Titanium phosphate glass microspheres for bone tissue engineering

Titanium-doped phosphate glasses containing zinc and strontium applied in bone regeneration

Phosphate bioactive glass has been studied for its advanced biodegradability and active ion release capability. Our previous research found that phosphate glass containing (P2O5)-(Na2O)-(TiO2)-(CaO)-(SrO) or (ZnO) showed good biocompatibility with MG63 and hMSCs. This study further investigated the application of 5 mol% zinc oxide or 17.5 mol% strontium oxide in titanium-doped phosphate glass for bone tissue engineering. Ti-Ca-Na-Phosphate glasses, incorporating 5% zinc oxide or 17.5% strontium oxide, were made with melting quenching technology. The pre-osteoblast cell line MC3T3-E1 was cultured for indirect contact tests with graded diluted phosphate glass extractions and for direct contact tests by seeding cells on glass disks. The cell viability and cytotoxicity were analysed in vitro over 7 days. In vivo studies utilized the tibial defect model with or without glass implants. The micro-CT analysis was performed after surgery and then at 2, 6, and 12 weeks. Extractions from both zinc and strontium phosphate glasses showed no negative impact on MC3T3-E1 cell viability. Notably, non-diluted Zn-Ti-Ca-Na-phosphate glass extracts significantly increased cell viability by 116.8% (P < 0.01). Furthermore, MC3T3-E1 cells cultured with phosphate glass disks exhibited no increase in LDH release compared with the control group. Micro-CT images revealed that, over 12 weeks, both zinc-doped and strontium-doped phosphate glasses demonstrated good bone incorporation and longevity compared to the no-implant control. Titanium-doped phosphate glasses containing 5 mol% zinc oxide, or 17.5 mol% strontium oxide have promising application potential for bone regeneration research.

Development of a ReaxFF reactive force field for ternary phosphate-based bioactive glasses

Phosphate-based glasses (PBGs) in the CaO-Na2O-P2O5 system have diverse applications as biomaterials due to their unique dissolution properties. A reactive force field (ReaxFF) has been developed to simulate these materials at the atomic level. The ReaxFF parameters of PBGs, including the interaction between phosphorus and calcium atoms, have been developed using a published code based on genetic algorithms. The training data, including the atomic charges, atomic forces, bond and angle parameters, and different differential energies, are chosen and measured from static quantum-mechanical calculations and ab initio molecular dynamics of PBGs. We did different short- and medium-range structural analyses on the bulk simulated PBGs with different compositions to validate the developed potential. Radial and angular distribution functions and coordination numbers of network formers and modifiers, as well as the network connectivity of the glass, are in agreement with experimental and previous simulations using both shell-model classical force fields and ab initio simulated data; for example, the coordination number of phosphorus is 4.0. This successful development of ReaxFF parameters being able to describe the bulk PBGs enables us to work on the dissolution behavior of the glasses, including the interaction of water molecules with PBGs, in future works.

A microfluidic route for synthesis of scandium oxide microspheres, their characterization and neutron activation

Radioactive scandium-46 microspheres have applications in mapping flow in a chemical reactor through a technique known as radioactive particle tracking (RPT). In the present study a novel microfluidic method has been developed for synthesis of controlled size scandium oxide microspheres. An inline/in-situ mixing of the scandium precursor and gelling agents was implemented which makes the microfluidic platform amenable for truly continuous operation. Microspheres of size varying from 937 to 666 μm were produced by varying O/A ratio from 10 to 30. Perfectly spherical and monodispersed (PDI <10 %) microspheres were obtained at O/A 15 and beyond. The morphology, elemental composition, and structure of the microspheres were analysed by SEM, EDS and XRD, respectively. Subsequently the microspheres were irradiated with thermal neutrons in a nuclear reactor to obtain radioactive Sc-46 oxide microspheres. The activity produced on each Sc-46 microspheres with different sizes was in the range 19.5-34.0 MBq.

