A natural biomineral for enhancing the biomineralization and cell response of 3D printed polylactic acid bone scaffolds

Incorporation of forsterite nanoparticles in a 3D printed polylactic acid/polyvinylpyrrolidone scaffold for bone tissue regeneration applications

Three-dimensional (3D) printing has facilitated the fabrication of customized scaffolds for the repair of complex bone defects. In this study, 3D-printed scaffolds composed of a mixture of polylactic acid-polyvinylpyrrolidone (PLA-PVP) incorporating different amounts of forsterite (F; Mg2SiO4) nanoparticles were fabricated using fused deposition modeling (FDM) technique. The incorporation of PVP and F nanoparticles into the PLA scaffold significantly decreased the water drop contact angle. The mechanical properties of the PLA-PVP scaffold were enhanced with the addition of 10 % F nanoparticles, as the compressive yield strength increased from 10.8 to 16.0 MPa and the elastic modulus from 83.52 to 108.41 MPa. However, the addition of F nanoparticles increased the degradation rate of the PLA-PVP scaffold over 8 weeks. Importantly, the addition of 10 % F nanoparticles into the PLA-PVP scaffold improved bioactivity and formation of apatite deposits on the scaffold after 4 weeks of immersion in simulated body fluid. Moreover, the PLA-PVP/10F scaffold showed strong MG63 cell adhesion and proliferation, as well as promoting osteogenic differentiation of rat bone marrow mesenchymal stem cells. At last, these findings suggest the PLA-PVP/10F scaffold is a promising candidate for application in bone defect repair.

Mandibular bone defect healing using polylactic acid-nano-hydroxyapatite-gelatin scaffold loaded with hesperidin and dental pulp stem cells in rat

Addressing mandibular defects poses a significant challenge in maxillofacial surgery. Recent advancements have led to the development of various biomimetic composite scaffolds aimed at facilitating mandibular defect reconstruction. This study aimed to assess the regenerative potential of a novel composite scaffold consisting of polylactic acid (PLA), hydroxyapatite nanoparticles (n-HA), gelatin, hesperidin, and human dental pulp stem cells (DPSCs) in a rat model of mandibular bone defect. The PLA-HA-GLA composite was synthesized using solvent casting-leaching and freeze-drying methods and subsequently treated with 11 mg of hesperidin. The physicochemical properties of the PLA-HA-GLA and PLA-HA-GLA-HIS composites were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermal gravimetric analysis (TGA). Additionally, the mechanical properties and cytotoxicity of DPSCs were assessed. Subsequently, PLA-HA-GLA and PLA-HA-GLA-HIS scaffolds with or without DPSCs were implanted into mandibular bone defects in rats, followed by histopathological, histomorphometric, and cone-beam computed tomography (CBCT) evaluations after eight weeks. SEM analysis revealed the porous structure of the fabricated PLA-HA-GLA and PLA-HA-GLA-HIS composites without aggregation. FTIR and XRD analyses confirmed the presence of functional groups and elements associated with PLA, HA, GLA, and hesperidin in the composites. Although the PLA-HA-GLA-HIS composite exhibited good thermal stability, its mechanical properties decreased after the addition of hesperidin. The cell viability of DPSCs on the surface of the PLA-HA-GLA-HIS scaffolds was statistically significant compared to that of the control group. Furthermore, histopathological, histomorphometric, and radiological evaluations demonstrated that the implantation of the DPSC-loaded PLA-HA-GLA-HIS scaffold had a beneficial effect on bone tissue reconstruction in rats with mandibular defects. These findings highlight the potential of DPSC-loaded PLA-HA-GLA-HIS composite scaffolds for spongy bone tissue engineering and mandibular defect repair.

