# Carbon Nanoparticles and Their Biomedical Applications
###### Abstract  
This review summarizes the current knowledge on current and future applications of carbon nanoparticles in medicine. The carbon nanoparticle family has a large number of representatives with unique physicochemical properties that make them good candidates for use in clinical medicine. The best-known (and most researched) carbon nanoparticles include graphene, graphene oxide, and carbon nanotubes. The main direction of use involves medical diagnostics, which includes bioimaging and the detection of chemicals or metabolites present in the body. Since the question of nanoparticle toxicity has not been fully answered, the use of nanoparticles in the fields of therapeutics (drug delivery), regenerative medicine (cell scaffolding, tissue engineering), and vaccine production is still under research and many in vivo studies are ongoing. These preclinical studies suggest that carbon nanoparticles have great potential for diagnosis and treatment; the results show that the nanoparticles used do not have significant toxic effects; however, great caution is needed before nanoparticles are introduced into routine clinical practice.  
carbon nanoparticles; graphene; MWCNT; biomedical applications; diagnostic; therapy +
Footnote †: journal: Medical Imaging  
from its derivates, by unzipping carbon nanotubes or via the evaporation of fullerene [8]. The most commonly used graphene derivatives, graphene oxide (GO) and reduced GO (rGO), are prepared by the oxidation of graphene. In these processes, graphene is treated with oxidizing agents: protonated solvents (nitric, sulfuric, or phosphoric acid, or their mixtures) and KMnO4, resulting in the formation of a covalent bond of carboxyl and hydroxyl groups to graphene. To form rGO, a reduction is then carried out in which most of the oxygen functional groups are removed by various processes, including treatment with vitamin C or hydrazine hydrate [9; 10].  
Carbon nanotubes (CNTs) are nanoparticles that have cylindrical tubular structures with a diameter of nanometers and are formed by rolling graphene sheets. CNTs are divided into single-walled CNTs and multi-walled CNTs according to the number of layers of graphene sheets [11].  
The most frequent methods of synthesizing carbon nanotubes involve chemical vapor deposition (CVD), arc discharge, and pulsed laser ablation. The CVD is performed using carbon-containing precursor gases, such as CO\({}_{2}\) or C\({}_{2}\)H\({}_{2}\), C\({}_{2}\)H\({}_{4}\), and other hydrocarbons. The temperature during CVD moves around 350-1000 \({}^{\circ}\)C. Various parameters, such as the reaction time, temperature, catalyst particle size, or type/velocity of the reaction gas affect the growth of CNTs [12]. The arc discharge method is based on the use of two graphite rods, which are used as cathode and anode electrodes. The direct current arc voltage is subsequently applied across the electrodes immersed in an inert gas (helium). During this method, fullerenes and CNTs are synthesized. Fullerenes are deposited as soot inside the chamber and multi-walled carbon nanotubes are deposited on the cathode [13]. Pulsed laser ablation of graphite is a very promising method. It is fast and inexpensive, does not require the use of a catalyst or vacuum, and produces a high purity product of the desired size and morphology [14].  
CNPs have found widespread use in various industries, including electronics, agriculture, food, pharmaceuticals, cosmetics, and medicine. In particular, carbon nanomaterials have many potential biomedical applications, including imaging, biosensors, anticancer drugs, drug delivery vehicles, and bioengineering [15; 16]. In this review, we focused on the use of various types of CNPs in different fields of medicine (Figure 2).  
Figure 1: Main types of carbon nanoparticles.