Polylactic Acid Fibers Research Articles

Controlled release of 18-β-glycyrrhetic acid by nanodelivery systems increases cytotoxicity on oral carcinoma cell line

The topical treatment for oral mucosal diseases is often based on products optimized for dermatologic applications; consequently, a lower therapeutic effect may be present. 18-β-glycyrrhetic acid (GA) is extracted from Glycirrhiza glabra. The first aim of this study was to test the cytotoxicity of GA on PE/CA-PJ15 cells. The second aim was to propose and test two different delivery systems, i.e. nanoparticles and fibers, to guarantee a controlled release of GA in vitro. We used chitosan and poly(lactic-co-glycolic) acid based nanoparticles and polylactic acid fibers. We tested both delivery systems in vitro on PE/CA-PJ15 cells and on normal human gingival fibroblasts (HGFs). The morphology of GA-loaded nanoparticles (GA-NPs) and fibers (GA-FBs) was investigated by electron microscopy and dynamic light scattering; GA release kinetics was studied spectrophotometrically. MTT test was used to assess GA cytotoxicity on both cancer and normal cells. Cells were exposed to different concentrations of GA (20–500 μmol l−1) administered as free GA (GA-f), and to GA-NPs or GA-FBs. ROS production was evaluated using dichlorodihydrofluorescein as a fluorescent probe. Regarding the cytotoxic effect of GA on PE/CA-PJ15 cells, the lowest TC50 value was 200 μmol l−1 when GA was added as GA-NPs. No cytotoxic effects were observed when GA was administered to HGFs. N-acetyl Cysteine reduced mortality induced by GA-f in PE/CA-PJ15 cells. The specific effect of GA on PE/CA-PJ15 cells is mainly due to the different sensitivity of cancer cells to ROS over-production; GA-NPs and GA-FBs formulations increase, in vitro, this toxic effect on oral cancer cells.

Morphology control of PLA microfibers and spheres via melt electrospinning

In conventional solution electrospinning, the morphologies (e.g., spheres, beaded fibers, and fibers) of electrospun products can be controlled by solution concentration. Here, we report that the morphologies and structures of polylactic acid (PLA) via melt electrospinning also can be adjusted from microfibers to microspheres by simply increasing the spinning temperature. It was found that with temperature increasing from 200 °C to 240 °C, the average diameter of melt-electrospun PLA fibers decreased from 58.46 to 2.96 μm. Then, beaded fibers and microspheres about 14.5 μm in diameter were collected when the spinning temperature was increased to 250 °C and 260 °C. In addition, we also found that the average PLA fiber diameter decreased with increasing the applied spinning voltage, and increased with the increase of spinning distance. To explain the formation mechanism of different PLA microstructures, rheological property and infrared spectra of PLA under different spinning temperatures were also tested.

Effect of Polyvinyl Alcohol Treatment on Mechanical Properties of Bamboo/Polylactic Acid Composites

Polylactic acid (PLA) and bamboo fiber are both green and biodegradable materials. However, the bonding of PLA and bamboo fiber is poor, which limits the physical properties of paper. The effects of polyvinyl alcohol (PVOH) on PLA fiber/bamboo fiber composites were studied by measuring the tensile strength, tear resistance, and breaking length of the paper. In addition, the morphology of paper comprised of PLA fiber and bamboo fiber were investigated by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The tensile index, tear index, and breaking length of paper made with the 4 wt% PVOH-treated bamboo fiber and the untreated PLA fiber compared favorably with the paper made of the untreated bamboo fiber and PLA fiber increased 21.0%, 8.6%, and 20.8%, respectively. However, compared with the paper made of the untreated bamboo fiber and PLA fiber, the tensile index, tear index, and breaking length of the paper made with the treated PLA fiber and the treated bamboo fiber with 4 wt% PVOH solution were dramatically reduced by 30%, 18%, and 30%, respectively.

