The characteristics of the X‐ray attenuation in electrospun nano(n)‐ and micro(m)‐Bi2O3/polylactic acid (PLA) nanofibre mats with different Bi2O3 loadings were compared as a function of energy using ...mammography (i.e. tube voltages of 22–49 kV) and X‐ray absorption spectroscopy (XAS) (7–20 keV). Results indicate that X‐ray attenuation by electrospun n‐Bi2O3/PLA nanofibre mats is distinctly higher than that of m‐Bi2O3/PLA nanofibre mats at all energies investigated. In addition, with increasing filler loading (n‐Bi2O3 or m‐Bi2O3), the porosity of the nanofibre mats decreased, thus increasing the X‐ray attenuation, except for the sample containing 38 wt% Bi2O3 (the highest loading in the present study). The latter showed higher porosity, with some beads formed, thus resulting in a sudden decrease in the X‐ray attenuation.
Poly(lactic acid) (PLA) stands out as the most promising biodegradable alternative to conventional petrochemical‐based polymers for manufacturing of high‐performance materials applied in medicine, ...pharmacy, food, textile, and electronic industry. This review was aimed to present the conventional and up‐to‐date technologies for PLA processing including melt blending and molding, hot melt extrusion, 3D printing, foaming, impregnation, thermally induced phase separation, nano‐ and microparticles preparation, wet and dry spinning processes. In addition, the effect of the processing parameters and polymer characteristics on the properties of the final material was elaborated. Diverse possibilities to tailor properties of PLA‐based materials by variation in polymer characteristics and concentration, solvent selection, drying method, processing pressure and temperature, incorporation of bioactive components, and so on were highlighted. The examples of the relations between processing methods, parameters, and end‐product properties are given for a better understanding of all aspects that need to be perceived for fabrication of PLA‐based materials with required performances.
Polylactic acid (PLA) when combined with 3D-printing technology has been used in various fields owing to its excellent biodegradability. However, the application of PLA as a 3D-printing material is ...limited by several characteristics, such as its fragility with a poor impact resistance and poor dimensional stability. Recently, PLA has been processed to improve its properties and retain its biodegradable advantages, thus significantly enhancing the performance of PLA materials in several aspects, such as their mechanical properties, printability, print quality, and functionalization. This paper specifically focuses on PLA in 3D printing and reviews the latest processing methods of 3D-printed PLA developed in the last three years, including physical, chemical, and chemical/physical composite processing methods. It also introduces the processing methods and results of PLA in different extrusion stages, as well as its print quality and application in various printing processes. Finally, it reviews the functional processing of products in terms of applications. This review provides reliable data for further research on PLA, which can be used as a reference for the practical application and production of PLA and MEX.
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A conjugate of the antihypertensive drug, lisinopril, with triblock poly(lactic acid)-poly(ethylene glycol)-poly(lactic acid) (PLA-PEG-PLA) copolymer was synthesized by the reaction of PLA-PEG-PLA ...copolymer with lisinopril in the presence of dicyclohexylcarbodiimide and dimethylaminopyridine. The conjugated copolymer was characterized in vitro by hydrogen nuclear magnetic resonance (HNMR), Fourier transform infrared (FTIR), differential scanning calorimetry (DSC) and gel permeation chromatography (GPC) techniques. Then, the lisinopril conjugated PLA-PEG-PLA were self-assembled into micelles in aqueous solution. The resulting micelles were characterized further by various techniques such as dynamic light scattering (DLS) and atomic force microscopy (AFM). The results revealed that the micelles formed by the lisinopril-conjugated PLA-PEG-PLA have spherical structure with the average size of 162 nm. The release behavior of conjugated copolymer, micelles and micelles physically loaded by lisinopril were compared in different media. In vitro release study showed that in contrast to physically loaded micelles, the release rate of micelles consisted of the conjugated copolymer was dependent on pH of media where it was higher at lower pH compared to the neutral medium. Another feature of the conjugated micelles was their more sustained release profile compared to the lisinopril-conjugated copolymer and physically loaded micelles.
