Pure Poly L-lactic Acid Research Articles

Mechanical and Thermal Properties of Toughened Poly(L-lactic) Acid and Lignin Blends

Fully degradable poly(L-lactic) acid (PLLA) and lignin blends were prepared using the melt blending method. The impact strength of PLLA was dramatically improved by 52.4% and 36.6% with the addition of 5 wt% and 10 wt% of lignin, respectively. Meanwhile, the Young’s modulus was maintained. Polarized optical microscopy (POM) results indicated that lignin served as a nucleating agent for the heterogeneous crystallization of PLLA in blends, which was responsible for the improvement in the impact strength. The introduced lignin also promoted the cold-crystallization of PLLA, which was demonstrated by differential scanning calorimetry (DSC). The blends of PLLA with lignin are considered to be a promising material because of the improved toughness, the full degradability, and the lower price compared with pure PLLA.

Adverse Events Associated With Biodegradable Lactide-Containing Suture Anchors

To evaluate the occurrence of adverse events and inflammatory reactions related to the use of biodegradable anchors. A retrospective review of a consecutive series of arthroscopic shoulder procedures using biodegradable suture anchors performed by a single surgeon was undertaken. The database was purged of patient identifiers. The blinded data were analyzed for procedure type, anchor type and composition, associated procedures, and general demographic data. Anchor composition and number were recorded. A shoulder procedure after the index operation was considered an adverse event. The nature of these procedures was evaluated using medical records, operative images, and video, looking specifically for inflammatory reactions. Any anchor-related issues were documented. Three hundred sixty cases met the inclusion criteria. The procedure was a tendon repair (rotator cuff or biceps) in 265 cases and a labral repair (instability or SLAP) in 97, 2 of which were combined instability and tendon repairs. Nine different biodegradable anchors were identified, possessing 4 different polymer combinations. Adverse events (reoperations) were identified in 18 of 360 patients (5%): 13 tendon repairs and 5 labral/instability repairs. Only 2 were anchor related. In 1 tendon repair case, the anchor broke and an anchor fragment required removal. In 1 labral repair case, the anchor eyelet (a suture) loosened from the anchor body and eroded the humeral head. No cases of inflammatory synovitis wereobserved. No statistical difference in adverse event rates existed between tendon and labral repairs (P > .05). Anchor-specific adverse events occurred in 2 of 360 procedures (0.5%). One was anchor design related (the prominent head containing the suture eyelet broke off) in a poly-L-lactic acid (PLLA) anchor. One was anchor material related and occurred when the poly-levo (70%)/dextro (30%)-lactide anchor body reabsorbed, loosening the encased eyelet suture and allowing this suture to migrate into the joint. No inflammatory reactions were documented in the slowly degrading pure PLLA or more rapidly degrading biocomposite PLLA/β-tricalcium phosphate-based anchors. Level IV, retrospective review, therapeutic study.

Performance test of Nano-HA/PLLA composites for interface fixation

Objective: By in situ polymerization of poly-L-lactic acid (PLLA) and nano-hydroxyapatite (Nano-HA), and finding the best proportion of composite, so as to get ideal interface fixation material. Methods: According to a certain ratio (the mass fraction of Nano-HA, respectively, is 0%, 10%, 20%, 30% and 40%), composite PLLA and Nano-HA by in situ polymerization, and test the performance of this kind of new type of interface fixation such as, bending strength,compressive strength, elastic modulus, scanning electron microscopy (SEM) and degradation experiments in vitro. Then observe its mechanical properties, microstructure, the dispersion of Nano-HA in the PLLA and degradation rate of composite materials. Results: 1. Mechanical tests show that with the increase of Nano-HA content, the tensile strength decreases and the elastic modulus increases; with Nano-HA content of 20%, the bending strength of composite materials presents the peak value (156.8 MPa). 2. SEM scan shows the fracture surface of pure PLLA is relatively smooth; with Nano-HA content of 10%, the fracture surface shows a large number of dimples, and is obvious rough; with Nano-HA content of 20%, the fracture surface is uneven, forming a large number of dimples; with Nano-HA content of 30% or more, the fracture surface becomes more flat, and there are some small dimples. 3. Degradation experiments in vitro show the following: as the degradation time goes on, the pH values of degradation liquid is gradually reduced and the mechanical properties of composite materials also gradually have some decay. Conclusion: With Nano-HA content of 20%, the interface fixation material has a better mechanical properties and degradation properties. According to the best ratio, prepare Nano-HA/PLLA composite artificial materials with good performance.

