Structural changes of polylactic-acid (PLA) microspheres under hydrolytic degradation

1999 ◽  
Vol 71 (8) ◽  
pp. 1223-1230 ◽  
Author(s):  
M. F. Gonzalez ◽  
R. A. Ruseckaite ◽  
T. R. Cuadrado
Keyword(s):  
Polylactic Acid ◽  
Structural Changes ◽  
Hydrolytic Degradation

Preparation and study on the optical, mechanical, and antibacterial properties of polylactic acid/ZnO/TiO2 shared nanocomposites

2020 ◽  
Vol 36 (3) ◽  
pp. 285-311
Author(s):  
Ali Tajdari ◽  
Amir Babaei ◽  
Alireza Goudarzi ◽  
Razie Partovi
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Scanning Electron Microscopy ◽  
Antibacterial Activity ◽  
Optical Properties ◽  
Polylactic Acid ◽  
Field Emission ◽  
Antibacterial Properties ◽  
Hydrolytic Degradation ◽  
Scanning Electron

In this research, first, ZnO nanorods were synthesized by hydrothermal method and characterized in terms of morphological and structural properties by means of field emission scanning electron microscopy, Fourier transform infrared, and X-ray diffraction techniques. Subsequently, polylactic acid/ZnO, polylactic acid/TiO2, and polylactic acid/ZnO/TiO2 nanocomposites with different percentages of nanoparticles and two different types of ZnO morphologies were prepared and their microstructural, optical, mechanical, hydrolytic degradation, and antibacterial properties were investigated. Field emission scanning electron microscopy results of polylactic acid/ZnO and polylactic acid/TiO2 samples showed a proper dispersion and nanoparticle distribution for low percentages (up to 5 wt%) and increased aggregation for the higher percentages. Besides, a large increase in the aggregation tendency was observed for combined nanoparticles (polylactic acid/ZnO/TiO2 nanocomposites). Results of the tensile test, the UV–Vis absorption tests, and the hydrolytic degradation tests of the samples showed an enhanced mechanical (approximately 55% increase in the presence of 3–5 wt% of nanoparticles) and light absorption and degradation (approximately 85% increase in the presence of 3–10 wt% of nanoparticles) for the polylactic acid by incorporating nanoparticles. It was also observed that, in addition to the quality of dispersion and distribution of nanoparticles in the polymeric matrix, the type of morphology of nanoparticles can contribute to the improvement of these properties. The cylindrical morphology of ZnO played a greater role on improving the polylactic acid mechanical properties compared to the spherical ZnO morphology (approximately 20%). On the contrary, the increased polylactic acid optical properties and degradation with ZnO spherical morphology were more pronounced (approximately 60%). Interestingly, when both ZnO and TiO2 were added, a synergistic effect in the case of UV-shielding and degradation rate and alternatively, a detrimental effect on the mechanical properties were detected. (The polylactic acid optical properties increased by about 17% and its degradation more than doubled.) Furthermore, the antibacterial activity of polylactic acid was investigated against the two Gram-positive Listeria monocytogenes and Gram-negative bacteria Escherichia coli by incorporating nanoparticles. The results indicated that as the nanoparticle percentage increases, the antibacterial activity steadily increases.

scholarly journals Changes in Crystal Structure and Accelerated Hydrolytic Degradation of Polylactic Acid in High Humidity

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4324
Author(s):  
Yutaka Kobayashi ◽  
Tsubasa Ueda ◽  
Akira Ishigami ◽  
Hiroshi Ito
Keyword(s):  
Crystal Structure ◽  
Polylactic Acid ◽  
Hydrolytic Degradation ◽  
Gel Permeation Chromatography ◽  
Amorphous Region ◽  
Industrial Applications ◽  
Reduced Pressure ◽  
Specific Temperature ◽  
Time Changes ◽  
Random Scission

