The development of delivery systems for the immobilization of nucleic acid cargo molecules
is of prime importance due to the need for safe administration of DNA or RNA type
of antigens and adjuvants in vaccines. Nanoparticles (NP) in the size range of 20–200
nm have attractive properties as vaccine carriers because they achieve passive targeting
of immune cells and can enhance the immune response of a weakly immunogenic antigen
via their size. We prepared high capacity 50 nm diameter silica@zirconia NPs with
monoclinic/cubic zirconia shell by a green, cheap and up-scalable sol–gel method.
We studied the behavior of the particles upon water dialysis and found that the ageing
of the zirconia shell is a major determinant of the colloidal stability after transfer
into the water due to physisorption of the zirconia starting material on the surface.
We determined the optimum conditions for adsorption of DNA building blocks, deoxynucleoside
monophosphates (dNMP), the colloidal stability of the resulting NPs and its time dependence.
The ligand adsorption was favored by acidic pH, while colloidal stability required
neutral-alkaline pH; thus, the optimal pH for the preparation of nucleic acid-modified
particles is between 7.0–7.5. The developed silica@zirconia NPs bind as high as 207
mg dNMPs on 1 g of nanocarrier at neutral-physiological pH while maintaining good
colloidal stability. We studied the influence of biological buffers and found that
while phosphate buffers decrease the loading dramatically, other commonly used buffers,
such as HEPES, are compatible with the nanoplatform. We propose the prepared silica@zirconia
NPs as promising carriers for nucleic acid-type drug cargos.