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The present study investigates the utilization of nanoparticles based on poly-l-lactide (PLLA) and polyglycerol adipate (PGA), alone and blended, for the encapsulation of usnic acid (UA), a potent natural compound with various therapeutic properties including antimicrobial and anticancer activities. The development of these carriers offers an innovative approach to overcome the challenges associated with usnic acid's limited aqueous solubility, bioavailability, and hepatotoxicity. The nanosystems were characterized according to their physicochemical properties (among others, size, zeta potential, thermal properties), apparent aqueous solubility, and in vitro cytotoxicity. Interestingly, the nanocarrier obtained with the PLLA-PGA 50/50 weight ratio blend showed both the lowest size and the highest UA apparent solubility as well as the ability to decrease UA cytotoxicity towards human hepatocytes (HepG2 cells). This research opens new avenues for the effective utilization of these highly degradable and biocompatible PLLA-PGA blends as nanocarriers for reducing the cytotoxicity of usnic acid. [ABSTRACT FROM AUTHOR]

The present study investigates the utilization of nanoparticles based on poly-l-lactide (PLLA) and polyglycerol adipate (PGA), alone and blended, for the encapsulation of usnic acid (UA), a potent natural compound with various therapeutic properties including antimicrobial and anticancer activities. The development of these carriers offers an innovative approach to overcome the challenges associated with usnic acid’s limited aqueous solubility, bioavailability, and hepatotoxicity. The nanosystems were characterized according to their physicochemical properties (among others, size, zeta potential, thermal properties), apparent aqueous solubility, and in vitro cytotoxicity. Interestingly, the nanocarrier obtained with the PLLA-PGA 50/50 weight ratio blend showed both the lowest size and the highest UA apparent solubility as well as the ability to decrease UA cytotoxicity towards human hepatocytes (HepG2 cells). This research opens new avenues for the effective utilization of these highly degradable and biocompatible PLLA-PGA blends as nanocarriers for reducing the cytotoxicity of usnic acid.

Polylactide (PLA) is one of the most promising biodegradable and biocompatible polymer materials. Estimation of hydrolytic destruction of PLA is of high importance for their applications both at planning and at real-time exploitation. This paper reports on synthesis and applicability of fluorescein-O-dihexanoate as a pro-fluorescent marker of hydrolytic destruction of two types of PLA-based materials. Fluorescence enhancement correlated with adequately more fast destruction of poly-D,L-lactide as well as less stability to alkaline hydrolysis. Thus, applicability of fluorescein-O-dihexanoate for fluorescence-based estimation of hydrolytic destruction of PLA-based materials is shown in quite real time mode.

Background: A combination of bioceramics and polymeric materials has attracted the research community’s interest in bone tissue engineering. These composites are essential to support cell attachment, proliferation, and osteogenesis differentiation, which are vital as a classic strategy in bone tissue engineering. In this study, NiFe2O4/ZnO-coated poly L-Lactide (PLLA) was employed as a scaffold to evaluate the osteogenic differentiation capability of human adipose tissue derived mesenchymal stem cells (hAMSCs).Material and methods: The electrospun PLLA nanofibers were fabricated, coated with nanocomposite (NiFe2O4/ZnO), and evaluated by the water contact angle (WCA), tensile test, attenuated total reflectance fourier-transform infrared (ATR-FTIR) and scanning electron microscopy (SEM). Then, the osteogenic differentiation potential of hAMSCs was assessed using NiFe2O4/ZnO-coated PLLA compared to tissue culture plastic (TCP) and a simple scaffold (PLLA) in vitro conditions.Results: The adhesion, proliferation, and differentiation of hAMSCs were supported by the mechanical and biological properties of the NiFe2O4/ZnO-coated PLLA scaffold, according to SEM and 4′,6-Diamidino-2-phenylindole dihydrochloride (DAPI) staining patterns. During bone differentiation, Alkaline phosphatase (ALP) enzyme activity, biomineralization, calcium content, and osteogenic gene expression (ALP, Osteonectin, Osteocalcin, Collagen type I, and Runx2) were higher on NiFe2O4/ZnO-coated PLLA scaffold than on PLLA scaffold and TCP.Conclusion: Based on our results, the osteogenic differentiation of hAMSCs on the improved biological scaffold (PLLA coated with NiFe2O4/ZnO) could accelerate due to the stimulating effect of this nanocomposite.