In vitro immunomodulatory effect of solid versus porous phosphate-based glass microspheres using macrophages

This study aimed to investigate the immunomodulatory effect of two different forms of phosphate-based glass microspheres (solid and porous), on human macrophages. Human THP-1 monocytes were converted to M0 macrophages after being treated with 100 ng/mL phorbol 12-myristate 13-acetate for 48 h. The differentiated cells were analysed for the CD14 marker using flow cytometry. The adhesion, spreading, and viability of M0 macrophages grown directly or indirectly (extracts) at varying concentrations of solid and porous glass microspheres (GMs) were analysed via phase contrast microscopy, confocal microscopy, and XTT assay. The expression of IL-8, IL-1β, IL-6, IL-10, TNF-α, and IL-12p70 cytokines was investigated using flow cytometry. The conversion to M0 macrophages was confirmed by their adherent nature, increased granularity, and CD14 expression. The results showed that both solid and porous GMs or extracts favored the attachment, spreading, and proliferation of macrophages in a comparable manner to cells grown in a normal tissue culture medium. Only the higher concentration of porous GMs (10 mg/mL) changed the morphology of M0 macrophages and increased the expression of IL-1β and IL-8 pro-inflammatory cytokines; this could be related to the fast degradation nature of porous GMs. Of the six cytokines analysed, M0 macrophages grown directly or indirectly with GMs only expressed IL-1β, IL-10, and IL-8. Accordingly, solid microspheres may have advantages as regenerative agents due to their controlled degradation.

Multifunctional bioactive glasses with spontaneous degradation for simultaneous osteosarcoma therapy and bone regeneration

For the treatment of tumor-related bone defects resulting from surgical resection, simultaneous eradication of residual tumor cells and repair of bone defects represent a challenge. To date, photothermal therapy based on photothermal materials is used to remove residual tumor cells under near infrared light. However, most of photothermal materials have no function for bone repair, and even if combined with bioactive materials to enhance osteogenesis, they still cause potential harm to the body due to inability to degrade or poor degradability. Herein, multifunctional bioactive glasses (PGFe5-1100, PGCu5-1100) based on phosphate glass doped with transition metal elements were prepared for photothermal ablation, bone regeneration, and controllable degradation. The glasses exhibited excellent photothermal effect, which was derived from the electron in-band transition after light absorption due to energy level splitting of doped transition metal element and the subsequent electron nonradiative relaxation. The photothermal performance can be controlled by laser power density, element doping content and glass melting temperature. Moreover, the hyperthermia induced by the glasses can effectively kill tumor cells in vitro. In addition, the glasses degraded over time, and the released P, Ca, Na, Fe could promote bone cell proliferation and osteogenic differentiation. Therefore, these results successfully demonstrated that transition metal element-doped phosphate glasses have multifunctional abilities of tumor elimination, bone regeneration, and spontaneous degradation simultaneously with better biosecurity and bioactivity, which is believed to pave the way for the design of novel biomaterials for osteosarcoma treatment.

Development and physicochemical characterization of novel porous phosphate glass bone graft substitute and in vitro comparison with xenograft

The process of bone regeneration in bone grafting procedures is greatly influenced by the physicochemical properties of the bone graft substitute. In this study, porous phosphate glass (PPG) morsels were developed and their physicochemical properties such as degradation, crystallinity, organic content, surface topography, particle size and porosity were evaluated using various analytical methods. The in vitro cytotoxicity of the PPG morsels was assessed and the interaction of the PPG morsels with Dental Pulp Stem Cells (DPSCs) was studied by measuring cell proliferation and cell penetration depth. The cell-material interactions between PPG morsels and a commercially available xenograft (XG) were compared. The PPG morsels were observed to be amorphous, biocompatible and highly porous (porosity = 58.45%). From in vitro experiments, PPG morsels were observed to be non-cytotoxic and showed better cell proliferation. The internal surface of PPG was easily accessible to the cells compared to XG.

