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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.

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. [ABSTRACT FROM AUTHOR]

Silica@zirconia core@shell oxide nanoparticles of approx. 50 nm diameter were developed in view of an application as a novel carrier with adjuvant activities for cancer vaccines. To this end, the aim was to cover the surface of the nanocarrier by potent single stranded DNA (ssDNA) type immune stimulators used in cancer vaccination. Prior to characterizing the binding of ssDNA to the nanocarrier surface, the adsorption of deoxynucleoside monophosphate building blocks (dNMPs) was studied. After optimization of conditions for synthesis, solvent exchange and surface modification, the effects and possible interference of several buffers, such as HEPES, PIPES, MOPS and MOPSO, were also investigated. Formation of a new compound was revealed by UV–VIS spectroscopy during the recording of zeta potential vs. pH titration curves in the presence of HEPES and PIPES buffer in the neutral-acidic pH region. We identified this new species as gold ions etched from the electrode of the zeta cuvette, stabilized by the buffers via chelation, which is then followed by their conversion into gold nanoparticles. • Silica@zirconia core@shell nanoparticles of approx. 50 nm diameter were developed. • Adsorption of DNA building blocks in different biocompatible buffers was studied. • A side reaction in the zeta cuvette in the presence of buffers was revealed. • Gold ions etched from the electrode were stabilized by the HEPES and PIPES. • The gold ions converted to gold nanoparticles. [ABSTRACT FROM AUTHOR]