Fabrication and modification of dual-faced nano-mushrooms for tri-functional cell theranostics: SERS/fluorescence signaling, protein targeting, and drug delivery

Abstract

Smart nanocarriers with high SERS enhancement are inevitably important in cancer therapy for treating cells and recording their changes at the single-molecule scale. Therefore, this work reports an approach to fabricating and modifying mass-produced dual-faced and tri-functional nanoparticles for sequentially recognizing tumor cells, drug delivery, and real-time monitoring of biological responses. A one-step oxygen plasma process was employed to tailor commercially available fluorescent polystyrene beads into a corrugated upper hemisphere and simultaneously modify the entire surface with carboxylic groups. After depositing gold onto the corrugated hemisphere for SERS (using 633 nm laser excitation) while leaving the other smooth and clean hemisphere for fluorescence detection (via 488 nm or 532 nm laser excitation), the Au-coated fluorescent nano-mushrooms (AuFNMs) are formed with dual-surfaces of plasmonic gold semishells on the top and fluorescent carboxylated polystyrene at the bottom. Based on the unique structures and the self-generated functional surfaces of the AuFNMs, sulfo-NHS–SS–biotin disulfide linkers and anti-CD44 monoclonal antibodies can be simultaneously modified and added onto the top gold surfaces and the bottom carboxyl groups through Au–S and peptide bonds, respectively. The surface-modified AuFNM suspension, with >99% purity and uniform particle size in a concentration of ∼10¹⁰ particles per mL in 2 mL DI water, can be employed to target overexpressive glycoproteins (CD44) on the surfaces of cancer cells and release their loads via the cleavage of disulfide bonds in the cytoplasm. These AuFNMs exhibit a 12-fold higher cancer targeting ability on HeLa cells when compared to a normal chondrocyte cell. Three-dimensional confocal particle tracking and Raman mapping are used to demonstrate the AuFNMs' long-lasting single-particle fluorescence and superior biomolecule sensing ability.