Plastics play an essential role in food packaging; their primary function is to preserve the nature of the food, ensure adequate shelf life and ensure food safety. Plastics are being produced on a ...global scale in excess of 320 million tonnes annually, with demand rising to reflect the material in wide range of applications. Nowadays, the packaging industry is a significant consumer of synthetic plastic made from fossil fuels. Petrochemical-based plastics are regarded as the preferred material for packaging. Nonetheless, using these plastics in large quantities results in a long-standing environment. Environmental pollution and the depletion of fossil fuels have prompted researchers and manufacturers to develop eco-friendly biodegradable polymers to replace petrochemical-based polymers. As a result, the production of eco-friendly food packaging material has sparked increased interest as a viable alternative to petrochemical-based polymers. Polylactic acid (PLA) is one of the compostable thermoplastic biopolymers that is biodegradable and renewable in nature. High-molecular-weight PLA can be used to produce fibres, flexible, non-wovens, hard and durable materials (100,000 Da or even higher).The chapter focuses on food packaging techniques, food industry waste, biopolymers, their classification, PLA synthesis, the importance of PLA properties for food packaging, and technologies used to process PLA in food packaging.
The dissipative particle dynamics (DPD) simulation was used to study the morphologies and structures of the paclitaxel‐loaded PLA‐b‐PEO‐b‐PLA polymeric micelle. We focused on the influences of PLA ...block length, PLA‐b‐PEO‐b‐PLA copolymer concentration, paclitaxel drug content on morphologies and structures of the micelle. Our simulations show that: (i) with the PLA block length increase, the self‐assemble structure of PLA‐b‐PEO‐b‐PLA copolymers with paclitaxel vary between onion‐like structure (core‐middle layer‐shell) to spherical core‐shell structure. The PEO shell thins and the size of the PLA core increases. The onionlike structures are comprised of the PEO hydrophilic core, the PLA hydrophobic middle layer, and the PEO hydrophilic shell, the distribution of the paclitaxel drug predominantly occurs within the hydrophobic intermediate layer; (ii) The system forms a spherical core‐shell structure when a small amount of the drug is added, and within a certain range, the size of the spherical structure increases as the drug amount increases. When the drug contents (volume fraction) cdrug = 10%, it can be observed that the PLA4‐b‐PEO19‐b‐PLA4 spherical structures connect to form rod‐shaped structures. With the length of PLA block NPLA = 8, as the paclitaxel drug concentrations cdrug = 4%, PEO has been insufficient to completely encapsulate the PLA and paclitaxel drug beads. To enhance drug loading capacity while maintaining stability of the system in aqueous solution, the optimal composition for loading paclitaxel is PLA4‐b‐PEO19‐b‐PLA4; the drug content is not higher than 4%; (iii) The paclitaxel‐loaded PLA4‐b‐PEO19‐b‐PLA4 micelle undergo the transition from onionlike (core‐middle layer‐shell) to spherical (core‐shell) to rod‐shaped and lamellar structure as the PLA4‐b‐PEO19‐b‐PLA4 copolymer concentration increases from ccp = 10% to 40%.
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•In-situ ethylene-propylene-diene terpolymer (EPDM) nanofibrils were achieved.•UV-crosslinking was able to freeze in-situ fibrillated EPDM nanofibrils.•EPDM nanofibril-reinforced ...polylactic acid (PLA) showed ductile fracture behavior.•PLA/EPDM foams with outstanding insulating performance were prepared.
Polylactic acid (PLA) is a promising biomass and biodegradable polymer but suffers from its brittle feature and poor foaming ability. Thus, many ductile polymers have been used to modify PLA through compounding. Although some of them can improve the toughness, the strength and rigidness of PLA are seriously scarified due to the large dosage, poor dispersion, and see-island structures. Herein, UV-crosslinking-assisted in-situ fibrillation was developed to fabricate ethylene-propylene-diene terpolymer (EPDM) nanofibril-reinforced PLA composites. Twin-screw compounding followed by melt blowing was used to stretch EPDM phase into nanofibrils, while UV-crosslinking was proposed to stabilize the EPDM nanofibrils in the final PLA/EPDM composites. Thanks to UV-crosslinking, EPDM nanofibrils with an average diameter of 94.3 nm were achieved in PLA. Due to the heterogeneous nucleating effect of UV-crosslinked EPDM nanofibrils, the crystallization rate of PLA was significantly enhanced, and refined crystal morphology with fibrous structures was obtained. Surprisingly, merely 3 wt% of UV-crosslinked EPDM nanofibrils remarkably enhanced the mechanical properties of PLA. The tensile toughness and impact strength were increased by 620% and 440%, respectively, without sacrificing strength and rigidness. Moreover, the UV-crosslinked EPDM nanofibrils also significantly improved the foaming ability of PLA. The PLA/UV-crosslinked EPDM foam with an expansion ratio of up to 28-fold was achieved for the first time by mold-opening microcellular injection molding. With the presence of UV-crosslinked EPDM nanofibrils, the expansion ratio and cell population density of the foams can be increased by 470% and 5 orders of magnitude, respectively. Owing to the super-high expansion ratio and unique micro/nanoscale structures on cell walls, the 28-fold expanded PLA/EPDM foam exhibited outstanding thermally insulating performance with a thermal conductivity of as low as 26.3 mW/m∙K.
