Poly L-lactide Acid Research Articles

Synthesis of core–shell ZnO nanoparticles and their effect on mechanical and antibacterial properties for PLLA/ZnO nanocomposites

AbstractTo overcome the inherent brittleness of renewable poly(l‐lactide) acid (PLLA) and enable it for use in a wide application, we successfully synthesized the toughening agent of ZnO nanoparticles grafted by poly(caprolactone‐co‐d‐lactide) (ZnO‐g‐PCLDLA) via sequential open‐loop polymerization. First, ZnO was silanized to produce hydroxyl groups on the surface of the nanoparticles. Initiated by hydroxyl groups on the ZnO core, the rubbery PCLDLA composed of caprolactone‐d‐lactide co‐polymeric segments and d‐lactide homo‐polymeric segments was successively polymerized, forming ZnO core–shell nanoparticles. PLLA/ZnO‐g‐PCLDLA nanocomposites were prepared by solution blending. The nanocomposites with 10 wt% ZnO‐g‐PCLDLA exhibited superior ductility, whose elongation at break was about 54 times higher than that of neat PLLA. This considerable increment of toughness was attributed to the rubbery shell of PCLDLA and the enhanced interfacial interaction from the interfacial stereocomplex crystallites, formed by co‐crystallization of the PLLA matrix and d‐lactide homo‐polymeric segments of the PCLDLA shell on ZnO. The PLLA/ZnO‐g‐ PCLDLA nanocomposite films possessed outstanding antimicrobial properties against Staphylococcus aureus and Escherichia coli. Positive ZnO produces an electrostatic force to interact with the negatively charged membrane of bacteria, thereby damaging the cell membrane and achieving significant antibacterial effects.Highlights ZnO‐g‐PCLDLA core–shell nanoparticles were constructed by sequential ROP. The ZnO core provided high rigidity and antimicrobial properties. The rubbery PCLDLA shell provided high elasticity and ductility. Interfacial interaction was greatly enhanced by the SC crystallites. The PLLA nanocomposite films exhibited outstanding antimicrobial activity.

Effects of Recepteur D’origine Nantais/Phosphatidylinositol 3 Kinase Pathway Mediated by Polymer Biodegradable Sustained-Release Materials on Proliferation and Apoptosis of Uterine Fibroids

This research was aimed to investigate the effects of biodegradable letrozole (LE) sustained release (SR) polymer material on the biological behavior of uterine fibroids (UFs) and RON/PI3K signaling pathway (SPW). Poloxamer 188 (P188) and poly L lactide acid (PLLA) were selected to prepare the degradable SR electrospinning (ES) materials LE/P188/PlLA-1 (LE concentration: 6.25%), LE/P188/PLLA-2 (LE concentration: 12.25%), and LE/P188/PLLA-3 (LE concentration: 25%) with different concentrations of LE. UF cells were then co-cultured with free LE and degradable SR ES materials. Cell proliferation and apoptosis were detected by MTT and flow cytometry, respectively. The expression changes of apoptosis-related proteins (Bcl-2, Bax, and caspase-3), epithelial-mesenchymal transition (EMT)-related proteins (E-cadherin, N-cadherin, Vimentin), and RON/PI3K SPW-related proteins (RON and PI3K) were detected by western blot. The average diameter of LE/P188/PLLA-1, LE/P188/PLLA-2, and LE/P188/PLLA-3 were (145.6±20.8) nm, (158.1±16.3) nm, and (173.4±20.1) nm, respectively. Moreover, it possessed the obvious characteristics of LE, P188, and PLLA. LE/P188/PLLA-3 had the lowest SR rate of LE but the longest SR duration. Compared with normal cells, the proliferation inhibition rate (PIR) and apoptosis rate (AR) of LE and its degradable SR ES materials were increased (P <0.05). While expressions of Bax, caspase-3, E-cadherin, and PI3K were increased, Bcl-2, N-cadherin, Vimentin, and RON were decreased (P <0.05). In contrast to the free LE, the cell proliferation inhibition rate (PIR) and apoptosis promotion rate (APR) of LE degradable SR ES materials were increased, the levels of Bax, caspase-3, E-cadherin, and PI3K were increased, and the levels of Bcl-2, N-cadherin, Vimentin, and RON were decreased (P <0.05). The results herein were concentration-dependent. The preparation of LE degradable SR ES materials with P188/PLLA can improve the therapeutic effect of LE. LE degradable SR ES materials can effectively inhibit the proliferation of UFs, promote cell apoptosis, inhibit its EMT process and activation of RON/PI3K SPW in a concentration-dependent manner.

