| Objective:To assess the protective effects of different radiation protection agents on allograft tendon underγirradiation sterilization.The crosslinker(1-ethyl-3-[3-dimethyl aminopropyl]carbodiimide,EDC),free radical scavenger(vitamin C)or two protective agents in combination to pre-protect the allograft tendon,irradiate with different doses.To compare changes in tendon morphology and biomechanical properties.Methods:90 fresh tendons,including hamstrings,long fibula tendons,short fibula tendons,and achilles tendon,removed the fatty tissue around the tendon,cut off the irregular parts and broad fascia.The cross-sectional area,length and thickness of tendons included in the study were not statistically different.After cryogenic freezing(-80℃)for 3 months,took it out and thawed at room temperature for 2 hours.The radiation protection agent used the cross-linking agent EDC and the free radical scavenger vitamin C.The radiation dose was set at 25 k Gy and 50 k Gy.Based on the different radiation protection agents and radiation doses used,all cryogenic frozen tendons were divided into 9 groups,10 in each group:cryogenic freezing of non-irradiated tendons(control group);tendons with 25 k Gy irradiation dose and no radiation protection agent(25 k Gy group);tendons with 50 k Gy irradiation dose and no radiation protection agent(50 k Gy group);tendons with 25 k Gy irradiation and crosslinker EDC(EDC25 group);tendons with 50 k Gy irradiation and crosslinker EDC(EDC50 group);tendons with 25 k Gy irradiation dose and free radical scavenger vitamin C(vitamin C25 group);tendons with 50 k Gy irradiation dose and free radical scavenger vitamin C(vitamin C50 group);tendons with 25 k Gy irradiation dose and crosslinker EDC and free radical scavenger vitamin C(EDC+vitamin C25 group);tendons with 50 k Gy irradiation dose and crosslinker EDC and free radical scavenger vitamin C(EDC+vitamin C50 group).After the grouping,the tendons of each group were treated and irradiated according to the corresponding conditions.After the irradiation,the morphology and biomechanical properties were tested.Morphology includes general morphology and biochemical test.The general morphology mainly observes whether the cross-sectional area,initial length and thickness of each group of tendons after irradiation have changed.The biochemical test is mainly to determine the content of hydroxyproline in the tendon and observe the catabolism of collagen in the tendon under different treatments.The biomechanical test included cyclic loading test and tensile fracture test.The cyclic loading test mainly observed the cyclic creep of tendons.The tensile fracture test mainly observed the ultimate load,maximum stress,elastic modulus and toughness of tendons.One way ANOVA was used to compare the cross-sectional area,initial length and thickness of the tendons in each group.Two independent sample t-tests were used to compare hydroxyproline content,cyclic creep,ultimate load,maximum stress,elastic modulus and toughness of tendons with and without radiation protectant.Results:General morphological showed that the average cross-sectional area of the control group was the largest(78.60±1.75 mm~2)in the nine groups of tendons,and the smallest(74.41±2.78 mm~2)in the 25 k Gy group.There was no statistical difference in the average cross-sectional area of tendons in 9 groups(F=1.907,p=0.0892).Among the initial length of tendons in 9 groups,the average initial length of vitamin 25 group was the largest(56.24±0.84 mm),and the average initial length of EDC50 group was the smallest(55.04±1.07 mm).There was no statistical difference in the average initial length of tendons in 9 groups(F=1.849,p=0.0996).Among the thickness of tendons in 9 groups,the average thickness of control group was the largest(4.28±0.22 mm),and the average thickness of EDC50 group was the smallest(4.02±0.11 mm).There was no statistical difference in the average thickness of tendons in 9 groups(F=1.849,p=0.0996).The results of the biochemical test showed that the hydroxyproline content