Amperometric Immunosensor Based on a Protein A/Deposited Gold Nanocrystals Modified Electrode for Carbofuran Detection

In this paper, an amperometric immunosensor modified with protein A/deposited gold nanocrystals (DpAu) was developed for the ultrasensitive detection of carbofuran residues. First, DpAu were electrodeposited onto the Au electrode surface to absorb protein A (PA) and improve the electrode conductivity. Then PA was dropped onto the surface of DpAu film, used for binding antibody Fc fragments. Next, anti-carbofuran monoclonal antibody was immobilized on the PA modified electrode. Finally, bovine serum albumin (BSA) was employed to block the possible remaining active sites avoiding any nonspecific adsorption. The fabrication procedure of the immunosensor was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), respectively. With the excellent electroconductivity of DpAu and the PA’s oriented immobilization of antibodies, a highly efficient immuno-reaction and detection sensitivity could be achieved. The influences of the electrodeposition time of DpAu, pH of the detection solution and incubation time on the current response of the fabricated immunosensor were investigated. Under optimized conditions, the current response was proportional to the concentration of carbofuran which ranged from 1 to 100 ng/mL and 100 ng/mL to 100 μg/mL. The detection limit was 0.1924 ng/mL. The proposed carbofuran immnuosensor exhibited high specificity, reproducibility, stability and regeneration performance, which may open a new door for ultrasensitive detection of carbofuran residues in vegetables and fruits

Towards rapid electrochemical test system of polyanilino-laccase-on-gold enzyme nanobiosensor for water estrogens

>Magister Scientiae - MScCurrent water treatment technologies do not remove many endocrine disruptor compounds (EDCs) such as 17α-ethynylestradiol (EE2) in its entirety, and the amount of these pollutants that continues to enter the aquatic environment through wastewater effluents is still capable of causing harmful health effects. Therefore the development of simpler and more sensitive biosensor system for detection of EE2 must be developed which have high responsiveness, low cost and easy handling. Therefore the aim of this study was to work towards the development of rapid test system of polyaniline-laccase on gold enzyme nanobiosensor (PANI-PSSA/Lac/Glu) for water estrogens. Preliminary studies were first done on the materials used in this study: estrogens, laccase, gold nanoparticles (AuNPs), and electropolymerized PANI-PSSA. Laccase was shown to be active towards EE2 and the enzyme could be stored for over three months. EE2 solution also could be used for over three months. Buffer used in this study was found to be suitable. Phosphoric acid (H3PO4) was a suitable electrolyte than hydrochloric acid (HCl) to be used for the electropolymerization of aniline and was used because it has same ions as the McIlvaine buffer (McIlB) which the post-deposition CVs indicated the formation of electrochemically very stable film. AuNPs were successfully synthesized and its size was identified to be less than 22 nm. McIlB used for testing electrochemical properties of AuNP. CVs of GC/PANI-PSSA and GC/PANIPSSA/ Au showed no difference before and after exposure to aq. EE2 solution, an indication of being re-usable and could also serve as stable immobilising platform in laccase biosensor. When interrogating with electrochemical impedance spectroscopy (EIS), the charge transfer resistance (Rct) of both GC/PANI-PSSA and GC/PANI-PSSA/Lac/Glu showed an average increase by about 2.4% and 21% before and after exposure of EE2, respectively. This shows that the GC/PANI-PSSA/Lac/Glu was a functional EE2 biosensor and showing a positive step towards achieving a re-usable biosensor for EE2 as a model water estrogen. Future work Page | vi will focus on exploring different ways of improving the biosensor’s surface regeneration and its sensitivity to EE2

Desenvolvimento de imunossensor eletroquímico para a detecção de Salmonella sp. em leite a partir da goma do cajueiro carboximetilada.

Tese (Doutorado em Biotecnologia) - Rede Nordeste de Biotecnologia, Universidade Estadual do Ceará, Fortaleza. Co-orientadora: Roselayne Ferro Furtad

Biological Monitoring of Oxygen and Nitric Oxide: The Development and Characterisation of Real-Time Microelectrochemical Sensors.

The main aims of this thesis were to develop and characterise monomer modified oxygen (O2) sensors that could withstand the harsh setting of an in-vivo environment, without the risk of alteration of the sensor components and the characterisation of nitric oxide (NO) sensors in-vitro, followed by the complete in-vivo characterisation under physiological conditions. The main result sought after for development of these novel O2 sensors, was the potential utilisation in a clinical setting. Chapter 1 introduces the background behind the monitoring of NO and O2 in the brain, the biosynthesis of NO in the brain, the biosynthesis of NO through the N-methyl-D-aspartate receptor (NMDA) and the potential role of NO in neurovascular coupling. Chapter 2 discusses the theory behind the project and Chapter 3 describes the experimental protocols utilised throughout this research. Chapter 4 discusses the development and characterisation of the monomer modified O2 sensors. The subsequent characterisation of the novel O2 sensors in-vivo is discussed in Chapter 5. The use of various perturbations to alter the O2 concentration for characterisation of the O2 sensors is described. The characterisation of the NO sensor types (Type 2 and Type 3 NO sensor) is discussed in Chapter 6, with response times, sensitivity and selectivity discussed in detail. The subsequent characterisation of these sensors in-vivo is described in Chapter 7. Systemic and local administrations of various inducers and inhibitors of nitric oxide synthesis were carried out to determine the sensors viability in monitoring the analyte in a physiological environment. In Chapter 8, another aspect of this research involving the simultaneous recording of the NO and O2 analytes in-vivo is described, which utilises a combination of the styrene modified carbon paste electrodes (SMCPEs) and methyl methacrylate modified carbon paste electrodes (MMCPEs) for the detection of O2 and the Type 2 and Type 3 sensors for the detection of NO. These results yield valuable information about the possible relationship between the two molecules. The final chapter (Chapter 9) details a summary of all of the chapters and concludes with a final discussion on the results attained