Single-Step Assembly of Cationic Lipid–Polymer Hybrid Nanoparticles for Systemic Delivery of siRNA

Abstract

The clinical success of therapeutics of small interfering RNA (siRNA) is still hindered by its delivery systems. Cationic polymer or lipid-based vehicles as the major delivery systems of siRNA cannot sufficiently satisfy siRNA therapeutic applications. It is hypothesized that cationic lipid-polymer hybrid nanoparticles may take advantage of both polymeric and lipid-based nanoparticles for siRNA delivery, while diminishing the shortcomings of both. In this study, cationic lipid-polymer hybrid nanoparticles were prepared by a single-step nanoprecipitation of a cationic lipid (N,N-bis(2-hydroxyethyl)-N-methyl-N-(2-cholesteryloxycarbonyl aminoethyl) ammonium bromide, BHEM-Chol) and amphiphilic polymers for systemic delivery of siRNA. The formed hybrid nanoparticles comprised a hydrophobic polylactide core, a hydrophilic poly(ethylene glycol) shell, and a cationic lipid monolayer at the interface of the core and the shell. Such hybrid nanoparticles exhibited excellent stability in serum and showed significantly improved biocompatibility compared to that of pure BHEM-Chol particles. The hybrid nanoparticles were capable of delivering siRNA into BT474 cells and facilitated the escape of loaded siRNA from the endosome into the cytoplasm. The hybrid nanoparticles carrying polo-like kinase 1 (Plk1)-specific siRNA (siPlk1) remarkably and specifically downregulated expression of the oncogene Plk1 and induced cancer cell apoptosis both in vitro and in vivo and significantly suppressed tumor growth following systemic administration. We demonstrate that this system is stable, nontoxic, highly efficient, and easy to scale up, bringing the clinical application of siRNA therapy one important step closer to reality.

Strategies for optimizing polymer-lipid hybrid nanoparticle-mediated drug delivery

“…[1,3] Since then, various PLN formulations have been developed to encapsulate a single anticancer drug, [4] or co-encapsulate a drug with a chemosensitizer, [1,3] a drug with a P-glycoprotein (P-gp) inhibitor, [5] or dual anticancer drugs of synergy. [6] PLN formulations have also been developed to deliver biologics for gene therapy and immunotherapy, including siRNA [7] or siRNA with an anticancer drug. [8] PLN formulations have been shown to circumvent efflux transporter-mediated multidrug resistance (MDR) in cancer cells [1,4,6,9] and increase antitumor efficacy while reducing systemic toxicity of the anticancer drugs.…”

“…Up to date, reported PLN formulations can be divided into two major categories as schematically illustrated in Figure 1: type A -monolithic matrix PLN, where polymer and drug(s) are homogeneously distributed in the solid lipid matrix, [1,[3][4][5][6][9][10][11][12] and type Bcore-shell PLN, where drug-containing polymer core is covered by a single layer of phospholipid. [7,8,13] The latter is sometimes called lipid-polymer hybrid nanoparticles (LPN) in literature. [7,8,13] Figure 1(a) and (b) portray the representative components and procedures used for preparation of type A PLN formulation for cationic drug (a) or anionic siRNA (b).…”

“…[7,8,13] The latter is sometimes called lipid-polymer hybrid nanoparticles (LPN) in literature. [7,8,13] Figure 1(a) and (b) portray the representative components and procedures used for preparation of type A PLN formulation for cationic drug (a) or anionic siRNA (b). For loading a cationic drug, for example, doxorubicin HCl or verapamil HCl, an anionic polymer, such as dextran sulfate or hydrolyzed polymer of epoxidized soybean oil was employed to neutralize the charge of the drug and bring the drug to melted lipid phase.…”

“…[13] Figure 1(d) portrays another example of type B PLN where siRNA was loaded at the interface between polymer core and cationic lipid in the shell by ionic complexation. [7] …”

“…For example, by tailoring the structure and material of PLN, siRNA can be released in cytoplasm rapidly while a codelivered anticancer drug being released in nuclei slower. [7,8] …”