Silver Nanoparticles Covered with pH-Sensitive Camptothecin-Loaded Polymer Prodrugs: Switchable Fluorescence "Off" or "On" and Drug Delivery Dynamics in Living Cells

A unique drug delivery system, in which silver nanoparticles (AgNPs) are covered with camptothecin (CPT)-based polymer prodrug, has been developed, and the polymer prodrug, in which the CPT is linked to the polymer side chains via an acid-labile β-thiopropionate bond, is prepared by RAFT polymerization. For poly(2-(2-hydroxyethoxy)ethyl methacrylate-co-methacryloyloxy-3-thiahexanoyl-camptothecin)@AgNPs [P(HEO₂MA-co-MACPT)@AgNPs], the polymer thickness on the AgNP surface is around 5.9 nm (TGA method). In vitro tests in buffer solutions at pH = 7.4 reveal that fluorescence of the CPT in the hybrid nanoparticles is quenched due to the nanoparticle surface energy transfer (NSET) effect, but under acidic conditions, the CPT fluorescence is gradually recovered with gradual release of the CPT molecules from the hybrid nanoparticles through cleavage of the acid-labile bond. The NSET "on" and "off" is induced by the CPT-AgNP distance change. This unique property makes it possible to track the CPT delivery and release process from the hybrid nanoparticles in the living cells in a real-time manner. The internalization and intracellular releasing tests of the hybrid nanoparticles in the HeLa cells demonstrate that the lysosome containing the hybrid nanoparticles displays CPT blue fluorescence due to release of the CPT under acidic conditions, and the drug-releasing kinetics shows fluorescence increase of the released CPT with incubation time. The cytotoxicity of hybrid nanoparticles is dependent on activity of the acid-labile bond. Therefore, this is a potential efficient drug delivery system in cancer therapy and a useful approach to study the mechanism of release process in the cells.

Fabrication of Functional Nano-objects through RAFT Dispersion Polymerization and Influences of Morphology on Drug Delivery

To study the influence of self-assembled morphologies on drug delivery, four different nano-objects, spheres, nanorods, nanowires, and vesicles having aldehdye-based polymer as core, were successfully prepared via alcoholic RAFT dispersion polymerization of p-(methacryloxyethoxy)benzaldehyde (MAEBA) using poly((N,N'-dimethylamino)ethyl methacrylate) (PDMAEMA) as a macro chain transfer agent (macro-CTA) for the first time. The morphologies and sizes of the four nano-objects were characterized by TEM and DLS, and the spheres with average diameter (D) of 70 nm, the nanorods with D of 19 nm and length of 140 nm, and the vesicles with D of 137 nm were used in the subsequent cellular internalization, in vitro release, and intracellular release of the drug. The anticancer drug doxorubicin (DOX) was conjugated onto the core polymers of nano-objects through condensation reaction between aldehyde groups of the PMAEBA with primary amine groups in the DOX. Because the aromatic imine is stable under neutral conditions, but is decomposed in a weakly acidic solution, in vitro release of the DOX from the DOX-loaded nano-objects was investigated in the different acidic solutions. All of the block copolymer nano-objects show very low cytotoxicity to HeLa cells up to the concentration of 1.2 mg/mL, but the DOX-loaded nano-objects reveal different cell viability and their IC50s increase as the following order: nanorods-DOX < vesicles-DOX < spheres-DOX. The IC50 of nanowires-DOX is the biggest among the four nano-objects owing to their too large size to be internalized. Endocytosis tests demonstrate that the internalization of vesicles-DOX by the HeLa cells is faster than that of the nanorods-DOX, and the spheres-DOX are the slowest to internalize among the studied nano-objects. Relatively more nanorods localized in the acidic organelles of the HeLa cells lead to faster intracellular release of the DOX, so the IC50 of nanorods is lower than that of the vesicles-DOX.

Assembly of Double-Hydrophilic Block Copolymers Triggered by Gadolinium Ions: New Colloidal MRI Contrast Agents

Mixing double-hydrophilic block copolymers containing a poly(acrylic acid) block with gadolinium ions in water leads to the spontaneous formation of polymeric nanoparticles. With an average diameter near 20 nm, the nanoparticles are exceptionally stable, even after dilution and over a large range of pH and ionic strength. High magnetic relaxivities were measured in vitro for these biocompatible colloids, and in vivo magnetic resonance imaging on rats demonstrates the potential utility of such polymeric assemblies.

α-(Aminomethyl)acrylate: polymerization and spontaneous post-polymerization modification of β-amino acid ester for a pH/temperature-responsive material

Radical polymerizations of α-(aminomethyl)acrylates involved spontaneous post-polymerization modification triggered by breaking of the hydrogen bond and afforded pH/temperature responsive polymers.

One-pot synthesis and biological imaging application of an amphiphilic fluorescent copolymer via a combination of RAFT polymerization and Schiff base reaction

A novel one-pot strategy for the fabrication of AIE-based FONs was developed via a combination of RAFT polymerization and Schiff base reaction for the first time.

Synthesis and Aggregation of Double Hydrophilic Diblock Glycopolymers via Aqueous SET-LRP

A chemically unprotected mannose-containing acrylate (ManA) monomer was synthesized and polymerized by Cu(0)-mediated radical polymerization in water (SET-LRP). One-pot block copolymerization was achieved upon addition of a solution of N-isopropylacrylamide (NIPAm) or diethylene glycol ethyl ether acrylate (DEGEEA) forming thermoresponsive double hydrophilic diblock glycopolymers which revealed self-assembly properties in aqueous solution forming well-defined, sugar-decorated nanoparticles.