Chitosan microporous foam filled 3D printed polylactic acid-pearl macroporous scaffold: Dual-scale porous structure, biological and mechanical properties

A bone scaffold with well-designed porous structure and material composition is essential for bone regeneration as it supports various biological functions. In this study, a dual-scale porous polylactic acid-pearl/chitosan (PLA-P/CS) scaffold was developed by integrating 3D printing and conventional techniques. An interconnected macroporous PLA-P scaffold with pore sizes ranging from 680-800 μm was fabricated using FDM 3D printing. Additionally, a microporous CS foam with pore sizes of 10-200 μm was prepared via freeze-drying within the macropores of the 3D-printed scaffold. The microporous CS foam enhanced the scaffold's hydrophilicity while preserving its favorable mechanical properties. Moreover, the dual-scale porous structure demonstrated improved biomineralization, due to its larger specific surface area and increased nucleation sites, along with the electrostatic adsorption provided by the amino and hydroxyl functional groups of chitosan. Furthermore, cell culture experiments revealed the dual-scale porous structure, and the effects of CS enhanced the cellular response of BMSCs. More importantly, a 12-week in vivo study on rat skull defect repair demonstrated that the dual-scale porous PLA-P/CS scaffold exhibited enhanced bone formation. These findings suggest that designing a graded porous structure and optimizing material composition can effectively enhance biological responses, thereby facilitating bone regeneration.

A calcium sulfate hemihydrate self-setting interface reinforced polycaprolactone porous composite scaffold

The mechanical insufficiency and slow degradation of polycaprolactone (PCL) implants have attracted widespread attention among researchers. Herein, a PCL scaffold with self-setting properties containing calcium sulfate hemihydrate (CSH) was prepared using a triply periodic minimal surfaces (TPMS) design and selective laser sintering (SLS) technology. The results showed that the strength of the scaffold containing 10 wt% CSH was increased by 45.5% compared to the PCL one. More importantly, its strength can be further increased to 1.7 times that of the PCL scaffold after self-setting in water. Mechanism analysis suggests that mechanical strengthening can be attributed to the pinning effect through the newly grown columnar crystals embedded with PCL molecular chains. In addition, the degradation rate of the composite scaffold was approximately 6.8 times higher than that of the PCL one. The study believes that the increase in degradation rate is due to a dual effect, specifically the increase in permeability and the catalytic degradation of PCL in the acidic environment. Encouragingly, the composite scaffold showed a good ability to induce hydroxyapatite formation. Therefore, the self-setting mechanically enhanced composite scaffold is expected to have potential application prospects in bone defect repair.

Evaluation and optimization of physical, mechanical, and biological characteristics of 3D printed Whitlockite/calcium silicate composite scaffold for bone tissue regeneration using response surface methodology

Calcium phosphate-based bioscaffolds are used for bone tissue regeneration because of their physical and chemical resemblance to human bone. Calcium, phosphate, sodium, potassium, magnesium, and silicon are important components of human bone. The successful biomimicking of human bone characteristics involves incorporating all the human bone elements into the scaffold material. In this work, Mg-Whitlockite (WH) and Calcium Silicate (CS) were selected as matrix and reinforcement respectively, because of their desirable elemental composition and regenerative properties. The magnesium in WH increases mineralization in bone, and the silicon ions in CS support vascularization. The Mg-WH was synthesized using the wet chemical method, and powder characterization tests were performed. Response surface methodology (RSM) is used to design the experiments with a combination of material compositions, infill ratios (IFs), and sintering temperatures (STs). The WH/CS bioceramic composite is 3D printed in three different compositions: 100/0, 75/25, and 50/50 wt%, with IFs of 50%, 75%, and 100%. The physical and mechanical characterization study of printed samples is conducted and the result is optimized using RSM. ANOVA (Analysis of Variance) is used to establish the relationship between input parameters and responses. The optimized input parameters were the WH/CS composition of 50/50 wt%, IF of 50%, and ST of 1150 °C, which bring out the best possible combination of physical and mechanical characteristics. The RSM optimized response was a density of 2.27 g cm-3, porosity of 36.74%, wettability of 45.79%, shrinkage of 25.13%, compressive strength of 12 MPa, and compressive modulus of 208.49 MPa with 92% desirability. The biological characterization studies were conducted for the scaffold samples prepared with optimized input parameters. The biological studies confirmed the capabilities of the WH/CS composite scaffolds in bone regenerative applications.

