Abstract text (incl. figure legends and references)
I: Calcium phosphate nanoparticles (CaP-NPs) are of great interest in modern biomedicine because of their biocompatibility, biodegradability and possibility to target different cells. Their surface functionalization opens new pathways for a biomedical application, for imaging or enhanced targeting. CaP-NPs are easily taken up by cells and represent efficient carriers for biomolecules.
O: Elucidate the applicability of click chemistry by attaching fluorescently labelled model proteins, i.e. bovine serum albumin (BSA) and hemoglobin, as well as ultrasmall gold nanoparticles to the surface of CaP-NPs, to investigate their performance in cell uptake.
M&M: For colloidal stabilization, CaP-NPs were coated with polyethyleneimine (PEI) and a silica shell. To functionalize the surface of CaP-NPs with fluorescent proteins and gold nanoparticles, either azide groups or alkyne groups were covalently attached to the particle surface. This is a prerequisite for copper-catalyzed azide-alkyne cycloaddition (CuAAC; click chemistry) with alkyne-functionalized proteins or azide-functionalized gold nanoparticles. The characterization of CaP-NPs was performed by scanning electron microscopy (SEM) for the particle diameter and dynamic light scattering (DLS) to analyze the dispersibility. UV-Vis spectroscopy and atomic absorption spectrometry (AAS) were used to determine the number of attached ligands. The uptake by cells was studied by confocal laser scanning microscopy (CLSM).
R: Proteins were successfully clicked to the surface of CaP-NPs with a stable bond during and after cellular uptake. Furthermore, gold nanoparticles can be covalently attached to CaP-NPs, creating a multifunctional system to transport more than one agent into cells. All nanoparticles were successfully taken up by HeLa cells and were colloidally stable.
C: CaP-NPs can be covalently functionalized with model proteins and ultrasmall gold nanoparticles. The functionalized nanoparticles can act as efficient transporters into cells.