Silica@zirconia Core@shell Nanoparticles for Nucleic Acid Building Block Sorption

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.

Nanoscale cooperative adsorption for materials control

Adsorption plays vital roles in many processes including catalysis, sensing, and nanomaterials design. However, quantifying molecular adsorption, especially at the nanoscale, is challenging, hindering the exploration of its utilization on nanomaterials that possess heterogeneity across different length scales. Here we map the adsorption of nonfluorescent small molecule/ion and polymer ligands on gold nanoparticles of various morphologies in situ under ambient solution conditions, in which these ligands are critical for the particles’ physiochemical properties. We differentiate at nanometer resolution their adsorption affinities among different sites on the same nanoparticle and uncover positive/negative adsorption cooperativity, both essential for understanding adsorbate-surface interactions. Considering the surface density of adsorbed ligands, we further discover crossover behaviors of ligand adsorption between different particle facets, leading to a strategy and its implementation in facet-controlled synthesis of colloidal metal nanoparticles by merely tuning the concentration of a single ligand.

Fine-Tuning Dye Adsorption Capacity of UiO-66 by Mixed-Ligand Approach

Mixed ligand synthetic approach offers an alternative to engineer a specific character in metal-organic framework (MOFs) materials. Herein, we synthesized and characterized a well-known prototype zirconium based-MOF, so called UiO-66 and its mixed ligand derivatives UiO-66-xATA, where x is mole fraction (0.5, 0.75 and 1.0) and ATA is 2-animoterephthalate. The aim of the study is to observe whether the dye adsorption capacity can be tuned/enhanced by the ATA ligand substitution into the framework. We found that, at room temperature, UiO-66-0.75ATA shows the highest adsorption capacity toward various dye solution including methylene blue (MB), indigo carmine (IC) and congo red (CR). The optimum adsorption conditions in all four materials were found to be in a common trend where their adsorption capacities can be increased with decreasing pH and adsorbent dose, increasing of IC concentration, contact time and temperature. Pseudo-second order kinetics model fits best with their adsorption data, where UiO-66-ATA has the fastest rate of adsorption. Langmuir and Freundlich isotherms were found to best describe adsorption behaviour in ATA-containing UiO-66 and UiO-66 respectively, where adsorption processes were found to be physisorption. Confirming by thermodynamic studies, the adsorption in all four materials occurred spontaneously, driven by entropy. Computational studies showed ligand to metal charge transfer where the distribution of electron densities was varied with the amount of functionalized ligand. Adsorption mechanism is proposed as a synergistic interplay between electrostatic interaction and hydrogen bonding. The findings in this work broaden potential strategy to fine-tune the dye adsorption capacity in MOF materials.

Unveiling surface charge on chalcogen atoms toward the high aspect-ratio colloidal growth of two-dimensional transition metal chalcogenides

The steric effects of the ligands unveil the charged chalcogen sites which are induced by the ligand adsorption, thus promoting the anisotropic growth of two-dimensional transition metal chalcogenides (TMCs).

Rearrangement of protein structures on a gold nanoparticle surface is regulated by ligand adsorption modes

With development of the nanomedicine field and increasing hazards of exposure to nanobiological materials, research on protein corona is urgently required. In particular, the understanding of the mechanism of structural...