We report the development of multifunctional nanocluster composed of upconversion nanoparticle (UCNP) and gold nanorod (AuNR). Antibody to epidermal growth factor receptor (αEGFR) is further conjugated with the nanocluster so as to demonstrate specific binding to the EGFR-expressing bladder cancer cells and subsequent thermal ablation of the cells upon near-infrared (NIR) irradiation. AuNRs and UCNPs are synthesized by the methods reported in the literature. Since UCNPs are synthesized in an organic solvent, surface modification is needed to make them water soluble and also to enable the subsequent coupling with AuNR. For this, we use poly(maleic anhydride-alt­-1-octadecene) (PMAO). By mixing PMAO and UCNPs in toluene, PMAOs are attached on the UCNP surface through hydrophobic interaction. Upon subsequent addition of heterofunctional PEG, the amine group of the PEG binds with PMAO, producing carboxylic groups. This consequently makes the polymer hydrophilic and thus the coated UCNPs water soluble. The carboxylic groups are also used to attach αEGFR. Finally, the thiol groups on the free ends of the PEGs are used to bind with AuNR, completing the nanocluster. The synthesized nanoclusters are characterized by electron microscopy, optical microscopy and in vitro cell ablation experiments. Electro microscopy showed the successful formation of nanoclusters made of UCNPs and AuNRs. Fluorescence and dark-field optical microscopy revealed the presence of UCNPs, AuNRs and αEGFR on the cell membranes. Finally, NIR laser irradiation led to selective cell killing by thermal ablation. The successful demonstration of UCNP-AuNR nanocluster opens a door to new diagnostic and therapeutic approach for cancer.

Multifunctional nanoclusters for biomedical applications

249th National Meeting (2015)

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