Highly crystallized polylactic acid (PLA) is suitable for industrial applications due to its stiffness, heat resistance, and dimensional stability. However, crystal lamellae in PLA products might delay PLA decomposition in the environment. This study clarifies how the initial crystal structure influences the hydrolytic degradation of PLA under accelerated conditions. Crystallized PLA was prepared by annealing amorphous PLA at a specific temperature under reduced pressure. Specimens with varied crystal structure were kept at 70 °C and in a relative humidity (RH) of 95% for a specific time. Changes in crystal structure were analyzed using differential calorimetry and wide-angle X-lay diffraction. The molecular weight (MW) was measured with gel permeation chromatography. The crystallinity of the amorphous PLA became the same as that of the initially annealed PLA within one hour at 70 °C and 95% RH. The MW of the amorphous PLA decreased faster even though the crystallinity was similar during the accelerated degradation. The low MW chains of the amorphous PLA tended to decrease faster, although changes in the MW distribution suggested random scission of the molecular chains for initially crystallized PLA. The concentrations of chain ends and impurities, which catalyze hydrolysis, in the amorphous region were considered to be different in the initial crystallization. The crystallinity alone does not determine the speed of hydrolysis.

scholarly journals IN VITRO DEGRADATION OF POLYDIOXANONE (PDO) LIFTING THREADS IN HYALURONIC ACID (HA).

2019 ◽  
Vol 10 (1) ◽  
pp. 1-13
Author(s):  
Dubraska Suárez ◽  
Gladys J Velazco de Maldonado ◽  
Reynaldo Ortiz ◽  
Victor Garcia-Guevara ◽  
Blanca Miller-Kobisher
Keyword(s):  
Hyaluronic Acid ◽  
Key Words ◽  
Structural Changes ◽  
Hydrolytic Degradation ◽  
Central Core ◽  
In Vitro Degradation ◽  
Central Column ◽  
Rate Of Hydrolysis

Background: Recently, some clinicians have proposed implanting PDO threads imbibed in hyaluronic acid (HA). However, this is controversial since PDO sutures are hydrophilic and the presence of HA could increase the rate of hydrolysis. Aim: To demonstrate the degradation of PDO lifting threads in HA through ultramicroscopy. Materials and methods: Three, one cm long, segments of 23G PDO threads, where immersed in 1.5 ml non-crosslinked hyaluronic acid in previously labeled, sterile microcentrifuge tubes. These were observed by ultramicroscopy at 4x and 10x after 24, 48 and 72 hours. Results: Microphotographs taken after 24 hours already show structural changes in the fibers, presenting an increase in interlaminar spaces and dilution of violet pigmentation. At 48 hours, degradation continues. PDO hygroscopy is observed as aqueous content between the peripheral layers and the central core of the thread. Some fibers show breakage, and there is an increase in interlaminar and interfibrillar spaces. At 72 hours, as the pigment is released, larger empty spaces are observed in the central column of the thread, and there is disorganization of the peripheral fibrils with fraying all along the fiber. Conclusions: Hyaluronic acid induces rapid biodegradation of the PDO thread by hydrolysis beginning 24 hours after contact of the thread with the biomaterial. We hypothesize that non-crosslinked hyaluronic acid is a powerful catalyzing agent for hydrolytic degradation of the PDO thread, since this thread is highly hydrophilic. Thus, we suggest that clinically embedding PDO threads with HA will only accelerate biodegradation of the suture. Key words: Lifting threads, polydioxanone, hyaluronic acid, biodegradation, PDO hydrolysis

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

2017 ◽  
Vol 47 (6) ◽  
pp. 1305-1320 ◽  
Author(s):  
Judith Hahn ◽  
Annette Breier ◽  
Harald Brünig ◽  
Gert Heinrich
Keyword(s):  
Tissue Engineering ◽  
Anterior Cruciate Ligament ◽  
Polylactic Acid ◽  
Cruciate Ligament ◽  
Hydrolytic Degradation ◽  
Ligament Injury ◽  
Degradation Behaviour ◽  
Native Anterior Cruciate Ligament ◽  
Anterior Cruciate ◽  
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.

scholarly journals MECHANICAL PROPERTIES, MORPHOLOGY, AND HYDROLYTIC DEGRADATION BEHAVIOR OF POLYLACTIC ACID / THERMOPLASTIC POLYURETHANE BLENDS

