Fabrication and Characteristics of PCL Membranes Containing Strontium-Substituted Hydroxyapatite Nanofibers for Guided Bone Regeneration

Applications of Bioactive Strontium Compounds in Dentistry

Divalent cations have captured the interest of researchers in biomedical and dental fields due to their beneficial effects on bone formation. These metallic elements are similar to trace elements found in human bone. Strontium is a divalent cation commonly found in various biomaterials. Since strontium has a radius similar to calcium, it has been used to replace calcium in many calcium-containing biomaterials. Strontium has the ability to inhibit bone resorption and increase bone deposition, making it useful in the treatment of osteoporosis. Strontium has also been used as a radiopacifier in dentistry and has been incorporated into a variety of dental materials to improve their radiopacity. Furthermore, strontium has been shown to improve the antimicrobial and mechanical properties of dental materials, promote enamel remineralization, alleviate dentin hypersensitivity, and enhance dentin regeneration. The objective of this review is to provide a comprehensive review of the applications of strontium in dentistry.

Lysophosphatidic Acid/Polydopamine-Modified nHA Composite Scaffolds for Enhanced Osteogenesis via Upregulating the Wnt/Beta-Catenin Pathway

Guided bone regeneration (GBR) technology has been widely used for the regeneration of periodontal bone defects. However, the limited mechanical properties and bone regeneration potential of the currently available GBR membranes often limit their repair effectiveness. In this paper, serum-derived growth factor lysophosphatidic acid (LPA) nanoparticles and dopamine-decorative nanohydroxyapatite (pDA/nHA) particles were double-loaded into polylactic-glycolic acid/polycaprolactone (PLGA/PCL) scaffolds as an organic/inorganic biphase delivery system, namely, PP-pDA/nHA-LPA scaffolds. Physicochemical properties and osteogenic ability in vitro and in vivo were performed. Scanning electron microscopy and mechanical tests showed that the PP-pDA/nHA-LPA scaffolds had a 3D bionic scaffold structure with improved mechanical properties. In vitro cell experiments demonstrated that the PP-pDA/nHA-LPA scaffolds could significantly enhance the attachment, proliferation, osteogenic differentiation, and mineralization of MC3T3-E1 cells. In vivo, the PP-pDA/nHA-LPA scaffolds exhibited great cytocompatibility and cell recruitment ability in 2- and 4-week subcutaneous implantation experiments and significantly promoted bone regeneration in the periodontal defect scaffold implantation experiment. Moreover, LPA-loaded scaffolds were confirmed to enhance osteogenic activities by upregulating the expression of β-catenin and further activating the Wnt/β-catenin pathway. These results demonstrate that the biphase PP-pDA/nHA-LPA delivery system is a promising material for the GBR.

Barrier membranes for periodontal guided bone regeneration: a potential therapeutic strategy

Periodontal disease is one of the most common oral diseases with the highest incidence world-wide. In particular, the treatment of periodontal bone defects caused by periodontitis has attracted extensive attention. Guided bone regeneration (GBR) has been recognized as advanced treatment techniques for periodontal bone defects. GBR technique relies on the application of barrier membranes to protect the bone defects. The commonly used GBR membranes are resorbable and non-resorbable. Resorbable GBR membranes are divided into natural polymer resorbable membranes and synthetic polymer resorbable membranes. Each has its advantages and disadvantages. The current research focuses on exploring and improving its preparation and application. This review summarizes the recent literature on the application of GBR membranes to promote the regeneration of periodontal bone defects, elaborates on GBR development strategies, specific applications, and the progress of inducing periodontal bone regeneration to provide a theoretical basis and ideas for the future application of GBR membranes to promote the repair of periodontal bone defects.

