טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMuallem Merav
SubjectDevelopment and Characterization of Nanocrystals for
Biological Applications
DepartmentDepartment of Nanoscience and Nanotechnology
Supervisors Professor Efrat Lifshitz
Professor Yehuda Assaraf
Full Thesis textFull thesis text - English Version


Abstract

Nanotechnology and nanoscience have emerged to become one of the most exciting areas of research today. The electronic and atomic structures of the nanomaterials have unusual features, in accordance with their small sizes, following quantum mechanical rules instead of the laws of classical physics which govern by bulk materials. Hence, they are markedly different from those of bulk materials. Crystalline nanoparticles, also called nanocrystals (NCs), constitute a major class of nanomaterials and widely integrate in research and development for various in vitro and in vivo biological applications.

Semiconductor quantum dots (QDs) and magnetic nanoparticles (NPs) occupy the center of NCs field due to their unique electronic nature; quantum dots exhibit unique optical properties that are influenced by the quantum size effect, and magnetic nanoparticles show superparamagnetism phenomena. Due to their distinctive properties, these nanocrystals have great potential in the integration into biological applications. Quantum dots could be used in biosensors assays, cell labelling and targeting, in vivo imaging etc, while magnetic separation methods, magnetic resonance imaging and hypothermia treatments could be improved by magnetic nanoparticles.

This work concerns the development and characterization of semiconductor quantum dots and magnetic nanoparticles for biological uses. Wet chemistry synthesis was used for producing the colloidal NCs - QDs from group II-VI (CdTe and CdTe/CdTexSe1-x) and magnetic γ-Fe2O3 nanoparticles, followed by ligand exchange procedure in order to make the NCs suitable for biological media. Characterization includes morphological and size measurements by transmission electron microscope and spectroscopy techniques. Further, examinations for possible biological tissue damage were carried out by a novel and sensitive method.

Water soluble Cd-based QDs were observed as causing damage to cells; however, coating with outer shell helps in QDs stabilization, and reduces the damage to cells. On the other, water soluble magnetic γ-Fe2O3 nanoparticles had minimal effect on biologic tissues that were examined. In addition, decreasing the NCs concentration reduced the damage; hence, the damage is dose dependent, with a threshold concentration of NCs, where no damage occurs. 

The study is a cornerstone in wider research that should be done regarding utilizing QDs and magnetic NPs in biological applications. The water soluble particles could be suitable for biological use, if appropriate coating is introduced, and their use is restricted to a concentration that does not exceed a certain limit. Still, further work must be done until NCs are stable enough and biocompatible for biological environment for in vitro and in vivo assays.