This book is based mainly on an article entitled ¿An amperometric lactate biosensor based on lactate dehydrogenase immobilized onto graphene oxide nanoparticles modified pencil graphite electrode¿ published in Engineering in life Sciences in 2016. Graphene, a single layer of hexagonal packed carbon atoms, has received increasing attention in recent years. Because of its exceptional electronic, optical, mechanical and thermal properties, graphene has shown great promises for a wide range of applications.The book describes the preparation, characterization, immobilization of graphene oxide nanoparticles (GrONPs) onto pencil graphite electrode their kinetic properties and application in the construction of improved biosensor for determination of lactate in biological materials.The book includes seven chapters beside table of contents. The book is likely to provide valuable information for graduates, post graduates and researchers working in the field of nanotechnology, biosensor technology,biomedical engineering, sports medicine, and food technology.