Abstract
Surface initiated atom transfer radical polymerization (SI-ATRP) documented a simple but efficient technique to grow a dense polymer layer on any surface. Gold nanoparticles (AuNPs) give a broad surface to immobilize sulfhyryl group-containing initiators for SI-ATRP; in addition, AuNPs are the major nanoparticulate carriers for delivery of anti-cancer therapeutics, since they are biocompatible and bioinert. In this work, AuNPs with a disulfide initiator were polymerized with sulfoethyl methacrylate by SI-ATRP to decorate the particles with anionic corona, and branched polyethyeleneimine (PEI) and siRNA were sequentially layered onto the anionic corona of AuNP by electrostatic interaction. The in vitro anti-cancer effect confirmed that AuNP with anionic corona showed higher degrees of apoptosis as well as suppression of the oncogene expression in a siRNA dose-dependent manner. The in vivo study of tumor-bearing nude mice revealed that mice treated with c-Myc siRNA-incorporated AuNPs showed dramatically decreased tumor size in comparison to those with free siRNA for 4 weeks. Furthermore, histological examination and gene expression study revealed that the decorated AuNP significantly suppressed c-Myc expression. Thus, we envision that the layer-by-layer assembly on the anionic brushes can be potentially used to incorporate nucleic acids onto metallic particles with high transfection efficiency.
Highlights
Surface initiated atom transfer polymerization (SI-ATRP) was employed to decorate surfaces with dense layers of polymers to change the surface chemistry with desirable features [1,2]
any surface. Gold nanoparticles (AuNPs) were synthesized by adding the tri-sodium citrate as a reducing and capping reagent, and the surface citrate on the AuNP was substituted with disulfide initiator to polymerize sulfoethyl methacrylate monomer on the AuNP (SEMA@AuNP)
The surface charge of Sulfoethyl methacrylate (SEMA)@AuNP was controlled by manipulating the monomer for SI-ATRP because the outmost layers of AuNP were completely shielded by the high density of polymerized SEMA (pSEMA) [19]
Summary
Surface initiated atom transfer polymerization (SI-ATRP) was employed to decorate surfaces with dense layers of polymers to change the surface chemistry with desirable features [1,2]. Gold nanoparticles (AuNPs) have advantages of small size, non-cytotoxicity, non-immunogenicity, and the possibility of being used in imaging; they have the disadvantage of a rigid structure They are not appropriate for siRNA delivery as the flexible carrier; their surfaces can be modified by polymers using several types of methods. The SI-ATRP of a dense anionic polymer layer on the AuNPs surface enhanced the surface negative charge and elevated the subsequent decoration amount of PEI, which further increased the siRNA sequester efficiency in comparison to siRNA incorporation efficiency on PEI-modified bare AuNPs. Surface analysis of decorated particles as well as in vitro and in vivo tests were performed to determine the efficiency of these particles
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