Metal Ion-Doped Hydroxyapatite-Based Materials for Bone Defect Restoration

Hydroxyapatite (HA)-based materials are widely used in the bone defect restoration field due to their stable physical properties, good biocompatibility, and bone induction potential. To further improve their performance with extra functions such as antibacterial activity, various kinds of metal ion-doped HA-based materials have been proposed and synthesized. This paper offered a comprehensive review of metal ion-doped HA-based materials for bone defect restoration based on the introduction of the physicochemical characteristics of HA followed by the synthesis methods, properties, and applications of different kinds of metal ion (Ag+, Zn2+, Mg2+, Sr2+, Sm3+, and Ce3+)-doped HA-based materials. In addition, the underlying challenges for bone defect restoration using these materials and potential solutions were discussed.

Influence of mechanochemically fabricated nano-hardystonite reinforcement in polycaprolactone scaffold for potential use in bone tissue engineering: Synthesis and characterization

Bone tissue engineering (BTE) has gained significant attention for the regeneration of bone tissue, particularly for critical-size bone defects. The aim of this research was first to synthesize nanopowders of hardystonite (HT) through ball milling and then to manufacture composite scaffolds for BTE use out of polycaprolactone (PCL) containing 0, 3, 5, and 10 wt% HT by electrospinning method. The crystallite size of the synthesized HT nanopowders was 42.8 nm. including up to 5 wt% HT into PCL scaffolds resulted in significant improvements, such as a reduction in the fiber diameter from 186.457±15.74 to 150.021±21.99 nm, a decrease in porosity volume from 85.2±2.5 to 80.3±3.3 %, an improvement in the mechanical properties (ultimate tensile strength: 5.7±0.2 MPa, elongation: 47.5±3.5 %, tensile modulus: 32.7±0.9 MPa), an improvement in the hydrophilicity, and biodegradability. Notably, PCL/5%HT exhibited the maximum cell viability (194±14 %). Additionally, following a 4-week of submersion in simulated body fluid (SBF), the constructed PCL/HT composite scaffolds showed a remarkable capacity to stimulate the development of hydroxyapatite (HA), which increased significantly for the 5 wt% HT scaffolds. However, at 10 wt% HT, nanopowder agglomeration led to an increase in the fiber diameter and a decrease in the mechanical characteristics. Collectively, the PCL/5%HT composite scaffolds can therefore help with the regeneration of the critical-size bone defects and offer tremendous potential for BTE applications.

Preparation and Characterization of a Novel Tragacanth Gum/Chitosan/Sr-Nano-Hydroxyapatite Composite Membrane

It is a great challenge to obtain an ideal guided bone regeneration (GBR) membrane. In this study, tragacanth gum (GT) was introduced into a chitosan/nano-hydroxyapatite (CS/n-HA) system. The effects of different component ratios and strontium-doped nano-hydroxyapatite (Sr-HA) on the physical-chemical properties and degradation behavior of the CS/Sr-n-HA/GT ternary composite membrane were investigated using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle, electromechanical universal tester and in vitro soaking in simulated body fluid (SBF). The results showed that CS could be ionically crosslinked with GT through electrostatic interaction, and Sr-n-HA was loaded via hydrogen bond, which endowed the GT/CS/n-HA composite membrane with good tensile strength and hydrophilicity. In addition, the results of immersion in SBF in vitro showed that CS/n-HA/GT composite membranes had different degradation rates and good apatite deposition by investigating the changes in pH value, weight loss, water absorption ratio, SEM morphology observation and tensile strength reduction. All results revealed that the CS/Sr-n-HA/GT (6:2:2) ternary composite membrane possessed the strongest ionic crosslinking of GT and CS, which was expected to obtain more satisfactory GBR membranes, and this study will provide new applications of GT in the field of biomedical membranes.

