The pro-angiogenic properties of multi-functional bioactive glass composite scaffolds

Biomedical applications of natural-based polymers combined with bioactive glass nanoparticles

The combination of natural polymers with nanoparticles allowed the development of functional bioinspired constructs. This review discusses the composition, design, and applications of bioinspired nanocomposite constructs based on bioactive glass nanoparticles (BGNPs).

Extracellular Matrix-Coated Composite Scaffolds Promote Mesenchymal Stem Cell Persistence and Osteogenesis

Composite scaffolds of bioactive glass and poly(lactide-co-glycolide) provide advantages over homogeneous scaffolds, yet their therapeutic potential can be improved by strategies that promote adhesion and present instructive cues to associated cells. Mesenchymal stem cell (MSC)-secreted extracellular matrix (ECM) enhances survival and function of associated cells. To synergize the benefits of an instructive ECM with composite scaffolds, we tested the capacity of ECM-coated composite scaffolds to promote cell persistence and resultant osteogenesis. Human MSCs cultured on ECM-coated scaffolds exhibited increased metabolic activity and decreased apoptosis compared to uncoated scaffolds. Additionally, MSCs on ECM-coated substrates in short-term culture secreted more proangiogenic factors while maintaining markers of osteogenic differentiation. Upon implantation, we detected improved survival of MSCs on ECM-coated scaffolds over 3 weeks. Histological evaluation revealed enhanced cellularization and osteogenic differentiation in ECM-coated scaffolds compared to controls. These findings demonstrate the promise of blending synthetic and natural ECMs and their potential in tissue regeneration.

Biodegradable ceramic-polymer composites for biomedical applications: A review

The present work focuses on the state-of-the-art of biodegradable ceramic-polymer composites with particular emphasis on influence of various types of ceramic fillers on properties of the composites. First, the general needs to create composite materials for medical applications are briefly introduced. Second, various types of polymeric materials used as matrices of ceramic-containing composites and their properties are reviewed. Third, silica nanocomposites and their material as well as biological characteristics are presented. Fourth, different types of glass fillers including silicate, borate and phosphate glasses and their effect on a number of properties of the composites are described. Fifth, wollastonite as a composite modifier and its effect on composite characteristics are discussed. Sixth, composites containing calcium phosphate ceramics, namely hydroxyapatite, tricalcium phosphate and biphasic calcium phosphate are presented. Finally, general possibilities for control of properties of composite materials are highlighted.

Bioactive and Antibacterial Glass Powders Doped with Copper by Ion-Exchange in Aqueous Solutions

In this work, two bioactive glass powders (SBA2 and SBA3) were doped with Cu by means of the ion-exchange technique in aqueous solution. SBA2 glass was subjected to the ion-exchange process by using different Cu salts (copper(II) nitrate, chloride, acetate, and sulphate) and concentrations. Structural (X-ray diffraction-XRD), morphological (Scanning Electron Microscopy-SEM), and compositional (Energy Dispersion Spectrometry-EDS) analyses evidenced the formation of crystalline phases for glasses ion-exchanged in copper(II) nitrate and chloride solutions; while the ion-exchange in copper(II) acetate solutions lead to the incorporation of higher Cu amount than the ion-exchange in copper(II) sulphate solutions. For this reason, the antibacterial test (inhibition halo towards S. aureus) was performed on SBA2 powders ion-exchanged in copper(II) acetate solutions and evidenced a limited antibacterial effect. A second glass composition (SBA3) was developed to allow a greater incorporation of Cu in the glass surface; SBA3 powders were ion-exchanged in copper(II) acetate solutions (0.01 M and 0.05 M). Cu-doped SBA3 powders showed an amorphous structure; morphological analysis evidenced a rougher surface for Cu-doped powders in comparison to the undoped glass. EDS and X-ray photoelectron spectroscopy (XPS) confirmed the Cu introduction as Cu(II) ions. Bioactivity test in simulated body fluid (SBF) showed that Cu introduction did not alter the bioactive behaviour of the glass. Finally, inhibition halo test towards S. aureus evidenced a good antimicrobial effect for glass powders ion-exchanged in copper(II) acetate solutions 0.05 M.

Europium-Containing Mesoporous Bioactive Glass Scaffolds for Stimulating in Vitro and in Vivo Osteogenesis

