Influence of the Topology of Poly(L-Cysteine) on the Self-Assembly, Encapsulation and Release Profile of Doxorubicin on Dual-Responsive Hybrid Polypeptides

Abstract

Τhe synthesis of a series of novel hybrid block copolypeptides based on poly(ethylene oxide) (PEO), poly(l-histidine) (PHis) and poly(l-cysteine) (PCys) is presented. The synthesis of the terpolymers was achieved through a ring-opening polymerization (ROP) of the corresponding protected N-carboxy anhydrides of Nim-Trityl-l-histidine and S-tert-butyl-l-cysteine, using an end-amine-functionalized poly(ethylene oxide) (mPEO-NH2) as macroinitiator, followed by the deprotection of the polypeptidic blocks. The topology of PCys was either the middle block, the end block or was randomly distributed along the PHis chain. These amphiphilic hybrid copolypeptides assemble in aqueous media to form micellar structures, comprised of an outer hydrophilic corona of PEO chains, and a pH- and redox-responsive hydrophobic layer based on PHis and PCys. Due to the presence of the thiol groups of PCys, a crosslinking process was achieved further stabilizing the nanoparticles (NPs) formed. Dynamic light scattering (DLS), static light scattering (SLS) and transmission electron microscopy (TEM) were utilized to obtain the structure of the NPs. Moreover, the pH and redox responsiveness in the presence of the reductive tripeptide of glutathione (GSH) was investigated at the empty as well as the loaded NPs. The ability of the synthesized polymers to mimic natural proteins was examined by Circular Dichroism (CD), while the study of zeta potential revealed the “stealth” properties of NPs. The anticancer drug doxorubicin (DOX) was efficiently encapsulated in the hydrophobic core of the nanostructures and released under pH and redox conditions that simulate the healthy and cancer tissue environment. It was found that the topology of PCys significantly altered the structure as well as the release profile of the NPs. Finally, in vitro cytotoxicity assay of the DOX-loaded NPs against three different breast cancer cell lines showed that the nanocarriers exhibited similar or slightly better activity as compared to the free drug, rendering these novel NPs very promising materials for drug delivery applications.

Polypeptide-Based Systems: From Synthesis to Application in Drug Delivery

“…mPEO-b-PHis-b-PCysMicelles Doxorubicin D H ~120-210 nm depending on copolymer composition and drug loading; antiproliferative activity of DOX-loaded NPs was comparable to free DOX in three breast cancer cell lines (MCF-7, T-47D, and MDA-MB231)[107] P(Glu-co-Phe) Nanogels Doxorubicin D H = 150 nm (PDI = 0.36); more effective cell penetration in comparison with submicron-sized CaCO 3 +Dextran sulfate particles; effective inhibition activity of nanoformulations toward breast cancer cells (MCF7); sustained DOX release in vivo (rats) for 3 weeks after intraperitoneal administration[449] mPEG-b-P(Glu-co-Glu(OEtCl)); mPEG-b-P(Glu-co-Glu(OEtCl)-110 nm; X-ray-responsive Se−Se bond in nanogels; enhanced DOX release after X-ray irradiation due to nanogel disintegration; a synergistic effect of chemo-and radiotherapy and fewer side effects toward human A549 lung carcinoma-bearing nude mice[450] …”