Nadja M. Maldonado Luna - University of Puerto Rico - Mayaguez
Co-Author(s): Sonia Bailon Ruiz, University of Puerto Rico-Ponce
The use of semiconductors Quantum Dots (QDs) in the biomedical field is dependent of their bio-compatibility, solubility in water and no toxicity. It is expected that nanoparticles with different coatings and sizes can behave in different ways at cellular level by interacting with cell organelles and can impart damage and potential cellular death. Particle size is an essential property that manages the potential toxicity of this nanostructure. Based on these considerations, this research is addressed on the generation of two sizes of water-stable CdTe/S quantum dots with different coating species such as glutathione (a peptide) and thioglycolic acid (TGA). Two sizes of CdTe/S QDs covered with TGA were previously synthesized by microwave irradiation, optically characterized using a UV-Vis spectrophotometer and a Spectrofluorometer. The morphology was evaluated using HRTEM analysis. CdTe/S QDs of larger size evidenced a shoulder peak in the range 580 nm-600 nm which suggested the formation of a structure like a solid solution containing Cd, Te and S. High emission peak at 640 nm was observed, characteristic of nanomaterials based in CdTe. Whereas, CdTe/S QDs of smaller size revealed a band gap peak in the range 550 nm -570 nm, a fluorescence peak at 574 nm was observed. Glutathione was used to functionalize the QDs as an attempt on obtaining a biocompatible and nontoxic surface. Emission peaks at 636 nm was observed for large size glu-capped QDs and at 571 nm for small size glu-capped QDs. The toxicity of cadmium acetate Cd(CH₃CO₂)₂, small size and large size CdTe/S Q’Dots in aquatic organisms was evaluated. Experiments of exposure of brine shrimp Artemia Salina to cadmium and Q’Dots solutions were carried out at time intervals of 18 -24 h and 36-48 h. These experiments showed that as the concentration of Cd(CH₃CO₂)₂ increased, the mortality rate increased in Artemia Salina. The mortality observed could be attributed to the generation of reactive oxygen species by cadmium solutions in Artemia Salina. Funtionalized CdTe/S Q’Dots were found to be less toxic than non-funtionalized Q’Dots. However, “small size” glutathione-capped CdTe/S Q’Dots exhibited more toxicity to Artemia Salina than “large size” glutathione-capped Q’Dots, and can be attributed to its cover (TGA) and particle size, since as size of nanoparticles decreases, its toxic effects increase. Future research includes the coating of different sizes of CdTe/S Q’Dots using other biomolecules like cysteine and albumin to study their toxicity in Artemia Salina and establish a model of toxicity based on size and coating agent correlation. References: Rajabi, S., Ramazani, A., Hamidi, M. & Naji, T. 2015. Artemia Salina as a model organism in toxicity assessment of nanoparticles. DARU Journal of Pharmaceutical Sciences. 23(20):1-6. Bailón, S. & Perales, O. 2017. Generation of singlet oxygen by water stable CdSe(S) and ZnSe(S) quantum dots. Applied Materials Today. 9:161-166.
Funder Acknowledgement(s): Thanks to Dr. Luis Alamo from PUCPR for providing the nanoparticles and access to the fluorescence microscope. Lab colleagues, Julio Rivera and Jousen Merced for their help during the toxicity experiments. We also thank UPR-Ponce for providing institutional funding, Instrument Grant by NHI-PRINBRE, and PR-LSAMP.
Faculty Advisor: Sonia Bailon Ruiz, email@example.com
Role: All parts of this research were conducted by me along side Dr. Bailon's mentoring.