Blood-clotting mimetic behavior of biocompatible microgels

Recent advances in hydrogel chemistry have led to the development of various soft materials capable of self-healing. Nevertheless, their self-healing capabilities are primitive compared to the responsive and adaptive strategies of blood clotting and wound healing in the human body. We developed a novel microgel system that mimics the process of blood clotting. Electrospun polylactic acid (PLA) fibers were entrapped inside the microgels of a hyaluronic acid conjugate with hesperidin side groups crosslinked by Fe ions; the resulting hydrogels showed fast self-healing and magnetic responsive properties. By applying an external magnetic field, which mimicked blood flow, the microgels successfully aggregated at target sites, like platelets. The aggregates were stable, as demonstrated by resistance to sonication for 30min, and their moduli spanned tens to hundreds of kPa, demonstrating the mechanical integrity of the artificial clots. Like fibrin, the PLA fibers successfully strengthened the aggregates due to formation of uniform fiber-reinforced hydrogels; the artificial clots containing fibers had a 300% improved modulus and 50% increased hardness relative to the hydrogels without fibers. This unique intelligent system can be utilized in future self-healing systems, delivery systems, and devices with microfluidic channels.

Measuring 3D Forces during Capillary Network Remodelling

Patterning of capillary networks is essential for the proper systemic distribution of cells, nutrients, and oxygen in developing as well as adult healthy and unhealthy tissues. Mechanical models describing the relation between blood flow and angiogenesis, vessel pruning, etc. had been introduced in biology at earlier times with great success [1]. Along with these studies, in vitro models of sprouting angiogenesis have shown mechanical descriptions of the interaction of endothelial cells/extracellular matrix (ECM) [2, 3]. Nevertheless, the lack of appropriate methods for in vivo and in situ force measurement had hampered the study of the forces that capillary wall components apply on the ECM during formation/pruning of capillaries. Here, we show that, by developing a new method for imaging and measuring forces in vivo and in situ, we can describe mechanically the remodelling of capillary networks. We introduced a multiphoton imaging system that surpasses the simultaneous channel acquisition problems that the present commercial systems have, but retains the ability of deep imaging with subcellular resolution. To quantify the forces we introduced a reference system in the chorioallantoic membrane (CAM) of the chicken embryo by adding a tunable biocompatible fluorescent nanofibres matrix (electrospun polylactic acid fibres in a predesigned arrangement) that was minimally invasive and able to deform following the deformation of the CAM stroma. We numerically modelled the system as fibres on an elastic material (CAM) and, by characterising mechanically the system, we could retrieve forces on the nN/nm scale. We also identified the formation of new functional connections and found an oscillatory behaviour of the forces that we interpret with a simple biomechanical model of damping oscillations, where the periodicity depends on the matrix structure. The damping term drives the system to a quiescent state.

Additive Manufacturing of PLA and CF/PLA Binding Layer Specimens via Fused Deposition Modeling

As one of the most popular additive manufacturing techniques, fused deposition modeling (FDM) is successfully applied in aerospace, automotive, architecture, and other fields to fabricate thermoplastic parts. Unfortunately, as a result of the limited nature of the mechanical properties and mass in raw materials, there is a pressing need to improve mechanical properties and reduce weight for FDM parts. Therefore, this paper presents an experiment of a special polylactic acid (PLA) and carbon fiber (CF)/PLA-laminated experimental specimen fabricated using the FDM process. The mechanical properties and mass analysis of the new composites for the PLA and CF/PLA binding layer specimen are investigated experimentally. Through the experimental analysis, one can conclude that the mass of laminated specimen is lighter than the CF/PLA specimen, and the tensile and flexural mechanical properties are higher than the pure PLA specimen.