Processing and properties of graphene-reinforced polylactic acid nanocomposites for bioelectronic and tissue regenerative functions

An in-situ polymer-solution-processing approach enables the efficient production of uniform graphene-reinforced polylactic acid (G-PLA) nanocomposites with notable physical and biomedical properties. The approach effectively enhances the interfacial bonding between graphene and PLA by creating graphene dangling bonds and defects during exfoliation. As a result, an 182 % increase in Young's modulus and an 85 % increase in tensile strength can be achieved in G-PLA. Only 0.5 wt% graphene addition can reduce the contact angle of the composite from 75.3 to 70.4 and reduce its oxygen permeability by 23 %. The improved hydrophilicity, hermeticity, and mechanical properties make G-PLA an excellent encapsulation material for implantable bioelectronics. Moreover, the composite surface attributes and cell behaviors at the material-tissue interface are investigated histologically through the culture of stem cells on as-synthesized G-PLA. G-PLA composites can significantly boost cell proliferation and regulate cell differentiation towards vascular endothelium, offering tissue regeneration at the surface of implants to recover the injured tissues. The degradation rate of G-PLA nanocomposite can also be regulated since the graphene slows down the autocatalytic chain splitting induced by the terminal carboxylic acid groups of PLA. Therefore, such G-PLA nanocomposites with physical and biomedical properties regulated by graphene loading enable the development of next-generation implantable electronic systems providing both sensing and tissue engineering functions for complicated applications such as implanted sensors monitoring the healing of fractured bones or intracranial pressure.

New trends of additive manufacturing using materials based-on natural fibers and minerals : A systematic review

Polymeric materials based on natural fibers and minerals are currently being researched and their development is still in its infancy but is expected to increase in the coming years (being nowadays a hot topic). Their main advantage is that they make it possible to use waste and by-products of agricultural, forestry, and mineral origin to generate materials for Additive Manufacturing. Since their use reduces the need for other synthetic polymers derived from petroleum and other non-natural fibers that generate a high environmental impact, this type of material is a sustainable, environmentally friendly, biodegradable solution that can be integrated into the value chain of certain industries and, finally, favors the circular economy. This study presents a bibliometric analysis, meta-analysis, and systematic literature review focusing on plant-based fibers and minerals in biocomposites from a holistic perspective. To learn about the potential of these new materials at an industrial level and to learn about the benefits they can have for society, the strengths, weaknesses, opportunities, and threats have been evaluated. The results strongly suggest that these materials will undergo intensive development in the upcoming years, with a substantial increase in their integration across industries.

Printed polylactic acid/akermanite composite scaffolds for bone tissue engineering; development and surface modification

The susceptibility of bone tissues to various factors such as ageing, accidents, and diseases has led to extensive tissue engineering research focusing on bone tissues. Hence, this research also aims to determine the optimal amount of Akermanite (AK) addition to the polylactic acid scaffold for bone tissue engineering applications, as well as the effects of surface modification on its properties. The Akermanite was synthesized using the sol-gel method. Then, composite scaffolds of polylactic acid, including 0, 10, 20, and 30 wt% AK, were printed via the fused deposition modelling (FDM) process. These scaffolds were labelled as PLA, 10 wt% AK, 20 wt% AK, and 30 wt% AK, respectively. The X-ray diffraction analysis confirmed the production of the AK high-purity phase. Cell viability tests on composite scaffolds confirmed non-toxicity, and cell adhesion improved with AK addition. Mechanical testing showed that the compressive strength of composite scaffolds increased by increasing the AK content of the composite. This study recommended the 20 wt% AK scaffold as the optimal composition for bone tissue engineering. The surface-modification of polylactic acid/AK composite scaffolds using sodium hydroxide showed that it can be suitable for advanced tissue structures and medical applications, contributing to advancements in tissue engineering and medical technology for improved bone treatments.

