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

Carolyne B. Braga, Ronaldo A. Pilli, Catia Ornelas, Marcus Weck

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish (US)
Pages (from-to)5290-5306
Number of pages17
Issue number12
StatePublished - Dec 13 2021

ASJC Scopus subject areas

  • Bioengineering
  • Biomaterials
  • Polymers and Plastics
  • Materials Chemistry


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