Investigation of the In Vitro Degradation of a Novel Polylactide/Nanohydroxyapatite Composite for Artificial Bone

We prepared the poly‐L‐lactic acid (PLLA)/nanohydroxyapatite (n‐HA) composite and investigated the in vitro degradation of pure PLLA material and PLLA/n‐HA composites in order to identify a suitable and ideal artificial bone tissue repair material. The water uptake, weight loss, and changes in the PBS pH value and in the mechanical properties of material were measured during the processes that PLLA and PLLA/n‐HA biological composites were degraded in PBS. We also performed electron microscopic scanning of the material fracture surface and observed the microscopic morphologies of materials during the degradation process. We found that the degradation rate of the PLLA/n‐HA material was slower than the PLLA material, and there was a little degradation of the PLLA/n‐HA material at early stages. The PLLA/n‐HA material also maintained the initial mechanical strength better than the pure PLLA material. The PLLA/n‐HA material is thus a better material for artificial bone than the pure PLLA material.

Ornithoctonus huwenna spider silk protein attenuating diameter and enhancing strength of the electrospun PLLA fiber

AbstractSpider silk and poly‐L‐lactic acid (PLLA) are both good bio‐medical materials. PLLA/spidroin composite nano‐fibers were obtained by electrospinning with the mixed solution of Ornithoctonus huwenna spider silk/1,1,1,3,3,3,‐hexafluoro‐2‐propanol (HFIP) and PLLA/HFIP. The morphology, molecular conformations, crystallinity degree and mechanical property of the electrospun fibers were investigated by means of SEM, FT‐IR, XRD, and tensile test. The results indicated that spider silk protein attenuated the fiber diameter and enhanced the mechanical property of the electrospun PLLA fibers. The diameter of electrospun PLLA fibers were micron level (>500 nm), while with the addition of spider silk protein, the diameter of the PLLA/spidroin composite fibers decreased significantly, reaching nano‐scale (<500 nm), and the diameter of the composite fibers displayed a bipolar distribution of coarse fibers (>300 nm) and fine fibers (<300 nm). The FT‐IR and XRD analysis showed that the blend nano‐fibers had higher crystallinity, and a phase separation occurred. The mechanical property of the electrospun fiber mat was improved by adding a certain amount of spider silk protein in the PLLA/HFIP solution. When the mass fraction of the spider silk protein was 4%, the breaking strength of the electrospun PLLA/spidroin composite nano‐fiber mat was 112% of pure PLLA micro‐fiber mat's. Copyright © 2010 John Wiley & Sons, Ltd.

Evaluation of In-Vitro Cytotoxicity of Composite Materials Composed of Poly-L-lactic Acid and β-Tricalcium Phosphate

Composite material film composed of Poly-L-lactic acid (PLLA) and β-tricalcium phosphate (β-TCP) was prepared by a solvent evaporation technique. Cellular cultivation in vitro, Von Kossa staining and MTT assay were performed. The results of cytotoxicity test show that cells cultured in extracts of PLLA/β-TCP and on the surface of composite showed normal growth and proliferation, mineralization nodules were observed for fibroblasts cultured in PLLA/β-TCP extract at day 7. Compared with pure PLLA materials, β-TCP in the PLLA composite facilitate both adhesion and proliferation of rat fibroblasts on the PLLA/β-TCP composite film.

Fabrication and characterization of nano-composite scaffold of PLLA/silane modified hydroxyapatite

In order to improve the interfacial connection of hydroxyapatite (HAP) to poly- l-lactic acid (PLLA), γ-methacryloxypropyl-trimethoxysilane (γ-MPS) was used as a coupling agent to modify the surface of nano-HAP (NHAP) particles. The FTIR and XPS results showed γ-MPS was successfully bonded on the surface of NHAP. Silane modified nano-HAP (MNHAP) and PLLA were fabricated to nano-composite scaffold by a thermally induced phase separation method. The characterization of the composite scaffold showed that the scaffold had a nano-fibrous PLLA network (fiber size 100–800 nm), an interconnective microporous structure (1–8 μm) and high porosity (>90%). MNHAP was homogeneously distributed in the scaffold, also partly set in the nano-PLLA fibers. As a result, the compressive modulus and the protein adsorption of PLLA/MNHAP (80:20, w/w) composite scaffold increased to 4.2-fold and 2.8-fold compared with those of a pure PLLA scaffold. Incorporating MNHAP into PLLA network also buffered the pH reduction and reduced the weight loss in vitro degradation significantly.

