The Application Of Modification Of Poly (l-lactide) In Urology

Poly(l-lactide) (PLLA) is a well known biomaterial today, however it can not meet the actual requirement of many medical problems. According to the actual requirements of Urology, Some studies have been made to improve the properties of PLLA. We have developed a PLLA urethral stent with BaSO4, which can be displayed precisely under X-ray. The polymer urethral stent was used to treat urethral stricture. And we blended lecithin into PLLA for the scaffold of bladder tissue engineering.The previously developed biodegradable urethral stents would likely to be covered by epithelium. Thus the broken pieces of the stent would perforate through the mucosa and injury urethral tissue. We designed and fabricated slight self-expand spiral stent based on PLLA/BaSO4 (PLLA viscous molecular weigth 15×104 g/mol), named named as UroFlow15(UF15). According to structure of PLLA, two types of the stent were named as Whole PLLA structure stent and the suture structure stent, respectively. The stent can be displayed precisely under X-ray, so it is convenient to observe the situation of the stent after the operation. 34 patients were involved. No stent was covered by epithelium, thus the stents can be taken out or discharge with urine, without injury of urethral. UF15 can support the urethra for about 8-10 months. The urine stones are difficult to adhere and grow on the stent surface because of the mechanism of surface degradation of PLLA. Therefore there is no urethra stone which can be observed macroscopically on the stent surface. The Uroflow stent is now in the production phase.Lecithin was, for the first time, blended with PLLA to prepare scaffold material for tissue engineering applications in the present study. Solution blending was used to incorporate Lecithin (containing 0-10 wt%) with PLLA to enhance the blend films biocompatibility, hydrophilicity and toughness while maintaining mechanical strength of PLLA. The results of FTIR-ATR analysis indicated that the amino groups of lecitin existed in the films. DSC analysis indicated that Tg decreased with the increase of lecithin content in the blend films. The percentage elongation markedly increased with increase of lecithin content. The proliferation and viability of the vascular smooth muscle cell cultures on PLLA/Lecithin(containing 3-7 wt%) films were significantly enhanced compared to pure PLLA on tissue culture plates.Bladder regeneration is a critical issue in Urology. In Tissue Engineering research, we fabricated the three-dimensional bladder scaffolds with the PLLA/Lecithin (containing 5 wt%) blending material by freeze-drying. The surface feature and porosity of the blending system scaffold is similar to those of PLLA scaffold, therefore, adding lecithin into PLLA had no effect to the surface feature and porosity of the scaffold. Compared with PLLA scaffold, the mechanical strength of the PLLA/Lecithin scaffold decreased. And we studied the cell culture on the PLLA/Lecithin scaffold for Rabbit's bladder smooth muscle cells in vitro. It is obvious that the PLLA/Lecithin scaffold is more beneficial for the cells adhesion and proliferation than PLLA scaffold.