The aim of this study is to investigate the feasibility and efficacy of a novel biomimetic poly‐l‐lactide (PLLA) nanofiber membrane in repairing anterior urethral strictures from both preclinic and clinic. Biomimetic PLLA membrane was fabricated layer by layer according to the structure of human extracellular matrix. Microstructure, tensile strength, and suture retention strength were fully assessed. Before the clinical application, the safety and toxicology test of the biomimetic PLLA membrane was performed in vitro and in experimental animals. The patients underwent urethroplasty used dorsal onlay or lateral onlay technique. Then, they were followed up for 1 month, 3 months, 6 months, and then annually after the surgery. The mechanical experiments showed well property for application. Biomimetic PLLA membrane was safe according to the in vitro and animal studies. Then, a total of 25 patients (mean age 48.96 years) were included in the study from September 2016 to December 2018. After a mean follow‐up of 33.56 months, 20 patients successfully treated with biomimetic PLLA membrane. Five patients (2 bulbar and 3 penile) suffered postoperational urethral stricture recurrence. None of infection or urinary fistula or any other adverse events related to the use of biomimetic PLLA membrane were observed during the follow‐up period for all patients. The preliminary result confirmed the feasibility and efficacy of the biomimetic PLLA membrane as a novel material for anterior urethral repair. The long‐term effects with more patients should be investigated in further studies. [ABSTRACT FROM AUTHOR]

Abstract The aim of this study is to investigate the feasibility and efficacy of a novel biomimetic poly‐l‐lactide (PLLA) nanofiber membrane in repairing anterior urethral strictures from both preclinic and clinic. Biomimetic PLLA membrane was fabricated layer by layer according to the structure of human extracellular matrix. Microstructure, tensile strength, and suture retention strength were fully assessed. Before the clinical application, the safety and toxicology test of the biomimetic PLLA membrane was performed in vitro and in experimental animals. The patients underwent urethroplasty used dorsal onlay or lateral onlay technique. Then, they were followed up for 1 month, 3 months, 6 months, and then annually after the surgery. The mechanical experiments showed well property for application. Biomimetic PLLA membrane was safe according to the in vitro and animal studies. Then, a total of 25 patients (mean age 48.96 years) were included in the study from September 2016 to December 2018. After a mean follow‐up of 33.56 months, 20 patients successfully treated with biomimetic PLLA membrane. Five patients (2 bulbar and 3 penile) suffered postoperational urethral stricture recurrence. None of infection or urinary fistula or any other adverse events related to the use of biomimetic PLLA membrane were observed during the follow‐up period for all patients. The preliminary result confirmed the feasibility and efficacy of the biomimetic PLLA membrane as a novel material for anterior urethral repair. The long‐term effects with more patients should be investigated in further studies.

This work reports the synthesis and characterization of nanohydroxyapatite (nHA) and nanowhitlockite (nWH), which were further incorporated to poly-l-lactic acid (PLLA) to study their effects on the structure, mechanical properties, antibacterial potential, and cytotoxicity of PLLA. SEM images of PLLA–nHA and PLLA–nWH revealed uniform dispersion of nanoparticles in polymer. FTIR spectroscopy showed shift in functional group position and indicated transformation of PLLA α′ to more crystalline PLLA α, which was further confirmed by X-ray diffraction. The mechanical properties of the materials showed that addition of nanoparticles have made PLLA ductile and strong pertaining to the effective dissipation of loads across the interfaces, enabling them to delay the crack growth by avoiding stress concentration sites. PLLA–nWH10% showed the highest antibacterial activity against Gram-positive bacteria Listeria monocytogenes and Staphylococcus aureus. In vitro cytocompatibility of PLLA–nWH10% was highest, 98%, at day 7 against fibroblasts MC3T3-E1 (osteoblastic cell line), whereas all nanocomposites have enhanced cell viability (94%) as compared to pure PLLA. Alizarin red assay showed twofold increase in calcification at day 14 with PLLA–nWH as compared to PLLA–nHA. It was clearly observed that binary system PLLA–nWH at all concentrations had good dispersion and interfacial interaction resulting in improved mechanical and enhanced osteoconductive properties as compared to PLLA–nHA. [ABSTRACT FROM AUTHOR]

