Electro-optic properties of a side chain poly(norbornene-dicarboximide) system with an appended phenyl vinylene thiophene chromophore

Near-Infrared Fluorescent Micelles from Poly(norbornene) Brush Triblock Copolymers for Nanotheranostics

This contribution describes the design and synthesis of multifunctional micelles based on amphiphilic brush block copolymers (BBCPs) for imaging and selective drug delivery of natural anticancer compounds. Well-defined BBCPs were synthesized via one-pot multi-step sequential grafting-through ring-opening metathesis polymerization (ROMP) of norbornene-based macroinitiators. The norbornenes employed contain a poly(ethylene glycol) methyl ether chain, an alkyl bromide chain, and/or a near-infrared (NIR) fluorescent cyanine dye. After block copolymerization, post-polymerization transformations using bromide-azide substitution, followed by the strain-promoted azide-alkyne cycloaddition (SPAAC) allowed for the functionalization of the BBCPs with the piplartine (PPT) moiety, a natural product with well-documented cytotoxicity against cancer cell lines, via an ester linker between the drug and the polymer side chain. The amphiphilic BBCPs self-assembled in aqueous media into nano-sized spherical micelles with neutral surface charges, as confirmed by dynamic light scattering analysis and transmission electron microscopy. During self-assembly, paclitaxel (PTX) could be effectively encapsulated into the hydrophobic core to form stable PTX-loaded micelles with high loading capacities and encapsulation efficiencies. The NIR fluorescent dye-containing micelles exhibited remarkable photophysical properties, excellent colloidal stability under physiological conditions, and a pH-induced disassembly under slightly acidic conditions, allowing for the release of the drug in a controlled manner. The in vitro studies demonstrated that the micelles without the drug (blank micelles) are biocompatible at concentrations of up to 1 mg mL^-1 and present a high cellular internalization capacity toward MCF-7 cancer cells. The drug-functionalized micelles showed in vitro cytotoxicity comparable to free PPT and PTX against MCF-7 and PC3 cancer cells, confirming efficient drug release into the tumor environment upon cellular internalization. Furthermore, the drug-functionalized micelles exhibited higher selectivity than the pristine drugs and preferential cellular uptake in human cancer cell lines (MCF-7 and PC3) when compared to the normal breast cell line (MCF10A). This study provides an efficient strategy for the development of versatile polymeric nanosystems for drug delivery and image-guided diagnostics. Notably, the easy functionalization of BBCP side chains via SPAAC opens up the possibility for the preparation of a library of multifunctional systems containing other drugs or functionalities, such as target groups for recognition.

ROMP Synthesis of Side-Chain Ferrocene-Containing Polyelectrolyte and Its Redox-Responsive Hydrogels Showing Dramatically Improved Swelling with β-Cyclodextrin

A new side-chain ferrocene (Fc)-containing polyelectrolyte has been synthesized by controlled ring-opening metathesis polymerization of a water-soluble Fc-containing norbornene-based quaternary ammonium salt, as well as the corresponding covalently cross-linked polyelectrolyte hydrogel. In order to provide Fc-containing supramolecular polyelectrolyte hydrogels whose swelling property is largely improved by host-guest interaction, a covalently cross-linked polyelectrolyte hydrogel is soaked into the β-CD aqueous solution to form β-CD@Fc supramolecular polyelectrolyte hydrogel, or alternatively the quaternary ammonium salt supramolecular monomer is first formed, then copolymerized with a crosslinking agent to fabricate the supramolecular hydrogel with better water absorption ability. All the Fc-containing hydrogels exhibited good redox-responsiveness with swelling-shrinking behaviors by chemically reversibly adjusting the disassembly/assembly of β-CD@Fc inclusion complexes. This is the first example of side-chain Fc-containing polycationic supramolecular hydrogels possessing swelling-shrinking properties based on the splitting/combining of β-CD and Fc units, and potential applications are expected as controlled drug delivery and actuators.