Effects of UV Irradation on Electrospun PLLA and PAN in the Production of Short Electropun Fibres Using Ultrasonication Method

This work showed that exposure of ductile electrospun polymers, namely poly-L-Lactide acid (PLLA) and polyacrylonitrile (PAN) to UV-Ozone, leads to the embrittlement of fibres. Young’s modulus for PLLA and PAN increased by 39% and 78%, respectively. Meanwhile, the ductility was reduced by 23% for PLLA and 40% for PAN. The SEM images show that the UV irradiation resulted in a surface pitted of PLLA and no changes in PAN surface morphology. The ATR-FTIR results indicate that this treatment did not change the chemical structure of the electrospun PLLA and PAN fibres. The as-spun polymers that failed to be scission directly using ultrasonication can now be fragmented into micron-length short fibres after the UV irradiation treatment. The minimum time to produce the short fibres is 18 mins for PAN and 29 mins for PLLA. It indicates ultrasonication is suitable for producing short electrospun fibres, even for ductile materials.

Synergistic effect of GMA and TMPTA as co-agent to adjust the branching structure of PLLA during UV-induced reactive extrusion

Abstract In this work, glycidyl methacrylate (GMA) and trimethylol propanetriacrylate (TMPTA) are employed to adjust the branching structure of poly L-lactide acid (PLLA) during reactive extrusion induced by UV irradiation. The reaction of GMA epoxide with terminal carboxyl or hydroxyl groups at PLLA chain end can introduce C=C groups onto PLLA molecular chains. Chain branching reaction occurred via the free-radical grafting reaction of the vinyl group in TMPTA with both PLLA backbone and the C=C group terminated PLLA induced by UV irradiation. As a result, varied branching levels can be obtained by changing the ratio of GMA and TMPTA. The characterizations of rheological properties and size exclusive chromatograph correlated to the chain branches were performed to evaluate the chain branching extent. The increases in shear viscosity and storage modulus at terminal zone, and the reduced branching degree were observed in the branched PLLA samples. The results from 1H-NMR and FIRT indicate that the grafting reaction of GMA onto PLLA take place successfully. Thus, this study proposes a strategy to adjust LCB-PLA structure using GMA and TMPTA as co-agents, which is of great importance for the industrialization of PLA products.

Short and long-term effects of nanobiomaterials in fish cell lines. Applicability of RTgill-W1

Nanobiomaterials (NBMs) are nanostructured materials for biomedical applications that can reach aquatic organisms. The short and long-term effects of these emerging contaminants are unknown in fish. The RTgill-W1 cell line has been proposed as a model to predict the acute toxicity of chemicals to fish (OECD Test Guideline nº 249). We assessed the applicability of this cell line to study the short and long-term toxicity of 15 NBMs based on hydroxyapatites (HA), lipid (LSNP/LNP), gold, iron oxide, carbon, poly l-Lactide acid (PLLA) fibers with Ag and poly (lactide-co-glycolide) acid. Two more rainbow trout cell lines (RTL-W1, from liver, and RTS-11, from spleen) were exposed, to identify possible sensitivity differences among cells. Exposures to a range of concentrations (0.78–100 μg/mL) lasted for 24 h. Additionally, the RTgill-W1 was used to perform long-term (28 d exposure) and recovery (14 d exposure/14 d recovery) assays. Cells were exposed to the 24 h-IC20 and/or to 100 μg/mL. A triple cytotoxicity assay was conducted. After 24 h, only PLLA Fibers-Ag showed cytotoxicity (IC50 < 100 μg/mL). However, the NBMs in general provoked concentration-dependent effects after long-term exposures, except the LSNPs. A recovery of viability was only observed for AuNPs, AuNRods, Fe3O4PEG-PLGA, MgHA-Collag_Scaffolds, Ti-HA and TiHA-Alg NPs.These results evidenced the need to test the long-term toxicity of NBMs and showed differences in cytotoxicity probably associated to different mechanisms of toxic action. The RTgill-W1 was useful to screen short and long-term toxicities of NBMs and appears as a promiseful model to assess possible toxicity of NBMs in fish.

