Porous Polylactic Acid Scaffolds Research Articles

Microdroplets Encapsulated with NFATc1-siRNA and Exosomes-Derived from MSCs Onto 3D Porous PLA Scaffold for Regulating Osteoclastogenesis and Promoting Osteogenesis.

Osteoporotic-related fractures remains a significant public health concern, thus imposing substantial burdens on our society. Excessive activation of osteoclastic activity is one of the main contributing factors for osteoporosis-related fractures. While polylactic acid (PLA) is frequently employed as a biodegradable scaffold in tissue engineering, it lacks sufficient biological activity. Microdroplets (MDs) have been explored as an ultrasound-responsive drug delivery method, and mesenchymal stem cell (MSC)-derived exosomes have shown therapeutic effects in diverse preclinical investigations. Thus, this study aimed to develop a novel bioactive hybrid PLA scaffold by integrating MDs-NFATc1-silencing siRNA to target osteoclast formation and MSCs-exosomes (MSC-Exo) to influence osteogenic differentiation (MDs-NFATc1/PLA-Exo). Human bone marrow-derived mesenchymal stromal cells (hBMSCs) were used for exosome isolation. Transmission electron microscopy (TEM) and confocal laser scanning microscopy were used for exosome and MDs morphological characterization, respectively. The MDs-NFATc1/PLA-Exo scaffold was fabricated through poly(dopamine) and fibrin gel coating. Biocompatibility was assessed using RAW 264.7 macrophages and hBMSCs. Osteoclast formations were examined via TRAP staining. Osteogenic differentiation of hBMSCs and cytokine expression modulation were also investigated. MSC-Exo exhibited a cup-shaped structure and effective internalization into cells, while MDs displayed a spherical morphology with a well-defined core-shell structure. Following ultrasound stimulation, the internalization study demonstrated efficient delivery of bioactive MDs into recipient cells. Biocompatibility studies indicated no cytotoxicity of MDs-NFATc1/PLA-Exo scaffolds in RAW 264.7 macrophages and hBMSCs. Both MDs-NFATc1/PLA and MDs-NFATc1/PLA-Exo treatments significantly reduced osteoclast differentiation and formation. In addition, our results further indicated MDs-NFATc1/PLA-Exo scaffold significantly enhanced osteogenic differentiation of hBMSCs and modulated cytokine expression. These findings suggest that the bioactive MDs-NFATc1/PLA-Exo scaffold holds promise as an innovative structure for bone tissue regeneration. By specifically targeting osteoclast formation and promoting osteogenic differentiation, this hybrid scaffold may address key challenges in osteoporosis-related fractures.

A tailored bioactive 3D porous poly(lactic-acid)-exosome scaffold with osteo-immunomodulatory and osteogenic differentiation properties

Polylactic acid (PLA) is a versatile and biodegradable scaffold widely used in biomedical fields to repair tissue defects. Exosomes derived from mesenchymal stem cells (MSCs) are nano-sized extracellular vesicles, which play an important role in tissue engineering in recent years. The primary focus of this study was to develop a bioactive 3D PLA scaffold using exosome-based strategy to improve its osteogenic and immunoregulatory potential. We firstly successfully isolated MSC-derived exosomes (MSC-Exo). Morphological analysis revealed that MSC-Exo exhibits a typical cup-shaped morphology with high expression of exosomal marker CD63. MSC-Exo internalization into recipient cells were also investigated using flow cytometry and confocal laser scanning microscopy. Porous 3D PLA scaffold coated MSC-Exo were used for immunoregulatory and osteogenic testing. Exosomes released from 3D PLA scaffold were validated in RAW264.7 and hBMSCs. The cell proliferation and live/dead assay indicated high biocompatibility for PLA-Exo scaffold. Additionally, PLA-Exo scaffold could reduce the pro-inflammatory marker expression and reactive oxygen species (ROS) production, indicating potential immunoregulatory potential. It is also confirmed that PLA-Exo scaffold could potentiate osteogenic differentiation in the osteogenesis assay. In conclusion, our results demonstrate this bioactive 3D-printed PLA scaffolds with MSC-Exo modification holds immunoregulatory potential and favor osteogenic differentiation, thus having potential applications in bone tissue regeneration.

