Graphene-based nanostructures from green processes and their applications in biomedical sensors

Graphene has unusual physical properties such as high thermal and electrical conductivity, high elasticity, and unique optical properties, making it suitable for a variety of biomedical applications in biosensing and drug delivery. Nanostructures of graphene and graphene derivatives have been fabricated and applied to different types of biosensors. In this article, we have reviewed recent advances in the fabrication of graphene-and graphene-derivatives-based nanomaterials, with a particular focus on green processes for producing bio-based graphene nanostructures. The various methods used to synthesize a few layers of graphene sheets, including the top-down and bottom-up approaches, have been thoroughly discussed. The benefits of using those green processes and current challenges are analyzed. We also discussed the applications of these nanomaterials in biomedical sensors. Current reviews for graphene-based nanostructures in biomedical sensors provide brief summaries of current technologies. We have reviewed current state-of-the-art graphene-based biosensors and provided an in-depth summary of their working mechanism and use of graphene nanomaterials to enhance their sensitivities. We have grouped these sensors based on their working principles, such as optical and electrochemical sensors for detecting and quantifying a variety of biomolecules and cells. The performance of the graphene nanomaterial-based biosensors have been compared with conventional biosensing techniques, and their pros and cons are discussed. We concluded the article by summarizing our findings, discussing current challenges, and outlining the future directions of using graphene-based nanostructures for biosensing applications.