ORIGINAL PAPER Carbon nanotubes/pentacyaneferrate-modified chitosan nanocomposites platforms for reagentless glucose biosensing A. M. Parra-Alfambra & E. Casero & M. A. Ruiz & L. Vázquez & F. Pariente & E. Lorenzo Received: 14 March 2011 /Revised: 17 May 2011 /Accepted: 19 May 2011 /Published online: 3 June 2011 # Springer-Verlag 2011 Abstract The design, characterization and applicability of a nanostructured biosensor platform are described. The biosen- sor is developed through the immobilization of three components: a polymeric chitosan network previously mod- ified with a redox mediator (denoted as PCF-Pyr-Ch), an enzyme (glucose oxidase, chosen as a model) and carbon nanotubes onto a solid glassy carbon electrode (C). In order to assess the influence of the nanomaterial in the performance of the resulting analytical device, a second biosensor, free of carbon nanotubes, is developed. The characterization of both biosensing platforms was performed in aqueous phosphate buffer solutions using atomic force microscopy technique. In the presence of glucose, both systems exhibit a clear electro- catalytic activity, and glucose could be amperometrically determined at +0.35 V versus Ag/AgCl. The performance of both biosensors was evaluated in terms of sensitivity, detection limit and linear response range. Finally, the enhancement of the analytical response induced by the presence of carbon nanotubes was evaluated. Keywords Carbon nanotubes . Chitosan . Glucose oxidase . Reagentless electrochemical biosensor . AFM Introduction The development of bioanalytical platforms based on enzyme immobilization onto transducer surfaces in such a way that they retain their full activity and stability has become one of the most important issues in the field of bionanotechnology. Since the immobilization process implies an intimate contact between the enzyme and the solid surface, an alteration of the three-dimensional confor- mation of the enzyme can be induced, leading to a diminution of the catalytic activity that hinders the enzyme functionality. Moreover, a second inconvenience derived from the immobilization process is that the direct electron transfer between the immobilized enzyme and the trans- ducer is hindered due to the redox centre being usually buried into the three-dimensional structure of the enzyme. Although one of the most important approaches reported in the literature to solve this problem is the employment of a redox mediator in solution, the operational simplicity of the resulting analytical device is reduced. In order to overcome this drawback, a good alternative is to incorporate the redox mediator into the transducer, leading to the development of reagentless enzyme electrochemical biosensors. In the last years, the use of nanomaterials in the development of electrochemical biosensors has received considerable attention as a strategy to promote the electron transfer between the enzyme and the transducer. In particular, the employment of carbon nanotubes is very adequate because they have shown excellent electrocata- lytic properties leading to the improvement of (bio)sensor performance [1–3]. Recent studies have shown that chitosan, a positively charged polysaccharide, displays excellent properties to be used as a polymeric network for engineering the different biosensor compounds onto a transducer, leading to an A. M. Parra-Alfambra : E. Casero : M. A. Ruiz : F. Pariente : E. Lorenzo (*) Departamento de Química Analítica y Análisis Instrumental and IMDEA Nanociencia, Facultad de Ciencias, c/Francisco Tomás y Valiente, No. 7, Campus de Excelencia de la Universidad Autónoma de Madrid, 28049 Madrid, Spain e-mail: encarnacion.lorenzo@uam.es L. Vázquez Instituto de Ciencia de Materiales de Madrid (CSIC), c/Sor Juana Inés de la Cruz No. 3, Campus de Excelencia de la Universidad Autónoma de Madrid, 28049 Madrid, Spain Anal Bioanal Chem (2011) 401:883–889 DOI 10.1007/s00216-011-5128-7