Amino Acid-Driven Dimensional Reduction of CsPbBr3 Nanocrystals.

Inspired by biomineralization, the recent incorporation of organic molecules into inorganic lattices shows interesting optical properties and tunability. We functionalize all inorganic CsPbBr3 perovskite nanocrystals (PNCs) with amino acid (AA) cysteine using the water-hexane interfacial approach. Along with the AA cysteine, we added AuBr3 salt into the aqueous phase, leading to the formation of a Au-cysteine thiolate complex to activate the aqueous to nonaqueous phase transportation of the AA via a molecular shuttle, oleylamine. The interaction between CsPbBr3 PNCs and the Au-cysteine thiolate complex is probed using optical spectroscopy, which reveals dimensional reduction of the parent PNCs to form CsPbBr3 nanoplatelets (NPls) and subsequent phase transformation to CsPb2Br5 NPls. X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy conclusively support the above chemical transformation reaction via interfacial chemistry. We propose a mechanistic insight into the dimensional growth in one direction in the presence of AAs via preferential ligand binding to specific facets, leading to transformation from 3D cubes to 2D NPls, while, presumably, the phase transformation occurs via the CsBr stripping mechanism upon prolonged interaction with water. Since AAs are building blocks for several redox-active complex biological moieties, including proteins, investigation of the interaction of AAs with PNCs may be advantageous since the latter can act as a fluorescent probe for bioimaging application.

Green tea extract as a cryoprotectant additive to preserve the motility and DNA integrity of human spermatozoa.

Cryopreservation impairs sperm quality and functions, including motility and DNA integrity. Antioxidant additives in sperm freezing media have previously brought improvements in postthawed sperm quality. Green tea extract (GTE) is widely considered as an excellent antioxidant, and its beneficial role has been proven in other human cells. This study aims to evaluate the GTE as a potential additive in cryopreservation media of human spermatozoa. In part one, the semen of 20 normozoospermic men was used to optimize the concentration of GTE that maintains sperm motility and DNA integrity against oxidative stress, induced by hydrogen peroxide (H2O2). Spermatozoa were treated with GTE at different concentrations before incubation with H2O2. In part two, the semen of 45 patients was cryopreserved with or without 1.0 ng ml-1 GTE. After 2 weeks, the semen was thawed, and the effect on sperm motility and DNA fragmentation was observed. Our data showed that GTE significantly protected sperm motility and DNA integrity against oxidative stress induced by H2O2when added at a final concentration of 1.0 ng ml-1. We found that the addition of 1.0 ng ml-1 GTE to cryopreservation media significantly increased sperm motility and DNA integrity (both P < 0.05). More interestingly, patients with high sperm DNA damage benefited similarly from the GTE supplementation. However, there was no significant change in the reactive oxygen species (ROS) level. In conclusion, supplementing sperm freezing media with GTE has a significant protective effect on human sperm motility and DNA integrity, which may be of clinical interest.