Synthesis and Biocompatibility Evaluation of PCL Electrospun Membranes Coated with MTA/HA for Potential Application in Dental Pulp Capping

This study aimed to develop polycaprolactone (PCL) electrospun membranes coated with mineral trioxide aggregate/hydroxyapatite (MTA/HA) as a potential material for dental pulp capping. Initially, the PCL membrane was prepared by an electrospinning process, which was further surface coated with MTA (labeled as PCLMTA) and HA (labeled as PCLHA). The physico-chemical characterization of the fabricated membranes was carried out using field emission scanning electron microscopy (FE-SEM)/Energy dispersive X-ray (EDX), X-ray diffraction (XRD), Raman spectroscopy, and contact angle analysis. The biocompatibility of the human dental pulp stem cells (hDPSCs) on the fabricated membranes was checked by XTT assay, and the hDPSCs adhesion and spreading were assessed by FE-SEM and confocal microscopy. The wound healing ability of hDPSCs in response to different electrospun membrane extracts was examined by scratch assay. The surface morphology analysis of the membranes by FE-SEM demonstrated a uniform nanofibrous texture with an average fiber diameter of 594 ± 124 nm for PCL, 517 ± 159 nm for PCLHA, and 490 ± 162 nm for PCLMTA. The elemental analysis of the PCLHA membrane indicated the presence of calcium and phosphorous elements related to HA, whereas the PCLMTA membrane showed the presence of calcium and silicate, related to MTA. The presence of MTA and HA in the PCL membranes was also confirmed by Raman spectroscopy. The water contact analysis demonstrated the hydrophobic nature of the membranes. The results indicated that PCL, PCLHA, and PCLMTA membranes were biocompatible, while PCLMTA exhibited better cell adhesion, spreading, and migration.

3D Polycaprolactone/Gelatin-Oriented Electrospun Scaffolds Promote Periodontal Regeneration

Periodontitis is a worldwide chronic inflammatory disease, where surgical treatment still shows an uncertain prognosis. To break through the dilemma of periodontal treatment, we fabricated a three-dimensional (3D) multilayered scaffold by stacking and fixing electrospun polycaprolactone/gelatin (PCL/Gel) fibrous membranes. The biomaterial displayed good hydrophilic and mechanical properties. Besides, we found human periodontal ligament stem cell (hPDLSC) adhesion and proliferation on it. The following scanning electron microscopy (SEM) and cytoskeleton staining results proved the guiding function of fibers to hPDLSCs. Then, we further analyzed periodontal regeneration-related proteins and mRNA expression between groups. In vivo results in a rat acute periodontal defect model confirmed that the topographic cues of materials could directly guide cellular orientation and might provide the prerequisite for further differentiation. In the aligned scaffold group, besides new bone regeneration, we also observed that angular concentrated fiber regeneration in the root surface of the defect is similar to the normal periodontal tissue. To sum up, we have constructed electrospun membrane-based 3D biological scaffolds, which provided a new treatment strategy for patients undergoing periodontal surgery.

In vitro and in vivo biocompatibility of decellularized cellulose scaffolds functionalized with chitosan and platelet rich plasma for tissue engineering applications

This study describes the fabrication of cellulose scaffold (CS) and cellulose-chitosan (CS/CHI) scaffolds from the immature endosperm of Borassus flabellifer (Linn.) (BF) loaded with platelet rich plasma (PRP). Thus, developed scaffolds were evaluated for their physicochemical and mechanical behavior, growth factor release and biological performance. Additionally, in vivo response was assessed in a sub cutaneous rat model to study vascularization, host inflammatory response and macrophage polarization. The results of this study demonstrated that CS and CS/CHI scaffolds with PRP demonstrated favorable physiochemical and morphogical properties. The scaffold groups CS-PRP and CS/CHI-PRP were able to release growth factors in a well sustained manner under physiological conditions. The presence of PRP in cellulosic scaffolds did show significant differences in their behavior when investigated under in vitro studies, where the release of diverse cytokines improved the cellular proliferation and differentiation of osteoblasts. Finally, the PRP enriched scaffolds when studied under in vivo conditions showed increased angiogenesis and re-epithelialization with adequate collagen deposition and tissue remodeling. Our results suggest that besides the conventional carrier systems, this new-generation of plant-based cellulosic scaffolds with/without any modification can serve as a suitable carrier for PRP encapsulation and release, which can be used in numerous tissue regenerative therapies.