The effect of foaming process with supercritical CO2 on the morphology and properties of 3D porous polylactic acid scaffolds

AbstractA systematic study was carried out in order to identify the optimum processing conditions for the preparation of PLA 3D porous structures applying foaming with supercritical CO2 (sc‐CO2). Both the depressurization rate and the CO2 saturation pressure had a significant effect on the obtained sc‐CO2 PLA structures. When sc‐CO2 was instantaneously depressurized, a thin wall pore structure was formed, characterized by anisotropy with pores diameter ranging from 100 to 650 μm, whereas the scaffold porosity varied between 85% and 95%. In this case, a decrease in the porosity percentage was observed with increasing saturation pressure. A trend of increase in the pores' size was recorded from 150 to 200 bar, followed by a decrease at 300 bar. Highly organized pore structures with thicker pore walls and pores with diameters within the range of 10–350 μm and porosity and 74%–77% were fabricated when a slow depressurization rate was applied. An optimum porous structure, with average pore diameter 340 μm and porosity 88% was prepared when Psat was maintained at 200 bar, followed by instantaneous depressurization. Although this scaffold included the biggest number of closed pores in its structure, it presented the highest degree of pore interconnectivity due to CO2 bubbles' coalescence.

Dental pulp stem cell-derived extracellular matrix: autologous tool boosting bone regeneration

Background aimsTo facilitate artificial bone construct integration into a patient's body, scaffolds are enriched with different biologically active molecules. Among various scaffold decoration techniques, coating surfaces with cell-derived extracellular matrix (ECM) is a rapidly growing field of research. In this study, for the first time, this technology was applied using primary dental pulp stem cells (DPSCs) and tested for use in artificial bone tissue construction. MethodsRat DPSCs were grown on three-dimensional-printed porous polylactic acid scaffolds for 7 days. After the predetermined time, samples were decellularized, and the remaining ECM detailed proteomic analysis was performed. Further, DPSC-secreated ECM impact to mesenchymal stromal cells (MSC) behaviour as well as its role in osteoregeneration induction were analysed. ResultsIt was identified that DPSC-specific ECM protein network ornamenting surface-enhanced MSC attachment, migration and proliferation and even promoted spontaneous stem cell osteogenesis. This protein network also demonstrated angiogenic properties and did not stimulate MSCs to secrete molecules associated with scaffold rejection. With regard to bone defects, DPSC-derived ECM recruited endogenous stem cells, initiating the bone self-healing process. Thus, the DPSC-secreted ECM network was able to significantly enhance artificial bone construct integration and induce successful tissue regeneration. ConclusionsDPSC-derived ECM can be a perfect tool for decoration of various biomaterials in the context of bone tissue engineering.

Degradation of 3D-Printed Porous Polylactic Acid Scaffolds Under Mechanical Stimulus.

Polylactic acid (PLA) is a biodegradable polymer commonly used as a scaffold material to repair tissue defects, and its degradation is associated with mechanical stimulus. In this study, the effect of mechanical stimulus on the degradation of 3D-printed PLA scaffolds was investigated by in vitro experiments and an author-developed numerical model. Forty-five samples with porosity 64.8% were printed to carry out the degradation experiment within 90 days. Statistical analyses of the mass, volume fraction, Young’s modulus, and number average molecular weight were made, and the in vitro experiments were further used to verify the proposed numerical model of the scaffold degradation. The results indicated that the mechanical stimulus accelerated the degradation of the PLA scaffold, and the higher mechanical stimulus led to a faster degradation of the scaffolds at the late stage of the degradation process. In addition, the Young’s modulus and the normalized number average molecular weight of the PLA scaffolds between the experiments and the numerical simulations were comparable, especially for the number average molecular weight. The present study could be helpful in the design of the biodegradable PLA scaffolds.