Bone tissue engineering offers a possible strategy for regenerating large bone defects, in which how to design beneficial scaffolds for accelerating bone formation remains significantly challenging. Europium, as an important rare earth element, has been used as a solid-state lighting material. However, there are few reports on whether Eu can be used for labeling bone tissue engineering scaffolds, and its biological effect on bone cells and bone tissue regeneration is unknown. In this study, we incorporated Eu into mesoporous bioactive glass (Eu-MBG) scaffolds by an in situ cotemplate method to achieve a bifunctional biomaterial with biolabeling and bone regeneration. The prepared Eu-MBG scaffolds have highly interconnective large pores (300-500 μm), a high specific surface area (140-290 m(2)/g), and well-ordered mesopores (5 nm) as well as uniformly distributed Eu. The incorporation of 2-5 mol % Eu into MBG scaffolds gives them a luminescent property. The in vitro degradation of Eu-MBG scaffolds has a functional effect on the change of the luminescence intensity. In addition, Eu-MBG can be used for labeling bone marrow stromal cells (BMSCs) in vitro and still presents a distinct luminescence signal in deep bone tissues in vivo to label new bone tissue via release of Eu ions. Furthermore, the incorporation of different contents of Eu (1, 2, and 5 mol %) into MBG scaffolds significantly enhances the osteogenic gene expression of BMSCs in the scaffolds. The Eu- and Si-containing ionic products released from Eu-MBG scaffolds distinctly promote the osteogenic differentiation of BMSCs. Critically sized femur defects in ovariectomized (OVX) rats are created to simulate an osteoporotic phenotype. The results show that Eu-MBG scaffolds significantly stimulate new bone formation in osteoporotic bone defects when compared to MBG scaffolds alone and Eu may be involved in the acceleration of bone regeneration in OVX rats. Our study for the first time reports that the incorporation of the rare earth element Eu into bioscaffolds has the ability to accelerate bone regeneration in vivo, and thus, the prepared Eu-MBG scaffolds possess bifunctional properties with biolabeling and bone regeneration.

Adhesive Bioactive Coatings Inspired by Sea Life

Inspired by nature, in particular by the marine mussels adhesive proteins (MAPs) and by the tough brick-and-mortar nacre-like structure, novel multilayered films are prepared in the present work. Organic-inorganic multilayered films, with an architecture similar to nacre based on bioactive glass nanoparticles (BG), chitosan, and hyaluronic acid modified with catechol groups, which are the main components responsible for the outstanding adhesion in MAPs, are developed for the first time. The biomimetic conjugate is prepared by carbodiimide chemistry and analyzed by ultraviolet-visible spectrophotometry. The buildup of the multilayered films is monitored with a quartz crystal microbalance with dissipation monitoring, and their topography is characterized by atomic force microscopy. The mechanical properties reveal that the films containing catechol groups and BG present an enhanced adhesion. Moreover, the bioactivity of the films upon immersion in a simulated body fluid solution is evaluated by scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. It was found that the constructed films promote the formation of bonelike apatite in vitro. Such multifunctional mussel inspired LbL films, which combine enhanced adhesion and bioactivity, could be potentially used as coatings of a variety of implants for orthopedic applications.

Evaluation of in vivo angiogenetic effects of copper doped bioactive glass scaffolds in the AV loop model

effects of 3D scaffolds made from 45S5 bioactive glass (BG) doped with 1 wt. % copper ions in the arteriovenous loop model of the rat.

Materials and Methods: An arteriovenous loop was built in the groin of 10 rats and inserted in 1% copper doped 45S5 BG scaffolds and fibrin. The scaffold and the AV loop were inserted in Teflon isolation chambers and explanted 3 weeks after implantation. Afterwards the scaffolds were analyzed by Micro-CT and histology regarding vascularization. Results were compared to plain 45S5 BG-based scaffolds from a previous study.

Results: Micro-CT and histological evaluation showed consistent vascularization of the constructs. A tendency towards an increased vascularization in the copper doped BG group compared to plain BG constructs could be observed. However, therewas no significant difference in statistical analysis between both groups.

Conclusions: This study shows results that support an increased angiogenetic effect of 1% copper doped 45S5 BG compared to regular 45S5 BG scaffolds in the rat arteriovenous loop model although these tendencies are not backed by statistical evidence. Maybe higher copper doses could lead to a statistically significant angiogenetic effect.

Biological behavior of bioactive glasses and their composites

This review summarizes current developments in improving the biological behavior of bioactive glasse and their composites.

Bioceramics and Scaffolds: A Winning Combination for Tissue Engineering

In the last few decades, we have assisted to a general increase of elder population worldwide associated with age-related pathologies. Therefore, there is the need for new biomaterials that can substitute damaged tissues, stimulate the body’s own regenerative mechanisms, and promote tissue healing. Porous templates referred to as “scaffolds” are thought to be required for three-dimensional tissue growth. Bioceramics, a special set of fully, partially, or non-crystalline ceramics (e.g., calcium phosphates, bioactive glasses, and glass–ceramics) that are designed for the repair and reconstruction of diseased parts of the body, have high potential as scaffold materials. Traditionally, bioceramics have been used to fill and restore bone and dental defects (repair of hard tissues). More recently, this category of biomaterials has also revealed promising applications in the field of soft-tissue engineering. Starting with an overview of the fundamental requirements for tissue engineering scaffolds, this article provides a detailed picture on recent developments of porous bioceramics and composites, including a summary of common fabrication technologies and a critical analysis of structure–property and structure–function relationships. Areas of future research are highlighted at the end of this review, with special attention to the development of multifunctional scaffolds exploiting therapeutic ion/drug release and emerging applications beyond hard tissue repair.

