Functionally Labeled Polymers And Nanoparticles : : Synthetic Strategies And In Vivo Analysis
- Author(s): Randolph, Lyndsay M.
- et al.
In the development of labeled polymers and polymeric nanoparticles for biomedical applications, one desires synthetic approaches that allow the most direct route to incorporate functional moieties. We contend the most desirable route is via the direct incorporation of functional groups during the polymerization process itself as monomers and/or chain transfer agents. In this work, we utilize ring-opening metathesis polymerization (ROMP) due to the high functional group tolerance of initiators and the ability to synthesize well-defined polymers of low dispersity and high molecular weight. Our research group has had great success in developing peptide-polymeric nanomaterials with ROMP via a graft-to strategy for the incorporation of peptide substrates of matrix matalloproteinases (MMPs). However, this technique does not allow for complete conjugation of peptide substrates to the polymer backbone. For this reason we sought to develop peptidyl monomers that contain a MMP peptide substrate for graft-through polymerization. Amphiphilic block-copolymers were synthesized with the peptidyl- monomer as the hydrophilic block and slowly transitioned into water to form nanoparticles (NPs). A pilot study determined that if the peptide substrate is displayed on the shell of a polymeric nanoparticle, it no longer maintains bioactivity. To further demonstrate the utility of labeling polymeric nanomaterials, a series of amphiphilic block copolymers end-labeled with dyes were synthesized and formulated into micellar nanoparticles. Dye monomer and chain transfer agent combinations were chosen that are known to operate either as a FRET acceptor (rhodamine) or as a quencher (DABCYL) of the donors, fluorescein and/or EDANS. Dye-labeled block copolymers were formulated into micellar nanoparticles, such that, the NP contained both a donor and acceptor. The FRET properties of mixed micellar nanoparticles were characterized by fluorescence spectroscopy and fluorescence lifetime. Lastly, we endeavored to move toward more clinically relevant systems that utilize MRI as an imaging modality. For this reason, polymers were synthesized containing the FDA approved MRI-contrast agent gadolinium-1,4,7,10-tetraazacyclododecane-1,4,7,10- tetraacetic acid (Gd-DOTA). Gd-containing hydrophilic and amphiphilic block copolymers were synthesized that were capable of self-assembly into spherical and fibril-shaped morphologies. Utilizing a 7T MRI scanner, polymeric nanomaterials were injected into the peritoneal cavity (IP injection) of healthy C57Bl/6 mice to analyze the retention and biodistribution of these polymer materials