Facile manufacturing of fused-deposition modeled composite scaffolds for tissue engineering—an embedding model with plasticity for incorporation of additives

The fused-deposition modeling (FDM) process is carried out at an elevated temperature, preventing the addition of biological factors, drugs, bioactive compounds, etc, during fabrication. To overcome this disadvantage, a 3D interlinked porous polylactic acid (PLA) scaffold was fabricated by FDM, followed by the embedding of a polycaprolactone (PCL) scaffold into the pores of the PLA at room temperature, yielding a PLA-PCL scaffold. In addition, PLA-PCL scaffolds with nanohydroxyapatite (PLA-PCL-nHAP) and multiwalled carbon nanotubes (PLA-PCL-MWCNT) were also fabricated. Here, the FDM-fabricated PLA scaffold functions as the structural component, whereas the embedded PCL scaffold acts as the functional component, which provides a the ability to functionalize the scaffolds with the desired chemical or biological materials. The embedding process is straightforward, cost effective, and does not require sophistication. A mechanical characterization of the scaffolds suggests that the Young’s modulus of the PLA-PCL scaffold (16.02 MPa) was higher than that of the FDM-fabricated PLA (9.98 MPa) scaffold, by virtue of embedded PCL matrix. In addition, finite element analysis showed that the von Mises stress on a mandible with scaffolds was 4.04 MPa, whereas for a mandible with a defect, it was 6.7 MPa, confirming the stress distribution efficiency and mechanical stability of these scaffolds. Furthermore, field emission-scanning electron microscope analysis implied the presence of interlinked porous structures with pore diameters of 50 µm to 300 µm. X-ray diffraction results revealed an increased crystallinity (%) in the embedded models (PLA-PCL, PLA-PCL-nHAP and PLA-PCL-MWCNT), compared to a PLA printed scaffold. Additionally, Raman analysis revealed that the embedding process did not cause chemical alterations in the polymeric chains. In vitro analysis with human osteoblasts demonstrated the osteoconductive nature of the scaffold, which supported mineralization. In brief, the advantage of our model is that it helps to overcome the difficulties of manufacturing a filament with the desired additives for FDM, and offers the ability to incorporate the desired concentrations of heat-labile bioactive molecules during the embedding process at ambient temperatures.

High strength porous PLA gyroid scaffolds manufactured via fused deposition modeling for tissue-engineering applications

Gyroid polylactic acid (PLA) scaffolds with different unit cell sizes of 2 ​mm (G2), 2.5 ​mm (G25), and 3 ​mm (G3) were fabricated via fused deposition modeling for bone tissue engineering applications. The porosity of the PLA scaffolds ranged from 86% to 90%. The structural anisotropy value of the scaffolds was 3.80, 2.00, and 1.04 for G2, G25, and G3, respectively. Compressive test results indicated that both the dense PLA and porous PLA scaffolds showed elastic-plastic deformation behavior in both building and transverse directions. The compressive elastic modulus and yield strength of the scaffolds were 118–180 ​MPa and 2–8 ​MPa in the building direction and 106–138 ​MPa and 2.5–6.0 ​MPa in the transverse direction, respectively. The tensile elastic modulus and yield strength were 51–63 ​MPa and 1.5–4.5 ​MPa in the building direction and 11–17 ​MPa and 1–5 ​MPa in the transverse direction, respectively. The gyroid PLA scaffolds showed significantly higher values for compressive strength (up to three times) compared to other gyroid structures reported in the literature. The PLA scaffolds can be anticipated as promising scaffold biomaterials for bone tissue engineering applications by virtue of their bone-mimicking porous structure and good mechanical properties.