Towards 4th generation biomaterials: a covalent hybrid polymer-ormoglass architecture

Hybrid materials are being extensively investigated with the aim of mimicking the ECM microenvironment to develop effective solutions for bone tissue engineering. However, the common drawbacks of a hybrid material are the lack of interactions between the scaffold's constituents and the masking of its bioactive phase. Conventional hybrids often degrade in a non-homogeneous manner and the biological response is far from optimal. We have developed a novel material with strong interactions between constituents. The bioactive phase is directly exposed on its surface mimicking the structure of the ECM of bone. Here, polylactic acid electrospun fibers have been successfully and reproducibly coated with a bioactive organically modified glass (ormoglass, Si-Ca-P2 system) covalently. In comparison with the pure polymeric mats, the fibers obtained showed improved hydrophilicity and mechanical properties, bioactive ion release, exhibited a nanoroughness and enabled good cell adhesion and spreading after just one day of culture (rMSCs and rEPCs). The fibers were coated with different ormoglass compositions to tailor their surface properties (roughness, stiffness, and morphology) by modifying the experimental parameters. Knowing that cells modulate their behavior according to the exposed physical and chemical signals, the development of this instructive material is a valuable advance in the design of functional regenerative biomaterials.

Reprint of: Review of bioactive glass: From Hench to hybrids

Bioactive glasses are reported to be able to stimulate more bone regeneration than other bioactive ceramics but they lag behind other bioactive ceramics in terms of commercial success. Bioactive glass has not yet reached its potential but research activity is growing. This paper reviews the current state of the art, starting with current products and moving onto recent developments. Larry Hench's 45S5 Bioglass® was the first artificial material that was found to form a chemical bond with bone, launching the field of bioactive ceramics. In vivo studies have shown that bioactive glasses bond with bone more rapidly than other bioceramics, and in vitro studies indicate that their osteogenic properties are due to their dissolution products stimulating osteoprogenitor cells at the genetic level. However, calcium phosphates such as tricalcium phosphate and synthetic hydroxyapatite are more widely used in the clinic. Some of the reasons are commercial, but others are due to the scientific limitations of the original Bioglass 45S5. An example is that it is difficult to produce porous bioactive glass templates (scaffolds) for bone regeneration from Bioglass 45S5 because it crystallizes during sintering. Recently, this has been overcome by understanding how the glass composition can be tailored to prevent crystallization. The sintering problems can also be avoided by synthesizing sol-gel glass, where the silica network is assembled at room temperature. Process developments in foaming, solid freeform fabrication and nanofibre spinning have now allowed the production of porous bioactive glass scaffolds from both melt- and sol-gel-derived glasses. An ideal scaffold for bone regeneration would share load with bone. Bioceramics cannot do this when the bone defect is subjected to cyclic loads, as they are brittle. To overcome this, bioactive glass polymer hybrids are being synthesized that have the potential to be tough, with congruent degradation of the bioactive inorganic and the polymer components. Key to this is creating nanoscale interpenetrating networks, the organic and inorganic components of which have covalent coupling between them, which involves careful control of the chemistry of the sol-gel process. Bioactive nanoparticles can also now be synthesized and their fate tracked as they are internalized in cells. This paper reviews the main developments in the field of bioactive glass and its variants, covering the importance of control of hierarchical structure, synthesis, processing and cellular response in the quest for new regenerative synthetic bone grafts. The paper takes the reader from Hench's Bioglass 45S5 to new hybrid materials that have tailorable mechanical properties and degradation rates.

Effect of ion release from Cu-doped 45S5 Bioglass® on 3D endothelial cell morphogenesis

Both silicate-based bioactive glasses and copper ions have demonstrated angiogenic activity and therefore represent promising bioinorganic agents for the promotion of vascularization in tissue-engineered scaffolds. This study examined the effect of ionic release products from 45S5 Bioglass® doped with 0 and 2.5 wt.% CuO (BG and Cu-BG respectively) on the formation of capillary-like networks by SVEC4-10 endothelial cells (ECs) seeded in a three-dimensional (3D) type I collagen matrix. Copper and silicon release following 24h dissolution increased non-proportionally with Cu-BG concentration in cell culture medium, while calcium levels were decreased below the initial medium concentration. EC network length, connectivity, branching, quantified by means of a 3D morphometric image analysis method, as well as proliferation and metabolic activity were reduced in a dose-dependent fashion by BG and Cu-BG ionic release products. This reduction was less prominent for BG compared to an equivalent concentration of Cu-BG, which was attributed to a lower extent of silicon release and calcium consumption. Moreover, a CuCl2 dose equivalent to the highest concentration of Cu-BG exhibited no effect on ECs. In conclusion, while the previously reported pro-angiogenic activity of both Bioglass® and copper may not be reflected in a direct response of ECs, this study provides a maximum glass concentration for non-harmful angiogenic stimulation to be examined in future work.