Utilization of GelMA with phosphate glass fibers for glial cell alignment

Glial cell alignment in tissue engineered constructs is essential for achieving functional outcomes in neural recovery. While gelatin methacrylate (GelMA) hydrogel offers superior biocompatibility along with permissive structure and tailorable mechanical properties, phosphate glass fibers (PGFs) can provide physical cues for directionality of neural growth. Aligned PGFs were fabricated by a melt quenching and fiber drawing method and utilized with synthesized GelMA hydrogel. The mechanical properties of GelMA and biocompatibility of the GelMA-PGFs composite were investigated in vitro using rat glial cells. GelMA with 86% methacrylation degree were photo-crosslinked using 0.1%wt photo-initiator (PI). Photocrosslinking under UV exposure for 60 s was used to produce hydrogels (GelMA-60). PGFs were introduced into the GelMA before crosslinking. Storage modulus and loss modulus of GelMA-60 was 24.73 ± 2.52 and 1.08 ± 0.23 kN/m² , respectively. Increased cell alignment was observed in GelMA-PGFs compared with GelMA hydrogel alone. These findings suggest GelMA-PGFs can provide glial cells with physical cues necessary to achieve cell alignment. This approach could further be used to achieve glial cell alignment in bioengineered constructs designed to bridge damaged nerve tissue.

Rapid conversion of highly porous borate glass microspheres into hydroxyapatite

This paper reports on the rapid development of porous hydroxyapatite (HA) microspheres with large external pores and fully interconnected porosity. These porous microspheres were produced by converting borates glasses (namely 45B5, B53P4 and 13-93B) into HA by immersing them in potassium phosphate media and simulated body fluid (SBF). Solid (SGMS) non-porous and highly porous (PGMS) microspheres were prepared from borate glasses via a novel flame spheroidisation process and their physicochemical properties including in vitro biological response were investigated. Morphological and physical characterisation of the PGMS showed interconnected porosity (up to 75 ± 5%) with average external pore sizes of 50 ± 5 μm. Mass loss, ion release, X-ray diffraction (XRD) and Scanning electron microscopy (SEM) analysis confirmed complete conversion to HA in 0.02 M K2HPO4 solution for the PGMS (with exception of 13-93B glass) and at significantly faster rates compared to their SGMS counterparts. However, 13-93B microspheres only converted to HA in Na2HPO4 solution. The in vitro SBF bioactivity studies for all the borate compositions showed HA formation and much earlier for PGMS compared to SGMS. Direct cell culture studies using hMSCs revealed that the converted porous HA microspheres showed enhanced pro-osteogenic properties compared to their unconverted counterparts and such are considered as highly promising candidate materials for bone repair (and orthobiological) applications.

Biomedical Radioactive Glasses for Brachytherapy

The fight against cancer is an old challenge for mankind. Apart from surgery and chemotherapy, which are the most common treatments, use of radiation represents a promising, less invasive strategy that can be performed both from the outside or inside the body. The latter approach, also known as brachytherapy, relies on the use of implantable beta-emitting seeds or microspheres for killing cancer cells. A set of radioactive glasses have been developed for this purpose but their clinical use is still mainly limited to liver cancer. This review paper provides a picture of the biomedical glasses developed and experimented for brachytherapy so far, focusing the discussion on the production methods and current limitations of the available options to their diffusion in clinical practice. Highly-durable neutron-activatable glasses in the yttria-alumina-silica oxide system are typically preferred in order to avoid the potentially-dangerous release of radioisotopes, while the compositional design of degradable glass systems suitable for use in radiotherapy still remains a challenge and would deserve further investigation in the near future.

Effect of varying the Mg with Ca content in highly porous phosphate-based glass microspheres

This paper reports on the role of phosphate-based glass (PBG) microspheres and their physicochemical properties including in vitro biological response to human mesenchymal stem cells (hMSCs). Solid and porous microspheres were prepared via a flame spheroidisation process. The Mg content in the PBG formulations explored was reduced from 24 to 2 mol% with a subsequent increase in Ca content. A small quantity of TiO₂ (1 mol%) was added to the lower Mg-content glass (2 mol%) to avoid crystallisation. Morphological and physical characterisation of porous microspheres revealed interconnected porosity (up to 76 ± 5 %), average external pore sizes of 55 ± 5 μm with surface areas ranging from 0.38 to 0.43 m² g^-1. Degradation and ion release studies conducted compared the solid (non-porous) and porous microspheres and revealed 1.5 to 2.5 times higher degradation rate for porous microspheres. Also, in vitro bioactivity studies using simulated body fluid (SBF) revealed Ca/P ratios for porous microspheres of all three glass formulations were between 0.75 and 0.92 which were within the range suggested for precipitated amorphous calcium phosphate. Direct cell seeding and indirect cell culture studies (via incubation with microsphere degradation products) revealed hMSCs were able to grow and undergo osteogenic differentiation in vitro, confirming cytocompatibility of the formulations tested. However, the higher Mg content (24 mol%) porous microsphere showed the most potent osteogenic response and is therefore considered as a promising candidate for bone repair applications.