Rapid Flow Synthesis of a Biomimetic Carbonate Apatite as an Effective Drug Carrier

A facile synthesis of apatite nanocrystals analogous to bioapatites with increased biocompatibility and biodegradability can remedy the shortcomings of the widely applied synthetic hydroxyapatite (HAp) for bone defect treatment. Here, we propose an expeditious synthesis method to develop a biomimetic B-type carbonate apatite (CAp) with a simple capillary microfluidic device at room temperature. The process not only eliminates fluctuations with the addition of carbonate but also produces safe CAp drug carriers through simultaneous alendronate incorporation to the CAp structure. CAp displayed superior mineralization on osteoblast-like MG-63 cells when compared with HAp and HAp drug carriers that were produced using identical methods. Furthermore, alendronate-incorporated CAp drug carriers potentially displayed higher cancer cell suppression when applied to breast cancer cells attached to the bone tissue model, which signifies enhanced cancer metastasis to bone suppression due to the likelihood of increased alendronate release of CAp owing to its faster dissolution. Overall, our results may provide promising opportunities for enhanced clinical CAp application for bone defect treatment, particularly for bone loss and cancer to bone metastasis.

Advances in Barrier Membranes for Guided Bone Regeneration Techniques

Guided bone regeneration (GBR) is a widely used technique for alveolar bone augmentation. Among all the principal elements, barrier membrane is recognized as the key to the success of GBR. Ideal barrier membrane should have satisfactory biological and mechanical properties. According to their composition, barrier membranes can be divided into polymer membranes and non-polymer membranes. Polymer barrier membranes have become a research hotspot not only because they can control the physical and chemical characteristics of the membranes by regulating the synthesis conditions but also because their prices are relatively low. Still now the bone augment effect of barrier membrane used in clinical practice is more dependent on the body’s own growth potential and the osteogenic effect is difficult to predict. Therefore, scholars have carried out many researches to explore new barrier membranes in order to improve the success rate of bone enhancement. The aim of this study is to collect and compare recent studies on optimizing barrier membranes. The characteristics and research progress of different types of barrier membranes were also discussed in detail.

Surface Modification of Decellularized Natural Cellulose Scaffolds with Organosilanes for Bone Tissue Regeneration

The utility of plant tissues as scaffolding materials has been gaining significant interest in recent years owing to their unique material characteristics that are ideal for tissue regeneration. In this study, the degradation and biocompatibility of natural cellulosic scaffolds derived from Borassus flabellifer (Linn.) (BF) immature endosperm was improved by chemical oxidation and surface functionalization processes. Briefly, thus obtained cellulosic scaffolds were sequentially processed via a detergent exchange decellularization process followed by sodium periodate mediated oxidation and organosilane-based surface modification using amino (NH₂)-terminated 3-aminopropyltriethoxysilane (APTES) and methyl (CH₃)-terminated octadecyltrichlorosilane (OTS). Post oxidation and surface functionalization, the scaffolds showed improved physiochemical, morphological, and mechanical properties. Especially, the swelling capacity, total porosity, surface area, degradation kinetics, and mechanical behavior of scaffold were significantly higher in modified scaffold groups. The biocompatibility analysis demonstrated excellent cellular adhesion, proliferation and differentiation of osteoblasts with an evident upregulation of mineralization. Subcutaneous implantation of these scaffolds in a rat model demonstrated active angiogenesis, enhanced degradation, and excellent biocompatibility with concomitant deposition of a collagen matrix. Taken together, the native cellulosic scaffolds post chemical oxidation and surface functionalization can exclusively integrate the potential properties of native soft tissue with ameliorated in vitro and in vivo support in bone tissue engineering for nonloading bearing applications.

