Synthesis and characterization of novel amino-modified calcium phosphate nanoparticles used for gene delivery applications

Calcium phosphate (CaP) has been in the point of interest for in-vitro gene delivery for many years because of its excellent biocompatibility and straight forward application. In this research, a simple single step method was developed to functionalize CaP nanoparticles (NPs) with aminosilane. The cationic surface charge was supposed to cause dispersion stability of the NPs mediated by electrostatic repulsion and to enable more complete condensation of pDNA. The physicochemical characterization revealed that depending on the pH during the synthesis step, two different crystalline phases of CaP NPs (brushite and hydroxyapatite (HaP)) were produced. Both CaP NPs had a size <150 nm and a narrow-size distribution. It turned out that brushite NPs had much higher density of amine groups on the surface in comparison to HaP NPs. Both types of NPs showed biodegradability, blood compatibility and a negligible cytotoxicity and had low effect on complement activation and cytokine secretion from macrophages. Both amino-CaP NPs were capable of binding pDNA, with brushite NPs because of their higher density of surface amine groups, being more efficient in condensation and consequently resulted in higher transfection efficiency in A549 and HEK293 cells. The potential of the new amino-modified CaP NPs to be stored in dried condition and to be re-dispersed easily as well as promising biological results showed the remarkable advancement regarding the use of CaP NPs in gene delivery.Für in-vitro Gentransfer wird seit vielen Jahren Calciumphosphat (CaP) verwendet, begründed durch seine ausgezeichneten Biokompatibilität und direkte Applikationsmöglichkeit. Davon ausgehend beschäftigt sich die vorliegende Arbeit mit der Entwicklung eines einstufigen Verfahrens zur Synthese von Aminosilan-funktionalisierten CaP Nanopartikeln (NP). Die Induzierung einer ausreichend kationischen Oberflächenladung begünstigt aufgrund elektrostatischer Abstoßung die Dispersionsstabilität der NP und führt zudem zu einer vollständigeren Kondensation der pDNA. Die physikochemische Charakterisierung zeigte, dass in Abhängigkeit des pH-Wertes während der Synthese zwei unterschiedliche kristalline Phasen der CaP NP (Brushit und Hydroxyapatit (HaP)) hergestellt werden konnten. Beide NPs hatten eine Größe