Designing laboratory-scale degradation experiments for polymer-based biomaterials is crucial for the development of safe and functional implants, in particular regarding high molecular weight polyesters. Within this work, we compared accelerated degradation of solvent cast HMW-PLLA and HMW-P3HB films at 55 °C (16 weeks) with enzyme-associated (proteinase K and lipases) real-time degradation at 37 °C (108 weeks). During real-time degradation, PLLA showed mass loss up to 83%, in contrast to accelerated conditions, where no changes occurred. Moreover, we observed wave-shape development of crystallinity for PLLA and PHB for both degradation conditions applied, whereby PLLA χ value nearly doubled to up to 75%. These results were used to develop a correlation model based on molecular weight decrease and were furthermore discussed in light of a detailed literature review. In summary, real-time in vitro studies could be adapted to accelerated protocols providing the same limiting conditions such as molecular weight and initial crystallinity are given.

Bioresorbable polymeric stents (BPS) offer possibilities to help address the long-term complications associated with permanent vascular implants, however in-vivo degradation behaviour is not yet fully understood. Here, finite element analysis (FEA) techniques based on physio-chemical reaction diffusion equations are used to predict and analyse BPS degradation behaviour. Physio-chemical degradation models for polymers, both amorphous and semi-crystalline, are incorporated into the FEA software package Abaqus/Standard allowing for BPS degradation rate predictions to be made, with a focus on poly-L-lactide (PLLA). The outputs of the degradation models are linked to mechanical behaviour via three different damage models which couple the changes in molecular weight and crystallinity with a hyperelastic constitutive model for PLLA mechanical behaviour. A simplified representation of a PLLA BPS in an artery is used as a demonstration case. The effects of applied degradation product diffusion boundary conditions on the molecular weight and crystallinity of PLLA BPS under simulated degradation are examined, and the impact of material heterogeneities and mechanical load boundary condition on the scaffolding performance and elastic properties of the degrading stent are investigated. The results suggest that the BPS performance are strongly dependent on the assumed boundary conditions, both in terms of degradation product diffusion and mechanical loading. [ABSTRACT FROM AUTHOR]

Background: Forged composites of raw particulate unsintered hydroxyapatite/poly-L-lactide (F-u-HA/PLLA) implants are widely used in surgeries because they possess high mechanical strength, bioactivity, and radio-opacity. We previously reported that F-u-HA/PLLA implants were useful for treating lateral tibial condylar, lateral humeral condylar, and ankle fractures. The study aim was to investigate the efficacy of F-u-HA/PLLA cannulated screws and FiberLoop® for treating transverse patellar fractures.Methods: From April 2013 to February 2019, 15 patients with transverse patellar fractures were treated with F-u-HA/PLLA cannulated screws and FiberLoop® as follows: Open reduction and internal fixation (ORIF) were performed with two F-u-HA/PLLA cannulated screws and a temporary fixation Kirshner wire (K-wire). Three No. 2 FiberLoops® were inserted into these two screw holes and the K-wire hole for temporary fixation. All patients were allowed to full weight-bearing gaits using a knee brace. Knee range of motion exercise was initiated on postoperative day 1. Knee flexion was restricted to ≤90° for 1 month postoperatively. Radiograph was performed to evaluate fracture healing, screw breakage, reduction loss, and screw radio-opacity. Clinical outcomes and postoperative complications were assessed.Results: The average follow-up was 16.0 months. All fractures were successfully united. Screw breakage, reduction loss, osteolysis, and radiolucent zones around the screws were not observed at the final radiographic follow-up. All F-u-HA/PLLA screw shadows were observed during the follow-up. The average range of flexion and extension were 132.0° and -2.7°, respectively. No patients experienced deep infection episodes, late aseptic tissue reactions, or foreign body reactions postoperatively. No patients complained of pain at the final follow-up. All patients returned to their pre-injury work level and activities of daily living.Conclusion: Our results strongly suggest that ORIF with F-u-HA/PLLA screws and FiberLoop® could be an alternative treatment option for transverse patellar fractures. [ABSTRACT FROM AUTHOR]

