Papers by Keyword: Poly(L-Lactide)

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Authors: Zi Qiang Zhang, Kun Hu, Hong Xu Huo, Kang Ning Chen, Bo Meng, Fu Zhai Cui
Abstract: This paper reported a newly designed retrievable urethral stent used in treatment of urethral strictures. The spiral urethral stent is made of Poly (l-lactide) (PLLA), adding barium sulphate (BaSO4) to certain content, which can be displayed precisely under X-ray after implanted in body. The stent was clinically tested in 32 patients with recurrent urethral strictures and was left in the urethra for 5 to 12 months. The response to the effect of the stent was assessed using symptom scores, peak flow rate (Qmax), residual urine volume (RUV), stent degradation, infection and outcome. During the treatment, there were not any inflammations found. The mechanical properties of the stent are almost the same as those of the PLLA stent without BaSO4. Improvements in patient symptom score, mean Qmax and RUV were significant at the 18 month follow-up. The infection was not observed. The stent was taken out easily through urethral forceps. In no patient was the stent obstructed by incrustation for up to 1.5 years.
Authors: Yun Qing Kang, Guang Fu Yin, Ke Feng Wang, Lin Luo, Ya Dong Yao
Abstract: Poly-L-lactide/β-tricalcium phosphate (PLLA/β-TCP) porous scaffold fabricated by freeze shrinking/particulate leaching was studied. The scaffold was immersed into simulated body fluid (SBF) for 1, 2, 3 and 4 weeks and analyzed by the SEM, XRD and FT-IR spectroscopy. The ability of inducing Ca-P formation was compared among the scaffolds with different content of β- TCP. SEM shows a typical feature of apatite precipitation. Diffraction peak of new crystal structure was detected by x-ray diffraction (XRD). IR Spectrum in which absorption bands arise from newly formed groups of carbonate apatite can be seen. At the same testing point, higher density of Ca-P crystal can be observed by SEM in scaffold with high content of β-TCP than in low group. Until 3 weeks, Ca-P individual crystal started on the wall of inner pore of pure PLLA. Porous PLLA/β-TCP composite scaffolds also indicate good ability of Ca-P formation in vitro, the ability of which to form apatite was enhanced by addition of each other that has different degradable mechanism.
Authors: Xi Ming Pu, Yun Qing Kang, Ai Zheng Chen, Li Liao, Guang Fu Yin
Abstract: 5-Fluorouracil-poly(L-lactide) (5-Fu-PLLA) microspheres have been co-precipitated in a process namely solution-enhanced dispersion by supercritical CO2 (SEDS). First, the 5-Fu is successfully micronized and then used to produce the 5-Fu-PLLA microspheres. The 5-Fu-PLLA microspheres synthesized in the SEDS process exhibited a rather spherical shape, smooth surface, and a narrow particle size distribution, where it ranged from 531 nm to 1280 nm, with a mean particle size of 793 nm. The dichloromethane residue in the 5-Fu-PLLA microspheres is 46 ppm. The average drug load of the 5-Fu-PLLA microspheres is 12.7%. The results of this study indicate that the SEDS process is an effective technique to co-precipitate 5-Fu and PLLA as composite microspheres.
Authors: Yun Qing Kang, Guang Fu Yin, Lin Luo, Ke Feng Wang, Yu Zhang
Abstract: In bone tissue engineering, porous scaffolds served as the temporary matrix are often subjected to mechanical stress when implanted in the body. Based on this fact, the goal of this study was to examine the effects of mechanical loading on the in vitro degradation characteristics and kinetics of porous scaffolds in a custom-designed loading system. Porous Poly(L-lactic acid)/β-Tricalcium Phosphate (PLLA/β-TCP) composite scaffolds fabricated by using solution casting/compression molding/particulate leaching technique (SCP) were subjected to degradation in simulated body fluid (SBF) at 37°C for up to 6 weeks under the conditions: with and without static compressive loading, respectively. The results indicated that the increase of the porosity and decrease of the compressive strength under static compressive loading were slower than that of non-loading case, and so did the mass loss rate. It might be due to that the loading retarded the penetration, absorption and transfer of simulated body fluid. These data provide an important step towards understanding mechanical loading factors contributing to degradation.
