Shuo Wang,Yongdong Yang,Gerry L. Koons,Antonios G. Mikos,Zhiye Qiu,Tianxi Song,Fuzhai Cui,Xiumei Wang
Porosity is indispensable for a bone tissue-engineered scaffold for facilitating endogenous cell migration and nascent bone ingrowth. In large-sized cranial bone defect repair, porous scaffolds meet great challenges to match cranial bone regeneration and provide sufficient protection with structural integrity. Therefore, the pore features of the scaffolds for cranial bone regeneration should differ from those typical porous scaffolds used in tubular bone repair and be finely tuned. In this study, a series of porous mineralized collagen/PCL scaffolds with different pore features were fabricated via freeze-drying and applied in a Sprague Dawley rat cranial bone calvarial defect model. The pore size for four groups increased from 10–45 μm to 40–130 μm. As scaffold porosity increased, the compressive strength decreased from 2.09 ± 0.12 MPa to 0.51 ± 0.04 MPa. The micro-computed tomography three-dimensional reconstruction images showed that as pore size and porosity increased, the amount of new bone formation had a maximum in group 3 (pore size: 20–100 μm, compressive strength: 1.06 ± 0.03 MPa). In addition, the histological and histomorphometric analyses showed a consistent tendency which confirmed the Micro-CT results. Meanwhile, histological findings including bony bridging, tissue response at the bone-implant interface and fibrous capsule thickness indicated that the dura mater pathway played the most important role in the regenerative process of this calvarial defect model.
Inspired by the stomatal feature of plant leaves, a photo-responsive membrane was developed to enhance the removal of irreversible membrane fouling and to control molecule release. Photo-responsive polymers were prepared by reacting the amine group of 4-amineazobenzene with about 3, 5 and 9 out of 12 carboxylic groups of PMAA which was grafted from P(VDF-CTFE) with a certain length. Subsequently, high-flux photo-responsive membranes (PRMs) were prepared from the heterogeneous polymers with different contents of photo-switchable azobenzene following a non-solvent-induced phase-inversion protocol. The pore size and surface hydrophilicity of PRMs could be reversibly increased by switching visible light to UV irradiation, which dramatically enhanced the backflushing efficiency on PRMs under UV irradiation. The “light-cleaning” process could recover more than 90% of the irreversible flux decline caused by typical organic foulant (BSA) and biological foulant (E. coli) on PRMs. The higher the content of azobenzene, the more obvious the pore size and hydrophilicity variation after light switching but the smaller the absolute pore size observed for PRMs. On the other hand, the light-switching gates of PRMs enabled the controlled release of molecules with different sizes. The novel PRM provided an efficient solution to mitigate irreversible membrane fouling and a light-triggered molecule release protocol, which would improve the membrane performance and further expand the application field of the membrane.
危险品化学品经营许可证（带存储）