Multimodular Bio-Inspired Organized Structures Guiding Long-Distance Axonal Regeneration.

Axonal bundles or axonal tracts have an aligned and unidirectional architecture present in many neural structures with different lengths. When peripheral nerve injury (PNI), spinal cord injury (SCI), traumatic brain injury (TBI), or neurodegenerative disease occur, the intricate architecture undergoes alterations leading to growth inhibition and loss of guidance through large distance. In order to overcome the limitations of long-distance axonal regeneration, here we combine a poly-L-lactide acid (PLA) fiber bundle in the common lumen of a sequence of hyaluronic acid (HA) conduits or modules and pre-cultured Schwann cells (SC) as cells supportive of axon extension. This multimodular preseeded conduit is then used to induce axon growth from a dorsal root ganglion (DRG) explant placed at one of its ends and left for 21 days to follow axon outgrowth. The multimodular conduit proved effective in promoting directed axon growth, and the results may thus be of interest for the regeneration of long tissue defects in the nervous system. Furthermore, the hybrid structure grown within the HA modules consisting in the PLA fibers and the SC can be extracted from the conduit and cultured independently. This “neural cord” proved to be viable outside its scaffold and opens the door to the generation of ex vivo living nerve in vitro for transplantation.

Engineered axon tracts within tubular biohybrid scaffolds

Injuries to the nervous system that involve the disruption of axonal pathways are devastating to the individual and require specific tissue engineering strategies. Here we analyse a cells-biomaterials strategy to overcome the obstacles limiting axon regeneration in vivo, based on the combination of a hyaluronic acid (HA) single-channel tubular conduit filled with poly-L-lactide acid (PLA) fibres in its lumen, with pre-cultured Schwann cells (SCs) as cells supportive of axon extension. The HA conduit and PLA fibres sustain the proliferation of SC, which enhance axon growth acting as a feeder layer and growth factor pumps. The parallel unidirectional ensemble formed by PLA fibres and SC tries to recapitulate the directional features of axonal pathways in the nervous system. A dorsal root ganglion (DRG) explant is planted on one of the conduit’s ends to follow axon outgrowth from the DRG. After a 21 d co-culture of the DRG + SC-seeded conduit ensemble, we analyse the axonal extension throughout the conduit by scanning, transmission electronic and confocal microscopy, in order to study the features of SC and the grown axons and their association. The separate effects of SC and PLA fibres on the axon growth are also experimentally addressed. The biohybrid thus produced may be considered a synthetic axonal pathway, and the results could be of use in strategies for the regeneration of axonal tracts.

Degradation modeling of poly-l-lactide acid (PLLA) bioresorbable vascular scaffold within a coronary artery.

In this work, a strain-based degradation model was implemented and validated to better understand the dynamic interactions between the bioresorbable vascular scaffold (BVS) and the artery during the degradation process. Integrating the strain-modulated degradation equation into commercial finite element codes allows a better control and visualization of local mechanical parameters. Both strut thinning and discontinuity of the stent struts within an artery were captured and visualized. The predicted results in terms of mass loss and fracture locations were validated by the documented experimental observations. In addition, results suggested that the heterogeneous degradation of the stent depends on its strain distribution following deployment. Degradation is faster at the locations with higher strains and resulted in the strut thinning and discontinuity, which contributes to the continuous mass loss, and the reduced contact force between the BVS and artery. A nonlinear relationship between the maximum principal strain of the stent and the fracture time was obtained, which could be transformed to predict the degradation process of the BVS in different mechanical environments. The developed computational model provided more insights into the degradation process, which could complement the discrete experimental data for improving the design and clinical management of the BVS.

