Polylactic Acid Concentration Research Articles

Ecotoxicty of 3D printing material Polylactic Acid (PLA) on sea urchin Paracentrotus lividus

In this study the ecotoxicity of 3D printing material [polylactic acid (PLA) investigated with marine echinoderm; sea urchin Paracentrotus lividus. To achieve this goal, (i) fertilization success, spermiyotoxicity and embriyotoxicity exposed to PLA concentrations (0.001, 0.005, 0.01, 0.1 and 1 g/L) were assessed for 72 h. For this purpose, our study is important to make comprehensive evaluations to ensure the safety of bioplastic formulations and to take measures to regulate the use of additives. At the same time, the additive used to increase the durability of bioplastic materials will also allow us to understand the long-term effects on ecosystems, wildlife and human health. Our aim is to minimize possible harm and ensure that the overall environmental impact of bioplastics remains positive.

A facile strategy for designing hollow-porous polymer microparticles with tunable structures

Biodegradable hollow-porous microparticles have shown great potentials in chemical and biomedical areas owing to their distinctive structural attributes. Herein, a simple but instructive strategy was proposed to construct hollow-porous polylactic acid (PLA) microparticles in one-step based on electrohydrodynamic atomization technology. Hollow-porous microparticles with fusiform, red blood cell and spherical shapes were successfully fabricated with production rates of 70 mg/h, 30 mg/h and 105 mg/h. A formation map in terms of flow rate ratio and PLA concentration was obtained to demonstrate the operating regions. Effects of key operating parameters were studied, showing that high voltage (11.4 kV−12.4 kV) and low PLA concentration conditions (2.5 %−3.5 %) are preferred to get well-structured particles. The evolutions of Taylor cone and atomization state were also explored experimentally and numerically to further understand the process. The prepared microparticles exhibit excellent sustained release performance and high encapsulation rate (>90 %). This strategy offers a satisfactory one-step method for preparing various structured hollow-porous polymer particles as drug carriers.

Preparation of interwoven structure composite paper via polylactic acid infiltrating fiber network

AbstractCellulose is commonly acknowledged as a sustainable material owing to its abundance and renewability. However, the abundance of hydroxyl groups makes the paper material highly hydrophilic, and the hydrogen bonds between the fibers are easily broken by water, leading to the degradation of mechanical properties. This work details the fabrication of a composite paper comprising interwoven cellulose and polylactic acid (PLA) structures through hot‐pressing and PLA impregnation onto handwritten paper derived from conventional wood pulp fibers as the substrate. The investigation assessed how varying PLA concentrations influenced the overall characteristics of the composite paper, including its morphology, structure, mechanical properties, water absorption behavior, and water contact angle. Experimental results revealed that the composite paper fabricated through our approach exhibited an intertwined structure comprising both PLA and cellulose. With a tensile index reaching 33.24 kN·m/kg and a mere 31.1% loss in tensile index post‐water treatment, the mechanical properties of the composite paper were significantly enhanced due to the robust interfacial compatibility between cellulose and PLA, as well as the adhesive effect of PLA. Furthermore, the composite paper (CP) is easily processable and amenable to thermoforming into paper trays as required, indicative of its potential applications in the packaging industry.

Fabrication of controlled-release silver nanoparticle polylactic acid microneedles with long-lasting antibacterial activity using a micro-molding solvent-casting technique.

