Egyptian corals-based calcium silicate (CaS) nanopowders doped with zinc/copper for improved chemical stability and treatment of calvarial defects

Developing low-cost nano-biomaterials using locally available raw materials is gaining significant prominence recently, e.g., to meet the UN’s sustainable development goals (Goal 3). In this work, amorphous calcium silicate (CaS) nanopowders were prepared from Egyptian corals (CaCO₃) as a low-cost bone restoration material due to their excellent bonding abilities with surrounding bone tissues, which in turn accelerated the bone healing process. Some of the developed CaS nanopowders was doped with different concentrations of Cu²⁺ and Zn²⁺ at the expense of the inherent Ca²⁺ in the raw materials. The nanopowders were characterized using X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), scanning electron microscope with energy-dispersive X-ray spectrometry (SEM-EDX), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) surface area measurements. Mechanical and bactericidal properties of the nanopowders were assessed followed by well-defined examinations of their abilities to support cell viability, proliferation and differentiation against osteosarcoma cells (MG63 cell lines). The obtained nanopowders were confirmed to be amorphous in nature with particle diameters mostly in two size ranges, namely, 5–10 nm and 15–92 nm. The nanopowders were found to have a good surface area influenced by the type of dopant materials. Notable enhancement in the mechanical (up to 6.76 MPa compressive strength) and antibacterial behaviors of the CaS nanopowders were observed after Zn²⁺ doping. The number of the differentiated cells after 72 h of incubation was increased, especially for CaS silicate Zn²⁺ doped nanopowders. Following these examinations of the nanopowders, their utility for the treatment of calvarial (top part of the skull) defects in a rat model was investigated. The developed Cu²⁺ or Zn²⁺ doped nanopowders enhanced the healing rate of calvarial defects and they demonstrated impressive biosafety towards repairing vital organs (brain, liver and kidney).