The Mineralization of Various 3D-Printed PCL Composites (original) (raw)
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Crystallization kinetics of PCL and PCL–glass composites for additive manufacturing
Journal of Thermal Analysis and Calorimetry, 2018
The non-isothermal crystallization kinetics of polycaprolactone (PCL) and PCL-glass composites, used in fused filament fabrication (FFF), was investigated. Films of PCL and PCL reinforced with powders of a bioactive glass, from the CaOÁP 2 O 5 ÁMgOÁSiO 2 system, were prepared by solvent casting process. Crystal structure of the samples was examined by X-ray diffraction (XRD), and thermal properties were assessed by differential scanning calorimetry (DSC), at different cooling rates (5, 10, 15 and 20°C min-1). The DSC curves of non-isothermal crystallization showed a significant dependence of crystallinity (X c) on the cooling rate. The relevant crystallization kinetic parameters were determined from DSC traces applying a combination of Avrami and Ozawa methods (Mo's method), Jeziorny method and Friedman method. It was observed that the presence of inorganic particles within the polymeric matrix clearly influenced the composite crystallization. The addition of glass particles allowed a decrease in X c and accelerated the PCL crystallization rate. The slower cooling rates tested proved to be suitable for the biofabrication of PCL-glass composites by FFF techniques.
3D printing and morphological characterisation of polymeric composite scaffolds
Engineering Structures
3D-printing is an efficient method of designing customised structures and producing synthetic bone grafts appropriate for bone implants. This research aimed to manufacture a new multi-functionalised 3D-printed poly(lactic acid)/carbonated hydroxyapatite (PLA/cHA) scaffolds with mass proportions of 100/0, 95/5 and 90/10 in a bid to verify their potential application in tissue regeneration. The filaments of these hybrid materials were obtained by extrusion technique and subsequently used to manufacture the 3D-printed scaffolds, using a fused deposition modelling (FDM) technique. The scaffolds were characterised based on their thermal properties, microstructure and geometry by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS), respectively, in addition to determination of their apparent porosities. The degradation of the scaffolds and the liberation of degradation products were evaluated in in vitro for different days under simulated physiological conditions. New microanalyses of mechanical behaviour of the materials: tensile and compression stresses, density, frequency analysis and optimisation with DSC were performed. While, evaluation of the surface luminance structure and the profile structure of the nanostructured PLA composite materials was done by SEM, in 3D printed form. The filter profile of cross-sectional view of the specimen was extracted and evaluated with Firestone curve of the Gaussian filter; checking the roughness and waviness profile of the structure. It was observed that the thermal properties of the composites were not affected by the manufacturing process. The microstructural analysis showed the effective incorporation of the ceramic filler in the polymer matrix as well as an acceptable PLA/cHA interaction. The degradation tests showed the presence of calcium and phosphorus in the studied medium, confirming their liberation from the composites during the incubation periods.
Journal of Biomedical Materials Research Part B: Applied Biomaterials, 2014
In this study, two different composition gel derived silica-rich (S2) or calcium-rich (A2) bioactive glasses (SBG) from a basic CaOAP 2 O 5 ASiO 2 system were incorporated into poly(e-caprolactone) (PCL) matrix to obtain novel bioactive composite scaffolds for bone tissue engineering applications. The composites were fabricated in the form of highly porous 3D scaffolds using following preparation methods: solvent casting particulate leaching (SCPL), solid-liquid phase separation, phase inversion (PI). Scaffolds containing 21% vol. of each bioactive glass were characterized for architecture, crystallinity, hydrolytic degradation, surface bioactivity, and cellular response. Results indicated that the use of different preparation methods leads to obtain highly porous (60-90%) materials with differentiated morphology: pore shape, size, and distributions. Thermal analysis (DSC) showed that the preparation method of materials and addition of bioactive glass particles into polymer matrix induced the changes of PCL crystallinity. Composites obtained by SCPL and PI method containing A2 SBG rapidly formed a hydroxyapatite calcium phosphate surface layer after incubation in SBF. Bioactive glasses used as filler in composite scaffolds could neutralize the released acidic by-products of the polymer degradation. Preliminary in vitro biological studies of the composites in contact with osteoblastic cells showed good biocompatibility of the obtained materials. Addition of bioactive glass into the PCL matrix promotes mineralization estimated on the basis of the ALP activity. These results suggest that through a process of selection appropriate methods of preparation and bioglass composition it is possible to design and obtain porous materials with suitable properties for regeneration of bone tissue. V C 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 00B: 000-000, 2014.