Carboxymethyl carrageenan immobilized on 3D-printed polycaprolactone scaffold for the adsorption of calcium phosphate/strontium phosphate adapted to bone regeneration

Three dimensional (3D) substrates based on natural and synthetic polymers enhance the osteogenic and mechanical properties of the bone tissue engineering scaffolds. Here, a novel bioactive composite scaffolds from polycaprolactone /kappa-carrageenan were developed for bone regeneration applications. 3D PCL scaffolds were fabricated by 3D printing method followed by coating with carboxymethyl kappa-carrageenan. This organic film was used to create calcium and strontium phosphate layers via a modified alternate soaking process in CaCl ₂ /SrCl ₂ and Na₂HPO₄ solutions in which calcium ions were replaced by strontium, with different amounts of strontium in the solutions. Various characterization techniques were executed to analyze the effects of strontium ion on the scaffold properties. The morphological results demonstrated the highly porous with interconnected pores and uniform pore sizes scaffolds. It was indicated that the highest crystallinity and compressive strength were obtained when 100% CaCl₂ was replaced by SrCl₂ in the solution (P-C-Sr). Incorporation of Sr onto the structure increased the degradation rate of the scaffolds. Mesenchymal stem cells (MSCs) culture on the scaffolds showed that Sr effectively improved attachment and viability of the MSCs and accelerated osteogenic differentiation as revealed by Alkaline phosphatase activity, calcium content and Real Time-Reverse transcription polymerase chain reaction assays.

Advances in Modification Methods Based on Biodegradable Membranes in Guided Bone/Tissue Regeneration: A Review

Guided tissue/bone regeneration (GTR/GBR) is commonly applied in dentistry to aid in the regeneration of bone/tissue at a defective location, where the assistive material eventually degrades to be substituted with newly produced tissue. Membranes separate the rapidly propagating soft tissue from the slow-growing bone tissue for optimal tissue regeneration results. A broad membrane exposure area, biocompatibility, hardness, ductility, cell occlusion, membrane void ratio, tissue integration, and clinical manageability are essential functional properties of a GTR/GBR membrane, although no single modern membrane conforms to all of the necessary characteristics. This review considers ongoing bone/tissue regeneration engineering research and the GTR/GBR materials described in this review fulfill all of the basic ISO requirements for human use, as determined through risk analysis and rigorous testing. Novel modified materials are in the early stages of development and could be classified as synthetic polymer membranes, biological extraction synthetic polymer membranes, or metal membranes. Cell attachment, proliferation, and subsequent tissue development are influenced by the physical features of GTR/GBR membrane materials, including pore size, porosity, and mechanical strength. According to the latest advances, key attributes of nanofillers introduced into a polymer matrix include suitable surface area, better mechanical capacity, and stability, which enhances cell adhesion, proliferation, and differentiation. Therefore, it is essential to construct a bionic membrane that satisfies the requirements for the mechanical barrier, the degradation rate, osteogenesis, and clinical operability.

Biomimetic three-layered membranes comprising (poly)-ε-caprolactone, collagen and mineralized collagen for guided bone regeneration

The distinct structural properties and osteogenic capacity are important aspects to be taken into account when developing guided bone regeneration membranes. Herein, inspired by the structure and function of natural periosteum, we designed and fabricated using electrospinning a fibrous membrane comprising (poly)--ε-caprolactone (PCL), collagen-I (Col) and mineralized Col (MC). The three-layer membranes, having PCL as the outer layer, PCL/Col as the middle layer and PCL/Col/MC in different ratios (5/2.5/2.5 (PCM-1); 3.3/3.3/3.3 (PCM-2); 4/4/4 (PCM-3) (%, w/w/w)) as the inner layer, were produced. The physiochemical properties of the different layers were investigated and a good integration between the layers was observed. The three-layered membranes showed tensile properties in the range of those of natural periosteum. Moreover, the membranes exhibited excellent water absorption capability without changes of the thickness. In vitro experiments showed that the inner layer of the membranes supported attachment, proliferation, ingrowth and osteogenic differentiation of human bone marrow-derived stromal cells. In particular cells cultured on PCM-2 exhibited a significantly higher expression of osteogenesis-related proteins. The three-layered membranes successfully supported new bone formation inside a critical-size cranial defect in rats, with PCM-3 being the most efficient. The membranes developed here are promising candidates for guided bone regeneration applications.

