Profiling Metal Oxides with Lipids: Magnetic Liposomal Nanoparticles Displaying DNA and Proteins

Metal oxides include many important materials with various surface properties. For biomedical and analytical applications, it is desirable to engineer their biocompatible interfaces. Herein, a phosphocholine liposome (DOPC) and its headgroup dipole flipped counterpart (DOCP) were mixed with ten common oxides. Using the calcein leakage assay, cryo-TEM, and z-potential measurement, these oxides were grouped into three types. The type 1 oxides (Fe3O4, TiO2, ZrO2, Y2O3, ITO, In2O3, and Mn2O3) form supported bilayers only with DOCP. Type 2 (SiO2) forms supported bilayers only with DOPC; type 3 (ZnO and NiO) are cationic and damage lipid membranes. Magnetic Fe3O4 nanoparticles were further studied for conjugation of fluorophores, proteins, and DNA to the supported DOCP bilayers via lipid headgroup labeling, covalent linking, or lipid insertion. Delivery of the conjugates to cells and selective DNA hybridization were demonstrated. This work provides a general solution for coating the type 1 oxides with a simple mixing in water, facilitating applications in biosensing, separation, and nanomedicine.