2020 ◽  
Vol 21 (1) ◽  
pp. 193-201
Author(s):  
Yose Fachmi Buys ◽  
Mimi Syakina Ahmad ◽  
Hazleen Anuar ◽  
Mudrikah Sofia Mahmud ◽  
Nur Aimi Mohd Nasir
Keyword(s):  
Mechanical Properties ◽  
Polylactic Acid ◽  
Thermoplastic Polyurethane ◽  
Hydrolytic Degradation ◽  
Polymeric Materials ◽  
Mechanical Analysis ◽  
Material Degradation ◽  
Compression Moulding ◽  
Degradation Behaviour ◽  
Internal Mixer

Polylactic acid (PLA) has attracted tremendous interest to be utilized as the replacement for petroleum-based polymers as it possesses good biodegradability, can be derived from renewable sources, and shows high mechanical strength. However, its inherent brittleness and low toughness has limited its usage in broader applications. In this work, PLA was melt blended with tough thermoplastic polyurethanes (TPU) in order to produce eco-friendly polymeric materials with balanced mechanical properties. Moreover, the miscibility and the hydrolytic degradation behaviour of PLA/TPU blends were also investigated as it is important to control material degradation behaviour in some applications. Five compositions of specimens, i.e. neat PLA, PLA/TPU 75/25 vol%, PLA/TPU 50/50 vol%, PLA/TPU 25/75 vol%, and neat TPU, were prepared by melt blending PLA with TPU using an internal mixer, followed by compression moulding. Tensile and impact tests were performed to evaluate the mechanical properties. From the tests, it was apparent that the elongation-at-break and impact strength of the blends increased as the TPU content increased. Dynamic Mechanical Analysis (DMA) and Scanning Electron Microscopy (SEM) observation were conducted to evaluate the miscibility of PLA/TPU blends. DMA results of the blends revealed two tangent delta peaks, indicating that the blends were immiscible, and the SEM micrographs supported this trend. Finally, hydrolytic degradation behaviour of PLA, TPU and PLA/TPU blends was investigated by measuring the weight loss after immersion of the specimens in alkaline solution at a predetermined time, i.e. every 24 hours for up to 8 days. It was found that the degradation behaviour is affected by blend composition, where PLA/TPU 50/50 vol% showed the fastest degradation rate. This result might be ascribed to the co-continuous morphology shown in the PLA/TPU blend 50/50 vol%. ABSTRAK: Polilaktik asid (PLA) telah menarik banyak minat untuk digunakan sebagai pengganti polimer berasaskan petroleum, kerana ia mempunyai biodegradabiliti yang baik, boleh diperolehi daripada sumber yang boleh diperbaharui, dan mempunyai kekuatan mekanikal yang tinggi. Walau bagaimanapun, kerapuhan dan keliatannya yang rendah telah menghadkan penggunaannya dalam aplikasi yang lebih luas. Dalam kajian ini, leburan PLA dicampurkan dengan poliuretan thermoplastik (TPU) bagi menghasilkan bahan polimer yang mesra alam beserta dengan sifat-sifat mekanikal yang seimbang. Selain itu, daya kebolehcampuran dan degradasi hidrolitik daripada campuran PLA/ TPU juga telah dikaji kerana bagi sesetengah aplikasi, faktor degradasi adalah sangat penting. Bagi menghasilkan lima komposisi sampel, iaitu PLA tulen, PLA/TPU 75/25 vol%, PLA/TPU 50/50 vol%, PLA/TPU 25/75 vol%, dan TPU tulen, PLA dan TPU telah dicairkan dan diadun menggunakan mesin pencampur internal, diikuti dengan kaedah pengacuan kompresi. Untuk mengkaji sifat-sifat mekanikal, ujian regangan dan impak telah dijalankan. Hasil ujian tersebut menunjukkan peningkatan nilai pemanjangan pada titik putus dan kekuatan impak, seiring dengan peningkatan komposisi TPU. Manakala, penilaian daya kebolehcampuran diantara PLA dan TPU dijalankan menggunakan analisis mekanikal dinamik (DMA) dan mikroskop pengimbas elektron (SEM). Keputusan DMA, hasil daripada campuran tersebut mendedahkan dua puncak tangen delta, menunjukkan bahawa dua campuran tersebut tidak memiliki daya bolehcampur yang baik. Kesimpulan ini disokong pula oleh gambar mikro dari hasil ujian SEM. Akhir sekali, degradasi hidrolitik PLA, TPU dan campuran PLA/TPU dikaji melalui pengukuran berat sampel setelah direndam di dalam larutan alkali pada masa yang ditetapkan, iaitu setiap 24 jam sehingga 8 hari. Hasil daripada ujian tersebut mendapati degradasi hidrolitik dipengaruhi oleh komposisi campuran. Campuran PLA/TPU dengan komposisi 50/50 vol% menunjukkan kadar penurunan berat yang paling cepat. Hasil ujian ini mungkin boleh dikaitkan dengan sifat morfologi co-continuous yang ditunjukkan dalam campuran PLA/TPU 50/50 vol%.