A nonplanar polylactide scaffold to be used in tissue engineering was obtained by freeze‐extraction method. Properties of the scaffold were modified by adding Eudragit® E100. The impact of the modification on morphology, porosity and pore size, mass absorbability, mechanical properties was determined. Scanning electron microscopy (SEM), hydrostatic weighing test, static compression test was used to this end. The chemical composition of the scaffold was defined based on infrared spectroscopy (FTIR) and energy‐dispersive X‐ray spectroscopy (EDX). Biocompatibility was confirmed by quantitative tests and microscopic observation. The obtained results show that the obtained scaffolds may be applied as a carrier of hydrophilic cellular growth factors for more efficient tissue regeneration. [ABSTRACT FROM AUTHOR]

Although the use of bioresorbable materials in stent production is thought to improve long-term safety compared to their durable counterparts, a recent FDA report on the 2-year follow-up of the first FDA-approved bioresorbable vascular stent showed an increased occurrence of major adverse cardiac events and thrombosis in comparison to the metallic control. In order to overcome the issues of first generation bioresorbable polymers, a series of polyethylene glycol-functionalized poly-L-lactide-co-ε-caprolactone copolymers with varying lactide-to-caprolactone content is developed using a novel one-step PEG-functionalization and copolymerization strategy. This approach represents a new facile way toward surface enhancement for cellular interaction, which is shown by screening these materials regarding their cyto- and hemocompatibility in terms of cytotoxicity, hemolysis, platelet adhesion, leucocyte activation and endothelial cell adhesion. By varying the lactide-to-caprolactone polymer composition, it is possible to gradually affect endothelial and platelet adhesion which allows fine-tuning of the biological response based on polymer chemistry. All polymers developed were non-cytotoxic, had acceptable leucocyte activation levels and presented non-hemolytic (

In the present study, the novel keratin-based 5-fluorouracil (5-FU) releasing nanofibrous system was electrospun. The pH sensitivity releasing performances of the nanofibres were optimised by a full-factorial matrix design of experiment (DoE) with two significant factors at two levels in different pH environments. This full-factorial DoE methods was applied to identify the main effects of these composite bio-functional nanofibres and investigate the interaction effects of multiple factors. The SEM images indicated that a more homogeneous microstructure of the composite nanofibres was observed at the low level of electrospun voltage, which was set at 15 kV. The FTIR test detected the characteristic peaks of keratin at 1630 and 1550 cm−1. The releasing performances were examined by ultraviolet and visible spectrophotometry. The results indicated that the ratio between keratin and poly-L-lactide is a major factor to control the sustained-releasing performance. A significant pH sensitivity of the composite nanofibres was achieved after adjusting the operational factors by DoE optimisation. The drug-loaded nanofibres with high content of keratin (50 wt%) released 48.5% of 5-FU in pH 7.4 solution while released 83.7% of 5-FU in pH 6.0 solution. The results indicated that these composite electrospun nanofibres can be used as a candidate of pH-triggered biomaterials. [ABSTRACT FROM AUTHOR]

As cartilage is incapable of self-healing upon severe degeneration because of the lack of blood vessels, cartilage tissue engineering is gaining importance in the treatment of cartilage defects. This study was designed to improve cartilage tissue regeneration by expressing tissue transglutaminase variant 2 (TGM2_v2) in mesenchymal stem cells (MSC) derived from bone marrow of rats. For this purpose, rat MSCs transduced with TGM2_v2 were grown and differentiated on threedimensional polybutylene succinate (PBSu) and poly-L-lactide (PLLA) blend scaffolds. The transduced cells could not only successfully express the short form transglutaminase-2, but also deposited the protein onto the scaffolds. In addition, they could spontaneously produce cartilage-specific proteins without any chondrogenic induction, suggesting that TGM2_v2 expression provided the cells the ability of chondrogenic differentiation. PBSu:PLLA scaffolds loaded with TGM2_v2 expressing MSCs could be used in repair of articular cartilage defects. [ABSTRACT FROM AUTHOR]