Porous bioactive glass micro- and nanospheres with controlled morphology: developments, properties and emerging biomedical applications

In recent years, porous bioactive glass micro/nanospheres (PBGSs) have emerged as attractive biomaterials in various biomedical applications where such engineered particles provide suitable functions, from tissue engineering to drug delivery. The design and synthesis of PBGSs with controllable particle size and pore structure are critical for such applications. PBGSs have been successfully synthesized using melt-quenching and sol-gel based methods. The morphology of PBGSs is controllable by tuning the processing parameters and precursor characteristics during the synthesis. In this comprehensive review on PBGSs, we first overview the synthesis approaches for PBGSs, including both melt-quenching and sol-gel based strategies. Sol-gel processing is the primary technology used to produce PBGSs, allowing for control over the chemical compositions and pore structure of particles. Particularly, the influence of pore-forming templates on the morphology of PBGSs is highlighted. Recent progress in the sol-gel synthesis of PBGSs with sophisticated pore structures (e.g., hollow mesoporous, dendritic fibrous mesoporous) is also covered. The challenges regarding the control of particle morphology, including the influence of metal ion precursors and pore expansion, are discussed in detail. We also highlight the recent achievements of PBGSs in a number of biomedical applications, including bone tissue regeneration, wound healing, therapeutic agent delivery, bioimaging, and cancer therapy. Finally, we conclude with our perspectives on the directions of future research based on identified challenges and potential new developments and applications of PBGSs.

Characterisation of osteogenic and vascular responses of hMSCs to Ti-Co doped phosphate glass microspheres using a microfluidic perfusion platform

Using microspherical scaffolds as building blocks to repair bone defects of specific size and shape has been proposed as a tissue engineering strategy. Here, phosphate glass (PG) microcarriers doped with 5 mol % TiO₂ and either 0 mol % CoO (CoO 0%) or 2 mol % CoO (CoO 2%) were investigated for their ability to support osteogenic and vascular responses of human mesenchymal stem cells (hMSCs). Together with standard culture techniques, cell-material interactions were studied using a novel perfusion microfluidic bioreactor that enabled cell culture on microspheres, along with automated processing and screening of culture variables. While titanium doping was found to support hMSCs expansion and differentiation, as well as endothelial cell-derived vessel formation, additional doping with cobalt did not improve the functionality of the microspheres. Furthermore, the microfluidic bioreactor enabled screening of culture parameters for cell culture on microspheres that could be potentially translated to a scaled-up system for tissue-engineered bone manufacturing.

Channeling Effect and Tissue Morphology in a Perfusion Bioreactor Imaged by X-Ray Microtomography

BACKGROUND

Perfusion bioreactors for tissue engineering hold great promises. Indeed, the perfusion of culture medium enhances species transport and mechanically stimulates the cells, thereby increasing cell proliferation and tissue formation. Nonetheless, their development is still hampered by a lack of understanding of the relationship between mechanical cues and tissue growth.

METHODS

Combining tissue engineering, three-dimensional visualization and numerical simulations, we analyze the morphological evolution of neo-tissue in a model bioreactor with respect to the local flow pattern. NIH-3T3 cells were grown under perfusion for one, two and three weeks on a stack of 2 mm polyacetal beads. The model bioreactor was then imaged by X-ray micro-tomography and local tissue morphology was analyzed. To relate experimental observations and mechanical stimulii, a computational fluid dynamics model of flow around spheres in a canal was developed and solved using the finite element method.

RESULTS

We observe a preferential tissue formation at the bioreactor periphery, and relate it to a channeling effect leading to regions of higher flow intensity. Additionally, we find that circular crater-like tissue patterns form in narrow channel regions at early culture times. Using computational fluid dynamic simulations, we show that the location and morphology of these patterns match those of shear stress maxima. Finally, the morphology of the tissue is qualitatively described as the tissue grows and reorganizes itself.

