Targeted Stealth Polymer Capsules Encapsulating Ln³⁺-Doped LaVO₄ Nanoparticles for Bioimaging Applications

We report synthesis of targeted PEGylated polymer capsules encapsulating Stoke's shift and upconverting LaVO₄ nanoparticles by following a unique approach for bioimaging applications. First, LaVO₄:Ln³⁺@silica (Ln³⁺ = Tb³⁺, Eu³⁺, and Yb³⁺/Er³⁺) core-shell nanoparticles are prepared by sol-gel method followed by layer-by-layer assembly of polymers and PEGylation over core-shell particles. Second, removal of silica core facilitates the trapping of LaVO₄:Ln³⁺ nanoparticles inside the PEGylated polymer capsules. Finally, capsules are surface modified with antibodies to target cancer cells. The nanoparticles-loaded polymer capsules are found to be internalized and biocompatible with various cells (e.g., HeLa, A498, H460, MCF-7, Schwann, L929, and IC-21) suggesting their applicability in different types of cells. In addition, the capsules modified with antibodies show more specific uptake suggesting their targeting ability by 3-fold for MCF-7 and 10-fold for H460 cancer cells. Moreover, the nanoparticle-loaded polymer capsules were internalized by HeLa cells via macropinocytosis mechanism. We observed localized bright Stoke's shift (Tb³⁺ ions, λ_ex = 488 nm) and upconversion (Er³⁺ ions, λ_ex = 980 nm) green fluorescence from cells suggesting their potential use as targeted bioimaging agents.