Quantitative determination of residual 1,4-dioxane in three-dimensional printed bone scaffold

Li, Ling; Long, Jing; Li, Long; Cao, Huijuan; Tang, Tingting; Xi, Xinghua; Qin, Ling; Lai, Yuxiao; Wang, Xinluan

Three-dimensional printing porous scaffolds are promising regenerative strategies for bone defect repair in orthopaedics [6, 7] . As a newly developed medical product, safety issues are considered as the most important ones. As a Class 2 solvent with less severe toxicity, content of residual 1,4-dioxane in the novel 3D printing PLGA/TCP scaffolds should be rigorously controlled [26] . We first developed an HS-GC-MS method for testing 1,4-dioxane in PLGA/TCP porous scaffolds. This method utilised a reproducible and highly recovery sample preparation process, a more efficient separation technology, and a specific singleion monitoring mass detection to quantify 1,4-dioxane in PLGA/TCP porous scaffolds. Different from the liquid or liquid-like sample [29, 30] , 1,4-dioxane should be extracted from the solid scaffold at the first step. Four solutions were used; as a result, the detected amount of 1,4-dioxane was exactly inversely related to its solubility in different solution, and Na 2 CO 3 solution showed the highest sensitivity due to the saltingout effect [32] . However, as the first method to test the gas from a solid porous structure, we further investigated the matrix effects of the different solutions. There were two different extraction systems, one in Na 2 CO 3 solution, retaining the porous structure of the scaffolds, and the other in DMF solution without any porous structures. In DMF solution, the scaffolds were dissolved into powders, and 1,4-dioxane was distributed in solution phase and gas phase. The detected amount was determined by its solubility in DMF, so the detected amount of 1,4-dioxane were the same in DMF with or without matrix blank scaffolds. In Na 2 CO 3 solution with the matrix blank scaffold, 1,4dioxane was distributed in three phases: scaffold, solution, and gas, and the detected amount was determined not only the solubility in Na 2 CO 3 but also the attachment in the porous scaffolds. Thus, the detected amount of 1,4dioxane in Na 2 CO 3 solution only was more than that in the Na 2 CO 3 solution with matrix blank scaffolds ( Figure 2C ). The fabricated porous scaffolds had both regular macropores, with the size among 300 mm to 500 mm, as well as irregular micropores with size from 5 mm to 50 mm pores (Figure 1Be1F) [11, 13] , which might be the cause of matrix effects. Thus, we selected DMF to extract 1,4-dioxane from the scaffolds as the pretreatment process of the GC-MS methods. The following method's validation results further confirmed the feasibility of this procedure.