Implant Surface Preparation

The chitosan coating (ChtG) was prepared according to the procedure described by Vakili et al. with slight modifications (Vakili and Asefnejad, 2020). 0.5% (w/v) chitosan was prepared in 0.5% (v/v) acidic solution by stirring the solution for 12 h on a magnetic stirrer. The film-forming solution was prepared following the procedure described by Zhang et al. with slight modifications (Zhang et al., 2019). Glycerol (0.4 g) was dispersed in 80 ml of acetic acid (1%, w/v) by stirring for at least 12 h (4°C). The prepared chitosan solution was added to the film-forming solution using a syringe pump (Infusomat^® Space, Braun, Barcelona, Spain), at a rate of 50 ml/h, stirring by mechanical shaker at 800 rpm. The implants were coated with Cht by immersion in the prepared solution, coating the entire implant surface. The coated implants were then dried in a drying oven with rotary drum and air blowing at 25°C for the formation of a uniform film, with a relative humidity of 50%, to avoid cracking and deformation of the coating (Figure 1C). CG implants did not receive any surface coating. Both CG and ChtG implants were sterilized by gamma irradiation. This method of sterilization in ChtG was preferred so as not to give rise to sterilization biases with GC. Other methods, such as ethylene oxide, in addition to leaving residues detrimental to health, could damage the molecular structure of the coating and its susceptibility to degradation, although the effects of sterilization on the stability of the molecular structure and the mechanical properties of the coating itself are unclear. Certain in vitro studies have shown that the early stages of mineralization are essentially independent of the sterilization method (Ueno et al., 2012; Türker et al., 2014).