Most topical drug delivery techniques do not provide therapeutic concentrations for treatment of surgical site and other local infections and, therefore, require some kind of enhancement, such as physical methods like microneedles, the subject of the present investigation. Here, controlled-release long-lasting antibacterial polylactic acid (PLA) microneedles containing 1, 3, and 5% silver nanoparticles (AgNP) were prepared using micro-molding solvent-casting technique. Microneedles were characterized using optical microscopy, SEM, FTIR, XRD, and DSC. Also, mechanical strength, barrier disruption ability, insertion depth, in-vitro release kinetics, antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa, and silver permeation through rat skin were studied. Microneedles showed good mechanical strength with no signs of failure at an optimum PLA concentration of 25%(w/v). FTIR revealed no chemical interaction between ingredients, and XRD confirmed presence of AgNP in microneedles. Microneedles penetrated the skin model at depth of up to 1143μm resulting 5-7 times increase in transepidermal water loss (TEWL). Release studies showed 2.2, 6.8, and 8.1µg silver release from the whole body (obeying Higuchi's release model) and 0.33, 0.45, and 0.78µg from the needles alone (obeying Fickian-cylindrical type release) for 1, 3, and 5% AgNP microneedles, respectively. Also, prolonged antibacterial activity (for 34days) was observed. Skin studies over 72h indicated that besides needles, silver is also released from the baseplate which had a marginal share in total silver permeation through the skin. In conclusion, a straightforward solvent-casting technique can be used to successfully prepare strong AgNP-containing PLA microneedles capable of long-lasting antibacterial activity.

The effects of polylactic acid bioplastic exposure on midgut microbiota and metabolite profiles in silkworm (Bombyx mori): An integrated multi-omics analysis

Polylactic acid (PLA) is a highly common biodegradable plastic and a potential threat to health and the environment. However, limited data are available on the effects of PLA exposure in the silkworm (Bombyx mori), a model organism used in toxicity studies. In this study, silkworms with or without PLA exposure (P1: 1 mg/L, P5: 5 mg/L, P25: 25 mg/L, and P0: 0 mg/L) for the entire 5th instar period were used to investigate the impact of PLA exposure on midgut morphology, larvae growth, and survival. Mitochondrial damage was observed in the P5 and P25 groups. The weights of the P25 posterior silk gland (5th day in the 5th instar), mature larvae and pupae were all significantly lower than those of the controls (P < 0.05). Dead worm cocoon rates and larva-pupa to 5th instar larvae ratios showed a positive and negative dose-dependent manner with respect to PLA concentrations, respectively. Additionally, reactive oxygen species levels and superoxide dismutase activity of the P25 midgut were significantly higher and lower when compared with controls, respectively (P < 0.05). The molecular mechanisms underlying the effects of PLA and associated physiological responses were also investigated. In the midgut metabolome, 127 significantly different metabolites (variable importance projection >1 and P < 0.05) were identified between the P0 and P25 groups and were mainly enriched for amino acid metabolism and energy supply pathways. The 16 S rDNA data showed that PLA altered microbial richness and structural composition. Microbiota, classified into 34 genera and 63 species, were significantly altered after 25 mg/L PLA exposure (P < 0.05). Spearman's correlation results showed that Bifidobacterium catenulatum and Schaalia odontolytica played potentially vital roles during exposure, as they demonstrated stronger correlations with the significantly different metabolites than other bacterial species. In sum, PLA induced toxic effects on silkworms, especially on energy- and protein-relevant metabolism, but at high concentrations (25 mg/L). This prospective mechanistic investigation on the effects of PLA on larval toxicity provides novel insight regarding the ecological risks of biodegradable plastics in the environment.

Assessment and Optimization of Thermal Stability and Water Absorption of Loading Snail Shell Nanoparticles and Sugarcane Bagasse Cellulose Fibers on Polylactic Acid Bioplastic Films.

The optimization and modeling of the parameters, the concentration of polylactic acid (PLA), sugarcane bagasse cellulose fibers (SBCF), and snail shell nanoparticles (SSNP), were investigated for the development of bioplastic films. With the aid of the Box-Behnken experimental design, response surface methodology was used to assess the consequence of the parameters on the water absorption and thermal stability of fabricated bioplastic films. Varied water absorption and thermal stability with different component loading were obtained, evidencing the loading effect of snail shell nanoparticles and sugar bagasse cellulose fibers on bioplastic film's water absorption and thermal stability. The quadratic polynomial model experiment data offered a coefficient of determination (R2) of 0.8422 for water absorption and 0.8318 for thermal stability, verifying the models' fitness to develop optimal concentration. The predicted optimal parameters were polylactic acid (99.815%), sugarcane bagasse cellulose fibers (0.036%), and snail shell nanoparticles (0.634%). The bioplastic developed with optimized concentrations of each component exhibited water absorption and thermal stability of 0.45% and 259.7 °C, respectively. The FTIR curves of bioplastic films show oxygen stretching in-plane carbon and single-bonded hydroxyl bending in the carboxylic acids functional group. SEM and TEM images of the bioplastic showed dispersion of the nanoparticles in the matrix, where SSNP is more visible than SBCF, which may be due to the lesser loading of SBCF. The improved properties suggest an optimum concentration of naturally sourced resources for developing bioplastic, which may be used for food and drug packaging for delivery.

