An improved blood hemorrhaging treatment using diatoms frustules, by alternating Ca and light levels in cultures.

Hemorrhage control requires hemostatic materials that are both effective and biocompatible. Among these, diatom biosilica (DBs) could significantly improve hemorrhage control, but it induces hemolysis (the hemolysis rate > 5%). Thus, the purpose of this study was to explore the influence of Ca2+ biomineralization on DBs for developing fast hemostatic materials with a low hemolysis rate. Here, CaCl2 was added to the diatom medium under high light (cool white, fluorescent lamps, 67.5 µmol m-2 s-1), producing Ca-DBs-3 with a particle size of 40-50 µm and a Ca2+ content of Ca-DBs-3 obtained from the higher concentration CaCl2 group (6.7 mmol L-1) of 0.16%. The liquid absorption capacity of Ca-DBs-3 was 30.43 ± 0.57 times its dry weight; the in vitro clotting time was comparable to QuikClot® zeolite; the hemostatic time and blood loss using the rat tail amputation model were 36.40 ± 2.52 s and 0.39 ± 0.12 g, which were 40.72% and 19.50% of QuikClot® zeolite, respectively. Ca-DBs-3 showed no apparent toxicity to L929 cells (cell viability > 80%) and was non-hemolysis (the hemolysis rate < 2%). This study prepared Ca-DBs-3 with a rapid hemostatic effect and good biocompatibility, providing a path to develop diatom biosilica hemostatic materials. Supplementary Information: The online version contains supplementary material available at 10.1007/s42995-023-00180-3.

Gold Nanoparticle-Functionalized Diatom Biosilica as Label-Free Biosensor for Biomolecule Detection.

Diatom biosilica (DBs) is the cell wall of natural diatom called frustule, which is made of porous hydrogenated amorphous silica possessing periodic micro- to nanoscale features. In this study, a simple, sensitive, and label-free photoluminescence (PL) immune-detection platform based on functionalized diatom frustules was developed. Gold nanoparticles (AuNPs) deposited on poly-dopamine-coated diatom frustules via in situ deposition which considerably decreased the intrinsic blue PL intensity of diatom biosilica. Then, goat anti-rabbit immunoglobulin G (IgG) was added to functionalize diatom biosilica-poly-dopamine-AuNPs (DBs-PDA-AuNPs). PL studies revealed that the specific binding with antigen rabbit IgG increased the peak intensity of PL in comparison with the non-complimentary antigen (human IgG). The enhancement in PL intensity of DBs-PDA had a linear correlation with antigen (rabbit IgG) concentration, whose limit of detection (LOD) reached 8 × 10-6 mg/ml. Furthermore, PL detection based on DBs-PDA-AuNPs showed a high detection sensitivity with the LOD as low as 8 × 10-9 mg/ml and spread over almost eight orders of magnitude, making it suitable for the sensitive quantitative analysis of immune complex compared with traditional fluorescence immunoassay. Hence, the study proves that the AuNP-functionalized diatom frustules can serve as an effective biosensor platform for label-free PL-based immunoassay.

The complex hydrogel based on diatom biosilica and hydroxybutyl chitosan for wound healing.

In this study, doxycycline (DOXY)-loaded diatom biosilica (DBs) were developed and coated with hydroxybutyl chitosan (HBC) hydrogel for wound healing. The HBC/DBs/DOXY composite hydrogel had significant inhibitory activity against S. aureus (100%) and E. coli (98%). In addition, the HBC/DBs/DOXY hydrogel showed minimum cytotoxicity on L929 cells in vitro, indicating the great biocompatibility of the composite hydrogel. The in vivo results demonstrated that HBC/DBs/DOXY composite hydrogel could promote the wound re-epithelialization and accelerate the healing. The wound closure was evaluated to be 99.4 ± 0.4% at day 12 after treated with the hydrogel, with the presence of neovascularization and collagen deposition, all indicating the great potential of HBC/DBs/DOXY hydrogel in wound healing.

Preparation, urease inhibition mechanisms, and anti-Helicobacter pylori activities of hesperetin-7-rhamnoglucoside.

This work investigated the effects of the bioflavonoid hesperetin-7-rhamnoglucoside isolated from Citrus uranium fruit peel on Helicobacter pylori (H. pylori). Separation and purity, crystalline state, and urease inhibition assays were carried out. Then, molecular docking and molecular dynamics (MD) simulations were conducted with urease as the target protein. Hesp was isolated from citrus peel with a purity of 95.14 µg mg-1 of dry raw material. X-ray diffraction analysis, hydrogen-1 nuclear magnetic resonance, Fourier transform infrared spectroscopy, and differential scanning calorimetry revealed that pure Hesp had the same crystallinity rating as the Hesp standard. The kinetic inhibition study demonstrated that Hesp inhibited H. pylori urease in a competitive and concentration-dependent manner with jack bean urease. In addition, bioimaging studies with laser scanning confocal microscopy and scanning electron microscopy illustrated that Hesp interacted with bacterial cells and induced membrane disruption by creating holes in the outer membranes of the bacterial cells, resulting in the leakage of amino acids. Importantly, molecular docking and 20 ns MD simulations revealed that Hesp inhibited the target protein through slow-binding inhibition and hydrogen bond interactions with active site residues, namely, Gly11 (O⋯H distance = 2.2 Å), Gly13 (O⋯H distance = 2.4 Å), Ser12 (O⋯H distance = 3.3 Å), Lys14 (O⋯H distance = 3.3 Å), and Arg179 (O⋯H distance = 2.7 Å). This work presents novel anti- H. pylori agents from natural sources.