Porous polylactic acid scaffolds for bone regeneration: A study of additively manufactured triply periodic minimal surfaces and their osteogenic potential

Three different triply periodic minimal surfaces (TPMS) with three levels of porosity within those of cancellous bone were investigated as potential bone scaffolds. TPMS have emerged as potential designs to resemble the complex mechanical and mass transport properties of bone. Diamond, Schwarz, and Gyroid structures were 3D printed in polylactic acid, a resorbable medical grade material. The 3D printed structures were investigated for printing feasibility, and assessed by morphometric studies. Mechanical properties and permeability investigations resulted in similar values to cancellous bone. The morphometric analyses showed three different patterns of pore distribution: mono-, bi-, and multimodal pores. Subsequently, biological activity investigated with pre-osteoblastic cell lines showed no signs of cytotoxicity, and the scaffolds supported cell proliferation up to 3 weeks. Cell differentiation investigated by alkaline phosphatase showed an improvement for higher porosities and multimodal pore distributions, suggesting a higher dependency on pore distribution and size than the level of interconnectivity.

Osteogenesis ability of CAD-CAM biodegradable polylactic acid scaffolds for reconstruction of jaw defects

Statement of problemReconstruction of alveolar bony defects is difficult using grafting materials in a powder form. A biodegradable scaffold material might simplify the procedure. PurposeThe purpose of this in vivo study was to evaluate osteogenesis ability of a biodegradable CAD-CAM–fabricated polylactic acid (PLA) scaffold enriched with calcium phosphate salts including hydroxyapatite (HA) and beta tricalcium phosphate (β-TCP) used to reconstruct mandibular defects in a dog model. Material and MethodsSurgical defects were made bilaterally in the mandible of male beagle dogs. Computerized tomography images were obtained for determination of the 3-dimensional shape of the defects after 3 months of healing. Porous PLA scaffolds were fabricated by milling custom-made CAD-CAM blocks into the desired shape. After milling, half of the scaffolds were prepared by filling the pores of the scaffolds by a mixture of HA and β-TCP. Scaffolds were inserted in the mandibular defects bilaterally. After a healing time of 8 weeks, the bone-scaffold interface was analyzed histomorphometrically to detect the amount of new bone formation. Stained histological sections were examined using a computer software and depth of new bone formation was assessed (n=14, α=.05). ResultsHistomorphometric analysis revealed that enriched scaffolds with calcium phosphates had significantly (t=4.4, P<.001) higher amounts of new bone formation (1.3 ±0.33 mm) compared with the controls (0.7 ±0.39 mm). Average new bone growth in enriched scaffolds was 1.3 mm while almost half this value was observed in uncoated scaffolds, 0.7 mm. ConclusionsWithin the limitations of this animal study, HA and β-TCP enhanced osteogenesis ability of CAD-CAM–fabricated PLA scaffolds.

Composite porous scaffold of PEG/PLA support improved bone matrix deposition in vitro compared to PLA-only scaffolds.

Controllable pore size and architecture are essential properties for tissue-engineering scaffolds to support cell ingrowth colonization. To investigate the effect of polyethylene glycol (PEG) addition on porosity and bone-cell behavior, porous polylactic acid (PLA)-PEG scaffolds were developed with varied weight ratios of PLA-PEG (100/0, 90/10, 75/25) using solvent casting and porogen leaching. Sugar 200-300 µm in size was used as a porogen. To assess scaffold suitability for bone tissue engineering, MLO-A5 murine osteoblast cells were cultured and cell metabolic activity, alkaline phosphatase (ALP) activity and bone-matrix production determined using (alizarin red S staining for calcium and direct red 80 staining for collagen). It was found that metabolic activity was significantly higher over time on scaffolds containing PEG, ALP activity and mineralized matrix production were also significantly higher on scaffolds containing 25% PEG. Porous architecture and cell distribution and penetration into the scaffold were analyzed using SEM and confocal microscopy, revealing that inclusion of PEG increased pore interconnectivity and therefore cell ingrowth in comparison to pure PLA scaffolds. The results of this study confirmed that PLA-PEG porous scaffolds support mineralizing osteoblasts better than pure PLA scaffolds, indicating they have a high potential for use in bone tissue engineering applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1334-1340, 2018.