Electron-Beam Irradiation of the PLLA/CMS/β-TCP Composite Nanofibers Obtained by Electrospinning

Nanofibrous materials produced by electrospinning processes have potential advantages in tissue engineering because of their biocompatibility, biodegradability, biomimetic architecture, and excellent mechanical properties. The aim of the current work is to study the influence of the electron beam on the poly L-lactide acid/ carboxy-methyl starch/β-tricalcium phosphate (PLLA/CMS/β-TCP) composite nanofibers for potential applications as bone-tissue scaffolds. The composite nanofibers were prepared by electrospinning in the combination of 5% v/v carboxy-methyl starch (CMS) and 0.25 wt% of β-TCP with the PLLA as a matrix component. The composites nanofibers were exposed under 5, 30, and 100 kGy of irradiation dose. The electron-beam irradiation showed no morphological damage to the fibers, and slight reduction in the water-contact angle and mechanical strength at the higher-irradiation doses. The chain scission was found to be a dominant effect; the higher doses of electron-beam irradiation thus increased the in vitro degradation rate of the composite nanofibers. The chemical interaction due to irradiation was indicated by the Fourier transform infrared (FTIR) spectrum and thermal behavior was investigated by a differential scanning calorimeter (DSC). The results showed that the electron-beam-induced poly L-lactide acid/carboxy-methyl starch/β-tricalcium phosphate (PLLA/CMS/β-TCP) composite nanofibers may have great potential for bone-tissue engineering.

Direct incorporation of mesenchymal stem cells into a Nanofiber scaffold \u2013 in vitro and in vivo analysis

Bony defects are a common problem in musculoskeletal surgery. Replacement with autologous bone grafts is limited by availability of transplant material. Sterilized cancellous bone, while being osteoconductive, has limited osteoinductivity. Nanofiber scaffolds are currently used for several purposes due to their capability of imitating the extracellular matrix. Furthermore, they allow modification to provide functional properties. Previously we showed that electrospun nanofiber scaffolds can be used for bone tissue regeneration. While aiming to use the osteoinductive capacities of collagen type-I nanofibers we saw reduced scaffold pore sizes that limited cellular migration and thus colonization of the scaffolds. Aim of the present study was the incorporation of mesenchymal stem cells into the electrospinning process of a nanofiber scaffold to produce cell-seeded nanofiber scaffolds for bone replacement. After construction of a suitable spinning apparatus for simultaneous electrospinning and spraying with independently controllable spinning and spraying devices and extensive optimization of the spinning process, in vitro and in vivo evaluation of the resulting scaffolds was conducted. Stem cells isolated from rat femora were incorporated into PLLA (poly-l-lactide acid) and PLLA-collagen type-I nanofiber scaffolds (PLLA Col I Blend) via simultaneous electrospinning and –spraying. Metabolic activity, proliferation and osteoblastic differentiation were assessed in vitro. For in vivo evaluation scaffolds were implanted into critical size defects of the rat scull. After 4 weeks, animals were sacrificed and bone healing was analyzed using CT-scans, histological, immunhistochemical and fluorescence evaluation. Successful integration of mesenchymal stem cells into the scaffolds was achieved by iteration of spinning and spraying conditions regarding polymer solvent, spinning distance, the use of a liquid counter-electrode, electrode voltage and spinning duration. In vivo formation of bone tissue was achieved. Using a PLLA scaffold, comparable results for the cell-free and cell-seeded scaffolds were found, while the cell-seeded PLLA-collagen scaffolds showed significantly better bone formation when compared to the cell-free PLLA-collagen scaffolds. These results provide support for the future use of cell-seeded nanofiber scaffolds for large bony defects.

Structural optimization and finite element analysis of poly-l-lactide acid coronary stent with improved radial strength and acute recoil rate.

Current poly-l-lactide acid (PLLA) scaffolds have issues of inadequate mechanical strength leading to thrombosis formation. Designing a novel bioabsorbable PLLA stent with a novel structure and improved mechanical property is urgently needed. In this study, stent structure modification and optimization based on bioresorbable vascular scaffold Version 1.1 (BVS 1.1, Abbott Laboratories) were conducted. The mechanical property of the redesigned stent was studied using both computerized finite element analysis and experimental mechanical deformation testing, including radial strength (RS), acute recoil (AR), foreshortening (FS), and bending stiffness (BS). The simulated and experimental results showed that the mechanical properties of the modified structure were significantly improved (modified stent vs. BVS 1.1: RS: 2.25 vs. 1.29 N/mm; AR: 3.03 vs. 4.41%; FS: 1.13 vs. 6.89%; BS: 1.49 vs. 0.72 N mm2 ).

Placenta mesenchymal stem cells differentiation toward neuronal-like cells on nanofibrous scaffold.