Bioactive glasses beyond bone and teeth: emerging applications in contact with soft tissues

The applications of bioactive glasses (BGs) have to a great extent been related to the replacement, regeneration and repair of hard tissues, such as bone and teeth, and there is an extensive bibliography documenting the role of BGs as bone replacement materials and in bone tissue engineering applications. Interestingly, many of the biochemical reactions arising from the contact of BGs with bodily fluids, in particular the local increase in concentration of various ions at the glass-tissue interface, are also relevant to mechanisms involved in soft tissue regeneration. An increasing number of studies report on the application of BGs in contact with soft tissues, aiming at exploiting the well-known bioactive properties of BGs in soft tissue regeneration and wound healing. This review focuses on research, sometimes involving preliminary in vitro studies but also in vivo evidence, that demonstrates the suitability of BGs in contact with tissues outside the skeletal system, which includes studies investigating vascularization, wound healing and cardiac, lung, nerve, gastrointestinal, urinary tract and laryngeal tissue repair using BGs in various forms of particulates, fibers and nanoparticles with and without polymer components. Potentially active mechanisms of interaction of BGs and soft tissues based on the surface bioreactivity of BGs and on biomechanical stimuli affecting the soft tissue-BG collagenous bonding are discussed based on results in the literature.

Zinc-containing bioactive glasses for bone regeneration, dental and orthopedic applications

Zinc is a vital and beneficial trace element found in the human body. Though found in small proportions, zinc performs a variety of functions in relation to the immune system, cell division, fertility and the body growth and maintenance. In particular, zinc is proven to be a necessary element for the formation, mineralization, development and maintenance of healthy bones. Considering this attractive attributes of zinc, recent research has widely focused on using zinc along with silicate-based bioactive glasses for bone tissue engineering applications. This paper reviews relevant literature discussing the significance of zinc in the human body, along with its ability to enhance antibacterial effects, bioactivity and distinct physical, structural and mechanical properties of bioactive glasses. In this context, even if the present analysis is not meant to be exhaustive and only representative studies are discussed, literature results confirm that it is essential to understand the properties of zinc-containing bioactive glasses with respect to their in vitro biological behavior, possible cytotoxic effects and degradation characteristics to be able to effectively apply these glasses in bone regeneration strategies. Topics attracting increasing research efforts in this field are elaborated in detail in this review, including a summary of the structural, physical, biological and mechanical properties of zinc-containing bioactive glasses. This paper also presents an overview of the various applications in which zinc-containing bioactive glasses are considered for use as bone tissue scaffolds, bone filling granules, bioactive coatings and bone cements, and advances and remaining challenges are highlighted.

Combining collagen and bioactive glasses for bone tissue engineering: a review

Collagen (COL), the most abundant protein in mammals, offers a wide range of attractive properties for biomedical applications which are the result of its biocompatibility and high affinity to water. However, due to the relative low mechanical properties of COL its applications are still limited. To tackle this disadvantage of COL, especially in the field of bone tissue engineering, COL can be combined with bioactive inorganic materials in a variety of composite systems. One of such systems is the collagen-bioactive glass (COL-BG) composite family, which is the theme of this Review. BG fillers can increase compressive strength and stiffness of COL-based structures. This article reviews the relevant literature published in the last 15 years discussing the fabrication of a variety of COL-BG composites. In vitro cell studies have demonstrated the osteogenic, odontogenic, and angiogenic potential of these composite systems, which has been confirmed by stimulating specific biochemical indicators of relevant cells. Bony integration and connective tissue vessel formation have also been studied by implantation of the composites in vivo. Areas of future research in the field of COL-BG systems, based on current challenges, and gaps in knowledge are highlighted.

Coating of bioactive glass particles with mussel-inspired polydopamine as a strategy to improve the thermal stability of poly(l-lactide)/bioactive glass composites

Coating bioactive glass particles with polydopamine hinders the degradation reaction occurring at high temperatures between PLLA and bioactive glass particles.

Bioactive copper-doped glass scaffolds can stimulate endothelial cells in co-culture in combination with mesenchymal stem cells

Bioactive glass (BG) scaffolds are being investigated for bone tissue engineering applications because of their osteoconductive and angiogenic nature. However, to increase the in vivo performance of the scaffold, including enhancing the angiogenetic growth into the scaffolds, some researchers use different modifications of the scaffold including addition of inorganic ionic components to the basic BG composition. In this study, we investigated the in vitro biocompatibility and bioactivity of Cu2+-doped BG derived scaffolds in either BMSC (bone-marrow derived mesenchymal stem cells)-only culture or co-culture of BMSC and human dermal microvascular endothelial cells (HDMEC). In BMSC-only culture, cells were seeded either directly on the scaffolds (3D or direct culture) or were exposed to ionic dissolution products of the BG scaffolds, kept in permeable cell culture inserts (2D or indirect culture). Though we did not observe any direct osteoinduction of BMSCs by alkaline phosphatase (ALP) assay or by PCR, there was increased vascular endothelial growth factor (VEGF) expression, observed by PCR and ELISA assays. Additionally, the scaffolds showed no toxicity to BMSCs and there were healthy live cells found throughout the scaffold. To analyze further the reasons behind the increased VEGF expression and to exploit the benefits of the finding, we used the indirect method with HDMECs in culture plastic and Cu2+-doped BG scaffolds with or without BMSCs in cell culture inserts. There was clear observation of increased endothelial markers by both FACS analysis and acetylated LDL (acLDL) uptake assay. Only in presence of Cu2+-doped BG scaffolds with BMSCs, a high VEGF secretion was demonstrated by ELISA; and typical tubular structures were observed in culture plastics. We conclude that Cu2+-doped BG scaffolds release Cu2+, which in turn act on BMSCs to secrete VEGF. This result is of significance for the application of BG scaffolds in bone tissue engineering approaches.

