Purpose : Low cytotoxicity and high cellular gene delivery capability are among the most important prerequisites for the selection of a non-viral carrier. In this study, we report the development of calcium phosphate (CAP) nanoparticles stabilized by a conjugate of the biological adhesive molecule, 3,4-dihydroxy-L-phenylalanine (dopa), and a nontoxic hydrophilic natural polymer, hyaluronic acid (HA), for targeted siRNA delivery to cancer cells.

Methods : Dopa-conjugated HA (dopa-HA) was synthesized by EDC/NHS chemistry and analyzed by spectrometry and 1H-NMR. Stabilized calcium phosphate nanoparticles containing siRNA (CAP/siRNA/dopa-HA) was prepared by simply mixing CaCl2 solution containing siRNA with a HEPES buffer containing Na2HPO4 and subsequent addition of a solution containing dopa-HA. The particles were characterized by using light scattering method and transmission electron microscope (TEM). The gene silencing and cancer cell-targeting ability of CAP/siRNA/dopa-HA was evaluated by monitoring cellular reporter activity (luciferase) in human colon carcinoma cells permanently expressing firefly luciferase. Confocal microscopy and FACS analysis were performed to assess CD44-specific cellular delivery. Bio-distribution and in vivo gene silencing of CAP/siRNA/dopa-HA nanoparticles were studied in an animal model bearing tumor xenograft.

Results : CAP/siRNA/dopa-HA can form compact nanoparticles that effectively protect siRNA from enzymatic degradation despite the structural drawbacks of siRNA, such as low charge density and short and rigid structure. In addition, stabilized CAP nanoparticles were able to maintain their colloidal stability in a physiological salt condition for over a week. The superior ability of CAP/siRNA/dopa-HA to maintain the integrity of encapsulated siRNA and the stability in solution of the nanoparticles allow this formulation to achieve improved intratumoral accumulation of siRNA and a high level of target gene silencing in solid tumors after systemic administration.

Conclusion Considering its biocompatibility, transfection efficacy, and tumor targeting capability, this stabilized organic-inorganic hybrid gene delivery platform should be considered a promising candidate carrier for systemic siRNA delivery and targeted cancer therapy.

Citation Format: Min Sang Lee, Jung Eun Lee, Eunkyoung Byun, Nak Won Kim, Haeshin Lee, Ji Hoon Jeong. Tumor-targeted delivery of siRNA using stabilized calcium phosphate nanoparticles based on bio-inspired hyaluronic acid conjugate. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 707. doi:10.1158/1538-7445.AM2014-707