Evolution of the properties of a poly(l-lactic acid) scaffold with double porosity duringin vitrodegradation in a phosphate-buffered saline solution (original) (raw)
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Journal of Materials Science: Materials in Medicine, 2004
The use of bioresorbable polymers as a support for culturing cells has received special attention as an alternative for the treatment of lesions and the loss of tissue. The aim of this work was to evaluate the degradation in cell culture medium of dense and porous scaffolds of poly(L-lactic acid) (PLLA) and poly(D,L-lactic acid-co-glycolic acid) (50:50) (PLGA50) prepared by casting. The adhesion and morphology of osteoblast cells on the surface of these polymers was evaluated. Thermal analyses were done by differential scanning calorimetry and thermogravimetric analysis and cell morphology was assessed by scanning electron microscopy. Autocatalysis was observed in PLGA50 samples because of the concentration of acid constituents in this material. Samples of PLLA showed no autocatalysis and hence no changes in their morphology, indicating that this polymer can be used as a structural support. Osteoblasts showed low adhesion to PLLA compared to PLGA50. The cell morphology on the surface of these materials was highly dispersed, which indicated a good interaction of the cells with the polymer substrate.
Biomaterials, 2005
This study investigated the in vitro degradation of porous poly(propylene fumarate) (PPF-based) composites incorporating microparticles of blends of poly(DL-lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) during a 26-week period in pH 7.4 phosphate-buffered saline at 37 1C. Using a fractional factorial design, four formulations of composite scaffolds were fabricated with varying PEG content of the microparticles, microparticle mass fraction of the composite material, and initial leachable porogen content of the scaffold formulations. PPF scaffolds without microparticles were fabricated with varying leachable porogen content for use as controls. The effects of including PLGA/PEG microparticles in PPF scaffolds and the influence of alterations in the composite formulation on scaffold mass, geometry, water absorption, mechanical properties and porosity were examined for cylindrical specimens with lengths of 13 mm and diameters of 6.5 mm. The composite scaffold composition affected the extent of loss of polymer mass, scaffold length, and diameter, with the greatest loss of polymer mass equal to 1575% over 26 weeks. No formulation, however, exhibited any variation in compressive modulus or peak compressive strength over time. Additionally, sample porosity, as determined by both mercury porosimetry and micro-computed tomography did not change during the period of this study. These results demonstrate that microparticle carriers can be incorporated into PPF scaffolds for localized delivery of bioactive molecules without altering scaffold mechanical or structural properties up to 26 weeks in vitro. r
Biodegradable poly(lactic acid)-based scaffolds: synthesis and biomedical applications
Journal of Polymer Research, 2017
Biodegradable polymers are identified as substantial materials for biomedical applications. These polymers have the ability to deteriorate through an unpretentious hydrolysis and eliminated through kidneys' functions or metabolic processes. Among widely used biodegradable polymers in biomedical applications, poly(lactic acid) (PLA) is becoming one of the most paramount polymers. Synthesizing PLA through melt/solution polycondensation polymerizations makes it relatively easy to tailor properties of final product. However, their synthesis reactions are affected by several parameters such as polymerization time, temperature, pressure, catalysts, and the polarity of the solvent. Moreover, equilibrium reactions are controlled through utilizing a hydrophilic monomer such as ethylene glycol (EG). These factors can strongly impact final properties of PLA. Thus, it is indispensable to comprehend the effect of operating parameters during the polymerization process. Optimizing synthesis conditions can be accomplished through reducing side reactions. Furthermore, this can be achieved through racemization by utilizing chain extenders to build high molecular weight and enhance thermal stability. In this review, the design and fabrication of porous PLA scaffolds and their physicomechanical behavior are reviewed. Different PLA scaffold parameters were investigated thoroughly, which include biocompatibility, biodegradability, and mechanical properties for different porosity and pore sizes to mimic the complex architecture of the natural tissue regeneration.