Bioceramics in ophthalmology

The benefits of ceramics in biomedical applications have been universally appreciated as they exhibit an extraordinarily broad set of physico-chemical, mechanical and biological properties which can be properly tailored by acting on their composition, porosity and surface texture to increase their versatility and suitability for targeted healthcare applications. Bioceramics have traditionally been used for the repair of hard tissues, such as bone and teeth, mainly due to their suitable strength for load-bearing applications, wear resistance (especially alumina, zirconia and composites thereof) and, in some cases, bone-bonding ability (calcium orthophosphates and bioactive glasses). Bioceramics have been also applied in other medical areas, like ophthalmic surgery; although their use in such a context has been scientifically documented since the late 1700s, the potential and importance of ceramic ocular implants still seem to be underestimated and an exhaustive, critical assessment is currently lacking in the relevant literature. The present review aims to fill this gap by giving a comprehensive picture of the ceramic-based materials and implants that are currently used in ophthalmology and pointing out the strengths and weaknesses of the existing devices. A prospect for future research is also provided, highlighting the potential of new, smart bioceramics able to carry specific added values which could have a significant impact on the treatment of ocular diseases.

Tissue engineering scaffolds of mesoporous magnesium silicate and poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) composite

Mesoporous magnesium silicate (m-MS) and poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL) composite scaffolds were fabricated by solvent-casting and particulate leaching method. The results suggested that the incorporation of m-MS into PCL-PEG-PCL could significantly improve the water adsorption of the m-MS/PCL-PEG-PCL composite (m-MPC) scaffolds. The in vitro degradation behavior of m-MPC scaffolds were determined by testing weight loss of the scaffolds after soaking into phosphate buffered saline (PBS), and the result showed that the degradation of m-MPC scaffolds was obviously enhanced by addition of m-MS into PCL-PEG-PCL after soaking for 10 weeks. Proliferation of MG63 cells on m-MPC was significantly higher than MPC scaffolds at 4 and 7 days. ALP activity on the m-MPC was obviously higher than MPC scaffolds at 7 days, revealing that m-MPC could promote cell differentiation. Histological evaluation showed that the introduction of m-MS into PCL-PEG-PCL enhanced the efficiency of new bone formation when the m-MPC scaffolds implanted into bone defect of rabbits. The results suggested that the inorganic/organic composite of m-MS and PCL-PEG-PCL scaffolds exhibited good biocompatibility, degradability and osteogenesis.

A review of the bioactivity of hydraulic calcium silicate cements

OBJECTIVES

In tissue regeneration research, the term "bioactivity" was initially used to describe the resistance to removal of a biomaterial from host tissues after intraosseous implantation. Hydraulic calcium silicate cements (HCSCs) are putatively accepted as bioactive materials, as exemplified by the increasing number of publications reporting that these cements produce an apatite-rich surface layer after they contact simulated body fluids.

METHODS

In this review, the same definitions employed for establishing in vitro and in vivo bioactivity in glass-ceramics, and the proposed mechanisms involved in these phenomena are used as blueprints for investigating whether HCSCs are bioactive.

RESULTS

The literature abounds with evidence that HCSCs exhibit in vitro bioactivity; however, there is a general lack of stringent methodologies for characterizing the calcium phosphate phases precipitated on HCSCs. Although in vivo bioactivity has been demonstrated for some HCSCs, a fibrous connective tissue layer is frequently identified along the bone-cement interface that is reminiscent of the responses observed in bioinert materials, without accompanying clarifications to account for such observations.

CONCLUSIONS

As bone-bonding is not predictably achieved, there is insufficient scientific evidence to substantiate that HCSCs are indeed bioactive. Objective appraisal criteria should be developed for more accurately defining the bioactivity profiles of HCSCs designed for clinical use.

