# Knowledge base: Warsaw University of Technology

Back

## Synthesis of cyclodextrin functionalized ZnO nanoparticles for cell imaging applications

### Piotr Krupiński

#### Abstract

During the last decade, Quantum Dots (QDs) have been applied dominantly in biological sciences. 1 Particularly they are used in biomedical imaging on various levels: from unique cells to the most complex organisms. Today QDs are not very far from being used even in human organisms.2 Thus, one of the most important issues regarding Quantum Dots is their biologically-orientred functionalization and water solubilization. We consider it unusually interesting to create a material combining the advantages of fluorescent QDs and cyclodextrins (CD) – oligosaccharides that not only play an important role in pharmaceutical sciences (where are used as efficient drug carriers), but also absorb more and more attention due to the wide range of their possible applications in chemistry of new materials.3 The aim of this work was to design a method of synthesis of ZnO nanoparticles functionalized with cyclodextrins from newly-designed novel oxozinc precursors and show their application in live cell imaging. In the first step, some carboxylic acids and amides known to form inclusion complexes with �-CD were transformed into their oxozinc derivatives and the resulting complexes were structurally characterized. The complex [Zn4(μ4-O)(O2CAd)6(DMF)2] is a unique example of a zinc oxocarboxylate adduct with a Lewis base (DMF). This result is an important argument in the discussion about structural nodes reactivity in microporous Metal-Organic Frameworks. Another complex — [Zn4(μ4-O)(ONHCPh)6] — is the very first example of structurally characterized oxozinc derivative of an amide. In the core of the obtained structures there is a molecular ZnO fragment included. Therefore, obtained compounds form a new group of promising nano-ZnO precursors, not considered in the literature before. Additionally, according to two dimensional NMR experiments (ROESY), the obtained compounds are capable of forming inclusion complexes with �-CD in the same way as simple carboxylic acids and amides. We obtained original precursors built from oxozinc cores that should be able to transform to ZnO and ligand shell capable of complexing the molecules of cyclodextrin. In the next stage, the obtained oxozinc complexes were hydrolized in the presence of cyclodextrin to give ZnO nanoparticles. This is the first example of a transformation of oxozinc complexes into semiconducting Quantum Dots. The reaction is performed in mild conditions and does not require high temperature or nitrogen atmosphere. We developed several variants of this method. Products obtained in solution, in dispertion and mechanochemically differ in size and optical properties. Moreover, cyclodextrin crystallization water was found to be a key factor in the process of nanocrystal growth. We also observed and discussed the difference in susceptibility to hydrolysis between the carboxylate and amide derivatives. Formation of cyclodextrin-coated ZnO QDs was confirmed by HRTEM, PXRD, TGA and DLS techniques. Depending on the conditions, nanoparticles with 2–6 nm wurzite core were reported. This values correspond with bright emission observed in the wide range of visible region (from blue to yellow). Hydrodynamic diameter of the obtained particles varied from 10 to 50 nm. The presence of sacharide coating resulted in moderate water solubility of CD@ZnO. The next part was aimed at determining the cytotoxicity of the obtained CD@ZnOon on two types of human cell lines. A possibility of a slight positive influence of low levels of exogenic ZnO on the cell lines was found. Nevertheless, high (in average higher than 100 mg / l) doses of QDs induce the decrease in cell viability. This is probably due to the oxidation stress caused by Zn2+ ions released from QDs. On the other hand, the toxic effect, even for very high nanoparticle doses, is evident only after more than a few hours of cell exposition to ZnO QDs. This time is longer than required for performing most of the imaging experimants involving living cells. During the final part of the work imaging experiments on CCD human foreskin fibroblast cell line involving the synthesized CD@ZnO nanoparticles were conducted. Intensive signal was observed in confocal microscope images. Pictures created by merging confocal and Vis channels proved that the fluorescence is emitted from the interior of the cells. These results demonstrated that CD@ZnO QDs can permeate the cell membrane and enter the cells. Nanoparticles were localised in periculear part of the cytosol and did not enter the nucleus. Furthermore, ZnO nanoparticles show high stability of fluorescence and were resistant to photobleaching. The main result of this work is the characterization of a new gruop of convenient precursors of zinc oxide quantum dots. We also developpped a synthesis method of non-toxic semiconductor nanoparticles, that undergo self-assembly resulting double-layer coating. The structure and properties of the resulting material make it an efficient fluorescent probe for cellular imaging.
Record ID
Diploma type
Master of Science
Author
Piotr Krupiński Piotr Krupiński,, Undefined Affiliation
Title in Polish
Synteza nanocząstek ZnO otoczonych cyklodekstrynami do zastosowań w obrazowaniu komórkowym
Supervisor
Janusz Lewiński (FC/DCOC) Janusz Lewiński,, Department Of Catalysis And Organometallic Chemistry (FC/DCOC)Faculty of Chemistry (FC)
Certifying unit
Faculty of Chemistry (FC)
Affiliation unit
Department Of Catalysis And Organometallic Chemistry (FC/DCOC)
Study subject / specialization
, Biotechnologia Chemiczna - Leki i Kosmetyki
Language
(pl) Polish
Status
Finished
Defense Date
29-11-2012
Issue date (year)
2012
Keywords in Polish
-
Keywords in English
-
Abstract in Polish
urn:pw-repo:WUT5d3305b853534082adb008623eecfa55