Investigating the Effect of PCL Concentrations on the Characterization of PLA Polymeric Blends for Biomaterial Applications.

Polylactic acid (PLA) and polycaprolactone (PCL) are synthetic polymers that are extensively used in biomedical applications. However, the PLA/PCL blend produced by ball milling, followed by pressure compaction and sintering, has not been extensively explored. The goal of this research is to investigate the effect of the composition of biomaterials derived from PLA and PCL prepared by ball milling, followed by pressure compaction and sintering, on mechanical and physical properties. PCL and PLA with various concentrations were blended utilizing a ball milling machine for 2 h at an 80-rpm rotation speed. The obtained mixture was placed in a stainless steel 304 mold for the compacting process, which uses a pressure of 30 MPa to create a green body. The sintering procedure was carried out on the green body created at 150 °C for 2 h using a digital oven. The obtained PLA/PCL blend was tested using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), density, porosity, and three-point bending. Following the interaction between PCL and PLA in the PLA/PCL blend, the FTIR spectra and XRD diffractograms obtained in this work revealed a number of modifications in the functional groups and crystal phase. The 90PLA specimen had the best mechanical properties, with a maximum force and displacement of 51.13 N and 7.21 mm, respectively. The porosity of the PLA/PCL blend decreased with increasing PLA concentration so that the density and flexural properties of the PLA/PCL blend increased. The higher PCL content decreased the stiffness of the PLA molecular chain, consequently reducing its flexural properties.

Short-term effect of poly lactic acid microplastics uptake by Eudrilus eugenia

The present study investigated the uptake of polylactic acid (PLA) microplastics, the most commonly used biodegradable plastic by Eudrilus eugeniae. It was done by observing their weight changes, biomass, and microplastics concentration after feeding them with a mixture of PLA and cow dung for 16 days at the ratio of 0%, 10%, 30%, 60%, and 80% w/w dry weight. The mortality rate of the earthworms for all the PLA concentrations during the 16 days of the feeding period was 0%. However, the microplastic significantly affected the earthworms' weight (P-value 0.00027), especially at 80% of PLA concentration. The earthworms had the lowest weight gain at 80%, followed by 60%, 30%, and 10% of PLA, respectively. The earthworms subjected to 80% and 10% of PLA had a similar pattern with the control. The PLA microplastics concentration factor (CF) in the vermicast was the highest at the 10% PLA than other treatments because Eudrilus eugeniae did not degrade the PLA. This study concludes that even though PLA is biopolymer-based, the earthworm cannot assimilate it. However, in the long run, there is a possibility of further degradation of the PLA MPs ejected in the vermicast due to the rich microbial environment provided by the earthworms and vermicast.

Microencapsulation of astaxanthin based on emulsion solvent evaporation and subsequent spray drying.