Polylactic acid–agave fiber biocomposites produced by rotational molding: A comparative study with compression molding

AbstractIn this work, the possibility to produce polylactic acid (PLA) and agave fiber biocomposites by dry‐blending and rotational molding was studied. The samples were also produced by compression molding to compare the effect of processing conditions on the biocomposites properties. In particular, the effect of fiber content (0–40 wt.%) on morphology, density, porosity, thermal (DSC) and mechanical properties (tension, flexion, impact and hardness) was studied. Also, a complete analysis of the internal air temperature profiles was performed to determine the thermal behavior of PLA during the rotational molding cycle. The results showed that rotomolded biocomposites were successfully produced but had higher porosity than compression molded ones due to the absence of pressure while forming. This led to different level of mechanical properties reduction as fiber content increases. Nevertheless, for compression‐molded biocomposites, crystallinity (30% at 30 wt.%), tensile modulus (14% at 30 wt.%) and impact strength (71% at 40 wt.%) improvements were obtained compared to neat PLA.

PLA-HPC Fibrous Membranes for Temperature-Responsive Drug Release

In this study, Polylactic acid and Hydroxypropyl cellulose (PLA-HPC) fibers were fabricated by electrospinning. Methylene blue (MEB), as a model hydrophilic drug was embedded into PLA-HPC fibrous membranes. SEM results depicted that fibers are smooth, cylindrical, uniform and it confirmed the incorporation of MEB in PLA fibers alter the fibers morphology. Studies show the on-demand release of drug from PLA-HPC fibrous membranes under temperature stimuli which were absent in membranes manufactured out of PLA. This can be attributed to reversible volume phase transitions of HPC molecules in response to applied external temperature. This study may provide more efficient strategies for developing materials with on-demand drug release capability.

Preventing collapsing of vascular scaffolds: The mechanical behavior of PLA/PCL composite structure prostheses during in vitro degradation.

The success of blood conduit replacement with synthetic graft is highly dependent on the architecture, and mechanical properties of the graft, especially for biodegradable grafts serving as scaffolds for in-situ tissue engineering. Particularly, the property of the radial compression recovery represents a critical to keep the patency during biointegration. Bi-component composite vascular grafts (cVG) made of polylactic acid (PLA) fabric and polycaprolactone (PCL) were developed with superior mechanical properties. In this research, the compressive and tensile properties of the prototypes were characterized when they were subjected to accelerated degradation. In addition, the prepared cVG were analyzed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD) to illustrate the gradual loss of mechanical properties. The results demonstrated that the cVG retained the circular cross-section even through its tensile strength decreased during degradation. The cVG samples containing a high percentage of PLA fibers lost their tensile strength faster, while the samples with lower PLA percentage lost the compressive resistance strength more quickly. This unique fabric-based composite biodegradable vascular prosthesis with an outstanding radical compression recovery could be a good candidate for in-situ formation of tissue engineered vascular graft.

Commingled Yarn Spinning for Thermoplastic/Glass Fiber Composites

Online commingled yarns were spun with three different polymeric matrices, namely polypropylene (PP), polyamide (PA) and polylactic acid (PLA) and glass fibers. Tailored sizings were applied for the three matrices and the resulting mechanical performance of unidirectional composites was evaluated and compared. Significant improvements in the fiber/matrix bonding were achieved by employed sizing chemistry in order to achieve multifunctional interphases. The pure silane coupling agents provide the best performance for all matrices investigated. However, an additional film former has to be added in order to achieve fiber processing. Film formers compatible to the matrices investigated were adapted. The consolidation behavior during isothermal molding was investigated for polypropylene matrix. Different fiber volume contents could be realized and the resulting mechanical properties were tested.

Electrospinning of polylactic acid fibres containing tea tree and manuka oil

Here the effect of tea tree and manuka essential oils (EOs) on the mechanical properties and antibacterial activity of electrospun polylactic acid (PLA) fibres is investigated. It is found that the essential oils work as plasticisers for PLA, lowering the glass transition temperature of the resulting composite fibres up to 60% and increasing elongation-at-break and tensile strength up to 12 times. Manuka EO is particularly successful in blocking the formation of biofilms of Staphylococcus epidermidis that is typically involved in nosocomial infections associated with implanted devices. The results demonstrate that natural extracts can be used to control the mechanical behaviour of PLA fibres and to confer antibacterial activity.

