The effect of sterilization methods on the cytotoxicity of ceramic medical implants

The choice of the sterilization method for ceramic implants is critically important, as it can affect the chemical and physico-mechanical properties of the material and its biocompatibility. Higher cytotoxicity, which is a possible side effect of sterilization, hinders osseointegration. This study aimed to determine the cytotoxicity of porous ceramic samples after sterilization using the most common methods. Samples of hydroxyapatite (HA), tricalcium phosphate (TCP), and aluminum oxide (AO) were prepared by stereolithography, and bone allograph samples were made using the DLP method. The annealing lasted for 4 hours, with a peak temperature of 800 °C and the temperature increment of 3 °C per minute; the sintering temperature was up to 1200 °C. We used the following sterilization methods: autoclaving at 1 atmosphere, 120 °C, for 45 minutes; radiation sterilization, 25 seconds with an absorbed dose of 25 kGy; plasma peroxide sterilization, 42 minutes; dry heat sterilization at 180 °C, for 60 minutes. Cytotoxicity was determined with the help of an MTT assay (24-hour exposure in a CO2 incubator). The results of the study: for HA, high porosity means growth of values in transition from autoclaving (0.1115) to plasma peroxide sterilization (0.2023). Medium and low porosity show similar results, with peaks in dry-heat sterilization (0.4954 and 0.4505). As for for AO, it exhibited high viability when subjected to this method. The TCP samples have shown stable results, but their low-porosity variation had the values growing after autoclaving (0.078 to 0.182, dry-heat sterilization). The study forms the basis for optimizing the ceramic implants manufacturing technology and sterilization methods to ensure their high biocompatibility.