Green-Synthesis-Derived CdS Quantum Dots Using Tea Leaf Extract: Antimicrobial, Bioimaging, and Therapeutic Applications in Lung Cancer Cells

Abstract

Low dimensional semiconductor quantum dots (<10 nm) have received great attention for potential use in biomedical applications (diagnosis and therapy) for which larger nanoparticles (>10 nm) are not suitable. Here, we demonstrate a green, biogenic synthesis route for making CdS quantum dots (QDs) with 2-5 nm particle size using tea leaf extract (Camellia sinensis) as a toxic-free particle stabilizing agent. We have explored the biological activity of these CdS QDs in different applications, namely; a) antibacterial activity b) bioimaging and c) apoptosis of lung cancer cells. The antibacterial activity of the CdS QDs has been studied against different types of bacteria growth, showing that CdS QDs effectively inhibit the bacterial growth and exhibit cytotoxicity towards A549 cancer cells when compared to a control (no QD treatment). We have compared this cytotoxicity effect on A549 cancer cells with a standard drug, cisplatin, showing comparable results. Additionally, these CdS QDs produce high contrast fluorescence images of A549 cancer cells indicating a strong interaction with the cancer cell. To further understand the role of CdS QDs in bioimaging and cytotoxicity effect in A549 cells, fluorescence emission and flow cytometry analysis were carried out. The fluorescence emission of CdS QDs were recorded with λexc= 410 nm, showing concentration dependence fluorescence emission centered at 670 nm. From the flow cytometry analysis, it is confirmed that the CdS QDs are arresting the A549 cell growth at the S phase of cell cycle, inhibiting further growth of lung cancer cell. The multifunctional advantages of Camellia sinensis extract mediated green CdS QDs will be of widespread interest in implementing in-vivo based bioimaging and therapeutic cancer treatment applications.

Facile synthesis of CdS Quantum dots for QDSSC with high photo current density

“…The images confirm the spherical morphology of the particles with size of 2-5 nm, which is less than excitonic Bohr radius (∼3 nm) of CdS thereby authenticating QD formation thereby the blue shift is observed in figure1(b). The inset of figure 2(b) shows the HRTEM image of a single QD with clear lattice fringes and the inter planar distance of 0.33 nm [21], which corresponds to preferred orientation of (111) of CdS QDs, as confirmed from XRD pattern ( figure 1(a)).…”

“…For green synthesis of CdS QDs, A. indica plant extract was prepared by following the procedure as reported in the literature [21,22]. The CdS QDs synthesis was rendered in two stages.…”

“…Loo et al (2012) explained about the synthesis of Ag nanoparticles from Camellia sinensis extract [20]. Kavitha et al (2018) have green synthesized CdS QDs using tea leaf extract and studied their antimicrobial activity [21]. Recently, copper indium sulphide-based ternary QDs have been fabricated as an alternative to Cd-and Pb-based QDs for QDSSCs; however the former QDs showed lesser efficacy [9].…”

“…Better control of nanomaterial toxicity can be done by the safe design of nanoparticles using greener research approach. Consequently, green chemistry-mediated synthesis of QDs is profoundly imperative to reduce its toxicity and extend its applications [12][13][14][15][16][17][18][19][20][21][22].…”

“…(a) TEM image (b) HRTEM of green CdS QDs (c) FTIR for leaf extract and green CdS QDs (d) Hemolytic analysis of green CdS QDs.comparison with CdS QDs[21]. Toxicity is studied on Human lung epithelial cells (A549) and the results areshown in figures 3(a)-(d).…”