Introduction: Transplantation of stem cells with a nanofibrous scaffold is a promising approach for spinal cord injury therapy. The aim of this work was to differentiate neural-like cells from placenta-derived mesenchymal stem cells (PDMSCs) using suitable induction reagents in three (3D) and two dimensional (2D) culture systems. Methods: After isolation and characterization of PDMSCs, the cells were cultivated on poly-L-lactide acid (PLLA)/poly caprolactone (PCL) nanofibrous scaffold and treated with a neuronal medium for 7 days. Electron microscopy, qPCR, and immunostaining were used to examine the differentiation of PDMSCs (on scaffold and tissue culture polystyrene [TCPS]) and the expression rate of neuronal markers (beta-tubulin, nestin, GFAP, and MAP-2). Results: qPCR analysis showed that beta-tubulin (1.672 fold; P ≤ 0.0001), nestin (11.145 fold; P ≤ 0.0001), and GFAP (80.171; P ≤ 0.0001) gene expressions were higher on scaffolds compared with TCPS. Immunofluorescence analysis showed that nestin and beta-tubulin proteins were recognized in the PDMSCs differentiated on TCPS and scaffold after 7 days in the neuroinductive differentiation medium. Conclusion: Taken together, these results delegated that PDMSCs differentiated on PLLA/PCL scaffolds are more likely to differentiate towards diversity lineages of neural cells. It proposed that PDMSCs have cell subpopulations that have the capability to be differentiated into neurogenic cells.

Super-Toughed PLA Blown Film with Enhanced Gas Barrier Property Available for Packaging and Agricultural Applications.

Polylactic acid (PLA) holds enormous potential as an alternative to the ubiquitous petroleum-based plastics to be used in packaging film and agricultural film. However, the poor viscoelastic behavior and its extremely low melt strength means it fails to meet the requirements in film blowing processing, which is the most efficient film processing method with the lowest costs. Also, the PLA’s brittleness and insufficient gas barrier properties also seriously limit PLA’s potential application as a common film material. Herein, special stereocomplex (SC) networks were introduced to improve the melt strength and film blowing stability of PLA; polyethylene glycol (PEG) was introduced to improve PLA’s toughness and gas barrier properties. Compared with neat poly(l-lactide) acid (PLLA), modified PLA is stable in the film blowing process and its film elongation at break increases more than 18 times and reaches over 250%, and its O2 permeability coefficient decreased by 61%. The resulting film material also has good light transmittance, which has great potential for green packaging applications, such as disposable packaging and agricultural films.

The Protective Effects of Cultured Mesenchymal Stem Cells onto the Surface of Electrospun Poly-L-Lactide Acid Scaffolds Coated with Matricaria Chamomilla L. Oil in Streptozotocin-Induced Diabetic Rabbits

Background: Although Matricaria chamomilla L. oil has been shown to contribute to the differentiation of mesenchymal stem cells (MSCs) into insulin-producing cells, the molecular mechanisms underlying its effect in the treatment of Type 1 Diabetes mellitus (T1DM) is still not available. Objectives: The purpose of this study was to evaluate the effect of cultured MSCs on the surface of electrospun Poly-L-Lactide acid (PLLA) scaffolds coated with Matricaria chamomilla L. oil in treatment of T1DM and clarify its possible mechanisms. Methods: The current experimental study was performed using a total number of 36 male New Zealand white rabbits in the Experimental Animal Unit of Shahid Beheshti University of Medical Sciences Tehran, Iran, in 2018. A rabbit model of T1DM was established through a single intraperitoneal injection of streptozotocin (STZ) (80 mg/kg body weight)-1 dissolved in 0.2 mL of normal saline. For 21 days after implantation of cultured MSCs on the surface of electrospun PLLA scaffolds coated with Matricaria chamomilla L. oil, blood glucose levels, plasma insulin levels, plasma and pancreatic glucagon-like peptide 1 (GLP-1) were evaluated. Results: The STZ-treated rabbits exhibited decreased levels of blood glucose (P < 0.01 vs. other groups except control), increased levels of plasma insulin (P < 0.01 vs. other groups except control), plasma and pancreatic GLP-1 (P < 0.001 vs. control, and P < 0.05 vs. other groups except control) at 21 days after implantation of cultured MSCs on the surface of electrospun PLLA scaffolds coated with Matricaria chamomilla L. oil. Conclusions: Collectively, our finding showed the presence of Matricaria chamomilla L. oil might improve survival and differentiation MSCs in insulin producing cells that can be attributed to antioxidant properties of its bioactive compounds.