Comparative data have been obtained on the effect of the absorbed dose of γ-radiation and electron beam on the radiation-induced degradation of poly-L-lactide in the presence of oxygen provided dose distribution through the irradiated polymer bulk is uniform and high-energy radiation heating is insignificant to cause change of relaxation and phase transitions in the polymer matrix. The efficiency of radiation-induced degradation of poly-L-lactide exposed to γ-radiation has been shown to be higher than that in the case of electron beam due to a longer irradiation time in the former case resulting in a more essential contribution of an oxidative component in degradation. [ABSTRACT FROM AUTHOR]

Vascular endothelial growth factor A (VEGF-A) is an important growth factor that plays a major role in angiogenesis. With different isoforms distributed in various tissues, the shortest isoform of VEGF-A is VEGF121, one of the physiologically functional variants next to VEGF165. It is well known that VEGF has a shorter half-life, and the stability of the protein must be considered in therapeutic aspects. Poly-l-lactide (PLA) microparticles can release the encapsulated protein in a sustained release mode. In this study, the VEGF121gene was cloned and expressed in a prokaryotic expression system (Escherichia coli). The recombinant VEGF121 was encapsulated with PLA microparticles and studied in vitro and ex ovo for the sustained release mechanism. The PLA-VEGF microparticles and the recombinant VEGF121 were explored for their bioactivity in human umbilical vein endothelial cells (HUVEC). VEGF released in vitro from PLA microparticles on days 1, 20, and 30 showed remarkable biological activity compared to PBS-loaded PLA microparticles such as the ability of the cells to proliferate, migrate, and form tubes similar to recombinant VEGF121. Besides, PLA-VEGF microparticles and the recombinant VEGF121 were also tested for their proangiogenic action in embryonated eggs by chicken chorioallantoic membrane assay (CAM), and the effect was observed in both forms. This study suggests that PLA-loaded VEGF microparticles in a sustainable release format can be effectively used in proangiogenic therapy and reduce the adverse effects caused due to multiple dosages. [ABSTRACT FROM AUTHOR]

We evaluated the efficacy of bioresorbable sternal reinforcement device (poly-l-lactide sternal pins) on sternal healing after median sternotomy in young children (with body weight less than 10 kg) with congenital heart disease (CHD). Data from 85 patients, who underwent CHD surgery through median sternotomy from October 2016 to May 2018, were collected and analyzed. Sternal pins were utilized in 85 patients (10 mm × 1 mm × 1 mm for patients with body weights less than 5 kg and 15 mm × 2 mm × 2 mm for those weighing between 5 and 10 kg) in addition to sternum closure with Ethicon PDSTMII running sutures (Group A), while 84 patients received the Ethicon sternal closure (Group B) with no pins. The occurrence of sternal dehiscence, anterior-posterior displacement, and high-low displacement was evaluated by physical examination and three-dimensional computed tomography at one month postoperatively. No anterior-posterior sternal displacement (0%) was observed in Group A, while 10 anterior-posterior displacements (11.9%) were observed in Group B (P < 0.01). The number of sternal caudal-cranial displacements in Groups A and B was 4 (4.71%) and 5 (5.35%), respectively (P = 0.870). While no sternal dehiscence (0%) was observed in Group A, 7 out of 84 patients (8.33%) in Group B exhibited obvious sternal dehiscence (P < 0.01). The bioresorbable poly-l-lactide sternal pins reduced an anterior-posterior sternal displacement and sternal dehiscence, which was accompanied by a significant improvement of an early sternal fixation. [ABSTRACT FROM AUTHOR]

