Nanomaterials For Subcellular Targeting:Strategy, Preparation And Application

Nanomaterial-cell interactions are key points for researches and clinical applications of various nanomedicines. Probing the subcellular distribution of nanomaterials holds great promises to elucidate the nanomaterial-cell interaction and promote the clinical translation of nanomedicines. Structural parameters (e.g., size, shape and softness) and surface property (e.g., charge property and hydrophilicity) of nanomaterials represent important factors influencing the subcellular distribution through mediation of the nanomaterial-cell membrane interaction, mechanism of cellular uptake, pathways of intracellular delivery, interaction with subcellular compartments or biomacromolecules. In this thesis, influencing factors of the nanomaterial-cell interaction, strategies and recent advances for subcellular targeting using nanomaterials are reviewed. Besides, two subcellular targeting nanoplatforms of nucleus and lysosome targeted nanoparticles were designed, prepared and tested for subcellular delivery or imaging purposes.1. Low pH triggered dissociation of large compound nanoparticles of oligo-L-lysine/Ir(III) complex for nucleus-targeted drug deliveryIn this section, we designed and synthesized an organometallic complex of oligo-L-lysine and iridium(III). The complex formed a kinetically frozen large compound nanoparticle (LINP) with a large size (ca.128 nm) in neutral water but dissociated into small nanoparticles (ca.28 nm) at acidic low pH. When incubated with HeLa cells, LINP was rapidly internalized by the cancer cells and dissociated into small nanoparticles within the acidic intracellular compartments (e.g., endosomes and lysosomes). The small nanoparticles escaped from the endo/lyso somes and stepped into the cytosol. With the help of oligo-Z-lysine on the surface acting as a nuclear targeting moiety, the cytosolic small nanoparticles entered and specifically accumulated within the nucleus via the nuclear pore complex. Due to the electrostatic interaction with the nuclear component DNA, the small nanoparticles were found to effectively release the cytotoxic Ir moiety within the nucleus, leading to significant apoptosis of the cancer cells. Further studies showed that the apoptosis was mediated via the caspase-3 pathway.2. Fluorescein-conjugated oligo(4-vinylphenyl phosphate) functionalized gold nanoprobe for specific labeling of the lysosome and imaging of extracellular acidification-induced lysosomal traffickingIn this section, an esterase active and scavenger-receptors recognizable fluorescein-conjugated oligo(4-vinylphenyl phosphate) was designed, synthesized and used for functionalization with a 16 nm gold nanoparticle, forming a nanoprobe, Au@OVP-Fluo. Due to quenching of the core gold nanoparticle, the nanoprobe (fluorescein) was non-fluorescent. However, after incubation with esterase, the enzyme hydrolyzed and released the gold-quenched fluorescein moiety, leading to significant fluorescence activation of the nanoprobe. After incubation with prostate cancer DU145 cells, the nanoprobe was recognized by cell membrane scavenger receptors and further internalized via caveoleo/actin microfilament mediated endocytosis. The nanoprobes were signicantly shuffled into the lysosome and this portion of nanoprobes specifically lighted up the lysosome owing to lysosome-induced fluorescence enhancement. Specifically, lysosomes are sole compartments containing various digestive inclusions which hydrolyzed and released the gold-quenched fluorescein molecules, leading to significant augmentation of fluorescence in the lysosome. Au@OVP-Fluo represented the first nanoparticle-based, enzyme-switchable fluorescence OFF-ON strategy for specific labeling of the lysosome in living cells.On account of specific lysosomal labeling, the nanoprobe was further used for imaging of extracellular acidification induced lysosomal trafficking. It was found that the lysosomes accumulated at the perinuclear region in neutral extracellular environment in different cancer cell lines (DU145, MCF-7 and HeLa). However, when acidic extracellular environment developed, the lysosomes translocated from the the perinuclear region to the cell surface for 4-6μm within 4 h for all the cancer cells. Since the acidic extracellular environment was greatly associated with tumors, imaging of this lysosomal displacement may function as a new methodology for cancer diagnosis.