Characterization of highly interconnected porous poly(lactic acid) and chitosan-coated poly(lactic acid) scaffold fabricated by vacuum-assisted resin transfer molding and particle leaching

Polylactic acid (PLA) scaffolds were prepared using vacuum-assisted resin transfer molding (VARTM), phase separation, solvent extraction, and particle leaching approaches. A chitosan (CS)-coated PLA scaffold was then fabricated using CS coating treatment. To control the pore morphology and porosity, different processing parameters, such as NaCl particle size and PLA solution concentrations were studied. The properties of porous PLA and CS-coated PLA scaffold, including the microstructure, porosity, water absorption, hydrophilicity, compression modulus, and compression strength were investigated. The results showed that PLA and CS-coated PLA scaffold with porosities as high as 94 %, water absorption up to 1200 %, and compressive modulus ranging from 241 to 442 kPa were produced. The pore morphology on the surface and within the scaffold showed the presence of multiple open pores with excellent interconnectivity. Additionally, the CS-coated PLA scaffold showed significantly improved hydrophilicity and mechanical properties compared to the untreated PLA scaffold. Hence, the CS-coated PLA scaffold was expected to exhibit a better biocompatibility than PLA scaffold because of the enhancement of the hydrophilicity.

Manufacture and characterization of porous Polylactic acid scaffold

Manufacture and characterization of porous Polylactic acid scaffold

Bio-safe fabrication of PLA scaffolds for bone tissue engineering by combining phase separation, porogen leaching and scCO2 drying

The present study reports a three-step bio-safe process for fabricating porous polylactic acid (PLA) scaffolds with a biomimetic design of the porosity and the architecture and applications in bone tissue engineering (bTE). The process starts with a PLA–ethyl lactate solution and involves the combination of thermal induced phase separation (TIPS) and supercritical CO2 (scCO2) drying techniques for the development of a nano-fibrous architecture. In a third step, it was further combined with a gelatin leaching technique to create an additional interconnected network of large pores of appropriate size and distribution.The effect of the size of the gelatin particles, selected in three different ranges: 100–200, 200–400 and 400–600μm, on the morphology, porosity and textural features of PLA scaffolds is assessed by means of scanning electron microscopy analysis, gravimetric measurements, image analysis and low-temperature N2 adsorption. Finally, in vitro cell culture tests are carried out by using human osteosarcoma cell line MG63 in order to evaluate the biological response of the different scaffolds prepared and to assess their potential for bTE applications.

Macroporous and nanometre scale fibrous PLA and PLA–HA composite scaffolds fabricated by a bio safe strategy

The present study deals with the design, fabrication and characterization of porous scaffolds for tissue engineering made of polylactic acid (PLA) and PLA containing hydroxyapatite (HA) nanoparticles. The main novelty relies on the fact that the fabrication of the scaffolds has been achieved avoiding totally the use of toxic chemicals. In particular, the scaffolds are obtained by combining both thermal induced phase separation (TIPS) using ethyl lactate (EL) solutions and supercritical CO2 (scCO2) drying processes. Furthermore, gelatin particles have been used as a leachable porogen and combined with the previous processes to improve the control of the pore structure features of the scaffolds. The results show that the developed technique allows for the fabrication of porous PLA scaffolds with HA concentrations up to 30 wt%. Furthermore, these scaffolds are characterized by an overall porosity as high as 98% and a double scale pore structure. In particular, the appropriate control of the TIPS process and the scCO2 drying allowed for the development of nanoscale fibrous PLA and PLA–HA structures starting from PLA/EL solutions. Concomitantly, the proper selection of the size range of gelatin particles as well as their spatial distribution in the mixture allowed imprinting an interconnected network of large pores inside the scaffolds.