Biomaterials, 2005
This study investigated the in vivo degradation of poly(propylene fumarate) (PPF)/poly(DL-lactic-co-glycolic acid) (PLGA) composite scaffolds designed for controlled release of osteogenic factors. PPF/PLGA composites were implanted into 15.0 mm segmental defects in the rabbit radius, harvested after 12 and 18 weeks, and analyzed using histological techniques to assess the extent of polymer degradation as well as the tissue response within the pores of the scaffolds. Polymer degradation was limited to micro-fragmentation of the scaffold at the ends and edges of the implant at both 12 and 18 weeks. The tissue within the pores of the scaffold consisted of fibrous tissue, blood vessels and some inflammatory cells. In areas where polymer breakdown was evident, an increased inflammatory response was observed. In contrast, areas of bone ingrowth into the polymer scaffold were characterized by minimal inflammatory response and polymer degradation. Our results show that minimal degradation of porous PPF occurs within 18 weeks of implantation in a rabbit model. Further, the in vivo degradation data of porous PPF/PLGA scaffolds are comparable with earlier obtained in vitro data.
In vitro degradation of PLLA/nHA composite scaffolds
Polymer Engineering & Science, 2013
Porous Poly-L-lactide (PLLA) scaffolds and PLLA/nanohydroxyapatite (nHA) composite scaffolds with interconnected pore networks and a porosity of over 90% were fabricated with lyophilization techniques. In this study, the degradation behavior of PLLA and PLLA/nHA composite scaffolds is investigated over 8 weeks in phosphate buffer solution at 37 C. Thermal analysis using differential scanning calorimetry (DSC) showed that the percent crystallinity of all the samples increased by approximately 10%, which represents a considerable increase in the glass transition temperature. The melting range enthalpy of the scaffolds did not change to lower temperatures as would be expected. The spectroscopic analysis performed by Fourier transform infrared spectroscopy suggested that nHA particles should not appreciably affect the absorbance pattern when evenly mixed with the PLLA. This is consistent with the analysis of the scaffold microstructure and morphology with scanning electron microscopy, which drew a low content of nHA with no significant effect on solvent crystallization or pore structure. The compressive modulus and the yield strength of the scaffolds were investigated in conjunction with the study of their degradation rates. In comparison with the mechanical properties of the PLLA scaffolds, which remained largely unchanged, those of the PLLA/nHA composite scaffolds decreased as the degradation progressed.
Journal of the Mechanical Behavior of Biomedical Materials, 2013
Two thermally induced phase separation (TIPS) methods have been used to fabricate biodegradable poly(L-lactic acid) (PLLA) tissue engineering scaffolds each with fibrous (F-TIPS) and porous (P-TIPS) microstructures. Three levels of PLLA concentration (3, 5 and 7 wt%) were employed in each fabrication method and both wet and dry specimens were studied. Simple compression testing revealed that an elastic-plastic representation of the mechanical behavior was possible for all specimens. Both elastic and plastic moduli were higher for the P-TIPS, for higher polymer concentration, and might be somewhat higher for dry as opposed to wet specimens. For F-TIPS specimens, permanent deformation occurred successively during cyclic deformation but a ''memory effect'' simplified the behavior. Although F-TIPS microstructure better resembled the natural extracellular matrix, human osteosarcoma fibroblast cells showed more consistent viability in the P-TIPS scaffolds under our unloaded test protocols. Biodegradation in cell culture medium resulted in a decreased elastic moduli for F-TIPS specimens. Information presented regarding the microstructure, mechanical properties and cell viability of these PLLA scaffolds that should help reduce the number of iterations involved in developing tissue engineering products.
The porous poly(lactic acid) (PLA) foams potential for tissue engineering usage are prepared by a modified solvent casting/particulate leaching method with different crystallinity. Since in typical method the porogens are dispersed in the solution and flow with the polymers during the casting and the crystallinity behavior of PLA chains in the limited space cannot be tracked, in this work the processing is modified by diffusing the PLA solution into a steady salt stack. With a thermal treatment before leaching while maintaining the stable structure of the porogens stack, the crystallinity of porous foams is made possible to control. The characterizations indicate that the porous PLA foams have a lower crystallizability than the bulk materials. Pores and caves of around 250 μm size are obtained in samples with different crystallinity. The macro-structures are not much impaired by the crystallization nevertheless the morphological effect of the heating process is still obvious.