Studies On Piezoelectric Immunosensors Based On Nanomaterials And Polyelectrolytes

In this paper,we developed three novel piezoelectric immunosensors by use of polyelectrolytes and nano-particles based on efficient immobilization of biomolecule and signal-amplified methods to improve detection sensitivity and reduce the detection limit. The detailed contents are shown as follows:(1) Polyelectrolytes and the self-assembled technology are combined for a novel biosensing interfacial design applied to an immunosensor for detecting human IgG. The QCM immunosensor as a model transducer was fabricated with poly(allylamine hydrochloride) (PAH) and then with gold nanoparticles resulting in a PAH-gold nanoparticles adsorption procedure for goat-anti-human IgG. The conditions of immobilizing goat-anti-human IgG are optimized. And the results revealed that the proposed procedure was superior to the traditional glutaraldehyde immobilization method. The proposed immunosensor in optimal conditions has a linear detection range of 5-550μg/mL for human IgG detection. Sensors obtained according to the new immobilization procedure exhibit better immunosensing performances including high sensitivity, nonspecific adsorption and favorable operational stability etc. Moreover, the proposed immunosensor has advantage in the simple and advantageous regeneration process. Analytical results indicate that the developed immobilization procedure is a promising alternative for the immobilization of biorecognition element on the electrode surface.(2) A novel biosensing interfacial design strategy has been proposed by the alternate adsorption of the oppositely charged polyelectrolytes. The surface of gold electrode of quartz-crystal microbalance as a model transducer was modified by use of mercaptoacetic acid (MAA) self-assembled monolayer (SAM) and the adsorption multilayers of the oppositely charged polyelectrolytes. MAA-SAM was first applied to the gold electrode surface of the crystal, and the positively charged chitosan was used as a double-sided linker to attach the negatively charged alginate-HSA antibodies to the negatively charged MAA-SAM layer. The assembly process and conditions were studied using the real-time-output device and the surface topologies of gold electrode of the resulting crystals were characterized by atomic force microscopy (AFM) imaging. The proposed immunosensor in optimal conditions has a linear detection range of 12.3-184.5μg/mL for HSA detection. Comparing with the direct immobilization method of antibodies, the immunosensor with the proposed immobilization procedure shows some advantages, such as improved sensitivity due to the well-retained antibody activity and the significantly extended detection range. In particular, the regeneration of the developed immunosensor was simple and fast. Analytical results indicate that the developed immobilization procedure is a promising alternative for the immobilization of biorecognition element on the electrode surface.(3) A piezoelectric immunosensor for detecting human IgG has been prepared, and the procedure is as follows: firstly, 11-thiol is constructed by the self-assembly technique onto a QCM immunosensor; secondly ,a zirconia film is electropolymerized onto the 11-thiol modified QCM immunosensor. These zirconia nanoparticles can largely adsorb goat-anti-human IgG for detecting human IgG.. The effects of experimental conditions such as the concentration of the antibody have been investigated, and the response performances, reproducibility and interferences of the biosensor are also tested. The proposed immunosensor in optimal conditions has a linear detection range of 5-450μg/mL for human IgG detection. The process for preparation zirconia nanopaticles is simple and convenient. Moreover, the proposed immunosensor has advantage in high sensitivity and advantageous regeneration process. It provide a new method for fabricating other immunosensor.