Local drug delivery has become indispensable in biomedical engineering with stents being ideal carrier platforms. While local drug release is superior to systemic administration in many fields, the incorporation of drugs into polymers may influence the physico-chemical properties of said matrix. This is of particular relevance as minimally invasive implantation is frequently accompanied by mechanical stresses on the implant and coating. Thus, drug incorporation into polymers may result in a susceptibility to potentially life-threatening implant failure. We investigated spray-coated poly-l-lactide (PLLA)/drug blends using thermal measurements (DSC) and tensile tests to determine the influence of selected drugs, namely sirolimus, paclitaxel, dexamethasone, and cyclosporine A, on the physico-chemical properties of the polymer. For all drugs and PLLA/drug ratios, an increase in tensile strength was observed. As for sirolimus and dexamethasone, PLLA/drug mixed phase systems were identified by shifted drug melting peaks at 200 °C and 240 °C, respectively, whereas paclitaxel and dexamethasone led to cold crystallization. Cyclosporine A did not affect matrix thermal properties. Altogether, our data provide a contribution towards an understanding of the complex interaction between PLLA and different drugs. Our results hold implications regarding the necessity of target-oriented thermal treatment to ensure the shelf life and performance of stent coatings.

Poly-L-lactide (PLLA) reinforced with nano-hydroxyapatite (HA) foams were fabricated using a novel method of microwave-assisted compression moulding. The microwave-assisted compression moulding is novel processing route of polymer-based composites, owing to its faster and uniform heating, better temperature control, which yields improved mechanical properties. Porosity in the PLLA+HA foams was introduced through porogen leaching route. The reinforcement in the form of nano-hydroxyapatite was added between 10 and 20 wt%. Porosity in the microwave processed foams was found in the range of 23–25%. The porosity in foams was observed to have homogeneously interconnected pores structure with narrower pore size distribution. The thermal behaviour of the developed foams was analysed using the thermogravimetric analysis and differential scanning calorimetry techniques. The glass transition temperature (Tg) and percentage crystallinity of the foams were assessed using the thermogravimetric analysis and differential scanning calorimetric curves. The maximum percentage crystallinity of 36.28% was obtained in case of PLLA + 15% HA foam. The mechanical characterisation of the microwave processed foams was carried out in terms of compressive and flexural behaviour. The foam with 20% HA reinforcement exhibited the maximum compressive strength (of the order of 21 MPa) and modulus of the order of 64.15 MPa. The foam with 10% reinforcement of HA exhibited maximum flexural strength of 59.32 MPa. The compressive strength of microwave processed foams was 10 times higher than the conventionally fabricated foams. [ABSTRACT FROM AUTHOR]

Obstructive salivary gland diseases are common conditions that arise following the disruption of the secretary ductal system and usually results in the swelling and pain of the affected gland(s). There has been an increase in the use of sialendoscopy for the treatment and diagnosis of obstructive salivary gland infection. If damage occurs to a duct or papilla following sialendoscopy, a stent may be necessary to prevent restenosis and for maintaining the salivary duct open after complete sialendoscopy. Currently, there are only non-biodegradable salivary duct stents available. The aim of the current study was to establish a methodology for the fabrication of a biodegradable poly-L-lactide (PLLA) salivary duct stent and to examine its function in an animal model. In the current study, PLLA was used to fabricate a salivary duct stent, which was compared with other commercially available non-biodegradable products. The mechanical tests revealed that the tensile strength of the PLLA stent was similar to that of the commercially available non-biodegradable stents. The Young's modulus, which measures the stiffness of a solid material, was significantly higher for the PLLA stent compared with the commercially available non-biodegradable stents. In addition, the current study demonstrated that the PLLA salivary duct stent was easily used with current sialendoscopy techniques, allowing accurate stent placement in an animal model. [ABSTRACT FROM AUTHOR]