Nanostructured polymer composites for bone and tissue regeneration

Nanostructured polymer composites have gained significant attention in recent years for their remarkable potential in bone and tissue regeneration. Moreover, with the integration of 3D printing technology, these composites hold promise for use in personalized medicine, where patient-specific scaffolds can be tailored to enhance therapeutic outcomes. Therefore, this review article aims to provide a comprehensive overview of the latest advancements in the development and application of nanostructured polymeric composites within the field of tissue engineering and bone regeneration. Here, the potential of biopolymers, natural polymers, and 3D-printed polymers to craft biocompatible, non-toxic, and mechanically robust composites is discussed in brief. Further, the fabrication techniques for 3D scaffolds and various forms of nanocomposites, including nanoparticles, nanocapsules, nanofibers, nanogels, and micelles for bone and tissue regeneration, are listed. Also, particular emphasis is placed on the role of nano-scaffolds and in situ hydrogels in bone and tissue regeneration. Overall, this review provides a concise and authoritative summary of the current state-of-the-art in nanostructured polymer composites for regenerative medicine, highlighting future directions and potential clinical applications.

Alkaline etching assisted polydopamine coating for enhanced cell-material interactions on 3D printed polylactic acid scaffolds

The implant surface chemistry and topography are primary factors regulating the success and survival of bone scaffold. Surface modification is a promising alternative to enhance the biocompatibility and tissue response to augment the osteogenic functionalities of polyesters like PLA. The study employed the synergistic effect of alkaline hydrolysis and polydopamine (PDA) functionalization to enhance the cell-material interactions on 3D printed polylactic acid (PLA) scaffold. Comprehensive characterization of the modified PLA highlights the improvements in the physical, chemical and cell-material interactions upon two-step surface modification. The X-ray photoelectron spectroscopy (XPS) analysis substantiated enhanced PDA deposition with a ∼8.2% increase in surface N composition after surface etching due to homogeneous PDA deposition compared to the non-etched counterpart. The changes in surface chemistry and morphology upon dual surface modification complemented the human osteoblast (HOS) attachment and proliferation, with distinct cell morphology and spreading on PDA coated etched PLA (Et-PLAPDA) scaffolds. Moreover, substantial improvement in osteogenic differentiation of UMR-106 cells on etched PLA (Et-PLA) and Et-PLAPDA highlights the suitability of alkali etching-mediated PDA deposition to improve mineralization on PLA. Overall, the present work opens insights to modify scaffold surface composition, topography, hydrophilicity and roughness to regulate local cell adhesion to improve the osteogenic potential of PLA.

Functionalized BP@(Zn+Ag)/EPLA Nanofibrous Scaffolds Fabricated by Cryogenic 3D Printing for Bone Tissue Engineering

This study fabricates a functionalized scaffold by cryogenic three-dimensional (3D) printing using an aminated poly-L-lactic acid (EPLA) solution containing nanosilver/zinc-coated black phosphorus (BP@(Zn+Ag)) nanocomposites. The nanocomposites are prepared by a green method of in situ photodeposition of silver and zinc nanoparticles (AgNPs and ZnNPs) on BP nanosheets (BPNs) under visible light irradiation without any chemical reductant. Scanning electron microscope (SEM) and X-ray energy dispersive spectrometer (EDS) confirm the uniform distribution of BP@(Zn+Ag) nanoparticles in the EPLA nanofibrous matrix. The in vitro tests show that the fabricated BP@(Zn+Ag)/EPLA nanofibrous scaffold exhibits excellent antibacterial activity (over 96%) against E. coli and S. aureus, as well as enhanced cell viability and osteogenic activity to facilitate the growth and differentiation of osteoblasts. The in vivo rat calvarial defect model also demonstrates that the BP@(Zn+Ag)/EPLA nanofibrous scaffold promotes new bone tissue formation around the implant site. Therefore, the prepared multifunctional 3D printed BP@(Zn+Ag)/EPLA nanofibrous scaffold has great potential for bone tissue engineering (BTE) applications.