Multifunctional mesoporous bioactive glasses for effective delivery of therapeutic ions and drug/growth factors

Regeneration of large-size bone defects represents a significant challenge clinically, which requires the use of scaffolds with multifunction, such as anti-bacterial activity, and stimulation of osteogenesis and angiogenesis. It is known that functional ions or drug/growth factors play an important role to stimulate tissue regeneration. Mesoporous bioactive glasses (MBG) possess excellent bioactivity and drug-delivery ability as well as effective ionic release in the body fluids microenvironment due to its specific mesoporous structure and large surface area. For these reasons, functional ions (e.g. lithium (Li), strontium (Sr), Copper (Cu) and Boron (B)) and drug/growth factors (e.g. dexamethasone, vascular endothelial growth factor (VEGF) and bone morphogenetic protein (BMP)) have been incorporated into MBG, which shows high loading efficiency and effective release. The release of therapeutic ions and drug/growth factors from MBG offers it multifunctional properties, such as improved osteogenesis, angiogenesis, anti-bacterial/cancer activity. However, there is no a systematic review about delivery of therapeutic ions and drugs/growth factors from MBG for the functional effect on the tissue regeneration despite that significant progress has been achieved in the past five years. Therefore, in this review, we mainly focused on the new advances for the functional effect of delivering therapeutic ions and drugs/growth factors on the ostegeogenesis, angiogenesis and antibacterial activity. It is expected that the review will offer new concept to develop multifunctional biomaterials for bone regeneration by the synergistic effect of therapeutic ions and drug/growth factors.

Enhancement mechanisms of graphene in nano-58S bioactive glass scaffold: mechanical and biological performance

Graphene is a novel material and currently popular as an enabler for the next-generation nanocomposites. Here, we report the use of graphene to improve the mechanical properties of nano-58S bioactive glass for bone repair and regeneration. And the composite scaffolds were fabricated by a homemade selective laser sintering system. Qualitative and quantitative analysis demonstrated the successful incorporation of graphene into the scaffold without obvious structural damage and weight loss. The optimum compressive strength and fracture toughness reached 48.65 ± 3.19 MPa and 1.94 ± 0.10 MPa·m^1/2 with graphene content of 0.5 wt%, indicating significant improvements by 105% and 38% respectively. The mechanisms of pull-out, crack bridging, crack deflection and crack tip shielding were found to be responsible for the mechanical enhancement. Simulated body fluid and cell culture tests indicated favorable bioactivity and biocompatibility of the composite scaffold. The results suggest a great potential of graphene/nano-58S composite scaffold for bone tissue engineering applications.

Biomaterials for orbital implants and ocular prostheses: overview and future prospects

The removal of an eye is one of the most difficult and dramatic decisions that a surgeon must consider in case of severe trauma or life-threatening diseases to the patient. The philosophy behind the design of orbital implants has evolved significantly over the last 60 years, and the use of ever more appropriate biomaterials has successfully reduced the complication rate and improved the patient's clinical outcomes and satisfaction. This review provides a comprehensive picture of the main advances that have been made in the development of innovative biomaterials for orbital implants and ocular prostheses. Specifically, the advantages, limitations and performance of the existing devices are examined and critically compared, and the potential of new, smart and suitable biomaterials are described and discussed in detail to outline a forecast for future research directions.

Silicate bioceramics enhanced vascularization and osteogenesis through stimulating interactions between endothelia cells and bone marrow stromal cells

The facts that biomaterials affect the behavior of single type of cells have been widely accepted. However, the effects of biomaterials on cell-cell interactions have rarely been reported. Bone tissue engineering involves osteoblastic cells (OCs), endothelial cells (ECs) and the interactions between OCs and ECs. It has been reported that silicate biomaterials can stimulate osteogenic differentiation of OCs and vascularization of ECs. However, the effects of silicate biomaterials on the interactions between ECs and OCs during vascularization and osteogenesis have not been reported, which are critical for bone tissue regeneration in vivo. Therefore, this study aimed to investigate the effects of calcium silicate (CS) bioceramics on interactions between human umbilical vein endothelial cells (HUVECs) and human bone marrow stromal cells (HBMSCs) and on stimulation of vascularization and osteogenesis in vivo through combining co-cultures with CS containing scaffolds. Specifically, the effects of CS on the angiogenic growth factor VEGF, osteogenic growth factor BMP-2 and the cross-talks between VEGF and BMP-2 in the co-culture system were elucidated. Results showed that CS stimulated co-cultured HBMSCs (co-HBMSCs) to express VEGF and the VEGF activated its receptor KDR on co-cultured HUVECs (co-HUVECs), which was also up-regulated by CS. Then, BMP-2 and nitric oxide expression from the co-HUVECs were stimulated by CS and the former stimulated osteogenic differentiation of co-HBMSCs while the latter stimulated vascularization of co-HVUECs. Finally, the poly(lactic-co-glycolic acid)/CS composite scaffolds with the co-cultured HBMSCs and HUVECs significantly enhanced vascularization and osteogenic differentiation in vitro and in vivo, which indicates that it is a promising way to enhance bone regeneration by combining scaffolds containing silicate bioceramics and co-cultures of ECs and OCs.

In vitro endothelial cell response to ionic dissolution products from boron-doped bioactive glass in the SiO2–CaO–P2O5–Na2O system

As it has been established that boron (B) may perform functions in angiogenesis and osteogenesis, the controlled and localized release of B ions from bioactive glasses (BGs) is expected to provide a promising therapeutic alternative for regenerative medicine of vascularized tissues, such as bone.