The use of bioabsorbable poly-L-lactide acid miniplate and screw (FIXSORB®-MX ) for bone fixation in mandibular fracture: cases reports

Objective: This report aims to elucidate the degree of degradation of bioabsorbable poly-L-lactide acid (PLLA) devices and the influence of these materials on the surrounding tissues in the human body.Methods: Two patients with fractured mandibles underwent treatment using a biodegradable fixation system. In the first case, the plates and screws were removed along with extraction of an impacted wisdom tooth at 6 months after surgery, and in the second case, the same procedure was performed 12 months after surgery. Changes in the physical properties of the materials and histologic alterations in the periosteum and bone associated with the bioabsorbable plates were assessed.Results: The materials demonstrated adequate degradation in the human body, and skeletal stability proved sufficient for the duration of mandibular bone healing without complications after surgery.Conclusion: On the basis these findings, it can be concluded that PLLA implants are useful for the fixation of human mandibular fractures.

Surface Hydrophilicity of Poly(l-Lactide) Acid Polymer Film Changes the Human Adult Adipose Stem Cell Architecture.

Current knowledge indicates that the molecular cross-talk between stem cells and biomaterials guides the stem cells’ fate within a tissue engineering system. In this work, we have explored the effects of the interaction between the poly(l-lactide) acid (PLLA) polymer film and human adult adipose stem cells (hASCs), focusing on the events correlating the materials’ surface characteristics and the cells’ plasma membrane. hASCs were seeded on films of pristine PLLA polymer and on a PLLA surface modified by the radiofrequency plasma method under oxygen flow (PLLA+O2). Comparative experiments were performed using human bone-marrow mesenchymal stem cells (hBM-MSCs) and human umbilical matrix stem cells (hUCMSCs). After treatment with oxygen-plasma, the surface of PLLA films became hydrophilic, whereas the bulk properties were not affected. hASCs cultured on pristine PLLA polymer films acquired a spheroid conformation. On the contrary, hASCs seeded on PLLA+O2 film surface maintained the fibroblast-like morphology typically observed on tissue culture polystyrene. This suggests that the surface hydrophilicity is involved in the acquisition of the spheroid conformation. Noteworthy, the oxygen treatment had no effects on hBM-MSC and hUCMSC cultures and both stem cells maintained the same shape observed on PLLA films. This different behavior suggests that the biomaterial-interaction is stem cell specific.

Computational Analysis of the Utilisation of the Shape Memory Effect and Balloon Expansion in Fully Polymeric Stent Deployment.

The desire to overcome the limitations of cardiovascular metal stents is driven by the global clinical need to improve patient outcomes. The opportunity for fully polymeric stents made from materials like Poly-L-lactide Acid (PLLA) is significant. Unfortunately, this potential has not been fully realised due to pressing concerns regarding the radial strength and recoil associated with material stiffness and recoverability. In an effort to achieve effective and reliable performance, it is conceivable that a certain degree of shape memory effect (SME) could be beneficial in order to improve on high recoil associated with fully polymeric stents. In this paper, a computational model is presented to explore this possibility, using a stent geometry based on that of a commercially available polymeric stent (Abbott Absorb). The model predicts improvements in the recoil behaviour if the stent is subjected to temperature changes (introducing the shape memory effect to the material) prior to implantation compared to balloon inflation alone. The analysis indicates that combination of self-expansion and balloon inflation is capable of reducing stent recoil to a desirable level (5%). Additionally, the analysis suggests that the recoil is not strongly related to expansion rate variation. However, the stent expansion rate is critically linked to the maximum stresses in the material, with significantly higher stresses found if the stent was deployed with a higher rate, leading to a significantly higher material failure risk. It is concluded that the model provides new insights that can guide the development of fully polymeric stents towards optimised clinical performance with the potential to improve patient outcomes.

In vitro analysis of a local polymeric device as an alternative for systemic antibiotics in Dentistry.

