epsilon-Polylysine-Capped Mesoporous Silica Nanoparticles as Carrier of the C9h Peptide to Induce Apoptosis in Cancer Cells

Apoptotic signaling pathways are altered in numerous pathologies such as cancer. In this scenario, caspase-9/PP2Ac alpha interaction constitutes a key target with pharmacological interest to re-establish apoptosis in tumor cells. Very recently, a short peptide (C9h) known to disrupt caspase-9/PP2Ac alpha interaction with subsequent apoptosis induction was described. Here, we prepared two sets of mesoporous silica nanoparticles loaded with safraninO (S2) or with C9h peptide (S4) and functionalized with epsilon-polylysine as capping unit. Aqueous suspensions of both nanoparticles showed negligible cargo release whereas in the presence of pronase, a marked delivery of safraninO or C9h was observed. Confocal microscopy studies carried out with HeLa cells indicated that both materials were internalized and were able to release their entrapped cargos. Besides, a marked decrease in HeLa cell viability (ca. 50%) was observed when treated with C9h-loaded S4 nanoparticles. Moreover, S4 provides peptide protection from degradation additionally allowing for a dose reduction to observe an apoptotic effect when compared with C9h alone or in combination with a cell-penetrating peptide (i.e., Mut3DPT-C9h). Flow cytometry studies, by means of Annexin V-FITC staining, showed the activation of apoptotic pathways in HeLa as a consequence of S4 internalization, release of C9h peptide and disruption of caspase-9/PP2Ac alpha interaction.