This report addresses the challenges of controlled drug delivery for peptide and protein therapeutics by introducing a novel approach of nano formulation fabricated in aqueous media applying ...stereo‐interaction mechanism with poly(D‐lactide)‐polyethylene glycol (D‐PLA‐PEG). To overcome the inherent poor stability of peptide and protein therapeutics, stereocomplexation of the peptide, insulin, is applied, onto D‐PLA‐PEG in aqueous media. Nanoparticles of ≈400 nm are spontaneously formed when water‐soluble D configured PLA‐PEG diblock copolymer and L‐ configured insulin interlock into a stereocomplex, owing to their concave convex fitness. In vitro release of insulin from stereocomplex in phosphate buffer solution (PBS) pH 7.4 solution shows sustained release for 14 weeks. The therapeutic efficacy of the PLA‐insulin stereocomplex nanoparticles are evaluated in diabetic Akita mice. Blood glucose levels and body weight are closely monitored for a period of 17 weeks, revealing a significant reduction in glucose levels of the Akita mice treated with insulin stereocomplex, as well as normal body weight gain. These findings suggest that the stereocomplex nanoparticles of insulin‐D‐PLA‐PEG present a promising and effective sustained and extended release platform for insulin. Notably, the use of water‐soluble D‐PLA‐PEG for stereocomplexation in water expands the applicability of this approach to fabricate controlled delivery systems for peptide and protein therapeutics.
Extended release of peptide drugs is of great need. Stereo‐interaction between water‐soluble D‐PLA‐PEG copolymer and insulin, interlock into stereocomplex nanoparticles releasing insulin for 14 weeks in vitro. The release is dominated by the degradation of the PLA chain, resulting in decomplexation and insulin release. In vivo insulin release in diabetic mice, significantly lowers glucose blood levels for 14 weeks. This delivery concept can be applied to any peptide.
Electrospinning technique was used to obtain a new class of biopolymer/inorganic nanoparticle hybrid fibers fabricated by using poly(lactic acid) (PLA) as the biopolymer matrix and lanthanum ...phosphate nanoparticles (LaPO4) as energy down-converting materials. Before being incorporated and electrospun with the PLA, the LaPO4 nanostructures obtained from microwave-assisted hydrothermal method were studied to have a depth understanding related to their synthesis parameters, since it is known they adopt different structures and morphologies with the temperature and pH. Highly hydrophobic samples of LaPO4 nanoparticles in hexagonal and monoclinic phases with mixed morphologies (rods and semi-spherical) were detected in samples calcined at 400 °C while those calcined at 600 °C consisted mainly in monoclinic phase with semi-spherical morphologies. Smallest particles in semi-spherical and orthorhombic morphologies obtained at pH 1 and 11 were detected after processing them through electrospinning technique and distributed uniformly into the PLA. The vibrational analysis suggested that the ester group (RCOOR') in PLA plays a key role in the interaction with the LaPO4 nanoparticles. These materials can find practical applications in biomedical areas for replacing conventional polymers.
Fully dense PLA blocks were manufactured by 3D-printing, depositing a polymer filament in a single direction via the fusion deposition method (FDM). Specimens were cut from printed blocks using ...conventional machining and were used to perform tension, compression and fracture experiments along different material directions. The elasto-plastic material response was found to be orthotropic and characterised by a strong tension-compression asymmetry; the material was tougher when loaded in the extrusion direction than in the transverse direction. The response of the unidirectional, 3D-printed material was compared to that of homogeneous injection-moulded PLA, showing that manufacturing by 3D-printing improves toughness; the effects of an annealing thermal cycle on the molecular structure and the mechanical response of the material were assessed.
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•3D-printed PLA displays an elasto-plastic, orthotropic mechanical response with a strong tension/compression asymmetry.•The material is tougher when tested in the extrusion direction (KIC=5MPam) than in the transverse direction (KIC=4MPam).•Manufacturing by 3D-printing results in higher toughness than manufacturing by injection-moulding (KIC=3MPam).•Annealing at a temperature below Tg has negligible effect on crystallinity and stiffness but reduces the strength 10 to 30%.
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