Abstract A bone fixation device made of unsintered hydroxyapatite (u-HA) particles uniformly dispersed in a poly- l -lactide matrix and reinforced by compressive forging (uniformly dispersed composite; UDC) has been clinically applied in several fields. However, it has reported some foreign body reactions over a long implantation period due to its slow bioresorbability. To further enhance its bioresorbability, we developed devices comprising a fibrous assembly of poly- l -lactide only three-dimensionally intertwined with particulate hydroxyapatite/poly- l -lactide composite. The biological behavior of the proposed material, provisionally referred to as complementarily reinforced composite (CRC), was compared with that of UDC in vivo. Cylindrical rods of UDC and CRC with 3.2-mm diameters were inserted bilaterally into the intramedullary distal femurs of 32 male Japanese white rabbits. Eight rabbits were euthanized at four, eight, 12, and 25 weeks after insertion. There were no significant differences between the mechanical properties of UDC and CRC over time. However, the results from histological analyses, surface characterization, radiological analyses, and push-out mechanical testing substantiated CRC's superior affinity to bone and enhanced bioactivity and bioresorbability in comparison with UDC. These characteristics were attributed to the dispersive marbling morphology produced by the CRC material's successive connectivity of u-HA particles throughout the PLLA matrix, which would accelerate PLLA hydrolysis degradation by H 2 O intrusion and enhance the bioactivity of u-HA particles exposed on the interface soon after implantation. Graphical abstract Unlabelled Image Highlights • A novel composite was developed. • It comprised fibrous poly- l -lactide assembly and hydroxyapatite/poly- l -lactide. • Proposed composite has morphology and mechanical properties suitable for bone fixation. • Proposed composite had higher bone affinity at earlier stage. • Poly- l -lactide was hydrolyzed and composite's cross-sectional area reduced by ~4%. [ABSTRACT FROM AUTHOR]

This work assessed biodegradation, by Aspergillus, Fusarium, Penicillium and Parengyodontium fungi, of four samples of poly-ε-caprolactone (PCL), three samples of poly-L-lactide (PLA) and one sample of poly-D,L-lactide (DL-PLA) produced by ring-opening polymerization initiated by aluminium complexes of corresponding lactones. Mesophilic fungal strains actively biodegrading PCL (F. solani) and PLA (Parengyodontium album and A. calidoustus) were selected. The rate of degradation by the selected fungi was found to depend on the physicochemical and mechanical properties of the polymers (molecular weight, polydispersity, crystallinity). The most degradable poly-ε-caprolactone sample was shown to have the lowest molecular weight; the most biodegradable polylactide DL-PLA had the lowest crystallinity. Mass spectral analysis of biodegraded polymer residues showed PCL to be degraded more intensively than PLA. It is established that in the case of Parengyodontium album the colonization of the films of polypropylene composites with DL-PLA is observed, which will undoubtedly contribute to their further destruction under the influence of abiotic factors in the environment. [ABSTRACT FROM AUTHOR]

Implantation of a biomaterial is one of the important trends in solving the problem of bone tissue loss. Calcium hydroxiapatite (HAp), as the most representative bone component is a serious candidate for such implantations. The synthetic polymer poly-L-lactide (PLLA) in HAp/PLLA is often used as a polymeric material, with a role in the substitution of bone tissue collagen fibers. Fibers of PLLA may strengthen HAp and its good bioresorption provides space for tissue remodeling. Differences in porosity, microstructure, compressive consistency as well as bioresorbility of HAp/ PLLA may be achieved by using PLLA with different molecular weights. In this study HAp/PLLA composites with PLLA of different molecular weights (50,000; 160,000 and 430,000) were implanted in mouse peritoneum in order to examine the influence of the molecular weight of PLLA on morphology changes. Microstructural changes of biomaterial (HAp/PLLA) surface were analyzed one week, three weeks and four months after their implantation using Scanning Electron Microscopy. The results showed a significant difference in tissue reactions on the applied biocomposites, depending on their molecular weight. The most intense proliferation of cells was induced by HAp/PLLA 50,000 compared to HAp/PLLA 430,000 and HAp/PLLA 160,000. In the vicinity of HAp/PLLA 430,000 abundant erythrocytes were observed. The differences in biological reactions on the examined biocomposites are significant for their practical applications. HAp/PLLA composite biomaterials of different types and resorption rates require specific designing and programming to become suitable for particular purposes in an organism.

