One-Step Synthesis of Nanosized and Stable Amino-Functionalized Calcium Phosphate Particles for DNA Transfection

Calcium phosphate (CaP) is used for in vitro transfection because of low toxicity and simple and low cost synthesis. The transfection results however vary because the precipitation lacks reproducibility and results in polydispersed, agglomerated particles. Here a reproducible, one-step procedure for the preparation of amino-modified CaP nanoparticles (NPs) is described using N -(2-aminoethyl)-3-aminopropyltrimethoxysilane as modifying and dispersing agent. The aim was to produce homogeneous, stable CaP NPs, which are loaded with DNA after particle formation. The refined wet-precipitation method yielded NPs with a narrow size distribution (∼140 nm) and positive zeta potential at physiological pH. FTIR and Raman spectroscopy analysis verified the aminosilane modification. Interestingly two types of CaP crystalline structures, Brushite and Hydroxyapatite, can be produced depending on the pH and without hydrothermal treatment. Both CaP crystalline phases were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET) analysis. Both showed very low toxicity and enabled reproducible transfection of A549 cells. The higher surface functionalization density of Brushite NPs led to superior pDNA condensation capability and higher transfection in lower NP concentration. The advantages of the improved synthesis are the achievement of stable, crystalline CaP NPs in higher yield and narrow distributed size achieved by agglomeration reduction even without hazardous surfactant.