Efficient Bioactive Surface Coatings with Calcium Minerals: Step-Wise Biomimetic Transformation of Vaterite to Carbonated Apatite

Carbonated apatite (CAp), known as the main mineral that makes up human bone, can be utilized in conjunction with scaffolds to increase their bioactivity. Various methods (e.g., co-precipitation, hydrothermal, and biomimetic coatings) have been used to provide bioactivity by forming CAp on surfaces similar to bone minerals. Among them, the use of simulated body fluids (SBF) is the most popular biomimetic method for generating CAp, as it can provide a mimetic environment. However, coating methods using SBF require at least a week for CAp formation. The long time it takes to coat biomimetic scaffolds is a point of improvement in a field that requires rapid regeneration. Here, we report a step-wise biomimetic coating method to form CAp using calcium carbonate vaterite (CCV) as a precursor. We can manufacture CCV-transformed CAp (V-CAp) on the surface in 4 h at least by immersing CCV in a phosphate solution. The V-CAp deposited surface was analyzed using scanning electron microscopy (SEM) images according to the type of phosphate solutions to optimize the reaction conditions. X-ray diffraction (XRD) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) analysis validated the conversion of CCV to V-CAp on surfaces. In addition, the bioactivity of V-CAp coating was analyzed by the proliferation and differentiation of osteoblasts in vitro. V-CAp showed 2.3-folded higher cell proliferation and 1.4-fold higher ALP activity than the glass surface. The step-wise method of CCV-transformed CAp is a biocompatible method that allows the environment of bone regeneration and has the potential to confer bioactivity to biomaterial surfaces, such as imparting bioactivity to non-bioactive metal or scaffold surfaces within one day. It can rapidly form carbonated apatite, which can greatly improve time efficiency in research and industrial applications.

Biomimetic Scaffolds-A Novel Approach to Three Dimensional Cell Culture Techniques for Potential Implementation in Tissue Engineering

Biomimetic scaffolds imitate native tissue and can take a multidimensional form. They are biocompatible and can influence cellular metabolism, making them attractive bioengineering platforms. The use of biomimetic scaffolds adds complexity to traditional cell cultivation methods. The most commonly used technique involves cultivating cells on a flat surface in a two-dimensional format due to its simplicity. A three-dimensional (3D) format can provide a microenvironment for surrounding cells. There are two main techniques for obtaining 3D structures based on the presence of scaffolding. Scaffold-free techniques consist of spheroid technologies. Meanwhile, scaffold techniques contain organoids and all constructs that use various types of scaffolds, ranging from decellularized extracellular matrix (dECM) through hydrogels that are one of the most extensively studied forms of potential scaffolds for 3D culture up to 4D bioprinted biomaterials. 3D bioprinting is one of the most important techniques used to create biomimetic scaffolds. The versatility of this technique allows the use of many different types of inks, mainly hydrogels, as well as cells and inorganic substances. Increasing amounts of data provide evidence of vast potential of biomimetic scaffolds usage in tissue engineering and personalized medicine, with the main area of potential application being the regeneration of skin and musculoskeletal systems. Recent papers also indicate increasing amounts of in vivo tests of products based on biomimetic scaffolds, which further strengthen the importance of this branch of tissue engineering and emphasize the need for extensive research to provide safe for humansbiomimetic tissues and organs. In this review article, we provide a review of the recent advancements in the field of biomimetic scaffolds preceded by an overview of cell culture technologies that led to the development of biomimetic scaffold techniques as the most complex type of cell culture.

Cellular, Molecular and Clinical Aspects of Aortic Aneurysm-Vascular Physiology and Pathophysiology

A disturbance of the structure of the aortic wall results in the formation of aortic aneurysm, which is characterized by a significant bulge on the vessel surface that may have consequences, such as distention and finally rupture. Abdominal aortic aneurysm (AAA) is a major pathological condition because it affects approximately 8% of elderly men and 1.5% of elderly women. The pathogenesis of AAA involves multiple interlocking mechanisms, including inflammation, immune cell activation, protein degradation and cellular malalignments. The expression of inflammatory factors, such as cytokines and chemokines, induce the infiltration of inflammatory cells into the wall of the aorta, including macrophages, natural killer cells (NK cells) and T and B lymphocytes. Protein degradation occurs with a high expression not only of matrix metalloproteinases (MMPs) but also of neutrophil gelatinase-associated lipocalin (NGAL), interferon gamma (IFN-γ) and chymases. The loss of extracellular matrix (ECM) due to cell apoptosis and phenotype switching reduces tissue density and may contribute to AAA. It is important to consider the key mechanisms of initiating and promoting AAA to achieve better preventative and therapeutic outcomes.

