in size (about 10 nm), were fabricated by one-step electrodeposion on Au microelectrode in solution containing chitosan and chloride trihydrate. The nano-structure CHI-AuNPs composite film offers abundant amine groups, good conductivity, excellent biocompatibility and stability for antibody immobilization. The combination of aflatoxin B 1 (AFB 1 ) with immobilized antibody introduces a barrier to electron transfer, resulting in current decreasement. The morphologies and characterizations of modified microelectrodes were investigated by scanning electron microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Fourier transform infrared spectroscopy (FT-IR). The proposed non-enzyme and label-free immunosensor exhibited high sensitive amperometric response to AFB 1 concentration in two linear ranges of 0.1 to 1 ng mL −1 and 1 to 30 ng mL −1 , with the detection limit of 0.06 ng mL −1 (S/N=3). The immunoassay was also applied for analysis of maize samples spiked with AFB 1 . Considering the sample extraction procedure, the linear range and limit of detection were assessed to be 1.6–16 ng mL −1 and 0.19 ng mL −1 respectively. The simple method showed good fabrication controllability and reproducibility for immunosensor design. [ABSTRACT FROM AUTHOR]