CONCLUSION

Altogether, our study points out the key role of local flow conditions on the tissue morphology developed on a stack of beads in perfusion bioreactors and provides new insights for effective design of hydrodynamic bioreactors for tissue engineering using bead packings.

In vitro cellular testing of strontium/calcium substituted phosphate glass discs and microspheres shows potential for bone regeneration

Phosphate-based glasses (PBGs) are ideal materials for regenerative medicine strategies because their composition, degradation rates, and ion release profiles can easily be controlled. Strontium has previously been found to simultaneously affect bone resorption and deposition. Therefore, by combining the inherent properties of resorbable PBG and therapeutic activity of strontium, these glasses could be used as a delivery device of therapeutic factors for the treatment of orthopaedic diseases such as osteoporosis. This study shows the cytocompatibility and osteogenic potential of PBGs where CaO is gradually replaced by SrO in the near invert glass system 40P2 O5 ·(16-x)CaO·20Na2 O·24MgO·xSrO (x = 0, 4, 8, 12, and 16 mol%). Direct seeding of MG63 cells onto glass discs showed no significant difference in cell metabolic activity and DNA amount measurement across the different formulations studied. Cell attachment and spreading was confirmed via scanning electron microscopy (SEM) imaging at Days 3 and 14. Alkaline phosphatase (ALP) activity was similarly maintained across the glass compositions. Follow-on studies explored the effect of each glass composition in microsphere conformation (size: 63-125 μm) on human mesenchymal stem cells (hMSCs) in 3D cultures, and analysis of cell metabolic activity and ALP activity showed no significant differences at Day 14 over the compositional range investigated, in line with the observations from MG63 cell culture studies. Environmental SEM and live cell imaging at Day 14 of hMSCs seeded on the microspheres showed cell attachment and colonisation of the microsphere surfaces, confirming these formulations as promising candidates for regenerative medicine strategies addressing compromised musculoskeletal/orthopaedic diseases.

Assessing behaviour of osteoblastic cells in dynamic culture conditions using titanium-doped phosphate glass microcarriers

Tissue engineering is a promising approach for bone regeneration; yet challenges remain that limit successful translation to patients. It is necessary to understand how real-world manufacturing processes will affect the constituent cells and biomaterials that are needed to create engineered bone. Bioactive phosphate glasses processed into microspheres are an attractive platform for expanding bone-forming cells and also for driving their osteogenic differentiation and maturation. The aim of this study was to assess whether Ti-doped phosphate glass microspheres could support osteoblastic cell responses in dynamic cell culture environments. Dynamic culture conditions were achieved using microwell studies under orbital agitation. Dimensionless parameters such as the Froude number were used to inform the choice of agitation speeds, and the impact on cell proliferation and microunit formation was quantified. We found that phosphate glass microspheres doped with titanium dioxide at both 5 and 7 mol% provided a suitable biomaterial platform for effective culture of MG63 osteoblastic cells and was not cytotoxic. Dynamic culture conditions supported expansion of MG63 cells and both 150 and 300 rpm orbital shake resulted in higher cell yield than static cultures at the end of the culture (day 13). The Froude number analysis provided insight into how the microunit size could be manipulated to enable an appropriate agitation speed to be used, while ensuring buoyancy of the microunits. These small-scale experiments and analyses provide understanding of the impact of fluid flow on cell expansion that will have increasing importance when scaling up to process technologies that can deliver clinical quantities of cell-microsphere units. Such knowledge will enable future engineering of living bone-like material using processing systems such as bioreactors that use mixing and agitation for nutrient transfer, therefore introducing cells to dynamic culture conditions.

The Antimicrobial Efficacy of Hypoxia Mimicking Cobalt Oxide Doped Phosphate-Based Glasses against Clinically Relevant Gram Positive, Gram Negative Bacteria and a Fungal Strain