Magnesium Hydroxide as a Versatile Nanofiller for 3D-Printed PLA Bone Scaffolds

Polylactic acid (PLA) has attracted much attention in bone tissue engineering due to its good biocompatibility and processability, but it still faces problems such as a slow degradation rate, acidic degradation product, weak biomineralization ability, and poor cell response, which limits its wider application in developing bone scaffolds. In this study, Mg(OH)2 nanoparticles were employed as a versatile nanofiller for developing PLA/Mg(OH)2 composite bone scaffolds using fused deposition modeling (FDM) 3D printing technology, and its mechanical, degradation, and biological properties were evaluated. The mechanical tests revealed that a 5 wt% addition of Mg(OH)2 improved the tensile and compressive strengths of the PLA scaffold by 20.50% and 63.97%, respectively. The soaking experiment in phosphate buffered solution (PBS) revealed that the alkaline degradation products of Mg(OH)2 neutralized the acidic degradation products of PLA, thus accelerating the degradation of PLA. The weight loss rate of the PLA/20Mg(OH)2 scaffold (15.40%) was significantly higher than that of PLA (0.15%) on day 28. Meanwhile, the composite scaffolds showed long-term Mg2+ release for more than 28 days. The simulated body fluid (SBF) immersion experiment indicated that Mg(OH)2 promoted the deposition of apatite and improved the biomineralization of PLA scaffolds. The cell culture of bone marrow mesenchymal stem cells (BMSCs) indicated that adding 5 wt% Mg(OH)2 effectively improved cell responses, including adhesion, proliferation, and osteogenic differentiation, due to the release of Mg2+. This study suggests that Mg(OH)2 can simultaneously address various issues related to polymer scaffolds, including degradation, mechanical properties, and cell interaction, having promising applications in tissue engineering.

A new composite fabricated from hydroxyapatite, gelatin-MgO microparticles, and compatibilized poly(butylene succinate) with osteogenic functionality

In this study, thermally processed recycled fish teeth (FT) and fish scales, magnesium oxide (MgO), and biobased polyesters were fabricated into new bioactive and environmentally friendly composites. The magnesium oxide was encapsulated into laboratory-made fish scale-derived gelatin to form gelatin-MgO microparticles. Hydroxyapatite (HA) and gelatin were obtained by heat-treating FTs and fish scales, respectively. Compatibilized poly(butylene succinate) (CPBS), i.e., poly(butylene succinate) (PBS) to which had been added acrylic acid-grafted PBS (PBS-g-AA) compatibilizer, was combined with HA/gelatin-MgO (GHA) to form CPBS/GHA composites. The structure and tensile properties of the composites were investigated. The CPBS/GHA composites improved the adhesion and proliferation of osteoblast cells. Osteoblast growth, osteoclast growth inhibition, and the antibacterial effect of CPBS/GHA composites were primarily due to the slow release of magnesium ions into the environment from the gelatin-MgO microparticles. Higher levels of calcium and phosphorus species were observed for various PBS/HA and CPBS/GHA composites immersed in simulated body fluid. Mineralization measurements indicated that calcium and phosphate ions precipitated in osteoblasts placed on PBS/HA and CPBS/GHA composites. The study successfully developed a new composite material containing 5 wt% gelatin/MgO (phr), CPBS/HA 10 wt% and 1.0 % gelatin/MgO (an optimum formula of MgO). This composite exhibited superior tensile strength, antibacterial effect, osteoclast growth enhancement, and osteoclast growth reduction. These results suggest that the composites may facilitate the formation of new bone formation in vivo. The CPBS/GHA composites displayed good bone tissue repair ability in engineering applications.