The Effect of Strontium-Substituted Hydroxyapatite Nanofibrous Matrix on Osteoblast Proliferation and Differentiation

Natural bone tissue consists primarily of bioapatite and collagen. Synthetic hydroxyapatite (HA) possesses good biocompatibility, bioactivity, and osteoconductivity due to its chemical and biological similarity to bioapatite. Hence, HA has been widely used as a bone graft, cell carrier and drug/gene delivery carrier. Moreover, strontium-substituted hydroxyapatite (SrHA) can enhance osteogenic differentiation and inhibit adipogenic differentiation of mesenchymal stem cells. Hence, SrHA has the potential to be used as a bone graft for bone regeneration. It is widely accepted that cell adhesion and most cellular activities are sensitive to the topography and molecular composition of the matrix. Electrospun polymer or polymer-bioceramic composite nanofibers have been demonstrated to enhance osteoblast differentiation. However, to date, no studies have investigated the effect of nanofibrous bioceramic matrices on osteoblasts. In this study, hydroxyapatite nanofiber (HANF) and strontium-substituted hydroxyapatite nanofiber (SrHANF) matrices were fabricated by electrospinning. The effect of the HANF components on MG63 osteoblast-like cells was evaluated by cell morphology, proliferation, alkaline phosphatase activity (ALP) and gene expression levels of RUNX2, COLI, OCN and BSP. The results showed that MG63 osteoblast-like cells exhibited higher ALP and gene expression levels of RUNX2, COLI, BSP and OCN on the SrHANF matrix than the HANF matrix. Hence, SrHANFs could enhance the differentiation of MG63 osteoblast-like cells.

An aqueous-based process to bioactivate poly(ε-caprolactone)/mesoporous bioglass composite surfaces by prebiotic chemistry-inspired polymer coatings for biomedical applications

Despite the wide use of aliphatic polyesters, such as poly(L-lactic acid) (PLLA) and poly(ε-caprolactone) (PCL), for many biomedical applications, these materials are limited due to their hydrophobic properties and lack of functional groups to bond with ligands to enhance the cell reorganization. Recently, a composite consisting of bioglass and PCL was demonstrated to enhance the mechanical strength and to improve the degradation rate. Although numerous approaches have been developed to improve the wettability of aliphatic polyesters to create a favorable interface with cells, only few surface modification methods can be independently applied to surfaces with different material. In this work, mesoporous bioglass (MBG) nanoparticles embedded in PCL films were modified by the polymerization of aminomalonitrile (AMN) with 3,4,5-trihydroxybenzaldehyde (THBA). The copolymer layer was further utilized as a mediator to conjugate chitosan and evaluate the antibacterial efficacy. Our results show that the hydrophilicity of the composite membranes significantly improved after treatment. In addition, after immersion in simulated body fluid (SBF) for 14 days, hydroxyapatite formation was only observed on the treated membranes. This result demonstrates that the surface treatment did not alter the MBG bioactivity. Moreover, the cell culture results reveal that the extension level of cells and expression of alkaline phosphatase activity (ALP) of osteoblast-like (MG63) cells were higher on treated composite films compared to untreated ones. The results imply that the treatment procedure can be simultaneously and homogeneously applied to the organic/inorganic composites. In addition, Staphylococcus aureus adhesion on AMN-co-THBA and chitosan/ AMN-co-THBA was significantly lower than untreated PCL. Moreover, the percentage of dead bacteria was highest on the chitosan/ AMN-co-THBA membranes. These results indicate that the AMN-co-THBA modification can be used in composite materials and complex constructs, and it provides a potential method to create versatile surface properties for biomedical applications.

