Pseudotannins self-assembled into antioxidant complexes

Abstract

Natural tannins are attractive as building blocks for biomaterials due to their antioxidant properties and ability to form interpolymer complexes (IPCs) with other macromolecules. One of the major challenges to tannin usage in biomedical applications is their instability at physiological conditions and a lack of control over the purity and reactivity. Herein, we report the synthesis and characterization of tannin-like polymers with controlled architecture, reactivity, and size. These pseudotannins were synthesized by substituting linear dextran chains with gallic, resorcylic, and protocatechuic pendant groups to mimic the structure of natural hydrolysable tannins. We demonstrate that these novel materials can self-assemble to form reductive and colloidally stable nanoscale and microscale particles. Specifically, the synthesis, turbidity, particle size, antioxidant power, and cell uptake of IPCs derived from pseudotannins and poly(ethylene glycol) was evaluated.

Activatable interpolymer complex-superparamagnetic iron oxide nanoparticles as magnetic resonance contrast agents sensitive to oxidative stress

“…Poly(gallol) was prepared as described previously [43]. Briefly, TBBA molecules were conjugated to a linear dextran backbone of either 40 or 200 kDa molecular weight and were then converted to phenols via a palladium black catalyzed deprotection reaction.…”

“…Poly(gallol)s were dissolved in a 1 M sodium carbonate buffer (pH 8) to convert the phenolic units to phenoxide salts, making them water soluble while limiting self-complexation and oxidation during storage. These poly(gallate) salts were lyophilized for storage until use [43]. …”

“…Complexed IPC-SPIOs were formed by hydrogen bonding between PEG and poly(gallol) [43]. Uncoated SPIOs and PEG 6, 10, 35, and 300 kDa-SPIOs were separately diluted to achieve a concentration of 2 mg of SPIOs per mL.…”

“…We present the synthesis and characterization of SPIOs with a coating of interpolymer complexed (IPC) poly(ethylene glycol) (PEG) and poly(gallol), a synthetic dextran-based tannin-inspired polymer [43]. Hydrophilic PEG is able to colloidally stabilize nanoparticles and increase blood circulation time by reducing opsonization and immune response [44–46].…”

“…Hydrophilic PEG is able to colloidally stabilize nanoparticles and increase blood circulation time by reducing opsonization and immune response [44–46]. Poly(gallol) polymers are designed to mimic the natural structure of tannins, exhibiting anti-oxidant, anti-inflammatory, and anti-microbial properties [43, 47]. In this nanoparticle, interpolymer complexation relies on hydrogen bonding between PEG and poly(gallol) (Figure 1A).…”