Near-Infrared Fluorescent Single-Walled Carbon Nanotubes for Biosensing

The objective of this article is to provide a comprehensive overview of the recent advancements in biosensing using near-infrared (NIR) fluorescent single-walled carbon nanotubes (SWCNTs). SWCNTs are cylindrical structures formed by rolling up a graphene layer, with their chiral index (n,m) defining their diameter and electronic, mechanical, and optical properties, making them metallic, semimetallic, or semiconducting. The semiconducting variants feature NIR fluorescence, which offers significant advantages for biological imaging and sensing due to deep tissue penetration and minimal background interference. Moreover, SWCNTs are highly photostable, demonstrating resistance to photobleaching and blinking. Owing to these unique optical properties, SWCNTs have been widely used as optical probes for monitoring a broad spectrum of biological analytes, ranging from small molecules to macromolecules. This review explores the photophysics of SWCNTs, their suitability for biosensing, and strategies for developing effective SWCNT-based sensors. This review begins with their photophysical properties, highlighting their relevance to biosensing, followed by key technical concepts. Additionally, biosensing principles, methods for optimizing functionalized SWCNTs, and diverse sensing approaches are also covered. Overall, this review intends to provide a foundational understanding of SWCNT-based biosensing, equipping readers with the knowledge needed to explore and apply these powerful nanomaterials in diverse biosensing applications.