Poly-l-lactic acid: Pellets to fiber to fused filament fabricated scaffolds, and scaffold weight loss study

Poly-l-lactic acid (PLLA) is a bioresorbable polymer used in a variety of biomedical applications. Many 3D printers employ the fused filament fabrication (FFF) approach with the ubiquitous low-cost poly-lactic acid (PLA) fiber. However, use of the FFF approach to fabricate scaffolds with medical grade PLLA polymer remains largely unexplored. In this study, high molecular weight PL-32 pellets were extruded into ∼1.7mm diameter PLLA fiber. Melt rheometric data of the PLLA polymer was analyzed and demonstrated pseudo-plastic behavior with a flow index of n=0.465 (<1). Differential scanning calorimetry (DSC) was conducted using samples from the extruded fiber to obtain thermal properties. DSC of the 3D printed struts was also analyzed to assess changes in thermal properties due to FFF. The DSC and rheometric analysis results were subsequently used to define appropriate FFF process parameters. Constant porosity scaffolds were FFF 3D printed with 4 distinct laydown patterns; 0/90° rectilinear (control), 45/135° rectilinear, Archimedean chords, and honeycomb using the in-house developed custom multi-modality 3D bioprinter (CMMB). The effect of laydown pattern on scaffold bulk erosion (weight loss) was studied by immersion in phosphate-buffered saline (PBS) over a 6-month period and measured monthly. A repeated measures analysis of variance (ANOVA) was performed to identify statistically significant differences between mean percent weight loss of the four laydown patterns at each time point (1–6 months). The resulting data follows distinct temporal trends, but no statistically significant differences between means at individual time points were found. Cross-sectional scanning electron microscope (SEM) images of the 6-month degraded scaffolds showed noticeable structural deterioration. The study demonstrates successful processing of PLLA fiber from PL-32 pellets and FFF-based 3D printing of bioresorbable scaffolds with pre-defined laydown patterns using medical grade PLLA polymer which could prove beneficial in biomedical applications.

A preclinical evaluation of polypropylene/polylacticacid hybrid meshes for fascial defect repair using a rat abdominal hernia model.

ObjectivesSynthetic mesh surgery for both abdominal and urogenital hernia repair is often unsatisfactory in the long-term due to postoperative complications. We hypothesized that a semi-degradable mesh hybrid may provide more appropriate biocompatibility with comparable mechanical properties. The aim was to compare its in vivo biocompatibility with a commercial polypropylene (PP) mesh.Methods72 rats were randomly allocated to either our new composite mesh (monofilament PP mesh knitted with polylactic-acid-fibers (PLA)) or to a commercially available PP mesh that was used as a control. 15, 90, and 180 days after implantation into the rat abdomen mesh tissue complexes were analysed for erosion, contraction, foreign body reaction, tissue integration and biomechanical properties.ResultsNo differences were seen in regard to clinical parameters including erosion, contraction or infection rates between the two groups. Biomechanical properties including breaking load, stiffness and deformation did not show any significant differences between the different materials at any timepoint. Macrophage staining did not reveal any significant differences between the two groups or between timepoints either. In regard to collagen I there was significantly less collagen I in the PP group compared to the PP/ PLA group at day 180. Collagen III did not show any significant differences at any timepoint between the two groups.ConclusionA PP/PLA hybrid mesh, leaving a low amount of PP after PLA degradation seems to have comparable biomechanical properties like PP at 180 days due to enhanced collagen production without significant differences in erosion, contraction, herniation or infection rates.

