# Carbon Nanoparticles and Their Biomedical Applications
## 9 Therapy--Delivery Platform, Treatment  
Drug treatment is systemic, affecting the whole body; to achieve the necessary concentration at the site of the effect (e.g., at the site of a tumor), it is often necessary to administer high doses that damage the body. The ability to target therapy can greatly increase efficacy and reduce systemic inflammation. CNPs are (almost) an ideal platform for drug delivery to various tissues (Figure 4). They have large loading capacities for different drug substances, including combinations of them. The functionalization of CNPs enhances the penetration and retention effects, allows targeting of specific tissues or molecules, and controls drug release. Released stimuli include pH, enzymatic activity, light, or temperature [74]. Figure 3: The principal of phototherapy. Legend: When using GO, it must first be reduced to rGO and functionalized with various substances (human serum proteins, hyaluronic acid, and pharmaceuticals). The functionalized rGO is then exposed to NIR and releases heat. Functionalized carbon nanotubes, graphene, fullerene, and other CNPs can bind anticancer, antimicrobial drugs, or proteins (monoclonal and polyclonal antibodies). Targeted therapy reduces the systemic toxicity of drugs and allows lower doses to be used to achieve the same therapeutic effect [75]. CNPs can be loaded, for example, with cisplatin, oxaliplatin, doxorubicin, methotrexate, gemcitabine, paclitaxel, tamoxifen, and rituximab. After administration, CNPs are attracted and retained in the tissues and the drug is released over several days [76]. [PERSON] et al. loaded paclitaxel onto polyethylene glycol (PEG)-graft-carbon nanotubes. Multi-walled nanotubes had a higher loading capacity and showed lower toxicity and higher efficacy in killing cancer cells (HeLa and MCF-7 cells) than free paclitaxel [77]. The same effect was documented with multiloaded carbon nanotubes with \(\beta\)-estradiol,  
Figure 4: NCP drug delivery system. Graphene conjugated with doxorubicin and a receptor specific for antigens expressed primarily on the target cell. The loaded graphene interacts with the cell membrane, enters the cell, and releases the drug (parts of the figure were drawn using pictures from Servier Medical Art. Servier, licensed under a Creative Commons Attribution 3.0 Unported License.). PEG, and lobaplatin [78]. Graphene oxide (GO)-PEG (GOP) loaded with protocatechuric acid (PA), chlorogenic acid (PC), and folic acid (FA) effectively killed hepatocellular carcinoma cells. The half-maximum inhibitory concentration (IC50) was for PC 40.78 \(\pm\) 1.92, CA 43.61 \(\pm\) 1.74, GOP-PC/CA 34.73 \(\pm\) 1.04, and for GOP-PC/CA-FA 26.79 \(\pm\) 1.63 [79]. CNPs can be functionalized with a wide range of molecules to target a specific type of cancer. One of these is folic acid because cancer cells overexpressing the folic acid receptors. Other options are, for example, monoclonal antibodies with an affinity for tumor markers, such as anti-HER2 in breast cancer or rituximab (anti-CD20) in lymphomas, and antibodies targeting the prostate-specific membrane antigen [80; 81; 82]. Nanoscale GOs loaded with doxorubicin and HN-1 (specific antigen) have been successfully used to treat oral squamous cell carcinoma. The particles were easily absorbed by cancer cells and, thus, showed significantly higher toxicity compared to free doxorubicin [83]. MWCNTs loaded with bromocriptine or doxorubicin can induce apoptosis or necrosis in lung and prostate cancer cells [84; 85]. Fullerene can also serve as a drug carrier. Conjugation with 5-aminolevulinic acid or doxorubicin may help to treat various types of cancers. Importantly, fullerene C60-\(\beta\)-cyclodextrintrin conjugated with doxorubicin improves drug delivery into the nucleus [86; 87]. Mesoporous carbon nanoparticles (MCNs) have great potential as a platform for anticancer drug delivery. [PERSON] et al. showed that MCNs are more efficient in the delivery and release of doxycycline than mesoporous silica nanoparticles [88].