| ?Background and Objective?Implant related infection is one of the most challenging complications in orthopaedics.How to prevent and treat infection is still a research hotspot in the field of orthopaedics.In particular,the research on antibacterial modification of the surface of implants has been paid more and more attention by scholars.In the early stage of this research group,the iodine was successfully loaded onto the surface of titanium implant by electrophoretic deposition method that using povidone iodine as electrolyte,and its iodine loading and antibacterial activity have been confirmed by energy spectrometer and in vitro antibacterial experiments.In this study,another way of in-vitro antibacterial experiment and an in-vivo antibacterial experiment were carried out to further determine and evaluate the antibacterial activity of this novel iodine-loaded titanium implant.?Methods?Experiment 1:an in-vitro antibacterial experiment using bacterial inoculation method.40 pieces titanium plate were polished and divided into four groups according to the different inoculation time of S.A(n=10 per group),and 20 of which were randomly taken for surface iodine-loaded treatment:Group A:the iodine-unloaded titanium plate with inoculation time of 2 hours;Group B:the iodine-unloaded titanium plate with inoculation time of 6 hours;Group C:the iodine-loaded titanium plate with inoculation time of 2 hours;Group D:the iodine-loaded titanium plate with inoculation time of 6 hours.The titanium plate was taken out,shaken,washed and diluted after two or six hours after the inoculation of the bacteria,and the dilution were culture for 24 hours,and then the evaluated and analyzed were performed by the colony counting.Experiment 2:establish an animal model of implant related infection.38polished titanium needles and 38 SD-rats were randomly divided into 4 groups:Group A(8 rats):the titanium needle was implanted into the marrow cavity of tibia after 30?l saline was injected;Group B,Group C,Group D(n=10 per group):the titanium needles were implanted into the marrow cavity of tibia after 30?l bacterial suspension of S.A with 1 x 10~4 CFU/ml,1 x 10~5 CFU/ml and 1 x 10~6 CFU/ml were respectively inoculated.All rats were anaesthetized for medial opening of right tibial tubercle,reaming,inoculation,implantation,sealing and suture.One week after the operation,evaluation and analysis were performed by general conditions,microbiology,and histopathology.Experiment 3:an in-vivo antibacterial experiment.10 of 20 polished titanium needles were randomly taken for surface iodine-loaded treatment,and 20 SD-rats were randomly divided into two groups(n=10 per group):Group A:the iodine-unloaded titanium needle was implanted into the marrow cavity of tibia after30?l bacterial suspension of S.A with 1×10~4 CFU/ml was inoculated;Group B:the iodine-loaded titanium needle was implanted into the marrow cavity of tibia after 30?l bacterial suspension of S.A with 1×10~4 CFU/ml was inoculated.The operation procedures of all rats were consistent with Experiment 2,and the evaluation and analysis were performed by general conditions,microbiology,histopathology including quantitative scoring one week after operation.?Results?Experiment 1:1.Comparing the groups of different plate and the same time of bacteria inoculation(Group A&Group C,Group B&Group D),regardless 2h or6h of the inoculation time,the colony counting in the iodine-loaded plate groups were significantly lower than the iodine-unloaded plate groups(P<0.05).2.Comparing the groups of the same iodine-loaded plate but different time of bacteria inoculation(Group C&Group D),the colony counting in the group with inoculation time of 6 hours was significantly lower than that in 2-hour group,and the difference was statistically significant(P<0.05).Experiment 2:one week after operation:1.The weight of all rats decreased to different degrees,accompanied by surgical limb movement limitation,and the degrees of Group A were lighter and Group D were heavier.2.All rats in Group A survived without obvious signs of infection,while the rats in Group B,Group C and Group D showed signs of infection,and rats in Group C and Group D died in different numbers.Respectively,the mortality rates in Group A-D were 0%?0%?30%?50%.Statistical analysis:Group A and Group B were compared respectively with Group D,the difference was statistically significant(P<0.05),while there was no significant difference in the other pairwise comparisons between each groups(P>0.05).3.Microbiological evaluation:by observing the colony counting of the results,it was found that the colonies in Group B,Group C and Group D were significantly more than Group A.Statistical analysis:comparing the results of Group B,group C,Group D with Group A,the difference was statistically significant(P<0.05);However,in the pairwise comparisons between Group B,Group C and Group D,the results showed no significant difference(P>0.05).4.Histopathological evaluation:the treated and HE-stained tissue specimens were observed under the microscope,it was found that the specimens with positive manifestations corresponded to the positive results of general conditions or microbiological evaluation.5.Summarized the results of each evaluation methods,it found that the infection rates Group A-D were 12.5%?80%?71.42%?100%.Statistical analysis:Group B,Group C and Group D were compared respectively with Group A,the difference was statistically significant(P<0.05).Experiment 3:one week after operation:1.The weight of all rats decreased to different degrees,accompanied by surgical limb movement limitation,and Group A is more severe than Group B.2.One animal died in group A,and 7 of the 9 animals survived showed signs of infection in varying degrees;all animals survived in group B,and 1 of the 10 animals showed signs of infection.The mortality rates of the two groups were statistically analyzed:there was no significant difference in mortality between Group A(10%)and Group B(0%)(P>0.05).3.Microbiological evaluation:by observing the colony counting of the results,it was found that Group A had more colonies than Group B;by comparing the results of all colonies or positive colonies between the two groups,the differences were all statistically significant(P<0.05).4.Histopathological evaluation:the treated and HE-stained tissue specimens were observed by the microscope,it was found that the specimens with positive manifestations under the microscope basically corresponded to the positive results of general conditions or microbiological evaluation;after analyzing the quantitative scores of inflammation and infection by histology,it was found that the total score of Group A was greater than that of Group B,and the difference was statistically significant(P<0.05).5.The infection rates of two groups that were summarized the results of each evaluation were statistically analyzed:the difference between Group A(88.9%)and Group B(40%)was statistically significant(P<0.05).?Conclusion?1.Through the study of in-vitro antimicrobial experiment of bacterial inoculation,we further confirmed that the iodine-loaded titanium implant developed by this research group had definite and sustained antimicrobial activityin the early stage;2.S.A inoculated at a dose of 30?l of 1 x 10~4 CFU/ml could stablly and reliable play an important role in the construction of rat tibial osteomyelitis model;3.On the basis of successful construction of the rat tibial osteomyelitis model,the results of the in-vivo antimicrobial experiments also confirmed that the iodine-loaded titanium implant can effectively prevent the occurrence and development of the early implant related infection in vivo.In conclusion,we believe that this iodine-loaded titanium implant developed by this research group is a new and effective antimicrobial material,which has a good prospect in the future clinical orthopaedics research on the prevention and treatment of implant related infection,and it is expected to be used in clinical practice through in-depth research and continuous improvement in the future. |
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