Natural Polyphenol Inspired Polycatechols for Efficient siRNA Delivery

There is a continuing quest to rationally fabricate polymeric biomaterials with both high transfection efficiency and minimal toxicity for the emerging opportunities in small interfering RNA(siRNA)delivery.Recently,this goal was promoted highly by developing a robust and efficient strategy to facilitate polymer-mediated RNAi using natural polyphenols with multiple phenol groups that could condense siRNA effectively into negatively charged nanoparticles(NPs).Further coating of these NPs with cationic polymers of low molecular weight enabled their intracellular siRNA delivery.Inspired by the structural and functional features of natural polyphenols,we aimed to further the development of low molecular weight polycatechols as a new class of efficient and biocompatible polymers for siRNA delivery in our current study.The fabricated polycatechols have benefits of requiring only one-step fabrication toward efficient siRNA nanoformulations.Moreover,they could deliver siRNA into cells and silence target genes both in vitro and in vivo.The resulting polycatechol/siRNA formulations were also functionally competent,demonstrating a successful,profound downregulation of a proinflammatory enzyme to attenuate chronic intestinal inflammation in an intestinal injury model.This study provides a new approach in chemistry for the development of efficient synthetic polymers for therapeutic siRNA delivery.

SYNTHESIS OF POLYCATECHOL WITH ELECTROCHEMICAL ACTIVITY AND ITS PROPERTIES

The electrochemical polymerization of catechol on platinum has been carried out using repeated potential cycling between -0.2 and 1.1 V (versus SCE). The electrolytic solution consisted of 0.2 mol dm(-3) catechol, 0.5 mol dm(-3) NaCl and 0.1 mol dm(-3) Na2HPO4 with pH 8.72. Catechol can not be polymerized at pH greater than or equal to 10.12. Polycatechol has an electrochemical lactivity at pH less than or equal to 4. The anodic and cathodic peak potentials of polycatechol shift towards more negative values as the pH of the solution increases from 1 to 4. The electrochemical activity of polycatechol hardly changes in this pH region, but it decreases slowly with time. This is caused by oxygen in air, which leads to an irreversible oxidation of polycatechol. This property is favorable for protecting metals from corrosion. Raman and FTIR spectra of polycatechol and catechol are quite different. AFM images of polycatechol films provide evidence that the image of the oxidized state of polycatechol is markedly different from that of the reduced one. This difference is caused by doping and dedoping of polycatechol.

Catechol-Based Polymers with High Efficacy in Cytosolic Protein Delivery

Polymers have been widely proposed as carriers for cytosolic protein delivery despite multiple barriers such as protein binding,cell internalization,and endosome escape during cytosolic delivery.Inspired by the strong binding affinity of natural polyphenols with proteins and cell membranes,herein we propose polyphenol modification to improve the efficacy of the protein delivery of cationic polymers.Catecholmodified dendrimers with balanced hydrophobic and hydrogen-bonding interactions show the highest efficacy for various cargo proteins and peptides while the pyrogallol-grafted ones exhibit the lowest efficacy due to increased ligand hydrophilicity.The catechol-based polymers efficiently deliver various bioactive proteins into the cytosol of live cells,exerting biofunctions after intracellular release,and successfully transmittingα-chymotrypsin into tumor cells in vivo to inhibit tumor growth.This study proves that polycatechols can serve as a family of highly efficient carriers for delivery of macromolecular biopharmaceuticals.