Polylactic acid/carbon fiber composites: Effects of polylactic acid-g-maleic anhydride on mechanical properties, thermal behavior, surface compatibility, and electrical characteristics

This study uses a reactive extrusion for the grafting of maleic anhydride on polylactic acid in order to form polylactic acid grafted maleic anhydride that serves as a compatibilizer between polylactic acid and carbon fiber. The effects of different ratios of the free radical initiator to maleic anhydride as well as the amounts of polylactic acid grafted maleic anhydride on the mechanical properties, interfacial compatibility, thermal behaviors, and electrical properties of the polylactic acid/carbon fiber composites are discussed. The test results indicate that using polylactic acid grafted maleic anhydride as compatibilizer improves the interfacial compatibility of polylactic acid/carbon fiber composites, which in turn contributes to a high electrical conductivity and the electromagnetic interference shielding effectiveness, while decreasing the surface resistance and increases. In addition, the amount of polylactic acid grafted maleic anhydride has a positive influence on their tensile properties, flexural strength, and impact strength. The differential scanning calorimetry results indicate that a high polylactic acid grafted maleic anhydride content is also conducive to crystallinity, but is not in related to the melting temperature. According to the scanning electronic microscope observation, the fractured composites that are inflicted by an impact have considerably few traces of the fibers being pulled out, which is ascribed to polylactic acid that can completely enwrap carbon fiber. Therefore, the incorporation of polylactic acid grafted maleic anhydride is proven to strengthen polylactic acid/carbon fiber composites, exemplified by their improved interfacial compatibility and properties.

Preparation of Magnetic Polylactic Acid Fiber Mats by Electrospinning

Poly(lactic acid) (PLA) is blended with Poly(ethylene glycol) (PEG) and magnetic nanoparticles (MNPs). A series of mixtures are converted to fibers via electrospinning at room temperature. The fiber diameter of PLA decreases on blending with PEG from 6 down to 3 micrometers and with PEG + MNPs down ca. 1 micrometer. The thermogravimetric study confirms the effect of blending, enhancing the stability on adding PEG to PLA. The magnetic properties of polymer fibers containing different concentrations of MNPs are studied by vibrating sample magnetometer. The fiber blends shows proportionally reduced saturation magnetization compared to pure magnetic nanoparticles. The MNPs –incorporated PLA-PEG nanocomposite mat show magnetization and therefore promise the possibility for temperature effects, such as hyperthermia treatment.

Electrospinning of porous polylactic acid fibers during nonsolvent induced phase separation

ABSTRACTIn this study, porous micron‐sized fibers of polylactic acid (PLA) are fabricated via electrospinning of PLA‐dichloromethane (DCM)‐hexane systems with no post treatment involved. Several compositions from the liquid‐liquid phase separated region of the phase diagram of this ternary system are selected and their electrospinnability are investigated throughout their phase separation process before gelation. We show that under constant processing and ambient parameters, there is a phase separation shelf time for each composition wherein the viscoelasticity of the systems is optimum to produce long, uniform porous fibers. For the first time, we investigate the effect of aging time during phase separation on the morphology of the electrospun fibers using scanning electron microscopy (SEM). Based on our results, certain phase separated systems provide a range of viscosity allowing for the production of porous spherical micro beads or fibers via electrospraying and electrospinning, respectively. It is also shown that obtaining long, uniform fibers from electrospinning of highly phase separated systems, e.g., a gel, is not feasible due to the high degree of crystallinity of their polymer‐rich domains and the solid‐like yielding behavior. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44862.

Long-term hydrolytic degradation study on polymer-based embroidered scaffolds for ligament tissue engineering

Following anterior cruciate ligament injury, a mechanically stable tissue replacement is required for knee stability and to avoid subsequent damages. Tissue engineering of the anterior cruciate ligament demands a biocompatible scaffold with a controllable degradation profile to provide mechanical support for 3 to 6 months. It has been argued that embroidered textile scaffolds made of polylactic acid and poly(lactic-co-ɛ-caprolactone) fibres are a promising approach for the ligament tissue engineering with an adapted functionalization and cell seeding strategy. Therefore, the hydrolytic degradation behaviour of embroidered scaffolds made of polylactic acid and a combination of polylactic acid and poly(lactic-co-ɛ-caprolactone) fibres was investigated under physiological conditions for 168 days. The changes in the mechanical behaviour, the molecular weights as well as the surface structures were analysed. Sufficient mechanical properties comparable to native anterior cruciate ligament tissue could be demonstrated for scaffolds made of polylactic acid fibres after 6 months under hydrolysis. These results clarify the potential of using embroidered scaffolds for ligament tissue engineering.