We studied human bone healing characteristics and the histological osteogenic environment by using devices made of a composite of uncalcined and unsintered hydroxyapatite (u-HA) and poly-L-lactide (PLLA). In eight cases of fixation, we used u-HA/PLLA screws for maxillary alveolar ridge augmentation, for which mandibular cortical bone block was used in preimplantation surgery. Five appropriate samples with screws were evaluated histologically and immunohistochemically for runt-related transcription factor 2 (RUNX2), transcription factor Sp7 (Osterix), and leptin receptor (LepR). In all cases, histological evaluation revealed that bone components had completely surrounded the u-HA/PLLA screws, and the bone was connected directly to the biomaterial. Inflammatory cells did not invade the space between the bone and the u-HA/PLLA screw. Immunohistochemical evaluation revealed that many cells were positive for RUNX2 or Osterix, which are markers for osteoblast and osteoprogenitor cells, in the tissues surrounding u-HA/PLLA. In addition, many bone marrow−derived mesenchymal stem cells were notably positive for both LepR and RUNX2. The u-HA/PLLA material showed excellent bioactive osteoconductivity and a highly biocompatibility with bone directly attached. In addition, our findings suggest that many bone marrow−derived mesenchymal stem cells and mature osteoblast are present in the osteogenic environment created with u-HA/PLLA screws and that this environment is suitable for osteogenesis.

Poly-L-lactide (PLLA) offers a unique possibility for processing into biocompatible, biodegradable, and implantable piezoelectric structures. With such properties, PLLA has potential to be used as an advanced tool for mimicking biophysical processes that naturally occur during the self-repair of wounds and damaged tissues, including electrostimulated regeneration. The piezoelectricity of PLLA strongly depends on the possibility of controlling its crystallinity and molecular orientation. Here, it is shown that modifying PLLA with a small amount (1 wt%) of crystalline filler particles with a high aspect ratio, which act as nucleating agents during drawing-induced crystallization, promotes the formation of highly crystalline and oriented PLLA structures. This increases their piezoelectricity, and the filler-modified PLLA films provide a 20-fold larger voltage output than nonmodified PLLA during ultrasound (US)-assisted activation. With 99% PLLA content, the ability of the films to produce reactive oxygen species (ROS) and increase the local temperature during interactions with US is shown to be very low. US-assisted piezostimulation of adherent cells directly attach to their surface (such as skin keratinocytes), stimulate cytoskeleton formation, and as a result cells elongate and orient themselves in a specific direction that align with the direction of PLLA film drawing and PLLA dipole orientation., (© 2023 The Authors. Small published by Wiley-VCH GmbH.)

Choosing materials for orthopedic implants often imposes strict requirements for the mechanical properties. Poly-L-lactide (PLLA) is widely employed for this purpose, however toughnening schemes are necessary for its suitable application. Blending of PLLA and biodegradable poly(L-lactide-co-ɛ-caprolactone) copolymer (PLCL) showing a thermoplastic-elastomeric behavior has been performed in an effort to toughen the PLLA without compromising its biodegradability and biocompatibility. The miscibility state of PLLA/PLCL blend system is studied by means of Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA). The mechanical properties will be also discussed, as well as, phase morphology observed by Scanning Electron Microscopy (SEM). Blends of PLLA/PLCL show different miscibility degrees depending on the blending process and the copolymer content. Blends prepared by melt-quenching show a miscibility window for compositions ≤30 wt% of PLCL, while a phase separation occurred in the rest of compositions. The toughness of PLLA was considerably improved by the addition of PLCL. The elongation at break was significantly increased. [ABSTRACT FROM AUTHOR]

The objective of this work is to develop a first level approximation hybrid model that predicts the rate of reduction of the elastic modulus for a composite internal fixation plate. The first level model combines a modified composite theory in which the bioresorbable constituent moduli and volume fractions are time-dependent, with predictions from a Finite Element (FE) model, but ignores viscoelastic effects. The FE model is used to predict relationships between geometrical constraints (material interfaces), while a theoretical combined elastic modulus is determined using the Reuss model. The composite internal fixation device design comprises Poly-L-lactide and Hydroxyapatite (HA/PLLA) and Titanium. The geometrical relationships established by the FE static model are combined with the theoretical mathematical model in order to predict the rate of decrease of the elastic modulus of the composite device. The first level model predicts that the composite plate modulus decreases at a rate that appropriately compensates for the increasing modulus of the healing bone during fracture healing. This suggests that the proposed composite fixation plate has a strong potential for improved fracture healing through the reduction of stress shielding while the fracture heals, and the elimination of stress shielding after fracture healing. [ABSTRACT FROM AUTHOR]