Chapter 17 - Fundamentals of health, safety, and regulation issues of carbon nanomaterial-based sensors

Abstract

Carbon nanomaterials (CNMs) such as graphene (GRA), carbon nanotubes (CNTs), and fullerenes are allotropes of carbon. CNMs possess exceptional mechanical, thermal, chemical, and optical properties. GRA is made up of a single layer of sp2-bonded carbon atoms arranged in a honeycomb-like lattice. GRA has excellent electrical conductivity and mechanical strength. GRA and its derivatives such as graphene oxide (GO), reduced graphene oxide (RGO), GRA nanoribbons are widely used in various electronic devices, batteries, and sensors. Fullerenes possess a three-dimensional closed mesh-like structure. Fullerenes are used in electronic devices, photocatalysis, and biomedical applications. Among the various CNMs, carbon nanotubes (CNTs) are unique and are widely used in various applications ranging from architecture to medicine. CNTs are typically graphene sheets rolled up into cylinders. CNTs are divided into two types: CNTs with single layers are called single-walled carbon nanotubes (SWCNTs) and CNTs with two are more layers are called multiwalled carbon nanotubes (MWCNTs). CNTs exhibit unique electronic and optical properties.There is a great deal of interest to use CNTs in sensing and biomedical fields due to their small size that can be comparable to cellular organelles. Due to their extremely small size, CNTs can be used inside the cells without much perturbation to vital cellular components. CNTs emit highly photostable near-infrared (NIR) photoluminescence that is sensitive to local environment. Due to their unique optical properties, CNTs are widely used in biosensing and medical imaging applications. Even though biosensing and imaging research is dominated by a wide variety of fluorescent dyes, fluorescent materials, quantum dots, and conjugated polymer nanoparticles, extensive research efforts are underway to develop CNM-based biosensors and imaging reagents. As a result, a wide variety of sensors for various analytes and imaging agents to target various cellular organelles and processes have already been developed based on CNMs in general and CNTs in particular. For example, CNTs such as SWCNTs are successfully used in DNA sensing through surface functionalization of SWCNTs with complementary oligonucleotides. CNTs functionalized with short DNA oligonucleotide were used as lipid reporters to probe the lipid flux in lysosomes. Functionalized CNTs are also used for targeted imaging and therapeutic applications. With the recent developments in fluorescence imaging in the second near-infrared window (NIR II), CNTs have become a hot research topic to develop various NIR II imaging agents for potential biomedical applications. On the contrary, CNTs are extensively used to develop electrochemical sensors for various analytes having biological and medical significance.