Bioactivity and antibacterial activity of strontium and silver ion releasing titanium

Abstract

To overcome problems associated with loosening of orthopedic implants and surgical site infections, we developed a novel, titanium (Ti)-based material that releases both strontium and silver ions (CaSrAg-Ti) based on alkali-and-heat treatment. The results of commercially pure Ti (cp-Ti), Ti that releases Sr ions only (CaSr-Ti), and the novel CaSrAg-Ti material were compared. Mechanical tests were performed to evaluate the in vivo bonding properties of CaSrAg-Ti and the bone-implant contact (BIC) ratio in histological specimens was determined at 4 and 8 weeks after implantation in a rat femur. Also, the in vitro antibacterial activities of this material against methicillinsusceptible Staphylococcus aureus (MSSA) were evaluated after a 24 h incubation period by assaying colony-forming units. In addition, antibacterial activities were evaluated in vivo at 7 days after implantation in a rat subcutaneous pocket model. There was direct contact between the bone and CaSrAg-Ti in histological specimens and no apparent signs of argyrosis in any rat. The bone-bonding strength and the BIC ratio were increased by 2.7-and 2.3-fold for CaSrAg-Ti vs. cp-Ti at 4 weeks and 2.2and 2.0-fold at 8 weeks, respectively. As compared with cp-Ti, the number of viable MSSA remaining on CaSrAg-Ti was reduced by 100 ± 0% in vitro and 94.2 ± 6.9% in vivo. Ti that releases Sr and Ag ions is a promising material that exhibits both bone-bonding properties and anti-MSSA activities.

Iodine-Loaded Calcium Titanate for Bone Repair with Sustainable Antibacterial Activity Prepared by Solution and Heat Treatment

“…Zadpoor concluded that, in the majority of the studies (25/33), the SBF immersion test proved successful in predicting the relative in vivo bioactivity of the materials. We also showed that the calcium titanate formed on Ti and its alloys bond to living bone; some other functional metal ions such as strontium, magnesium, and silver have also been incorporated insofar as the apatite formation in SBF is maintained [ 34 , 54 ]. Based on these reports, the bone-bonding capacity and cytotoxicity of the treated Ti and its alloy samples in the present study were assessed in terms of apatite formation in SBF and in cell culture, respectively.…”

“…To obtain antibacterial activity in addition to bioactivity, silver (Ag) has been incorporated into Ti and Ti alloy surfaces by modified solution and heat treatments in which Ti is soaked in a H 2 O 2 /AgNO 3 mixed solution [ 30 ], in a NaOH/AgC 2 H 3 O 2 mixed solution [ 31 ], or in a AgNO 3 solution following NaOH-CaCl 2 +SrCl 2 heat treatment [ 32 , 33 , 34 ]. Although the treated Ti displayed strong antibacterial activity against Staphylococcus aureus , Escherichia coli , and so on, in vitro, its in vivo antibacterial activity was insufficient [ 34 ] because only a low amount of Ag could be incorporated into the Ti surface due to the cytotoxicity of Ag. The range of Ag on Ti and Ti alloys that exhibits antibacterial activity without cytotoxicity is narrow, so accurate control of Ag release is required to achieve a proper balance between antibacterial activity and cytocompatibility [ 35 ].…”

Antimicrobial Properties of Strontium Functionalized Titanium Surfaces for Oral Applications, A Systematic Review

“…Furthermore, the Sr reservoir was maintained at more than 90% of its initial concentration while over 90% of the Ag concentration was released over a 30-day period [44]. In vivo blood serum ion concentration showed stable levels of Sr over a period of 28 days after placement in the right femoral bone of rats, ranging between 0.8 and 1 ppm; this value was almost three times higher than that of Ag [45].…”

“…Among the different included studies, Sr was applied either alone or in combination with other metal ions on Ti substrates using different application methods. Application methods of Sr included micro-arc oxidation [26,39,40], incorporation into hydroxyapatite (HA) coatings using either hydrothermal processes [41,42] or plasma spray-ing [43], or by using co-incident micro-blasting (CoBlast) [44] in addition to calcium (Ca) using alkali-and-heat treatment [45,46]. Moreover, Ti substrates were functionalized with Sr alone or Sr in combination with Ag [26] or Zn [40], HA coatings comprising different metal ions, either doped or incorporated into the HA coatings [41][42][43][44], or as Sr combined with calcium (Ca) alone [45,46] or with other metals: cobalt (Co), fluorine (F), and phosphate (P) [39].…”

“…However, Sr-functionalized surfaces did not show any antimicrobial effect against E. coli for any of the included studies, at either early or late timepoints (Table 2). The in vivo antimicrobial potential of combined Sr/Ag-modified surfaces was investigated by Masamoto et al [45]; however, Sr only-coated samples were not included and therefore the outcome of the test was not included in the analysis.…”