Tuning of biodegradation rate of PLLA scaffolds via blending with PLA

Blends of Poly-L-Lactic Acid (PLLA) with Poly-Lactic Acid (PLA) in different proportions (95/5, 90/10, 80/20, 70/30 and 60/40) were utilized in order to realize biodegradable and biocompatible scaffolds for soft tissue engineering applications. The scaffolds were produced via thermally induced phase separation (TIPS) starting from ternary systems where dioxane was the solvent and water the non-solvent. Morphology was evaluated by Scanning Electron Microscopy (average pore size and interconnection). Foams’ apparent density was also evaluated (porosity ranges from 87% to 92%). Moreover an in vitro biodegradation test of scaffolds was set-up in order to verify the rate of degradation of the various PLLA/PLA blends employed. The rate of degradation was calculated via WAXD, by analyzing the increment of cristallinity of the various PLLA/PLA scaffolds mantained for different times in a body mimicking fluid, in the presence or in the absence of cells. The results showed that it is possible to prepare scaffolds of PLLA/PLA via TIPS and to tune their average pore size by changing some experimental parameters (polymer concentration, solvent/non-solvent ratio, demixing temperature and time). The biodegradation tests highlighted some significant differences in terms of degradation rate between the PLLA/PLA foams and pure PLLA foam (used as control). The data confirm that morphology, mechanical properties and biodegrability of the foam using a blend of the scaffolds can be tuned by blending PLLA with PLA.

Fabrication of Mineralized Polymeric Nanofibrous Composites for Bone Graft Materials

Poly-L-lactic acid (PLLA) and PLLA/collagen (50% PLLA+50% collagen; PLLA/Col) nanofibers were fabricated using electrospinning. Mineralization of these nanofibers was processed using a modified alternating soaking method. The structural properties and morphologies of mineralized PLLA and PLLA/Col nanofibers were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and contact angle measurements. Human bone-derived osteoblasts were cultured on the materials for up to 1 week to assess the biological properties of the nanofibrous composites. Cell attachment on these nanocomposites was also tested within 1 h of culture at room temperature. The mechanical properties of the cell-nanocomposite constructs were determined using tensile testing. From our results, the bone-like nano-hydroxyapatite (n-HA) was successfully deposited on the PLLA and PLLA/Col nanofibers. We observed that the formation of n-HA on PLLA/Col nanofibers was faster and significantly more uniform than on pure PLLA nanofibers. The n-HA significantly improved the hydrophilicity of PLLA/Col nanofibers. From the results of cell attachment studies, n-HA deposition enhanced the cell capture efficacy at the 20-minute time point for PLLA nanofibers. The E-modulus values for PLLA+n-HA with cells (day 1 and day 4) were significantly higher than for PLLA+n-HA without cells. Based on these observations, we have demonstrated that n-HA deposition on nanofibers is a promising strategy for early cell capture.

Poly‐L‐lactic acid/hydroxyapatite hybrid membrane for bone tissue regeneration

Poly-L-lactic acid (PLLA)/hydroxyapatite (HA) hybrid membranes were fabricated via electrospinning of the PLLA/HA dispersion for use in bone tissue regeneration. The structural properties and morphologies of PLLA and PLLA/HA hybrid membrane were investigated by measuring the Brunauer-Emmett-Teller specific surface area, observations of SEM, and TEM. The dispersion and integrating of HA nanoparticles in the hybrid membrane were studied by energy dispersion X-ray analysis and FTIR. The mechanical properties of PLLA/HA membrane were also measured by tensile tests. For exploring biological behaviors of the hybrid membrane, in vitro degradation tests were carried out. The osteoblast cell (MG-63) was cultured in PLLA/HA hybrid membrane extract containing medium; the cell adhesion and growth capability were investigated by SEM observation and MTT assay. HA nanoparticles were not only dispersed in the PLLA but also reacted with the functional group of PLLA, resulting in strong surface bonding and high tensile strength of hybrid membrane. The cell adhesion and growth on the PLLA/HA hybrid membrane were far better than those on the pure PLLA membrane, which proves that the PLLA/HA hybrid membrane can be one of the promising biomaterials for bone tissue regeneration.

2820 ステレオコンプレックス型ポリ乳酸繊維の機械的特性に及ぼす環境効果(J08-2 バイオメカニクス,J08 生体・環境適合材料の創製・強度評価技術開発)

Stereocomplex-type polylactic acid (SCPLA) is gaining attention in the various field due to its melting point of 220℃, which is higher than that of pure poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA). However, exposure of polylactic acid (PLA) to environmental agents such as sunlight, water, heat, degrades its mechanical properties. This study reports the effect of water and high temperature environment on properties of PLA fiber. When SCPLA fiber was immersed in water at high temperature, tensile strength drastically decreased with the hydrolysis of SCPLA. Compared to the PLLA fiber, however, SCPLA fiber had a greater resistance to hydrolysis. When SCPLA fiber and PLLA fiber were immersed in water at high temperature, sem examination of these fibers revealed regular patterns of cracks running in the vertical direction to the fiber axis.