Biomedical Applications of Carbon-Based Nanomaterials
167
4.1.3 Fullerenes as a Photosensitizer
Photoexcitation of fullerenes is another important medical application. These can be
excited from ground state to 1 C 60 by photoirradiation. Whereas in the presence of
molecular oxygen, its excitation can result in highly toxic species forming superoxide
anion radical O 2
− [53]. In the presence of biological agents like guanosine, these
exited fullerenes can be reduced, making them potential photosensitizers for their use
in photodynamic therapy (PDT). C 60 fullerenes were conjugated with oligonucleotide
or acridine for their interaction with nucleic acids for increasing cytotoxicity in cancer
cells. Dendritic monoadduct C 60 was added to Jurkat cells, and on exposure to UV
light, the cell count has decreased approximately by 19% within two weeks [54]. They
have also been studied for biodistribution in tumour cells by radiotracer 125I-labeled
C60 (OH)x [55]. The polyethylene glycol-conjugated fullerene containing Gd3
+ ions
was used for PDT combined with MRI and the data signifies that photosensitizer
significantly promoted the tumour targetability and MRI activity [56]. Fullerenes
conjugated with hydrophilic cationic groups were used for PDT against mouse cancer
cell lines, and they were highly effective photosensitizers for killing cancer cells by
induction of apoptosis after illumination [57].
5 Carbon Quantum Dots (CQDs)
Carbon quantum dots (CQDs) are sometimes called carbon dots (CDs) are novel zerodimensional carbon-based nanomaterials with size less than 10 nm [58]. They are
synthesized using various techniques like chemical vapour deposition, laser ablation,
microwave heating, pyrolysis, and chemical oxidation method [59]. They have been
synthesized generally from organic materials like polymers and extracts of various
fruits [60, 61]. These CQDs are smaller and have strong fluorescence characteristics,
which are the inherited properties of traditional semiconductor quantum dots. They
are water-soluble with high chemical stability and can be easily functionalized [62].
CQDs bioprobes with good stability have been engineered for their applications
in live cells, tissues, and animals. During the last few years, their cytotoxicity evaluations were carried out on various cell lines without affecting the cell viability. The
CQDs functionalized with various groups and polymers such as PEG, PEI, BPEI
showed negligible cytotoxicity at lower concentrations when incubated for a short
time [63].
5.1 CQDs as Biosensors
The fluorescent property of CDs allows the detection and identification of a wide
range of analytes, drugs and macromolecules depending on high sensitivity and
easy operation. CDs have been used as a biosensing device to identify biological
167
4.1.3 Fullerenes as a Photosensitizer
Photoexcitation of fullerenes is another important medical application. These can be
excited from ground state to 1 C 60 by photoirradiation. Whereas in the presence of
molecular oxygen, its excitation can result in highly toxic species forming superoxide
anion radical O 2
− [53]. In the presence of biological agents like guanosine, these
exited fullerenes can be reduced, making them potential photosensitizers for their use
in photodynamic therapy (PDT). C 60 fullerenes were conjugated with oligonucleotide
or acridine for their interaction with nucleic acids for increasing cytotoxicity in cancer
cells. Dendritic monoadduct C 60 was added to Jurkat cells, and on exposure to UV
light, the cell count has decreased approximately by 19% within two weeks [54]. They
have also been studied for biodistribution in tumour cells by radiotracer 125I-labeled
C60 (OH)x [55]. The polyethylene glycol-conjugated fullerene containing Gd3
+ ions
was used for PDT combined with MRI and the data signifies that photosensitizer
significantly promoted the tumour targetability and MRI activity [56]. Fullerenes
conjugated with hydrophilic cationic groups were used for PDT against mouse cancer
cell lines, and they were highly effective photosensitizers for killing cancer cells by
induction of apoptosis after illumination [57].
5 Carbon Quantum Dots (CQDs)
Carbon quantum dots (CQDs) are sometimes called carbon dots (CDs) are novel zerodimensional carbon-based nanomaterials with size less than 10 nm [58]. They are
synthesized using various techniques like chemical vapour deposition, laser ablation,
microwave heating, pyrolysis, and chemical oxidation method [59]. They have been
synthesized generally from organic materials like polymers and extracts of various
fruits [60, 61]. These CQDs are smaller and have strong fluorescence characteristics,
which are the inherited properties of traditional semiconductor quantum dots. They
are water-soluble with high chemical stability and can be easily functionalized [62].
CQDs bioprobes with good stability have been engineered for their applications
in live cells, tissues, and animals. During the last few years, their cytotoxicity evaluations were carried out on various cell lines without affecting the cell viability. The
CQDs functionalized with various groups and polymers such as PEG, PEI, BPEI
showed negligible cytotoxicity at lower concentrations when incubated for a short
time [63].
5.1 CQDs as Biosensors
The fluorescent property of CDs allows the detection and identification of a wide
range of analytes, drugs and macromolecules depending on high sensitivity and
easy operation. CDs have been used as a biosensing device to identify biological