The development of a biodegradable material with antimicrobial properties for local applications is required in the prevention and treatment of infectious diseases. The objective of this study was to produce blends of poly-L-lactide acid (PLLA) synthetic polymer associated with several antimicrobials, as an alternative in the prevention and treatment of infections, as well as to evaluate its cytotoxicity, release of antimicrobials and inhibit bacteria growth. Blends of PLLA added with 20% Amoxicillin, Metronidazole, Clindamycin or Azithromicyn were used to produce Films (F) or Meshs (M) by casting and electrospinning methods, respectively. Standardized discs of the films and meshs were stored in buffer solutions (pH 5 or 7.4) and aliquots were analyzed by high performance chromatography (HPLC) during 168 hours. Cytotoxicity on human gingival fibroblasts was tested after 24, 48 and 72h by MTT reaction. The antimicrobial capacity was determined against P. gingivalis and S. pyogenes. The specimens were weighed after 3 and 6 months of storage for degradation analysis. SEM was performed to control interfaces and degradation. Antimicrobials presented a continuous and exponential drug release. Analysis showed that both M and F were able to inhibit S. pyogenes and P. gingivalis growth, indicating the release of active antimicrobial agents. The products were not toxic to the fibroblasts. Amoxicillin-film showed more degradation than PLLA at both pHs (p < 0.05), whereas Azithromycin-meshes were more degraded than PLLA at pH 7.4 (p < 0.05). PLLA association with antimicrobials is biocompatible and may represent a potential tool for the local delivery of antimicrobials.

Differentiation of mesenchymal stem cells -derived trabecular meshwork into dopaminergic neuron-like cells on nanofibrous scaffolds

Parkinson's disease (PD) is a neurodegenerative disorder of the brain which is produced by the damage to dopaminergic neurons. Stem cell transplantation with a nanofibrous scaffold is one of the encouraging strategies for Parkinson's disease therapy. In this study, human mesenchymal stem cells (MSCs) from eye trabecular meshwork (TM) were differentiated into dopaminergic neurons on nanofibrous scaffold.After Trabecular meshwork biopsy, MSCs were isolated, cultivated on Poly-l-Lactide Acid (PLLA) nanofibrous scaffold (fabricated by electrospinning methods) and treated with medium containing DMEM supplemented with RA, IBMX and forskolin for 7 days. Scanning electron microscopy imaging, qPCR and immunostaining were used to analyze differentiated TM-MSCs on scaffold and their expression of dopaminergic-specific markers such as TH and Nurr-1.qPCR analysis revealed the expression of dopaminergic neuron genes such as TH, Nurr-1 on fibrous scaffold as well as TCPS. Immunostaining revealed that the differentiated TM-MSCs on TCPS and Scaffold not only express TH and Nurr-1 genes, but also express TH protein.In conclusion, the results indicate that TM-MSCs might be a suitable source for cell transplantation therapy. In addition the nanofibrous scaffold reported herein could be used as a potential cell carrier for the central system diseases such as PD.

One-Step Fabrication of Bone Morphogenetic Protein-2 Gene-Activated Porous Poly-L-Lactide Scaffold for Bone Induction

Bone morphogenetic protein 2 (BMP2) is an efficacious inducer for the osteogenesis of mesenchymal stem cells (MSCs). Conventional applications of BMP2 have involved either the direct incorporation of BMP2 protein or ex vivo BMP2 gene transfer into stem cells prior to their transplantation. These approaches are able to promote bone formation to some extent; however, they are hampered by either the lack of stability and sustainability of BMP2 protein or the time-consuming and cost-prohibitive in vitro cell culture procedure. To overcome these limitations, we have developed a gene-activated poly-L-lactide acid (PLLA) scaffold with the encapsulation of recombinant adeno-associated viral (AAV) vector encoding a full-length cDNA of human BMP2 using an ice-based microparticle porogenization method that was recently developed. Results showed continuous release of AAV particles from the micropores of scaffolds for up to 1 week, subsequently transducing embedded human MSCs and producing functional BMP2. MSCs within scaffolds underwent efficacious osteogenesis, on the basis of osteoinductive gene expression and osteogenic differentiation, which resulted in robust new bone formation in vivo at 4 weeks. These findings show the potential of the technology toward developing clinical applications of a rapid, cost-effective, and potentially point-of-care approach for the repair of bone defects.