Synthesis of radial mesoporous bioactive glass particles to deliver osteoactivin gene

Synthesis of radial mesoporous bioactive glass particles to deliver osteoactivin gene.

Combination of silica nanoparticles with hydroxyapatite reinforces poly (l-lactide acid) scaffolds without loss of bioactivity

Composite scaffolds of poly(l-lactide acid) and hydroxyapatite are of great interest in bone tissue engineering, but their mechanical properties are typically inferior to scaffolds of pure poly(l-lactide acid) due to agglomeration of the particles and weak interfacial component interaction. Fabrication strategies like double sonication of hydroxyapatite or increasing the amount of this inorganic filler do not effectively enhance the mechanical performance. In this study, poly(l-lactide acid) composites combining two types of fillers, mesoporous silica (SiO2) nanoparticles and hydroxyapatite, were developed to reinforce the poly(l-lactide acid) scaffold without any loss of bioactivity. A 5% addition of SiO2 nanoparticles to hydroxyapatite nanopowder and subjecting the scaffold formulation to double sonication increased the Young’s modulus from 5 MPa (pure poly(l-lactide acid) scaffold) to almost 7 MPa (poly(l-lactide acid)/hydroxyapatite/SiO2 scaffold). In addition, the composite was able to deposit a layer of biomimetic hydroxyapatite both on the surface and interior of the scaffold after 21 days of immersion in a simulated body fluid. The manufacturing method was straightforward and economically viable and does not require any chemical modification of the particles’ surfaces.

Adipose- and bone marrow-derived mesenchymal stem cells display different osteogenic differentiation patterns in 3D bioactive glass-based scaffolds

Mesenchymal stem cells can be isolated from a variety of different sources, each having their own peculiar merits and drawbacks. Although a number of studies have been conducted comparing these stem cells for their osteo-differentiation ability, these are mostly done in culture plastics. We have selected stem cells from either adipose tissue (ADSCs) or bone marrow (BMSCs) and studied their differentiation ability in highly porous three-dimensional (3D) 45S5 Bioglass®-based scaffolds. Equal numbers of cells were seeded onto 5 × 5 × 4 mm³ scaffolds and cultured in vitro, with or without osteo-induction medium. After 2 and 4 weeks, the cell-scaffold constructs were analysed for cell number, cell spreading, viability, alkaline phosphatase activity and osteogenic gene expression. The scaffolds with ADSCs displayed osteo-differentiation even without osteo-induction medium; however, with osteo-induction medium osteogenic differentiation was further increased. In contrast, the scaffolds with BMSCs showed no osteo-differentiation without osteo-induction medium; after application of osteo-induction medium, osteo-differentiation was confirmed, although lower than in scaffolds with ADSCs. In general, stem cells in 3D bioactive glass scaffolds differentiated better than cells in culture plastics with respect to their ALP content and osteogenic gene expression. In summary, 45S5 Bioglass-based scaffolds seeded with ADSCs are well-suited for possible bone tissue-engineering applications. Induction of osteogenic differentiation appears unnecessary prior to implantation in this specific setting. Copyright © 2013 John Wiley & Sons, Ltd.

Immunomodulatory effect of a decellularized skeletal muscle scaffold in a discordant xenotransplantation model

Decellularized (acellular) scaffolds, composed of natural extracellular matrix, form the basis of an emerging generation of tissue-engineered organ and tissue replacements capable of transforming healthcare. Prime requirements for allogeneic, or xenogeneic, decellularized scaffolds are biocompatibility and absence of rejection. The humoral immune response to decellularized scaffolds has been well documented, but there is a lack of data on the cell-mediated immune response toward them in vitro and in vivo. Skeletal muscle scaffolds were decellularized, characterized in vitro, and xenotransplanted. The cellular immune response toward scaffolds was evaluated by immunohistochemistry and quantified stereologically. T-cell proliferation and cytokines, as assessed by flow cytometry using carboxy-fluorescein diacetate succinimidyl ester dye and cytometric bead array, formed an in vitro surrogate marker and correlate of the in vivo host immune response toward the scaffold. Decellularized scaffolds were free of major histocompatibility complex class I and II antigens and were found to exert anti-inflammatory and immunosuppressive effects, as evidenced by delayed biodegradation time in vivo; reduced sensitized T-cell proliferative activity in vitro; reduced IL-2, IFN-γ, and raised IL-10 levels in cell-culture supernatants; polarization of the macrophage response in vivo toward an M2 phenotype; and improved survival of donor-derived xenogeneic cells at 2 and 4 wk in vivo. Decellularized scaffolds polarize host responses away from a classical TH1-proinflammatory profile and appear to down-regulate T-cell xeno responses and TH1 effector function by inducing a state of peripheral T-cell hyporesponsiveness. These results have substantial implications for the future clinical application of tissue-engineered therapies.

