[Frontiers in Bioscience, Elite, 5, 622-642, January 1, 2013] 622 Role of nanostructured networks as analytical tools for biological systems Prem Chandra Pandey*, Dheeraj Singh Chauhan, Vandana Singh Department of Applied Chemistry, Institute of Technology, Banaras Hindu University, Varanasi-221005, India TABLE OF CONTENTS 1. Abstract 2. Introduction 3. Types of nanostructured networks 3.1. Organically modified silicates 3.2. Nanostructured polymers 3.3. Nanocrystalline metal oxides 3.4. Composite nanostructures 4. Properties of nanostructured networks for application in sensor devices 4.1. Effect of size 4.2. Surface area 4.3. Porosity 4.4. Biocompatibility 4.5. Catalytic activity 4.6. Electrical conductivity 5. Role of nanostructured networks in sensor development 5.1. Amperometric sensors 5.2. Potentiometric sensors 5.3. Conductometric sensors 6. Critical biosensors based on nanostructured networks 6.1. Glucose biosensors 6.2. Cholesterol biosensors 6.3. Urea biosensors 6.4. Lactate biosensors 6.5. DNA biosensors 6.6. Immunosensors 7. Conclusions and future prospects 8. Acknowledgements 9. References 1. ABSTRACT In recent years, nanostructured materials have emerged as potential candidates offering excellent prospects for interfacing the detection of biomolecules. Nanomaterials such as nanoparticles, nanostructured silicates, nano-sized metal oxides, nanostructured polymers, quantum dots, nanocomposites and sensing nanodevices are being utilized worldwide for fabrication of chemical sensors and sensor arrays with tailored characteristics and tuneable properties. Among above, the materials that create a matrix structure at the nanoscale level are particularly fascinating. The exceptional physical, chemical, mechanical and electrical properties of these matrices advocate their application in the electrode modification resulting in sensing devices and transducers with superior performance. Here we present an overview of different types of nanostructured networks that are applied in sensor development. The role of these materials in chemical sensors is described along with the techniques that are the backbone of the sensing process. Special attention has been given to some key sensors that are directly related to human physiology and have clinical significance. 2. INTRODUCTION The potential of nanostructured domain is increasingly recognized by the scientific society and the technological world. The same is corroborated with exponential rise in the number of research publications in this area. In addition, across the globe the biological, physical, chemical, engineering and materials science communities and government bodies have been organizing workshops, meetings and conferences around various aspects of research in nanoscience with increasing frequency. The exciting properties of nanomaterials present these systems as components of optical (1), electrical (2-4), electrochemical (5,6) and catalytic sensors and devices (7,8). Nanomaterials can be broadly classified into nanostructured and nanophase/nanoparticle materials. The former refer to condensed bulk materials made up of grains with grain sizes in the nanometer range, whereas the latter are usually the dispersive nanoparticles. The nanometer size here covers a wide range which can be as large as 100- 200 nm. Nanoparticles of noble metals, polymers, metal oxides etc. are of immense interest due to their chemical,