Additively manufactured BaTiO3 composite scaffolds: A novel strategy for load bearing bone tissue engineering applications

Piezoelectric ceramics, such as BaTiO₃, have gained considerable attention in bone tissue engineering applications thanks to their biocompatibility, ability to sustain a charged surface as well as improve bone cells' adhesion and proliferation. However, the poor processability and brittleness of these materials hinder the fabrication of three-dimensional scaffolds for load bearing tissue engineering applications. For the first time, this study focused on the fabrication and characterisation of BaTiO₃ composite scaffolds by using a multi-material 3D printing technology. Polycaprolactone (PCL) was selected and used as dispersion phase for its low melting point, easy processability and wide adoption in bone tissue engineering. The proposed single-step extrusion-based strategy enabled a faster and solvent-free process, where raw materials in powder forms were mechanically mixed and subsequently fed into the 3D printing system for further processing. PCL, PCL/hydroxyapatite and PCL/BaTiO₃ composite scaffolds were successfully produced with high level of consistency and an inner architecture made of seamlessly integrated layers. The inclusion of BaTiO₃ ceramic particles (10% wt.) significantly improved the mechanical performance of the scaffolds (54 ± 0.5 MPa) compared to PCL/hydroxyapatite scaffolds (40.4 ± 0.1 MPa); moreover, the presence of BaTiO₃ increased the dielectric permittivity over the entire frequency spectrum and tested temperatures. Human osteoblasts Saos-2 were seeded on scaffolds and cellular adhesion, proliferation, differentiation and deposition of bone-like extracellular matrix were evaluated. All tested scaffolds (PCL, PCL/hydroxyapatite and PCL/BaTiO₃) supported cell growth and viability, preserving the characteristic cellular osteoblastic phenotype morphology, with PCL/BaTiO₃ composite scaffolds exhibiting higher mineralisation (ALP activity) and deposited bone-like extracellular matrix (osteocalcin and collagen I). The single-step multi-material additive manufacturing technology used for the fabrication of electroactive PCL/BaTiO₃ composite scaffolds holds great promise for sustainability (reduced material waste and manufacturing costs) and it importantly suggests PCL/BaTiO₃ scaffolds as promising candidates for load bearing bone tissue engineering applications to solve unmet clinical needs.

β-Tricalcium phosphate contained beaded-fiber scaffolds characterized by high early osteoinductive activity for vascularized bone regeneration

The calcium phosphate component and surface topology of a scaffold are considered the two main factors that influence osteogenic differentiation. This research reports a one-step but effective scaffold preparation method that can regulate the morphology of nanofibers and control the distribution and release behavior of calcium phosphate nanoparticles (CaPs). Two beaded-on-string CaPs-loaded electrospun scaffolds (PT7.5 and PT4.5) with composite microstructures of microbeads and nanofibers were fabricated by adjusting the concentration of the electrospinning solution. The presence of the composite microstructure was conducive to the surface exposure and sustained release of bioactive components, which in turn could significantly promote the biomineralization and protein adsorption of the scaffold. A study of the human umbilical vein endothelial cells (HUVECs) and rat-bone marrow-derived mesenchymal stem cells (rBMSCs) revealed that cells cultured on scaffolds with composite microstructures (especially PT4.5) could enhance tube formation of the HUVECs and osteogenic differentiation of rBMSCs. The PT4.5 with significantly different microbead and nanofiber sizes presented the high potential to improve the early osteoinductive activity and angiogenesis of the CaPs-loaded electrospun scaffold and expand its advantage in bone regeneration.