45S5-Bioglass(®)-based 3D-scaffolds seeded with human adipose tissue-derived stem cells induce in vivo vascularization in the CAM angiogenesis assay

Poor vascularization is the key limitation for long-term acceptance of large three-dimensional (3D) tissue engineering constructs in regenerative medicine. 45S5 Bioglass(®) was investigated given its potential for applications in bone engineering. Since native Bioglass(®) shows insufficient angiogenic properties, we used a collagen coating, to seed human adipose tissue-derived stem cells (hASC) confluently onto 3D 45S5 Bioglass(®)-based scaffolds. To investigate vascularization by semiquantitative analyses, these biofunctionalized scaffolds were then subjected to in vitro human umbilical vein endothelial cells formation assays, and were also investigated in the chorioallantoic membrane (CAM) angiogenesis model, an in vivo angiogenesis assay, which uses the CAM of the hen's egg. In their native, nonbiofunctionalized state, neither Bioglass(®)-based nor biologically inert fibrous polypropylene control scaffolds showed angiogenic properties. However, significant vascularization was induced by hASC-seeded scaffolds (Bioglass(®) and polypropylene) in the CAM angiogenesis assay. Biofunctionalized scaffolds also showed enhanced tube lengths, compared to unmodified scaffolds or constructs seeded with fibroblasts. In case of biologically inert hernia meshes, the quantification of vascular endothelial growth factor secretion as the key angiogenic stimulus strongly correlated to the tube lengths and vessel numbers in all models. This correlation proved the CAM angiogenesis assay to be a suitable semiquantitative tool to characterize angiogenic effects of larger 3D implants. In addition, our results suggest that combinations of suitable scaffold materials, such as 45S5 Bioglass(®), with hASC could be a promising approach for future tissue engineering applications.

Taking a deep look: modern microscopy technologies to optimize the design and functionality of biocompatible scaffolds for tissue engineering in regenerative medicine

This review focuses on modern nonlinear optical microscopy (NLOM) methods that are increasingly being used in the field of tissue engineering (TE) to image tissue non-invasively and without labelling in depths unreached by conventional microscopy techniques. With NLOM techniques, biomaterial matrices, cultured cells and their produced extracellular matrix may be visualized with high resolution. After introducing classical imaging methodologies such as µCT, MRI, optical coherence tomography, electron microscopy and conventional microscopy two-photon fluorescence (2-PF) and second harmonic generation (SHG) imaging are described in detail (principle, power, limitations) together with their most widely used TE applications. Besides our own cell encapsulation, cell printing and collagen scaffolding systems and their NLOM imaging the most current research articles will be reviewed. These cover imaging of autofluorescence and fluorescence-labelled tissue and biomaterial structures, SHG-based quantitative morphometry of collagen I and other proteins, imaging of vascularization and online monitoring techniques in TE. Finally, some insight is given into state-of-the-art three-photon-based imaging methods (e.g. coherent anti-Stokes Raman scattering, third harmonic generation). This review provides an overview of the powerful and constantly evolving field of multiphoton microscopy, which is a powerful and indispensable tool for the development of artificial tissues in regenerative medicine and which is likely to gain importance also as a means for general diagnostic medical imaging.

Dental applications of nanostructured bioactive glass and its composites

To improve treatments of bone or dental trauma and diseases such as osteoporosis, cancer, and infections, scientists who perform basic research are collaborating with clinicians to design and test new biomaterials for the regeneration of lost or injured tissue. Developed some 40 years ago, bioactive glass (BG) has recently become one of the most promising biomaterials, a consequence of discoveries that its unusual properties elicit specific biological responses inside the body. Among these important properties are the capability of BG to form strong interfaces with both hard and soft tissues, and its release of ions upon dissolution. Recent developments in nanotechnology have introduced opportunities for materials sciences to advance dental and bone therapies. For example, the applications for BG expand as it becomes possible to finely control structures and physicochemical properties of materials at the molecular level. Here, we review how the properties of these materials have been enhanced by the advent of nanotechnology, and how these developments are producing promising results in hard-tissue regeneration and development of innovative BG-based drug delivery systems.

Effect of nano-sized bioactive glass particles on the angiogenic properties of collagen based composites

Angiogenesis is essential for tissue regeneration and repair. A growing body of evidence shows that the use of bioactive glasses (BG) in biomaterial-based tissue engineering (TE) strategies may improve angiogenesis and induce increased vascularization in TE constructs. This work investigated the effect of adding nano-sized BG particles (n-BG) on the angiogenic properties of bovine type I collagen/n-BG composites. Nano-sized (20-30 nm) BG particles of nominally 45S5 Bioglass® composition were used to prepare composite films, which were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The in vivo angiogenic response was evaluated using the quail chorioallantoic membrane (CAM) as an model of angiogenesis. At 24 h post-implantation, 10 wt% n-BG containing collagen films stimulated angiogenesis by increasing by 41 % the number of blood vessels branch points. In contrast, composite films containing 20 wt% n-BG were found to inhibit angiogenesis. This experimental study provides the first evidence that addition of a limited concentration of n-BG (10 wt%) to collagen films induces an early angiogenic response making selected collagen/n-BG composites attractive matrices for tissue engineering and regenerative medicine.