Papers by Keyword: PLLA

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Authors: Naznin Sultana, Min Wang
Abstract: Poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) was used to make composite scaffolds for bone tissue engineering in our previous studies. To control the degradation rate and process of composite scaffolds, PHBV was blended with poly(L-lactic acid) (PLLA), which has a much higher degradation rate than PHBV, and PHBV/PLLA blends were used as polymer matrices for composite scaffolds. Composite scaffolds based on these blends and containing nano-sized hydroxyapatite (nHA) were fabricated using an emulsion freezing / freeze-drying technique. Non-porous films of PHBV/PLLA blends were prepared using the solvent casting method. In vitro degradation tests of non-porous PHBV/PLLA blends and porous composite scaffolds were conducted by immersing samples in phosphate buffered saline (PBS) for various periods of time. It was found that the composition of polymer blends affected water uptake of films and scaffolds. For PHBV/PLLA-based scaffolds, the incorporated nHA particles also significantly increased water uptake within the initial immersion time. Both PHBV/PLLA blends and composite scaffolds underwent rapid weight losses within the first few weeks. The degradation of composite scaffolds arose from the dissolution of nHA particles and degradation of the PLLA component of polymer blends. Composite scaffolds exhibited enhanced adsorption of bovine serum albumin (BSA), a model protein, in the current study.
1399
Authors: Xin Zhang, Min Wang, Xiao Yan Yuan, Jia Chen Kang
Abstract: Electrospinning is investigated by many groups around the world for constructing fibrous tissue engineering scaffolds. Incorporating biomolecules such as growth factors in fibers is becoming common for enhancing the biological performance of electrospun scaffolds. However, biomolecules may lose bioactivity if they are exposed to organic solvent during electrospinning. In emulsion electrospinning, an aqueous biomolecule solution is emulsified and water-in-oil emulsions are then electrospun into core-shell structured fibers, with biomolecules being contained in the core of fibers, which helps to avoid biomolecule-solvent contact and also reduce the initial burst release. In this investigation, for a comparative study, poly (L-lactic acid) was made into solid and core-shell structured fibers via conventional electrospinning and emulsion electrospinning, respectively. The two electrospinning techniques and resultant fibers were compared in terms of processing parameters (polymer concentration, applied voltage, working distance, etc.) and fiber characteristics (morphology, diameter, structure, etc.). Solvent properties such as conductivity and volatility affected fiber morphology and diameter. The polymer concentration range usable for emulsion electrospinning was narrower than that for conventional electrospinning owing to changes in viscosity.
390
Authors: Hui Li Shao, Xian Jue Zhou, Xue Chao Hu
Abstract: Synthesis of Poly(L-lactide) (PLLA) by the ring-opening polymerization (ROP) of L-lactides in supercritical carbon dioxide (SC-CO2) with co-solvent were studied. Effects of kinds of co-solvent on the molecular weight (MW) and the molecular weight distribution (MWD) of the resultant polymers were investigated by the gel permeation chromatography (GPC). The resultant polymers were also characterized with 1H NMR, 13C NMR and FT-IR. It was found that PLLA with high purity and almost without racemization could be obtained by this technology and the acetone is the best co-solvent for this kind of polymerization. By using stannous octoate as initiator and acetone as co-solvent, PLLA having a weight-average molecular weight (Mw) near to 9×104 and polydispersity index (PDI) of 1.7 was successfully synthesized.
1377
Authors: D.P. Li, Xiao Hong Wang, B. Meng, Qing Ling Feng, Fu Zhai Cui
347
Authors: Jia Chen Kang, Min Wang, Xiao Yan Yuan
Abstract: Electrospinning of poly(L-lactic acid) (PLLA) and gelatin separately to form nonwoven PLLA or gelatin nanofibrous membranes was investigated. Factors that could affect the fiber morphology and fiber diameter were studies for PLLA and gelatin, respectively. The polymer solution concentration was found to play a dominant role in the formation of defected or nondefected ultrafine fibers. Using a specially designed experimental setup with separate syringe pumps for polymer solutions and separate power supplies for high voltages for electrospinning, PLLA-gelatin bicomponent fibrous membranes were formed with PLLA fibers interweaving with gelatin fibers. Multicomponent fibrous scaffolds can be very useful for tissue engineering and/or controlled release applications.
1454
Authors: Monika Kučerová, Petr Lenfeld
Abstract: The Paper deals with problematics of analysis of shrinkage biodegradable polymer materials PLA and PLLA in consequence with setup of parameters. Samples for analysis were prepared by technology of injection molding with parameters set according to Taguchi method. The parameters setting consist of injection speed, holding pressure, temperature and wall thickness. Dependency of parameters measured inside of the mold was compared to parameters set on molding machine. By this comparison we have received data for material processing in praxis.