Composites Science and Technology, 2019
Composites have clinical application for their ability to mimic the hierarchical structure of human tissues. In tissue engineering applications the use of degradable biopolymer matrices reinforced by bioactive ceramics is seen as a viable process to increase osteoconductivity and accelerate tissue regeneration, and technologies such as additive manufacturing provide the design freedom needed to create patient-specific implants with complex shapes and controlled porous structures. In this study a medical grade poly(Llactide) (PLLA) was used as matrix while apatite-wollastonite (AW) was used as reinforcement (5 wt% loading). Premade rods of composite were pelletized and processed to create a filament with an average diameter of 1.6 mm, using a twin-screw extruder. The resultant filament was 3D printed into three types of porous woodpile samples: PLLA, PLLA reinforced with AW particles, and PLLA with short AW fibres. None of the samples degraded in phosphate buffered solution over a period of 8 weeks, and an average effective modulus of 0.8 GPa, 1 GPa and 1.5 GPa was obtained for the polymer, particle and fibre composites, respectively. Composite samples immersed in simulated body fluid exhibited bioactivity, producing a surface apatite layer. Furthermore, cell viability and differentiation were demonstrated for human mesenchymal stromal cells for all sample types, with mineralisation detected solely for biocomposites. It is concluded that both composites have potential for use in critical size bone defects, with the AW fibre composite showing greater levels of ion release, stimulating more rapid cell proliferation and greater levels of mineralisation.
Multiscale porosity in mesoporous bioglass 3D-printed scaffolds for bone regeneration
Materials SCIENCE & ENGINEERING C-Materials for Biological Applications, 2021
In order to increase the bone forming ability of MBG-PCL composite scaffold, microporosity was created in the struts of 3D-printed MBG-PCL scaffolds for the manufacturing of a construct with a multiscale porosity consisting of meso-micro-and macropores. 3D-printing imparted macroporosity while the microporosity was created by porogen removal from the struts, and the MBG particles were responsible for the mesoporosity. The scaffolds were 3Dprinted using a mixture of PCL, MBG and phosphate buffered saline (PBS) particles, subsequently leached out. Microporous-PCL (pPCL) as a negative control, microporous MBG-PCL (pMBG-PCL) and non-microporous-MBG-PCL (MBG-PCL) were investigated. Scanning electron microscopy, mercury intrusion porosimetry and micro-computed tomography demonstrated that the PBS removal resulted in the formation of micropores inside the struts with porosity of around 30% for both pPCL and pMBG-PCL, with both constructs displaying an overall porosity of 80-90%. In contrast, the MBG-PCL group had a microporosity of 6% and an overall porosity of 70%. Early mineralisation was found in the pMBG-PCL postleaching out and this resulted in the formation a more homogeneous calcium phosphate layer when using a biomimetic mineralisation assay. Mechanical properties ranged from 5 to 25 MPa for microporous and non-microporous specimens, hence microporosity was the determining factor affecting compressive properties. MC3T3-E1 metabolic activity was increased in the pMBG-PCL along with an increased production of RUNX2. Therefore, the microporosity within a 3D-printed bioceramic composite construct may result in additional physical and biological benefits.
