This work introduces a novel chitosan-based siRNA nanoparticle delivery system for RNA interference in vitro and in vivo. The formation of interpolyelectrolyte complexes between siRNA duplexes (21-mers) and chitosan polymer into nanoparticles, ranging from 40 to 600 nm, was shown using atomic force microscopy and photon correlation spectroscopy. Rapid uptake (1 h) of Cy5-labeled nanoparticles into NIH 3T3 cells, followed by accumulation over a 24 h period, was visualized using fluorescence microscopy. Nanoparticle-mediated knockdown of endogenous enhanced green fluorescent protein (EGFP) was demonstrated in both H1299 human lung carcinoma cells and murine peritoneal macrophages (77.9% and 89.3% reduction in EGFP fluorescence, respectively). In addition, Western analysis showed approximately 90% reduced expression of BCR/ABL-1 leukemia fusion protein while BCR expression was unaffected in K562 (Ph(+)) cells after transfection using nanoparticles containing siRNA specific to the BCR/ABL-1 junction sequence. Effective in vivo RNA interference was achieved in bronchiole epithelial cells of transgenic EGFP mice after nasal administration of chitosan/siRNA formulations (37% and 43% reduction compared to mismatch and untreated control, respectively). These findings highlight the potential application of this novel chitosan-based system in RNA-mediated therapy of systemic and mucosal disease.

Delivery technologies are required for realizing the clinical potential of molecular medicines. This work presents an alternative technology to preformulated delivery systems by harnessing the natural transport properties of serum albumin using endogenous binding of gapmer antisense oligonucleotides (ASOs)/albumin constructs. We show by an electrophoretic mobility assay that fatty acid-modified gapmer and human serum albumin (HSA) can self-assemble into constructs that offer favorable pharmacokinetics. The interaction was dependent on fatty acid type (either palmitic or myristic acid), number, and position within the gapmer ASO sequence, as well as phosphorothioate (PS) backbone modifications. Binding correlated with increased blood circulation in mice (t1/2 increased from 23 to 49 min for phosphodiester [PO] gapmer ASOs and from 28 to 66 min for PS gapmer ASOs with 2× palmitic acid modification). Furthermore, a shift toward a broader biodistribution was detected for PS compared with PO gapmer ASOs. Inclusion of 2× palmitoyl to the ASOs shifted the biodistribution to resemble that of natural albumin. This work, therefore, presents a novel strategy based on the proposed endogenous assembly of gapmer ASOs/albumin constructs for increased circulatory half-life and modulation of the biodistribution of gapmer ASOs that offers tunable pharmacokinetics based on the gapmer modification design.

Bone remodeling and regeneration are highly regulated multistep processes involving posttranscriptional regulation by microRNAs (miRNAs). Here, we performed a global profiling of differentially expressed miRNAs in bone-marrow-derived skeletal cells (BMSCs; also known as stromal or mesenchymal stem cells) during in vitro osteoblast differentiation. We functionally validated the regulatory effects of several miRNAs on osteoblast differentiation and identified 15 miRNAs, most significantly miR-222 and miR-423, as regulators of osteoblastogenesis. In addition, we tested the possible targeting of miRNAs for enhancing bone tissue regeneration. Scaffolds functionalized with miRNA nano-carriers enhanced osteoblastogenesis in 3D culture and retained this ability at least 2 weeks after storage. Additionally, anti-miR-222 enhanced in vivo ectopic bone formation through targeting the cell-cycle inhibitor CDKN1B (cyclin-dependent kinase inhibitor 1B). A number of additional miRNAs exerted additive osteoinductive effects on BMSC differentiation, suggesting that pools of miRNAs delivered locally from an implanted scaffold can provide a promising approach for enhanced bone regeneration.