Biocompatible Nanoengineering of Graphene based Materials for Sensor Applications

Personalized healthcare and diagnostics is one of the most active areas of research in both academia and industry. Point-of-care sensing devices for monitoring and regulating from simple ions to large complex molecules are essential in our everyday life. These simple and inexpensive devices permit an individual to perform urgent diagnostic analyses without the need of a professional training or expensive laboratory facilities. Application of these point-of-care sensing devices has the potential to revolutionize the healthcare sectors particularly in developing countries with limited access to modern hightech facilities or in other sectors such as food quality control, forensics and environmental monitoring. Nanomaterials are very promising for the development of these sensing devices. Graphene, an atomically thick layer of graphite, is considered as one of the most fascinating nanomaterials due to its unique physicochemical properties and versatile application potential. The aim of this PhD project is to develop graphene based low cost point-of-care electrochemical sensing devices for a broad range of applications. To maintain the low-cost profile and reduce environmental footprint, we have demonstrated the biocompatible nanoengineering of graphene, which is nanoscale functionalization to improveits biocompatibility, stability and easy processability for the development of chemosensing and biosensing platforms.The first graphene based chemosensing application was graphene biofunctionalized with the small biomolecule dopamine and was used for melamine detection. In the next step, twenty different amino acids were used for the green synthesis of nitrogen doped graphene. Among all twenty aminoacids, lysine was found as the most efficient one and the resulting nitrogendoped graphene was used for dopamine chemosensing. For other graphene based biosensing applications, graphene was first functionalized with a branched polymer to derive a biocompatible graphene matrix for stable accommodation of more complex bio-recognition element such as enzymes. The biocompatible engineered graphene was used for novel glucose biosensing. In the next step, the pre-synthesized biocompatible graphene was functionalized with a redox active molecule, ferrocene. The as synthesized redox active and biocompatible graphene was further functionalized with enzymes and used for glucose and cholesterol biosensing. Finally, the bio-functionalized graphene was step wisely converted to aprintable ink and further used for fabrication of flexible and screen-printedbiosensing devices. The screen printed electrodes were tested for the glucose level measurements in real human serum samples, and found to be closely comparable with the results obtained by the standard clinical methods in a hospital.