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Multilayered protection and functionalization of organohalide perovskite nanocrystals for biomedical applications
Dissertation

Multilayered protection and functionalization of organohalide perovskite nanocrystals for biomedical applications

Ozgun Acar
Doctor of Philosophy (Ph.D.), Drexel University
Jun 2024
DOI:
https://doi.org/10.17918/00010453
pdf
Acar_Ozgun_20245.64 MB
PDF Embargoed Access, Embargo ends: 31 Aug 2026

Abstract

Bioconjugation Nanoparticle synthesis Organohalide perovskite nanocrystalf Surface functionalization Surface modification Water-stable Materials Science and Engineering Biomedical Engineering Materials Science Nanotechnology
Organohalide perovskite nanocrystals (OHPNCs) are semiconductor nanoparticles with ABX3 structure. They are of great interest due to their promising electronic and optical properties and have been studied for applications such as solar cells and light-emitting diodes (LEDs). However, the challenge against their practical use in solar cells and LEDs is their lack of stability against environmental factors such as moisture, heat, and light. Meanwhile, due to their high photoluminescence quantum yield, another potential application of OHPNCs is in bioimaging as a molecular probe by conjugating with antibodies for antigen specific imaging. Here the additional challenge is to stabilize OHPNCs in aqueous environment. In this work, we took a multilayer coating approach to modify the surface of methylammonium lead bromide (MAPbBr3) OHPNCs to protect and functionalize the OHPNCs to allow conjugation of antibodies to create OHPNC molecular probes for bioimaging. First, commonly used oleic acid (OA) was replaced by stearic acid (SA) as a surface ligand which has a higher melting temperature to increase stability. Second, tetraethyl orthosilicate (TEOS) was used to create linkage among OHPNCs and minimize contact with 1% water in toluene providing better suspension and photoluminescence stability. Third, to provide further protection in a complete water environment, Pluronic F127 triblock copolymer was introduced to create cluster of OHPNCs covered by F127 together with a non-ionic surfactant Kolliphor HS 15 to enhance the coverage. An optimal condition of the amount of SA, TEOS, F127, and HS 15 was found that can stabilize OHPNCs in water for more than a year. Once the OHPNCs were stabilized by the multilayer approach, F127 was carboxylated using carbonyldiimidazole (CDI) chemistry together with diglycolic acid (DGA). Subsequently, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC)/N-hydroxysuccinimide (NHS) coupling was used to conjugate carboxylated OHPNC clusters with amine groups on Alexa Fluor 350 IgG antibodies to evaluate conjugation. It was found that carboxylation of F127 was not enough to lead to sufficient antibody conjugation due to the size of F127. Alternatively, capping the OHPNC clusters with succinic acid provides ample carboxyl groups leading to significant amide bond formation with amine groups and higher degree of conjugation.

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