Evaluation Of The Biocompatibility Of Some Medical Materials

Objective: Biocompatibility assessment is pivotal for biomaterials researches,so it is a urgent task that how to establish standard and efficacious assessment systems.We aim for ⑴ investigating in vitro and vivo biocompatibility of some medical materials, such as polyacrylamide hydrogel, hydroxyapatite, chitosan, diamond-like carbon, monitored by the ISO 10993-1(1997 and national standard GB/T16886(1-1997.⑵ analyzing the expression of PCNA and Ki67 in capsules surrounded the impant materials, using immunohistochemistry to deeply study the influence of biomaterials on host animals and explore the new index for biocompatibility.Methods: (1)after 24h,48h,72h for L929 cells cultured with the aqueous extracts of six types of biomaterials (GSN,HA,CHI,DLC,FH,IT) with controls, the cell proliferation levels(RGR) were tested in the MTT assay; In the agar overlay assay, the same size sterile materials with controls placed on the agar Sub-Strate,cultured with L929 cells for 24h, the decolor zone index (ZI)and cell lysis index (LI) were recorded in the convert microscope and the cytotoxicity grades were assessed by ZI/LI. (2) We examined 24 health rabbits, implanted in muscles in the backs with different materials, to assess the influence of different materials(HA,GSN,FH,IT) on reactions of the body to these implants after 7d,20d,30d,45d,75d,90d. Histological sections stained with hematoxylin and eosin(HE) were examined. Fibrous capsule thickness (FCT) was measured by image analysis system.(3)S-P immunohistology was performed. Two kinds of monoclonal antibodyies for PCNA and Ki67 were used to detect the capsules proliferation. Individually, serial sections were analyzed to obtain the number of nucleated cells, including PCNA.or K i67. The counts were made using a system of microscopic, high-power fields (HPF) outlined with an ocular grid, each field measuring 54 ×54 mm at ×400 on a Nikon microscope and counting the positively stained cells in each field. Proliferation index was generated based on the number of positive-staining cells per total number of cells in a HPF.Results: (1)In the MTT assay, after 72h, for 100% and 50% GSN extract liquids ,the percents cell survival were respectively 53.01%,79.28%, and the cytotoxicity grades were moderate (++) levels,mild(+)levels, compared to the severe cytotoxicity (++++) of the positive control .A t-test performed on the GSN extracts showed a significant difference from the negative control(P<0.05), whereas other tested materials extracts were non-cytotoxic(－),similar to the negative control(P>0.05). (2)In the agar overlay assay, the positive control gave a score of 2/2,a moderately (++)cytotoxicity, whereas the values of Zone/Lysis of all tested materials were 0/0,non-cytotoxicity.(3) After implantation of 90 days , FH and IT caused only a blande slight inflammatory and thinner capsule thickness, whereas capsules around HA and GSN implants exhibited a more severe inflammatory with an increased capsule thickness. By the degree of inflammatory and the formation of capsule,the grades of FH,IT,GSN,HA were separately Ⅰ,Ⅰ;Ⅰ,Ⅰ;Ⅱ,Ⅱ;Ⅳ,Ⅲ. Most importantly, HA and GSN showed a stactistical difference of PCNA or Ki67 expression from IT(P<0.05).Unlike FH and IT,HA and GSN did not pass the test.(3)The total ratios of PCNA in each material of all times had positive relationship to the sum of capsule thickness(r=0.9540,t=4.4965,P<0.05〉,No significant association was found between the expression of Ki67 and capsule thickness.Conclusion: (1) DLC and CHI had non-cytotoxicity,and showed a good in vitro biocompatibility；(2) Both FH and IT were proved to have good biocompatibility in vitro.and vivo； (3) GSN moderately restrained the in vitro cultured cell proliferation.After implantation of 90 days, it showed a obvious tissue responses. (4) The distinct inhibitant for L929 cells proliferation was not observed in vitro tests of HA,but after implantation of 90 days, it exhibited a continuance and severe inflammatory,which instructs that...