Authors: Wen You Zhou, Min Wang, W.L. Cheung
Abstract: Nano-sized carbonated hydroxyapatite (CHAp) particles were firstly synthesized using a nanoemulsion method. TEM analyses revealed that as-synthesized nanoparticles were calcium-deficient and spherical in shape (diameter: 16.8±2.6nm). Biocomposite microspheres comprising CHAp nanoparticles and poly(L-lactide) (PLLA) were fabricated using the single emulsion solvent evaporation technique. SEM images showed that composite microspheres were mainly 5-30 μm in size despite the change of CHAp nanoparticle content. When the CHAp nanoparticle content in composite microspheres was below 10 wt%, all nanoparticles were encapsulated within the microspheres which possessed a nanocomposite structure. DSC results showed that the crystallinity of the PLLA matrix of microspheres increased from 38 to 42% when the CHAp nanoparticle content was increased from 0 to 20 wt%. The biocomposite microspheres should be a suitable material for constructing bone tissue engineering scaffolds.
Authors: I. Balać, P.S. Uskoković, R. Aleksić, M. Milovančević, Dragan P. Uskokovic
Authors: Xiu Ping Lu, Xing Wen, Fu Yan Zhu
Abstract: Blends of poly (3-hydroxybutyrate-co-4-hydroxybutyrate) [P (3HB-co-4HB)] with poly(L-lactide) (PLA) were prepared by melt-mixing and subsequent injection molding, and their mechanical properties and morphology were investigated. The results show that the tensile properties, impact strength and spherulitic morphology depend strongly on the composition of the blend. The point of transition shows that phase inversion takes place at composition with 40 weight fraction of PLA in the blend.
Authors: Kazuo Isama, Toshie Tsuchiya
Abstract: The effects of the γ-irradiatted PLLA on the osteoblasts and apatite formation were investigated in vitro. The PLLA sheet was γ-ray irradiated at the dose of 10, 25 or 50 kGy. The mouse osteoblast-like MC3T3-E1 cells and normal human osteoblast NHOst cells were micromass cultured on the PLLA sheet for 2 weeks, and then the proliferation and differentiation of the cells were determined. The proliferations of MC3T3-E1 and NHOst cells hardly changed with increasing irradiation dose. However, the differentiations of MC3T3-E1 and NHOst cells increased with irradiation dose. On the other hand, the surface of the PLLA sheet after soaking in the medium without the cells was characterized by SEM, EDX, FT-IR and XPS. The hydroxyapatite was formed on the surface of the PLLA sheet after soaking, and the amount of hydroxyapatite increased with irradiation dose. In summary, the γ-irradiated PLLA increased the differentiation of osteoblasts and also increased apatite-forming ability even without the osteoblasts. The osteoblast differentiation was enhanced well in the apatite formation on the surface of PLLA after the γ-irradiation.
Authors: Brian Yu Fung Pow, Arthur Fuk Tak Mak, Man Sau Wong, Mo Yang
Abstract: In this work, the effect of multiwalled carbon nanotubes (NWNTs) incorporation in poly(L-lactide) (PLLA) on the human osteoblast-like cell (Saos-2) growth behaviour was studied. The PLLA/MWCNT composite with different ratio of PLLA to MWCNT was fabricated using solvent-casting technique. MWCNT was detected by XRD and showed the successful incorporation of MWCNT into PLLA. Fixed amount of cells were cultured on different composite. Cell viability assay and scanning electron microscopy were used to evaluate cell adhesion, morphology and cytoskeleton development on the scaffolds. The activity of mitochondrial dehydrogenase (MD) enzyme was evaluated by MTT substrate and p-nitrophenyl phosphate substrate. The results demonstrated cytoskeleton fibre and good adhesion of osteoblast cells to the composite surface. No significant differences of cell viability were found for the PLLA/MWCNT composite and controls. The incorporation of MWCNT into PLLA can obviously enhance the MD activity. We believe that sample with more MWCNT provided favourite interactions to the human osteoblast-like cells, which indicate a potential candidate in bone tissue engineering.
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