A biomimetic approach to evaluate mineralization of bioactive glass-loaded resin composites
Journal of Prosthodontic Research, 2022
Bioactive glasses (BAG), first melt-derived in the late 1960s by Larry Hench, obtained good clinical results in dentistry, due to their properties of good bioactivity, when used to treat bone defects[1]. The composition of this bioactive glass was 45 wt% SiO 2 , 24.5 wt% Na 2 O, 24.5 wt% CaO, and 6 wt% P 2 O 5 , which was later termed as 45S5 or Bioglass®. Recently, various researchers have incorporated BAG into experimental[2-5] and commercial dental resin composite materials[6]. The release of calcium and phosphate ions was used as a means to assist with prevention of demineralization of dentine from an initial caries attack. Furthermore, BAG-containing resin composites can reduce bacterial penetration into marginal gaps due to their ability to increase local pH, precipitate apatite on the surface, or in this case within the gap[7]. In addition, a novel design of resin composite-based implant containing bioactive glass has successfully been used for many years[8,9]. The fiber-reinforced composite implants loaded with bioactive glass were supported to enhance biological bone repair and the formation of vascularized structures, in addition to providing improved antimicrobial properties for implants. Chemically speaking, this type of "bioactive" action is a mineralization reaction. At the beginning, a silica-rich layer with Si-OH groups forms on the surface by the exchange of Na + and Ca 2+ ions from the glass with surrounding H + ions, which increases surrounding pH. Then, Ca 2+ and PO 4 3− from surrounding solution forms amorphous calcium phosphate (ACP, Ca x (PO 4) y •nH 2 O)[10] on the surface, which is transformed into octacalcium phosphate (OCP, Ca 8 (HPO 4) 2 (PO 4) 4 •5H 2 O) [10] and finally evolves into nanocrystalline carbonated hydroxyapatite (CHA, Ca 10−x (PO 4) 6−x (CO 3) x (OH) 2−x−2y (CO 3) y) not hydroxyapatite (HA, Ca 10 (PO 4) 6 (OH) 2) in human body as bone or tooth enamel[11,12].
Structural Evolution of PCL during Melt Extrusion 3D Printing
Macromolecular Materials and Engineering
Screw-assisted material extrusion technique has been developed for tissue engineering applications to produce scaffolds with well-defined multi-scale microstructural features and tailorable mechanical properties. In this study, in situ timeresolved synchrotron diffraction was employed to probe extrusion-based 3D printing of polycaprolactone (PCL) filaments. Time-resolved X-ray diffraction measurements revealed the progress of overall crystalline structural evolution of PCL during 3D printing. Particularly, in situ experimental observations provide strong evidence for the development of strong directionality of PCL crystals during the extrusion driven process. Results also show the evidence for the realization of anisotropic structural features through the melt extrusion-based 3D printing which is a key development towards mimicking the anisotropic properties and hierarchical structures of biological materials in nature, such as human tissues.
Polymers, 2022
The most common three-dimensional (3D) printing method is material extrusion, where a pre-made filament is deposited layer-by-layer. In recent years, low-cost polycaprolactone (PCL) material has increasingly been used in 3D printing, exhibiting a sufficiently high quality for consideration in cranio-maxillofacial reconstructions. To increase osteoconductivity, prefabricated filaments for bone repair based on PCL can be supplemented with hydroxyapatite (HA). However, few reports on PCL/HA composite filaments for material extrusion applications have been documented. In this study, solvent-free fabrication for PCL/HA composite filaments (HA 0%, 5%, 10%, 15%, 20%, and 25% weight/weight PCL) was addressed, and parameters for scaffold fabrication in a desktop 3D printer were confirmed. Filaments and scaffold fabrication temperatures rose with increased HA content. The pore size and porosity of the six groups’ scaffolds were similar to each other, and all had highly interconnected structur...
Natural and Synthetic Polymer Fillers for Applications in 3D Printing—FDM Technology Area
Solids
This publication summarises the current state of knowledge and technology on the possibilities and limitations of using mineral and synthetic fillers in the field of 3D printing of thermoplastics. FDM technology can be perceived as a miniaturised variation of conventional extrusion processing (a microextrusion process). However, scaling the process down has an undoubtful drawback of significantly reducing the extrudate diameter (often by a factor of ≈20–30). Therefore, the results produced under conventional extrusion processing cannot be simply translated to processes run with the application of FDM technology. With that in mind, discussing the latest findings in composite materials preparation and application in FDM 3D printing was necessary.