Astaxanthin (AXT) is widely used in the food, drug, and cosmetics fields, but its applications are extremely limited by its intrinsic properties. Herein, a novel encapsulation system had been performed to fabricate AXT-loaded microcapsules through emulsion solvent evaporation and spray-dried methodologies. The influence of polylactic acid (PLA) concentrations on the characteristics of AXT-loaded dispersions and resultant microcapsules were investigated. The results showed that the sizes and zeta potentials of dispersions and microcapsules increased with increasing PLA content (9.8 to 24.6wt%). The encapsulation efficiency (EE) of the microcapsules increased with increasing PLA concentration up to 21.4wt%. The moisture content values, flowability, and bulk density of the obtained microcapsules decreased with increasing PLA content (9.8 to 24.6wt%). Furthermore, the cell culture experiment indicated that the obtained microcapsules had no cytotoxicity and possessed excellent antioxidant activity. This work provides a new strategy for fabricating AXT-enriched microcapsules and expands their application in nutritional products. PRACTICAL APPLICATION: This work fabricated a novel encapsulation system for AXT through emulsion solvent evaporation and spray drying methodologies. The obtained AXT-loaded microcapsules possessed great physical stability and could expand potential applications of AXT.

Effect of poly lactic acid trays on the optical and thermal properties of recycled poly (ethylene terephthalate)

AbstractTo progress towards a more sustainable plastic system, multiple interventions are required, including the decoupling from fossil feedstock. Biobased plastics therefore have to be integrated in plastic waste management systems. This should, however, not hamper the performance of current recycling systems. Several studies have previously suggested that the uptake of poly lactic acid (PLA) in this system would endanger poly (ethylene terephthalate) (PET) recycling. This study reports the estimated concentration of PLA in recycled PET and the effect of the presence of this impurity on the optical and thermal properties of recycled PET. The current concentrations of PLA in recycled PET in the Netherlands were modelled to vary between 0% and 0.019%. When the PLA consumption rises, the concentration in recycled PET can be kept below 1% with NIR technologies. The impact of 0.1 to 1% PLA in recycled PET on the optical and thermal properties was negligible. Conversely, the negative impact of 0.1% PVC was substantial. Also the impact of 0.1% EVOH on recycled PET was studied and like PLA found to be limited. This study therefore contravenes previous studies on the impact of PLA on the quality of recycled PET. The difference between this study and the previous studies is that within this study, recycled PET has been processed in agreement with industrial methods. Therefore, in case the sorting and recycling facilities maintain their current careful operation, no negative impact of PLA on PET recycling can be foreseen, and further integration of biobased plastics in the plastic waste management system can be pursued.

Asymmetrical ultrafiltration membranes based on polylactic acid for the removal of organic substances from wastewater

The continued use of non-biodegradable polymeric-based membranes for water purification has led to an unsustainable accumulation of waste at disposal, resulting in various environmental problems. In this study, eco-friendly asymmetric ultrafiltration (UF) membranes were fabricated from polylactic acid (PLA) with different polymer concentrations using the phase inversion method. The fabricated membranes were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle, porosity, and pore size analysis. Permeate flux and organic matter (bovine serum albumin (BSA)) rejection were evaluated using synthetic wastewater. The anti-fouling properties of PLA membranes were investigated through static adsorption and dynamic filtration of BSA. Furthermore, the performance of the best performing PLA membrane was evaluated via chemical oxygen demand (COD) rejection as well as membrane fouling using raw municipal wastewater obtained from a local wastewater treatment plant (WWTP) in Abu Dhabi (UAE). The results indicated that increasing the PLA concentration to 20 wt% improved BSA removal from synthetic and raw wastewaters by up to 92 and 89%, respectively, in addition to improving the membrane anti-fouling property. The post-filtration and after cleaning FT-IR spectra revealed high antifouling property with no detection of BSA peaks, SEM images confirmed the reduction in membrane's pore size as PLA concentration increased, resulting in enhancing the antifouling properties of the membranes. In conclusion, this study demonstrated that PLA-UF membranes could be a viable eco-friendly alternative to traditional crude oil-derived membranes.

"Smart" Polylactic Acid Films with Ceftriaxone Loaded Microchamber Arrays for Personalized Antibiotic Therapy.