133
Authors: Lin Li, Yi Li, Jia Shen Li, Lei Yao, Arthur F.T. Mak, Frank Ko, Ling Qin
Abstract: Poly-L-Lactide (PLLA) composites were prepared with nano silver particles with the weight ratios of nano silver particles to PLLA (Ag/PLLA) at 0.5%, 2.5%, 5%, 7.5% and 10% (w/w). In vitro cytotoxicity tests were conducted firstly to evaluate the cytotoxicity of the composites. The results indicated that PLLA, 0.5%, 2.5% and 5% Ag/PLLA composites were nontoxic to cells, while 7.5% and 10% Ag/PLLA composites were significantly toxic to cells. Cell proliferation experiments and antibacterial tests were also performed. 5% Ag/PLLA was found the best for cell proliferation with obvious antibacterial property. Thus, Ag/PLLA can be used as nontoxic scaffolds for tissue engineering with antibacterial property.
849
Authors: Hisashi Sato, Seiichiro Umaoka, Yoshimi Watanabe, Ick Soo Kim, Masakazu Kawahara, Masao Tokita
Abstract: Ti and Ti alloys are particularly attractive materials as the metallic implant-material. This is because that these alloys have low shear modulus and the good biological compatibility with bone. However, interfacial adhesion ability of bone and Ti alloy is low. As improvement method of the interfacial adhesion ability, bioaffinity material like hydroxyapatite has been coated on surface of the Ti alloys. However, such bioaffinity materials have low strength and wear resistance. In this study, Ti composites containing biodegradable poly-L-lactic-acid (PLLA) fiber were fabricated by spark plasma sintering (SPS) method. The PLLA fiber plays a role as reinforcement in Ti matrix, and can be gradually decomposed inside body with progress of time. By the decomposition of PLLA, pore is generated in Ti matrix, and bone simultaneously penetrates into the pore. Therefore, tightly bond between bone and Ti matrix can be expected. Using the Ti-PLLA composites fabricated by SPS method, microstructural observation and mechanical tests were performed. It was found that Ti-PLLA composite has laminate-layer structure with plate-like shape PLLA. Hardness and wear behavior of Ti-PLLA composite has anisotropy due to its structure. However, strength of the Ti-PLLA composite is low because of the imperfect sintering of Ti matrix. Since sintering of Ti matrix can be improved by changing the temperature of SPS, Ti-PLLA composite with anisotropic mechanical properties can be expected by SPS method.
3201
Authors: Bo Li, Li Hua Li, Chang Ren Zhou
Abstract: Solid freeform fabrication, known as rapid prototyping (RP) technology allows in designing the scaffold with pre-defined and controlled external and internal architecture.In this study we produce scaffolds with network of chitosan fibrils that mimic the extracellular matrix produced by the cells. These network scaffolds also consisting of nanoparticles of hydroxyapatite (HA) for stabilisation of scaffolds are characterised by environmental scanning electron microscopy and mechanical properties. ESEM showed that the scaffolds possess macropore (300µm), micropore and fibre network structure. The compressive strength and elastic modulus (E) for the scaffolds are 0.54± 0.02 MPa and 6.13± 0.60 MPa, respectively, which are increasing obviously. The biocompatibility of the woodpile-network scaffolds was investigated with osteoblastic cells. The result showed the distribution and proliferation of osteoblast orients along the chtosan fibre network, preferentially. After 4 weeks of culture, macropore channels are covered by cells in large part,while the areas without chitosan fibre network are covered rarely. The properties of these scaffolds indicate that they can be used for bone tissue engineering applications.
38
Authors: Joo Eon Park, Mitsugu Todo
Abstract: Novel reinforcements such as beam, film, and porous frame were developed to improve the mechanical properties of poly(L-lactide) (PLLA) scaffolds. A solid-liquid phase separation method was used to fabricate porous structures such as core portions and porous frame of reinforced scaffolds. The beam and film reinforcements were also fabricated from PLLA pellets by applying the thermal-press technique. In the standard scaffold, the localized deformation was characterized as buckling of the pore structures. On the contrary, the primary microstructural deformation mechanism in the beam and the film reinforced scaffolds was characterized as buckling deformation and interfacial failure of the matrix and the reinforcement respectively. It is also seen that the inner porous structure could maintain the initial structure without local buckling of the pore structure. The compressive mechanical properties of the reinforced scaffolds were dramatically improved by about 2 ~ 5 times compared to the standard scaffold.
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