Preparation And Characterization Of Artificial Chest Wall Based On Biodegradable PLLA/CHS Braid

Chest wall resection will be performed on the conditions such as primary tumors of chest wall or sternum, lung cancer and trauma. Large chest wall defects require chest wall reconstruction to provide enough stability for normal spontaneous breathing and cosmetic acceptability. The clinic materials used in chest wall reconstruction such as autogenous, heterogenous or metallic materials have some disadvantages associated with limited sources, non-infected inflammation or more traumas. At present much attention has been given to degradable polymers like poly(L-lactide) (PLLA), chitosan (CHS) and poly(ε-caprolactone) (PCL) for using in the field of chest wall reconstruction. The purpose of this dissertation is to design a degradable "sandwiched" artificial chest wall in which the PLLA/PCL molded plate was sandwiched between two layers of either PLLA/CHS braid. Dry-wet spinning, a new spinning process of PLLA fibers, was studied and compared to other spinning processes. The effects of the hot-drawing on the dry-wet spun fibers were characterized by means of POM, WAXD, DSC and tensile tester. Dry-wet spun PLLA fibers and wet spun chitosan fibers were blended and knitted into braid. In vitro degradation of PLLA/CHS braid and PLLA braid was investigated in phosphate buffered solution (pH 7.4) at 37℃for 6 months. The degradation mechanism was studied with regard to the mass loss, tensile properties of the braid and the average molecular weight, the degree of crystallinity and morphology of PLLA fiber. The osteoblast was cultured with the PLLA/CHS braid in vitro. The morphology of osteoblast in the early stage was observed by scanning electron microscope (SEM). Based on above research work, the main results obtained are as follows:1. PLLA fibers could be obtained by dry-wet spinning process.2. Compared to the melt-spun or dry-spun fibers, dry-wet-spun fibers have a pore-structure, the higher orientation, the lower crystallinity and tensile strength.3. The fibers produced by dry-wet spinning process exhibited higher orientation and tensile strength as the draw ratio increased. However, the tensile strength decreased with the higher draw ratio due to the broken structure of the fibers. 4. The increase of draw temperature is benefit to improve the crystallinity, orientation and tensile strength. However, too high draw temperature would damage tensile strength. The maximum tensile strength for dry-wet spun fibers was obtained at about 120℃.5. The mixedα,β-form crystal structure was formed due to a partial transformation of theα-crystalline into theβ-crystalline under a low draw temperature and a low draw ratio, measured by WAXD and DSC.6. The degradation speed of the dry-wet spun PLLA fibers was increased compared to melt-spun or dry spun PLLA fibers.7. Results suggested that the degradation of the PLLA fibers from PLLA braid in PBS followed a bulk degradation mechanism, whereas the PLLA fibers from PLLA/CHS braid apparently proceeded both by bulk and surface degradation.8. Osteoblast could well adhere to the surface of PLLA/CHS braid. The compatibility of PLLA/CHS braid with osteoblast was good.9. PLLA/PCL molded plate was studied, which could meet the requirement of flexibility property used as chest wall reconstruction.