Calcium phosphate (CaP) nanoparticles (NPs), due to its biocompatibility, has been extensively studied as one kind of gene delivery vectors for cancer therapy. However, its clinical application for gene therapy is hampered primarily due to its low stability and limited endosomal escape. Even though adsorption of DNA on the surface of CaP can improve the stability of nanoparticles, surface exposed DNA in blood is susceptible to enzymatic digestion and albumin interaction, which eventually leads to inefficient gene transfection. Therefore, we hypothesize that coated of DNA-CaP nanoparticles could be an efficient way to shield DNA from albumin interaction and facilitate endosomal escape, thus enhance gene transfection. Polyethylene glycol (PEG) has been frequently utilized to coat d...[ Read more ]

Calcium phosphate (CaP) nanoparticles (NPs), due to its biocompatibility, has been extensively studied as one kind of gene delivery vectors for cancer therapy. However, its clinical application for gene therapy is hampered primarily due to its low stability and limited endosomal escape. Even though adsorption of DNA on the surface of CaP can improve the stability of nanoparticles, surface exposed DNA in blood is susceptible to enzymatic digestion and albumin interaction, which eventually leads to inefficient gene transfection. Therefore, we hypothesize that coated of DNA-CaP nanoparticles could be an efficient way to shield DNA from albumin interaction and facilitate endosomal escape, thus enhance gene transfection. Polyethylene glycol (PEG) has been frequently utilized to coat delivery carriers to promote stability and elongate circulation time by preventing albumin agglomeration. Octaarginine (R8), a cationic cell penetrating peptide, has been extensively applied to facilitate cellular uptake as well as to promote endosomal escape. In this study, we combined the properties of PEG and R8 together to afford a polymer-peptide hybrid PEG₅R8. Stable ternary DNA-CaP-PEG₅R8 nanoparticles were formed by addition of PEG₅R8 as the third component into DNA-CaP nanoparticles at an N/P ratio of 40. TEM and DLS showed smaller sized nanoparticles. Systematically formulation-screening studies indicated that the component ratio as well as the order of component mixing dramatically impact on resulting nanoparticles physical properties. Biological studies showed that these ternary nanoparticles can protect genes from DNase I digestion, are biocompatible, and displayed observable gene transfection, implying the potential gene transfection capability. This study enriches our toolbox to make stable and functional CaP-based nanoparticles and opens a new avenue to further explore their potential as gene delivery carriers.