Testing active membranes for bone regeneration: A review

OBJECTIVES

Maxillofacial bone defects are the main hindering conditions for traditional dental implant strategies. Guided Bone Regeneration (GBR) is used to handle this situation. The principle of GBR is to use a membrane to prevent the colonization of soft tissue cells of the bone defect and favors the migration of osteogenic linages. Current membranes do not completely fulfill the requirements that an optimal membrane should have, sometimes resulting in non-predictable results. Thus, the need to develop an ideal membrane to perform this duty is clear. Recent developments in bio-manufacturing are driving innovations in membranes technology permitting the active participation of the membrane in the healing and regenerative process trough native tissue mimicking, drug-delivery and cells interaction, away from being a passive barrier. New membranes features need specific evaluation techniques, beyond the International Standard for membrane materials (last reviewed in 2004), being this the rationale for the present review. Nanotechnology application has completely shifted the way of analyzing structural characterization. New progresses on osteoimmmunomodulation have also switched the understanding of cells-membranes interaction.

DATA AND SOURCES

To propose an updated protocol for GBR membranes evaluation, critical reading of the relevant published literature was carried out after a MEDLINE/PubMed database search.

CONCLUSIONS

The main findings are that a potential active membrane should be assessed in its nanostructure, physicochemical and nanomechanical properties, bioactivity and antibacterial, osteoblasts proliferation, differentiation and mineralization. Immunomodulation testing for macrophages recruitment and M2 phenotype promotion in osteoblasts co-culture has to be achieved to completely analyze membranes/tissue interactions.

Towards 3D Multi-Layer Scaffolds for Periodontal Tissue Engineering Applications: Addressing Manufacturing and Architectural Challenges

Reduced periodontal support, deriving from chronic inflammatory conditions, such as periodontitis, is one of the main causes of tooth loss. The use of dental implants for the replacement of missing teeth has attracted growing interest as a standard procedure in clinical practice. However, adequate bone volume and soft tissue augmentation at the site of the implant are important prerequisites for successful implant positioning as well as proper functional and aesthetic reconstruction of patients. Three-dimensional (3D) scaffolds have greatly contributed to solve most of the challenges that traditional solutions (i.e., autografts, allografts and xenografts) posed. Nevertheless, mimicking the complex architecture and functionality of the periodontal tissue represents still a great challenge. In this study, a porous poly(ε-caprolactone) (PCL) and Sr-doped nano hydroxyapatite (Sr-nHA) with a multi-layer structure was produced via a single-step additive manufacturing (AM) process, as a potential strategy for hard periodontal tissue regeneration. Physicochemical characterization was conducted in order to evaluate the overall scaffold architecture, topography, as well as porosity with respect to the original CAD model. Furthermore, compressive tests were performed to assess the mechanical properties of the resulting multi-layer structure. Finally, in vitro biological performance, in terms of biocompatibility and osteogenic potential, was evaluated by using human osteosarcoma cells. The manufacturing route used in this work revealed a highly versatile method to fabricate 3D multi-layer scaffolds with porosity levels as well as mechanical properties within the range of dentoalveolar bone tissue. Moreover, the single step process allowed the achievement of an excellent integrity among the different layers of the scaffold. In vitro tests suggested the promising role of the ceramic phase within the polymeric matrix towards bone mineralization processes. Overall, the results of this study demonstrate that the approach undertaken may serve as a platform for future advances in 3D multi-layer and patient-specific strategies that may better address complex periodontal tissue defects.

Durability of LDPE/UHMWPE Composites under Accelerated Degradation

This study presents a detailed analysis of thermal and radiation resistances of low density polyethylene (LDPE)/ultra-high molecular weight polyethylene (UHMWPE) blends containing hydroxyapatite as functional filler and rosemary acting as antioxidant against oxidative degradation. Three main procedures, chemiluminescence (CL), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC), were applied for the determination of the degree of degradation when these materials are subjected to heat and radiation action. The crystallinity was also assessed for the characterization of diffusion peculiarities. The contributions of the mixing components are discussed based on their oxidation strength. The activation energies required for the oxidative degradation of the studied formulations were calculated.