Thesis (Ph.D.)--Chulalongkorn University, 2015

Upconverting nanoparticles (UCNPs) are particles that possess ability to convert low energy photons into high energy photons. This unique property makes the UCNPs suitable for biomedical applications such as cell fluorescence imaging, drug carriers and photodynamic therapy. However, the influence of the UCNPs morphology toward the particle-cell association is still unclear. Here the UCNPs based on NaYF4 doped with Yb and Tm of different shapes such as sphere, rod and prism are prepared. The three shaped water dispersible UCNPs particles have the same crystal phase structure and surface charge. Therefore, the as-prepared particles can be used for studying lipid bilayer membrane interaction, cellular uptake and cytotoxicity. The results indicate that the rod-shaped UCNPs give the highest cellular uptake into malignant melanoma (A-375) and liver carcinoma (HepG2) cell lines and highest cytotoxicity in A-375, HepG2 and normal lung (WI-38) cell lines. These results correspond well with the result of the highest particle-membrane association observed for this particle shape. Since the UCNPs can upconvert near infrared (NIR) light into lights in the UV-visible region, here we also develop the UCNPs with a highly-upconverted emission and then load the obtained material with a photosensitizer, meso-Tetraphenyltetrabenzo porphyrinatozinc (ZnTPTBP). The ZnTPTBP-loaded UCNPs show low toxicity against malignant melanoma (A-375) cell line and possess an ability to generate singlet oxygen when being irradiated with a 980 nm NIR laser. More importantly, we demonstrate the capability of the ZnTPTBP-loaded UCNPs to eradicate Propionibacterium acnes (P. acnes) under NIR irradiation.