Carbon Dots Derived from Tea Polyphenols as Photosensitizers for Photodynamic Therapy

Abstract

Photodynamic therapy (PDT) has become an emerging cancer treatment method. Choosing the photosensitizer (PS) compounds is one of the essential factors that can influence the PDT effect and action. Carbon dots (CDs) have shown great potential as photosensitizers in PDT of cancers due to their excellent biocompatibility and high generation of reactive oxygen species (ROS). Here, we used tea polyphenol as raw material for synthesized tea polyphenol carbon dots (T−CDs) that show dual emission bands of red and blue fluorescence and can efficiently generate hydroxyl radicals (OH) under mildly visible irradiation with a LED light (400–500 nm, 15 mW cm−2). The extremely low cytotoxicity and excellent biocompatibility of T−CDs without light irradiation were tested using MTT and hemolytic assay. Further, T−CDs have been shown by in vivo experiments, using a mouse breast cancer cell line (4T1) subcutaneously injected in the back of the mouse buttock as a model, to effectively inhibit the tumor cell proliferation in solid tumors and show an excellent PDT effect. In addition, pathological sections of the mice tissues after further treatment showed that the T−CDs had no apparent impact on the major organs of the mice and did not produce any side effect lesions. This work demonstrates that the as−synthesized T−CDs has the potential to be used as a PS in cancer treatment.

Recent Advances of Photoactive Near-Infrared Carbon Dots in Cancer Photodynamic Therapy

“…Additionally, many natural animal or vegetable derivatives can be used as precursors to prepare CDs [ 17 ]. Generally, as the rich carbon sources for bottom-up preparation, hydrothermal/solvothermal method [ 25 , 38 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ], microwave synthesis [ 51 ], microwave-assisted hydrothermal method [ 52 ], and solvent-free carbonization [ 53 ] are commonly used to treat precursors. Compared to the top-down method, bottom-up treatment has relatively mild conditions and richer sources of raw materials.…”

“…With the improvement of the CDs preparation method, the CDs have developed from the original blue-green light to the near-infrared CDs (NCDs). More importantly, many CDs have the ability to convert light energy into ROS and therefore be used as PSs for cancer PDT [ 23 , 24 , 25 , 26 , 27 ]. In particular, NCDs with an absorption wavelength above 650 nm have deeper tissue penetration, exhibiting good photodynamic effects to be used as photodynamic therapeutic PSs [ 28 ].…”

First-Principles Modeling of Bottom-Up Synthesis of Carbon Quantum Dots

“…XPS spectra also indicate some contribution from non-oxidized carbon atoms having sp 3 hybridization (similar to diamonds) [21,[25][26][27][28][29]. Finally, high-resolution transmission electron microscopy (HRTEM) yields images where the presence of some large round disk-like nanoparticles (the size above 2~3 nm and the thickness above 1.2 nm, see for example [13,[39][40][41][42]) with regular crystalline fringes is visible. This brief review of experimental results demonstrates that the model of nanographenes of sub-nanometer size standardly used to describe CQDs [43,44] needs to be revised.…”

“…Carbon quantum dots (CQDs) are a material that combines a multiplicity of applications with the abundance and cheapness of the production materials and the relative simplicity of the production methods [1][2][3][4][5][6][7]. The brief list of existing and promising applications includes solar cells and materials for energy conversion [8][9][10], bioimaging, drug delivery, and other medicinal applications [11][12][13][14][15][16][17] due to low cytotoxicity and high biocompatibility [14][15][16][17]. The sources for the fabrication of CQDs are somewhat diverse, from graphite and carbon nanofibers [18] to small organic molecules, such as citric acid and o-phenylenediamine (both discussed in this work), or natural products, such as tea leaves [13], seeds [19], or banana peels [20].…”

“…The brief list of existing and promising applications includes solar cells and materials for energy conversion [8][9][10], bioimaging, drug delivery, and other medicinal applications [11][12][13][14][15][16][17] due to low cytotoxicity and high biocompatibility [14][15][16][17]. The sources for the fabrication of CQDs are somewhat diverse, from graphite and carbon nanofibers [18] to small organic molecules, such as citric acid and o-phenylenediamine (both discussed in this work), or natural products, such as tea leaves [13], seeds [19], or banana peels [20]. The production of the CQDs does not require high pressures exceeding 30 bar, high temperatures (the usual temperatures for the synthesis are below 230-240 • C), particular reactants, sophisticated and costly equipment, or rare catalysts.…”