From Structure to Application: The Evolutionary Trajectory of Spherical Nucleic Acids.

Since the proposal of the concept of spherical nucleic acids (SNAs) in 1996, numerous studies have focused on this topic and have achieved great advances. As a new delivery system for nucleic acids, SNAs have advantages over conventional deoxyribonucleic acid (DNA) nanostructures, including independence from transfection reagents, tolerance to nucleases, and lower immune reactions. The flexible structure of SNAs proves that various inorganic or organic materials can be used as the core, and different types of nucleic acids can be conjugated to realize diverse functions and achieve surprising and exciting outcomes. The special DNA nanostructures have been employed for immunomodulation, gene regulation, drug delivery, biosensing, and bioimaging. Despite the lack of rational design strategies, potential cytotoxicity, and structural defects of this technology, various successful examples demonstrate the bright and convincing future of SNAs in fields such as new materials, clinical practice, and pharmacy.

Effect of Ion Corrosion on 517 Phase Stability.

The main hydration product and source of strength of magnesium oxysulfate cement is 5Mg(OH)2·MgSO4·7H2O (known as the 517 phase). Hardened pastes containing 92.38% of the 517 phase were synthesized in this study, and the influence of different types of chloride solutions on the stability and compressive strength of the 517 phase was investigated. X-ray diffraction and the Rietveld method were used to investigate the 517 phase transition in chloride solutions. Ion chromatography and inductively coupled plasma spectrometry were used to analyze the ion concentrations of the chloride solutions. Scanning electron microscopy and mercury injection porosimetry were used to investigate the effect of ion erosion on the microstructure and pore size distribution. The results showed that the crystal structure of 517 phase remained stable upon immersion in chloride solutions (except for the CaCl2 solution) up to 28 days, and there was no discernible attenuation in the compressive strength of the hardened pastes. Immersion of the 517 phase in CaCl2 solution for 28 days caused Ca2+ ions to combine with SO42- groups to generate CaSO4·2H2O, thereby decomposing the 517 phase. An increase in the concentration of magnesium and sulfate ions in the immersion solutions confirmed the decomposition of the 517 phase. Gel-like Mg(OH)2 was observed in the microstructure of the decomposed 517 phase, and the decomposition of the 517 phase increased the porosity of the hardened pastes.