of the 25 k Gy group,EDC25 group,vitamin C25 group,and EDC+vitamin C25 group were 2.8180±0.0881 ug/ml,2.5210±0.0462 ug/ml,2.4963±0.0713 ug/ml and 2.4671±0.0865 ug/ml,respectively.The hydroxyproline content in the 25 k Gy group was statistically different from the EDC25 group(p<0.001),the vitamin C25 group(p<0.001)and the EDC+vitamin C25 group(p<0.001).The hydroxyproline content of the 50 k Gy group,EDC50group,vitamin C50 group,and EDC+vitamin C50 group were 3.0169±0.1277ug/ml,2.6702±0.0426 ug/ml,2.8658±0.0314 ug/ml and 2.5014±0.0243 ug/ml,respectively.The hydroxyproline content in the 50 k Gy group was statistically different from the EDC50 group(p<0.001),the vitamin C50 group(p=0.0322)and the EDC+vitamin C50 group(p<0.001).The results of the cyclic loading test showed that the cyclic creep of the 25 k Gy group,EDC25 group,vitamin C25 group,and EDC+vitamin C25 group were 0.79±0.08%,0.44±0.05%,0.47±0.04%,and 0.39±0.04%,respectively.The cyclic creep in the 25 k Gy group was statistically different from the EDC25 group(p<0.001),the vitamin C25 group(p<0.001)and the EDC+vitamin C25 group(p<0.001).The cyclic creep of the 50k Gy group,EDC50 group,vitamin C50 group,and EDC+vitamin C50 group were0.95±0.05%,0.53±0.04%,0.80±0.08%,and 0.43±0.04%,respectively.The cyclic creep in the 50 k Gy group was statistically different from the EDC50group(p<0.001),the vitamin C50 group(p=0.0081)and the EDC+vitamin C50group(p<0.001).The results of the maximum stress showed that the maximum stress of the 25 k Gy group,EDC25 group,vitamin C25 group and EDC+vitamin C25group were 18.58±1.14 Mpa,22.56±0.90 Mpa,22.17±0.74 Mpa and 24.57±1.13 Mpa,respectively.The maximum stress in the 25 k Gy group was statistically different from the EDC25 group(p<0.001),the vitamin C25 group(p<0.001)and the EDC+vitamin C25 group(p<0.001).The maximum stress of the 50 k Gy group,EDC50 group,vitamin C50 group,and EDC+vitamin C50 group were 13.86±0.88Mpa、21.47±1.17 Mpa、15.77±1.53 Mpa and 24.37±1.17 Mpa,respectively.The maximum stress in the 50 k Gy group was statistically different from the EDC50group(p<0.001),the vitamin C50 group(p=0.0424)and the EDC+vitamin C50group(p<0.001).The results of the elastic modulus showed that the elastic modulus of the 25 k Gy group,EDC25 group,vitamin C25 group and EDC+vitamin C25group were 121.84±14.80 Mpa,181.86±4.86 Mpa,181.24±4.47 Mpa and 201.69±5.74 Mpa,respectively.The elastic modulus in the 25 k Gy group was statistically different from the EDC25 group(p<0.001),the vitamin C25 group(p<0.001)and the EDC+vitamin C25 group(p<0.001).The elastic modulus of the 50 k Gy group,EDC50 group,vitamin C50 group,and EDC+vitamin C50 group were 106.51±12.74 Mpa,172.23±5.00 Mpa,169.40±2.76 Mpa and 194.89±5.57 Mpa,respectively.The elastic modulus in the 50 k Gy group was statistically different from the EDC50 group(p<0.001),the vitamin C50 group(p<0.001)and the EDC+vitamin C50 group(p<0.001).The results of the toughness showed that the toughness of the 25 k Gy group,EDC25 group,vitamin C25 group and EDC+vitamin C25 group were 2.94±0.24 Mpa,2.91.±0.11 Mpa,2.93±0.13 Mpa and3.15±0.07 Mpa,respectively.The toughness in the 25 k Gy group was no statistically different from the EDC25 group(p=0.8410),the vitamin C25 group(p=0.9224)and the EDC+vitamin C25 group(p=0.0888).The toughness of the 50 k Gy group,EDC50 group,vitamin C50 group,and EDC+vitamin C50 group were 1.89±0.11Mpa,2.81±0.17 Mpa,1.90±0.09 Mpa and 3.08±0.10 Mpa,respectively.The toughness in the 50 k Gy group was statistically different from the EDC50 group(p<0.001)and the EDC+vitamin C50 group(p<0.001),but not from the vitamin C50group(p=0.8519).Conclusions:At 25k Gy radiation dose,EDC,vitamin C,or EDC combined with vitamin C can provide the same protection on morphology and biomechanical properties for tendons.At 50k Gy radiation dose,EDC or EDC combined with vitamin C can provide the same protection on morphology and biomechanical properties for tendons,and superior to vitamin C as a radiation protection agent. |
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