Diblock Copolymer Hydrophobicity Facilitates Efficient Gene Silencing and Cytocompatible Nanoparticle-Mediated siRNA Delivery to Musculoskeletal Cell Types

pH-responsive diblock copolymers provide tailorable nanoparticle (NP) architecture and chemistry critical for siRNA delivery. Here, diblock polymers varying in first (corona) and second (core) block molecular weight (<i>M</i>_n), corona/core ratio, and core hydrophobicity (%BMA) were synthesized to determine their effect on siRNA delivery in murine tenocytes (mTenocyte) and murine and human mesenchymal stem cells (mMSC and hMSCs, respectively). NP-mediated siRNA uptake, gene silencing, and cytocompatibility were quantified. Uptake is positively correlated with first block <i>M</i>_n in mTenocytes and hMSCs (<i>p</i> ≤ 0.0005). All NP resulted in significant gene silencing that was positively correlated with %BMA (<i>p</i> < 0.05) in all cell types. Cytocompatibility was reduced in mTenocytes compared to MSCs (<i>p</i> < 0.0001). %BMA was positively correlated with cytocompatibility in MSCs (<i>p</i> < 0.05), suggesting stable NP are more cytocompatible. Overall, this study shows that NP-siRNA cytocompatibility is cell type dependent, and hydrophobicity (%BMA) is the critical diblock copolymer property for efficient gene silencing in musculoskeletal cell types