Bacterial infections are a severe medical problem, especially in traumatology, orthopedics, and surgery. The local use of antibiotics-elution materials has made it possible to increase the effectiveness of acute infections treatment. However, the infection prevention problem remains unresolved. Here, we demonstrate the fabrication of polylactic acid (PLA) “smart” films with microchamber arrays. These microchambers contain ceftriaxone as a payload in concentrations ranging from 12 ± 1 μg/cm2 to 38 ± 8 μg/cm2, depending on the patterned film thickness formed by the different PLA concentrations in chloroform. In addition, the release profile of the antibiotic can be prolonged up to 72 h in saline. At the same time, on the surface of agar plates, the antibiotic release time increases up to 96 h, which has been confirmed by the growth suppression of the Staphylococcus aureus bacteria. The efficient loading and optimal release rate are obtained for patterned films formed by the 1.5 wt % PLA in chloroform. The films produced from 1.5 and 2 wt % PLA solutions (thickness—0.42 ± 0.12 and 0.68 ± 0.16 µm, respectively) show an accelerated ceftriaxone release upon the trigger of the therapeutic ultrasound, which impacted as an expansion of the bacterial growth inhibition zone around the samples. Combining prolonged drug elution with the on-demand release ability of large cargo amount opens up new approaches for personalized and custom-tunable antibacterial therapy.

Is the Polylactic Acid Fiber in Green Compost a Risk for Lumbricus terrestris and Triticum aestivum?

Polylactic acid (PLA) bioplastic was introduced to the market as an environmentally friendly potential solution for plastic pollution. However, the effects of bioplastic debris mixed with composts on soil macroinvertebrates, plant growth and soil conditions are still unknown. Soil macroinvertebrates are soil health indicators. A reduction in their abundance is a sign of soil degradation. The objectives of this study were (i) to assess PLA debris in greenhouse composts, and (ii) to test the ecotoxicological effects of PLA debris mixed with compost on Lumbricus terrestris, a soil organism model, and on Triticum aestevium, a plant growth model. The study was comprised of three stages: (1) determine the PLA debris size distribution in composts; (2) assess the ecotoxicological effects of real-world concentrations (0% to 5%) of PLA mixed with compost on earthworm mortality and reproduction; and (3) assess the influence of compost mixed with real-world PLA concentrations on plant growth and physicochemical soil conditions. One percent of PLA debris was found in green composts, 40% of composted PLA debris measured between 1–10 mm, with a concentration of 82.8 ± 17.4 microplastics.gram−1 compost. A concentration of 1% PLA in composts resulted in significant mortality in earthworms. No significant effects of PLA mixed with composts were observed on plant growth or soil physicochemical conditions. Further studies are required in order to test the effect of this biopolymer on different earthworm and plant’ species.

Superhydrophobicity of paperboard packaging by hierarchical surface roughness modification of polylactic acid electrospraying

Water resistance of paperboard packaging was improved by developing a hierarchical surface roughness structure through double-layer coating. Combination coating methods for the first layer were performed by rod coating containing kaolin or calcium carbonate (CaCO3) particle mixture in native starch solution as a coating formulation. The second layer coating was conducted by polylactic acid (PLA) electrospraying. Kaolin or CaCO3 average particle sizes of 0.5, 1.0 and 10 μm were prepared at 5%(w/v) and mixed into a 1.0% native starch solution for the first layer coating, while PLA electrospraying was set at 1%, 0.25% and 0.125% (w/v). Coating weight significantly increased after first layer coating and after PLA electrospraying, proportional to increase of particle size and PLA concentration. Surface roughness significantly decreased after first layer coating and further decreased after second layer electrospraying due to deposition of PLA particles in the valley areas of the pre-coated layer. PLA electrospraying at all concentrations significantly promoted increase of water contact angle regardless of pre-coating formulations. Water contact angle reached superhydrophobic level at 151.29 degrees for 0.05 μm of CaCO3 pre-coating with additional 0.125% (w/v) PLA electrospraying. The PLA nanoparticles (Ra = 0.036 μm) reduced the contact area of water molecules, enhancing water repellency. For water vapor transmission rate (WVTR), 0.05 μm kaolin pre-coating with 0.125% (w/v) PLA showed optimal improvement as a plate-like shape obstructed the water vapor. Double-layer coating improved mechanical properties when small particles and lower PLA concentrations were applied.

