Research Article Open Access Hafaiedh and Abdelghani, J Nanomedic Nanotechnol 2012, 6:2 DOI: 10.4172/2157-7439.1000275 J Nanomedic Nanotechnol ISSN:2157-7439 JNMNT an open access journal Functionalized Nanomaterials: Biomedical and Sensing Applications Keywords: Carboxyl multiwalled carbon nanotubes; Immunosenors; Impedance spectroscopy; Cyclic voltammetry Introduction Owing to their nano-dimensions, rich electronic states, large surface area, high mechanical strength, and excellent chemical and thermal stability, carbon nanotubes have attracted a great deal of interest [1]. Among the many potential applications [1-3], carbon nanotubes have recently become promising functional materials for the development of advanced biosensors [2] and gas sensors [4-6] with novel features. Tere are multiple possibilities for surface modifcation [7] of carbon nanotubes, but functionalization with antibodies has gained signifcant importance in recent years. Antibodies not only provide the required biocompatibility [8] but also alter the electrical and optical properties of nanotubes and make their surface sensitive to surroundings [8,9]. In previous work [10-12], we used carboxyl modifed thiol monolayers for immunosensor applications. We used impedance spectroscopy and quartz microbalance as transduction techniques. Te sample preparation was time consuming and we obtained a higher limit detection [10-12]. In this work, we used carboxyl multiwall carbon nanotubes for immunosensor application. Te obtained carbon nanotubes can be immobilized on gold electrode with the airbrushing technique. Te morphology of the deposited carboxyl carbon nanotubes was observed with Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Te electrochemical characterization of the carboxyl multiwall carbon nanotubes were achieved with cyclic voltammetry and impedance spectroscopy. Te results show that the immunosenosr response depends on the conductivity and the large surface-to-volume ratio attained with multiwall carbon nanotubes. Te response of the developed immunosensor was reproducible, with higher stability and with limit detection of 10 pg/ml antigen. Materials and Methods Reagents 1-ethyl-3-(3-(dimethylamino)-propyl)carbodiimide (EDC), N-hy- droxy succinimide (NHS) (Aldrich) and Albumin from Bovine Serum (BSA) were obtained from sigma Aldrich. Te Goat anti-rabbit IgG and Rabbit IgG were purchased from Pierce Biotechnology. Te MWCNTs (Nanocyl, Belgium) were grown by PVD (Pressure Vapor Deposition) with purity higher than 95%. Nanotubes were upto 50 micrometer in length and their outer and inner diameters ranged from 3 nm to 15 nm and 3 nm to 7 nm, respectively. Te bufer solution used for all experiments was phosphate bufered saline (PBS) containing 140 mM NaCl, 2.7 mM KCl, 0.1 mM Na 2 HPO 4 , 1.8 mM KH 2 PO 4 , pH=7 and the redox couple 3 4 6 6 ( ) / ( ) Fe CN Fe CN − − at a 5 mM concentration. All reagents were of analytical grade and ultrapure water (resistance 18.2 MΩ ․ cm −1 ) produced by a MilliporeMilli-Q system was used. Carboxyl MWCNT synthesis Te MWCNT used in the experiment were obtained from Nanocyl, S.A. Tey were synthesized by chemical vapor deposition and their purity was higher than 95%. Te nanotubes were upto 50 microns in length and their outer and inner diameters ranged from 3 to 15 nm and 3 to 7 nm, respectively. A uniform functionalization with carboxylic group was applied to the as provided carbon nanotubes in order to improve their dispersion and surface reactivity. More details can be found in reference [2]. In the second processing step, the functionalized carbon nanotubes were *Corresponding author: Imene Hafaiedh, Nanotechnology Laboratory, National Institute of Applied Science and Technology centre, Urbain Nord, Bp676, 1080 Charguia Cedex, Tunisia, Tel: +216 703 829; Fax: +216 70 704 329; E-mail: imen_haf@yahoo.fr Received September 26, 2012; Accepted October 16, 2012; Published October 20, 2012 Citation: Hafaiedh I, Abdelghani A (2012) Impedance Spectroscopy of Supported Multiwalled Carbon Nanotubes for Immunosensor Applications. J Nanomedic Nanotechnol 6:275. doi:10.4172/2157-7439.1000275 Copyright: © 2012 Hafaiedh I, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Impedance Spectroscopy of Supported Multiwalled Carbon Nanotubes for Immunosensor Applications Imen Hafaiedh 1 *, Sami Ameur 2 , Adnane Abdelghani 1 1 Carthage University, Nanotechnology Laboratory, National Institute of Applied Science and Technology, centre Urbain Nord, Bp676, 1080 Charguia Cedex, Tunisia 2 University of Sousse, Higher Institute of Agronomic Sciences of Chatt-Meriem, BP 47 ; 4042 Chatt-Meriem, Tunisia Abstract In this work, we used carboxyl multiwall carbons nanotubes for immunosensor application. The carbon nanotubes functionalisation can be achieved with Pressure Vapor Deposition (PVD) technique. The obtained carbon nanotubes can be immobilized on gold electrode with the airbrushing technique. The morphology of the deposited carboxyl carbon nanotubes was observed with Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The electrochemical characterization of the carboxyl multiwall carbon nanotubes was achieved with cyclic voltammetry and impedance spectroscopy. It shows a higher resistance and a good stability in water interface. For anti-rabbit IgG immobilization, the carboxyl carbon nanotubes were activated with EDC/NHS and non-specifc sites was blocked with Bovine Serum Albumin (BSA). The development of immunosensor for IgG detection was observed with the impedance spectroscopy. The results show that the immunosensor response depends on the conductivity and the large surface-to- volume ratio attained with multiwall carbon nanotubes. The response of the developed immunosensor was reproducible, with higher stability and with limit detection of 10 pg/ml antigen. Journal of Nanomedicine & Nanotechnology J o u r n a l o f N a n o m e d i c i n e & N a n o t e c h n o l o g y ISSN: 2157-7439