In recent years the use of nanoparticles in medical applications has boomed. This is because the various applications that provide these materials like drug delivery, cancer cell diagnostics and therapeutics [1-5]. Biomedical applications of Quantum Dots (QDs) are focused on molecular imaging and biological sensing due to its optical properties. The size of QDs can be continuously tuned from 2 to 10 nm in diameter, which, after polymer encapsulation, generally increases to 5 – 20 nm diminishing the toxicity. The QDs prepared in our lab have a diameter between 2 to 7 nm. Particles smaller than 5 nm can interact with the cells . Some of the characteristics that distinguish QDs from the commonly used fluorophores are wider range of emission, narrow and more sharply defined emission peak, brighter emission and a higher signal to noise ratio compared with organic dyes . In this paper we will show our progress in the study of the interaction of quantum dots in live cells for image and Raman spectroscopy applications. We will also show the results of the interaction of quantum dots with genomic DNA for diagnostic purposes.
This work reports the synthesis, structural characterization, and optical properties of ZrO2:Yb3+-Er3+ (2–1 mol%) nanocrystals. The nanoparticles were coated with 3-aminopropyl triethoxysilane (APTES) and further modified with biomolecules, such as Biotin-Anti-rabbit (mouse IgG) and rabbit antibody-AntiKi-67, through a conjugation method. The conjugation was successfully confirmed by Fourier transform infrared, zeta potential, and dynamic light scattering. The internalization of the conjugated nanoparticles in human cervical cancer (HeLa) cells was followed by two-photon confocal microscopy. The ZrO2:Yb3+-Er3+ nanocrystals exhibited strong red emission under 970-nm excitation. Moreover, the luminescence change due to the addition of APTES molecules and biomolecules on the nanocrystals was also studied. These results demonstrate that ZrO2:Yb3+-Er3+ nanocrystals can be successfully functionalized with biomolecules to develop platforms for biolabeling and bioimaging.
Er doped and Yb-Er-Tm codoped ZrO2 nanocrystals of average 80 nm in size were prepared by a sol-gel
process with the presence of nonionic (PLURONIC F-127) surfactant, and the up-conversion emission
was characterized under IR (980 nm) excitation. The effect of the codoped conditions on the crystalline
structure and photoluminescence properties were studied. A strong green emission was produced with 5
mol %, 0.2 mol %, 0.01 mol % of Yb3+-Er3+-Tm3+ codoped ZrO2 respectively. It was prepared Er doped
ZrO2 -SiO2 core-shell and SiO2 coated Er doped ZrO2 in 2-propanol and water, respectively. The presence
of the silica shell of average of 15 nm in thickness has been confirmed by transmition electron
microscopy. Photolumineiscence studies show that the silica shell does not affect the emission when the
nanoparticles are excited with 980 nm. The up-converting Yb3+-Er3+-Tm3+ codoped ZrO2 nanocrystal has
showed to be a powerful tool to future detection techniques. The viability of the nanoparticles of codoped
ZrO2 for biological imaging was confirmed by multiphotonic microscope imaging of cervix tissue with inserted codoped ZrO2 nanoparticles. The cervix tissue has a moderate dysplasia. The nanoparticles were
introduced at 80 % of the tissue depth (5 μm) without being functionalized.