Morphological analysis of fibrous webs electrospun from Polycaprolactone, polylactic acid and their blends in chloroform based solvent systems

In this study, polycaprolactone (PCL), polylactic acid (PLA), and PLA/PCL blend electrospun fibrous webs are prepared using chloroform based solvent systems at different concentrations. The solvents to be used with chloroform are selected in accordance with the morphological and rheological structures of the polymers. While the morphology of the produced networks is observed under a scanning electron microscope, fiber diameter measurements and pore analysis are performed with Image J Software System. Although bead-free webs could not be achieved for neat PCL samples, neat PLA samples and PCL/PLA blends result in smooth fiber surfaces with homogeneous fiber diameter distributions. The results show that the increase in PLA concentration does not cause much change in fiber diameter but induces an increase in the area of pores. Furthermore, in the PLA/PCL blend, it is determined that as the ratio of PCL in the mixture increases, the fiber diameter decreases even if there is an acceptable reduction in the average pore area.

Morphology and transport characterization of solution-processed rubrene thin films on polymer-modified substrates

In this report, the morpho-structural peculiarities and the crystallization mechanisms in solution-processed, solvent vapor annealed (SVA) thin films of rubrene (5,6,11,12-tetraphenylnaphthacene) on different substrates were investigated. The high-quality rubrene crystal films with a triclinic crystal structure were successfully prepared on the FTO substrates (glass slide coated with fluorine-tin-oxide) modified by PLA (polylactic acid) for the first time. The area coverage of rubrene crystal and the sizes of rubrene dendritic crystals increased with increasing thickness of PLA film and concentration of rubrene solution. For rubrene molecules, FTO wafers with rough surface provided the possibility of heterogeneous nucleation. During the SVA process, there were two kinds of forces acting on the diffusion of rubrene molecules: one force was provided by the residual chloroform solvent, which was perpendicular to the substrate, and the other force was provided by gaseous dichloromethane, which was parallel to the substrate. The synergy of these two forces was proposed to explain the nucleation and the crystallization processes of rubrene films. The higher nucleus of PLA/rubrene dendrites and the layer-by-layer stacking of needle-shaped nanocrystalline PLA/rubrene were important for exploring their kinetic formation process.

Parámetros de extrusión para la producción de un polímero termoplástico derivado de PLA-almidón

The purpose of this study was to develop a biodegradable thermoplastic polymer based on starch and polylactic acid (PLA) blends with mechanical properties adequate for a wide range of applications. A thermoplastic starch (TPS) was formulated using native corn starch, glycerol as a plasticizer ranging from 30 to 50% (w/w) and citric acid (1.0%, w/w) as a crosslinker. The TPS was mixed with polylactic acid (PLA) [0-50%, w/w]. The material was prepared by extrusion using a single screw extruder. The variables for the experiment design were PLA concentration, extrusion temperature, glycerol concentration, and velocity of the screw. Samples before and after extrusion were characterized by Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DCS), Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction. We evaluated the mechanical Young’s modulus, tensile strength, and elongation at break. All treatments were performed according to the experiment design. The results of the characterization of the material were analyzed using the response surface methodology (RSM). The RSM revealed the optimum PLA concentration, extrusion temperature, and screw velocity that would produce a corn starch-PLA biodegradable plastic with mechanical properties closer to those of the petroleum-derived plastics.

Studies on Semi-crystalline Poly Lactic Acid (PLA) as a Hydrophobic Coating Material on Kraft Paper for Imparting Barrier Properties in Coated Abrasive Applications