Effect of Layout Sequence on the Integrity of Poly-lactic Acid and Rice Straw Fibre Composites

This work reports the development of a composite material from both renewable resources and biodegradable materials: modification of poly-lactic acid (PLA) with rice straw fibre loading. PLA-RS fibres composites were prepared with different fibre loadings (5 – 15 vol%) with different layout sequence; sequential layering and batch-mixed using hot press. The flexural strength of the PLA-RS fibre composites prepared using the both sequential layering and batch-mixed reduced with increasing fibre loading but for batch-mixed, the flexural strength increased at 10 vol% fibre loading and reduced again thereafter. In this case, RS fibres were not able act as reinforcement for PLA.

Formation and Investigation of Electrospun PLA Materials with Propolis Extracts and Silver Nanoparticles for Biomedical Applications

An electrospun hydrophilic non-water-soluble biocompatible polylactic acid (PLA) nonwoven material was used as a delivery system for propolis ethanolic extract (PEE) and silver nanoparticles (AgNPs) that are known for their established antiseptic and antimicrobial activity. Combination of PEE and AgNPs in a single product should provide efficient antimicrobial protection and improved wound healing. Evaluations of PEE and AgNPs on morphology of electrospun materials, release kinetics of AgNPs and phenolic compounds, antibacterial properties, and cytotoxicity of electrospun PLA materials were performed. The presence of PEE or/and AgNPs resulted in denser mats formed by thicker PLA fibers. The average diameter of PLA microfibers was 168±29 nm. The average diameter of microfibers increased to 318±40 and 370±30 nm when 10 wt% and 20 wt% ethanol were added, respectively. Addition of 10 wt% or 20 wt% PEE increased the diameter to 282±25 and 371±25 nm, respectively. Suspension of AgNPs also caused the formation of thicker microfibers with 254±25 nm diameter. Electrospun PLA microfibers with PEE maintained viability of HaCaT cells. Testing of antimicrobial activity confirmed the ability of AgNPs containing PLA electrospun materials to inhibit the growth of microorganisms.

Plasma polymerised poly(methyl methacrylate) and cyclopropylamine films on polylactic acid nanofibres by electrospinning

Polylactic acid (PLA) is a thermoplastic, biodegradable polyester. It can be derived from natural resources such as corn starch, cassava starch or sugarcane. PLA can also be classified as a bioplastic. To produce PLA in the industrial scale, the most common ways are to polymerise two monomers: lactic acid and cyclic di-ester (lactide) with various metal catalysts in solution or suspension. PLA can be manufactured by injection moulding, extrusion, casting, and in most recent techniques such as electrospinning and three dimensional printing. The variety of different processes makes PLA available to a wide range of applications. PLA is soluble in tetrahydrofuran, dioxane, chlorinated solvents and heated benzene. The selected solubility provides limited choices for dissolving PLA into solution for electrospinning process to fabricate nanofibres. One advantage of using electrospinning is to create materials with very high porosities with complex geometry, maintaining its biodegradability, enhancing bio-adhesion and extracellular chemical signal transduction for cell culture. In this study, we fabricate PLA nanofibres by electrospinning and then coat these fibres with poly(methyl methacrylate) (PMMA) and cyclopropylamine (CPA) using plasma polymerisation. PMMA is a transparent, nontoxic thermoplastic polymer with highly stable physical and chemical properties whilst CPA is a volatile and chemically active molecule with a primary amine. In addition to fabrication, we also investigated the structure and morphology of the PLA fibres with/without PMMA/CPA coatings by SEM, EDS, FTIR and AFM. These fibres are tested for their biocompatibility via cell culture of 3T3 fibroblasts (mouse embryonic). The 3T3 cell line is the standard fibroblast commonly used for DNA transfection studies. The culture is assessed by MTT assays and cell proliferation to evaluated cellular activities on the PLA nanofibres.