Advanced micro- and nanofabrication technologies for tissue engineering

The ability of the living body to heal and regenerate itself following trauma is astonishing. Numerous events of repair and regeneration occur during our lifetime, most of which we are never aware of. Unfortunately, in some cases, the injury or defect cannot be adequately repaired solely by nature and medical intervention is required.

The Study of Microstructure and Biocompatibility for Porous Polylactic Acid Scaffolds

The polylactic acids (PLA) scaffolds materials have been used to be the scaffolds materials of bone, cartilage gristle, blood vessel, nerve and skin due to its bioactivity, biocompatibility and biodegradable, today, the porous polylactic acid scaffolds had widely applied to tissue engineering. In the paper, the advance in study of microstructure and biocompatibility for this material were summarized. The lack in study of microstructure and compatibility has been pointed out and some viewpoints for further investigations are also made in this paper.

Bone tissue engineering with novel rhBMP2‐PLLA composite scaffolds

The aims of the present study were to fabricate a novel porous polylactic acid (PLLA) composite scaffold and evaluate the capacity of the scaffold in carrying recombinant bone morphogenetic protein 2 (rhBMP2) for engineering bone formation. The structures of the PLLA scaffolds were evaluated by SEM and the controlled release of rhBMP2 from the composite scaffolds was assayed by ELISA. Bone induction by the scaffolds loaded with or without rhBMP2 was performed in the calf muscle of twenty Wistar rats for 3, 7, 10, 14, and 28 days. Tissue specimens were examined by Masson's trichrome and von Kossa stainings, and immunohistochemistry of bone proteins. Our results indicated that a moderate foreign body reaction was found in control scaffolds, which lasted for 4 weeks. The addition of rhBMP2 to this novel scaffold dramatically alleviated the adverse responses to PLLA. Enhanced deposition of collagen matrix and endochondral formation were observed in rhBMP2-PLLA scaffolds at 7-10 days, compatible with an early release of rhBMP2 in the composite scaffolds. Bone sialoprotein and osteopontin were demonstrated simultaneously. Von Kossa staining was observed in the test group at 10-14 days. In conclusion, the PLLA scaffolds exhibited the capability of carrying rhBMP2 for inducing bone formation within 2 weeks. These results suggest that rhBMP2-PLLA scaffold may be applicable in tissue engineering.

Human mesenchymal progenitor cell responses to a novel textured poly(L‐lactide) scaffold for ligament tissue engineering

Biocompatibility and cell seeding capability of a new cell scaffold made of textured polylactic acid (PLA) fibers was investigated as a new material for tissue engineering of anterior cruciate ligaments (ACL). Adhesion and proliferation of human mesenchymal progenitor cells (MPC) was investigated after 15 days by scanning electron microscopy and standard histology. Expression of collagen type I and III, fibronectin, tenascin C, decorin, smooth muscle actin, and the matrix metalloproteinases MMP-1 and MMP-2, as well as their tissue inhibitors TIMP-1 and TIMP-2 was analyzed using real-time PCR. Protein expression of collagen I and III, tenascin C, and proliferating nuclear antigen (PCNA) was determined by immunohistology. Apoptosis was analyzed by detection of p53 expression and TUNEL staining. MPC seeded the scaffold homogeneously and showed good cell growth and no increased rate of apoptosis. After 15 days, the matrix forming genes collagen type I, tenascin C, and decorin were upregulated, indicating the formation of a ligament-like matrix. MMP-1 and TIMP-1 were also significantly increased, suggesting initial matrix remodeling. It was concluded that the new porous PLA scaffold allowed homogeneous cell seeding, a fibroblastic phenotype and the production of a ligament-like matrix and, therefore, might be a suitable cell carrier for ACL tissue engineering.