This study investigated and explored the possible use of bio-based Poly lactic acid (PLA) as a barrier coating material on natural Kraft paper to fabricate coated abrasive products and to replace the conventional, non-biodegradable, synthetic polymer based barrier coating materials. PLA was coated on the Kraft paper using a solution coating process. The barrier properties of the PLA-treated Kraft paper were accordingly tested for application as a backing material in coated abrasive products. The concentration of PLA in solution was systematically increased from 5 wt% to 25 wt%. The coating thickness and coating weights were increased quantitatively with increasing solution concentrations. The morphology of the coating was characterized using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), contact angle, and surface roughness measurements. The mechanical properties of the PLA coating applied Kraft paper were quantified by measuring the tensile strength, bursting strength, air porosity and Cobb value in order to find its suitability as coated abrasive product. The thermal analysis carried out using DSC scan indicated the semi-crystalline nature of PLA. The coating’s analysis for air and water resistance indicated that the air and water resistance increased with increase in PLA coating thickness. The data from different studies revealed that the PLA coating with a coating weight of 9 g m−2 appeared to be the most ideal concentration over the untreated or other lower PLA g m−2 treated backing materials and proved to possess superior overall barrier properties that are essentially needed for the fabrication of coated abrasive products.

Electrospinning of PLA with DMF: Effect of polymer concentration on the bead diameter of the electrospun fibre

Electrospinning has been known for its’ ability in producing nanoporous fibres which uses electrical force to form a spinning jet out of a polymer solution. The electrospinning condition and polymer solution properties can influence the electrospinning jet formation as well as jet path. Polylactic acid (PLA) was dissolved in dimethylformamide (DMF) to produce a polymer solution. Bead is considered as a defect towards an electrospun fibres, yet previous study found that PLA/DMF produced beaded fibres for all concentrations. However, there is a limited study that explain the effect of concentration on the diameter of beads. Therefore, in this study we investigated the formation of electrospinning jet as well as the effect of PLA concentration of formation of beads, particularly the diameter of the beads. Polymer solution with different concentration was prepared. The concentration investigated in this study were 7.5, 10, 12.5, 15, 17.5, and 20 % w/v. Polymer solution was then subjected to the electrospinning process to evaluate the morphology of the electrospun produced via optical microscope. Simultaneously, the formation of electrospinning jet is observed with portable digital microscope. The morphology of the electrospun fibres, especially the fibre and bead diameter are analyzed using image analysis software, ImageJ. From this research, it is found that at voltage of 10 and 12.8 kV, a stable electrospinning jet can be formed which consists of ‘Taylor cone’, straight jet, and plume. Concentration from 7.5–20 % w/v were able to form electrospun fibres, yet only 12.5 and 15 % w/v PLA concentrations can produce an effective electrospun fibres with beads diameter of 3393 nm and 3642 nm, respectively. Also, the number of beads for both concentrations are 34 and 19, respectively. Since the main criteria in producing electrospun fibres is no beads or small and minimal beads at best, therefore 12.5 and 15 % w/v PLA concentration are considered as efficient electrospun fibres.

Oxygen-releasing nanofibers for breathable bone tissue engineering application.

Oxygen is a vital molecule for cell and tissue processes. Electrospun fibers have been extensively used as drug loading carriers due to possibility of well control over drug release with modulating fiber properties. However, they have not been used as depots for oxygen release. In the present study, an oxygen-releasing nanofibrous scaffold has been developed by electrospinning of polylactic acid/nano-calcium peroxide suspension with different polylactic acid concentrations (6.5 and 13% w/v). The electrospun fibers with calcium peroxide cargo provided oxygen content of 30-94 mmHg in a period of 14 days which lies well within the oxygen level of osseous tissue. The release profile of 13% polylactic acid fibers was different with that of 6.5% fibers with respects to the initial content of released oxygen and the release rate. Not only did 13% fibers supply oxygen with a slower rate, but also they resulted in a lower burst release of oxygen. Cell culture studies in hypoxia corroborated that 13% polylactic acid fibers better preserve cell viability comparing 6.5% counterparts as perceived by MTT assay. Moreover, they endowed more favored milieu for adherence, arrangement and migration of mesenchymal stem cells as confirmed by microscopy images. The oxygen-releasing fibers equally affected alkaline phosphatase, osteocalcin, and calcium deposition by mesenchymal stem cells most likely due to interplay between topographical and metabolic cues offered by 6.5 and 13% formulations.