scholarly journals Biological Compatibility of a Polylactic Acid Composite Reinforced with Natural Chitosan Obtained from Shrimp Waste

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1465 ◽  
Author(s):  
Yaret Torres-Hernández ◽  
Gloria Ortega-Díaz ◽  
Lucía Téllez-Jurado ◽  
Nayeli Castrejón-Jiménez ◽  
Alejandro Altamirano-Torres ◽  
...  
Keyword(s):  
Cell Viability ◽  
Polylactic Acid ◽  
Low Cost ◽  
Hydrolytic Degradation ◽  
Phosphate Buffer Solution ◽  
Morphological Characteristics ◽  
Buffer Solution ◽  
Composite Surface ◽  
Biological Compatibility

The aim of this work is to evaluate the effect of chitosan content (1, 3 and 5 wt %) dispersed in polylactic acid (PLA) on the structure and properties of composites. Also, the hydrolytic degradation, and the cell viability and adhesion of human MG-63 osteoblasts are analyzed to determine the composites’ suitability for use in tissue engineering. For the manufacture of the materials, natural chitosan was extracted chemically from shrimp exoskeleton. The composites were fabricated by extrusion, because it is a low-cost process, it is reproducible, and it does not compromise the biocompatibility of the materials. FT-IR and XRD show that the chitosan does not change the polymer structure, and interactions between the composite components are discarded. In vitro degradation tests show that the composites do not induce significant pH changes in phosphate buffer solution due to their low susceptibility to hydrolytic degradation. The adhesion and morphological characteristics of the osteoblasts are evaluated using confocal microscopy and scanning electron microscopy. The cell viability is determined by the MTT assay. Osteoblasts adhesion is observed on the surface of PLA and composites. A higher amount of chitosan, higher number of cells with osteoblastic morphology, and mineralized nodules are observed on the composite surface. The highest metabolic activity is evidenced at 21 days. The results suggest that the Polylactic acid/chitosan composites are potentially suitable for use as a biomaterial.

Hydrolytic degradation of polylactic acid (PLA) and its composites

2017 ◽  
Vol 79 ◽  
pp. 1346-1352 ◽  
Author(s):  
Moataz A. Elsawy ◽  
Ki-Hyun Kim ◽  
Jae-Woo Park ◽  
Akash Deep
Keyword(s):  
Polylactic Acid ◽  
Hydrolytic Degradation

scholarly journals Crystallization and degradation behaviour of multiblock copolyester blends in Langmuir monolayers

2021 ◽  
Author(s):  
Victor Izraylit ◽  
Yue Liu ◽  
Natalia A. Tarazona ◽  
Rainhard Machatschek ◽  
Andreas Lendlein
Keyword(s):  
Structural Changes ◽  
Soft Tissues ◽  
Soft Segment ◽  
Unmet Need ◽  
Hydrolytic Degradation ◽  
Langmuir Monolayers ◽  
Degradation Behaviour ◽  
Network Nodes ◽  
Fixation Devices ◽  
Hydrolysis Of

AbstractSupporting the wound healing of soft tissues requires fixation devices becoming more elastic while degrading. To address this unmet need, we designed a blend of degradable multiblock copolymers, which is cross-linked by PLA stereocomplexation combining two soft segments differing substantially in their hydrolytic degradation rate. The degradation path and concomitant structural changes are predicted by Langmuir monolayer technique. The fast hydrolysis of one soft segment leads to a decrease of the total polymer mass at constant physical cross-linking density. The corresponding increase of the average spacing between the network nodes suggests the targeted increase of the blend’s flexibility. Graphic abstract

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