Bioactive phosphate glasses are of considerable interest for a range of soft and hard tissue engineering applications. The glasses are degradable and can release biologically important ions in a controlled manner. The glasses can also potentially be used as an antimicrobial delivery system. In the given study, novel cobalt-doped phosphate-based glasses, (P₂O₅)₅₀(Na₂O)₂₀(CaO)_30-x(CoO)_x where 0 ≤ x (mol %) ≤ 10, were manufactured and characterized. As the cobalt oxide concentration increased, the rate of dissolution was observed to decrease. The antimicrobial potential of the glasses was studied using direct and indirect contact methods against both Escherichia coli (NCTC 10538) Staphylococcus aureus (ATCC 6538) and Candida albicans (ATCC 76615). The results showed strong, time dependent, and strain specific antimicrobial activity of the glasses against microorganisms when in direct contact. Antimicrobial activity (R) ≥ 2 was observed within 2 h against Escherichia coli, whereas a similar effect was achieved in 6 h against Staphylococcus aureus and Candida albicans. However, when in indirect contact, the dissolution products from the bioactive glasses failed to show an antimicrobial effect. Following direct exposure to the glasses for 7 days, osteoblast-like SAOS-2 cells showed a 5-fold increase in VEGF mRNA while THP-1 monocytic cells showed a 4-fold increase in VEGF mRNA expression when exposed to 10% CoO-doped glass compared with the cobalt free control glass. Endothelial cells stimulated with conditioned medium taken from cell cultures of THP-1 monocytes exposed to 10% CoO doped glass showed clear tubelike structure (blood vessel) formation after 4 h.

Antibacterial silver-doped phosphate-based glasses prepared by coacervation

Herein we report synthesis, characterization and antimicrobial activity of bioresorbable silver-doped polyphosphate glasses, produced via the coacervation method.

Physical properties and biocompatibility effects of doping SiO2 and TiO2 into phosphate-based glass for bone tissue engineering

Phosphate glass is continuing to gain more attention as potential bone substitutes. The ternary (P2O5-CaO-Na2O) is investigated in terms of both physical properties and biocompatibility by doping different percentages of SiO2 and TiO2. Two groups were prepared; the first has different percentages of TiO2 and SiO2, whereas the second group compositions have 5 mol% TiO2 and 5 mol% SiO2 being added to compensate the network-forming oxide P2O5 and the network-modifying oxide CaO. Density, mass loss, pH, DTA, XRD, and cation release experiments were performed to study the physicochemical properties of the compositions, while MG63 and hMS cells were used within in vitro cell culture to study their biocompatibility. Results showed that an increase in TiO2 content correlated with an increase in glass density, decreased mass loss, increased trend of Tg and Tm values, and Na+ and Ca2+ release in group 1. There was no improvement in the MG63 viability or the ability of hMSCs to differentiate into osteoblasts where TiO2 decreased in favour of SiO2. Furthermore, in group 2, 50P2O5–25CaO was less dense than 45P2O5–30CaO, degraded dramatically less, had lower Tg and Tm values and released less Na+ and Ca(2+). The synergistic effect of doping 5 mol% TiO2 and 5 mol% SiO2 increased the MG63 viability in both compositions and was found 45P2O5–30CaO to have promising results in terms of the ability of hMSCs to differentiate into osteoblasts. To conclude, substituting TiO2 in place of SiO2 improved the physical properties and the biocompatibility of (P2O5-CaO-Na2O) glass system, whereas doping 5 mol% SiO2 and 5 mol% TiO2 together in place of P2O5 and CaO had a synergistic effect in controlling their degradation rate and improving their biological responses.

Flame-Spheroidized Phosphate-Based Glass Particles with Improved Characteristics for Applications in Mesenchymal Stem Cell Culture Therapy and Tissue Engineering

The chemical formulation of phosphate-based glasses (PBGs) can be tailored to fit particular end applications such as bone tissue engineering. While most reports to date have evaluated the effect of PBG chemical formulation on bone cells, this study specifically explored the manufacturing process, the changes in physical and chemical properties of PBG particles after flame spheroidization, and subsequent effects on human mesenchymal stem cells (hMSCs), a prime cell type for regenerative medicine applications. Flame spheroidization involves feeding irregular PBG particles (microparticles, MP) into a hot flame, causing them to melt and mold into solid spherical PBG particles (microspheres, MS). The laser diffraction analysis showed an increase in the volume-weighted mean diameter of particles from 48 to 139 μm after spheroidization and also revealed changes in the chemical composition of smaller MS (< 45 μm in size), whereas MS in other size ranges did not show significantly different chemical composition compared to MP. Additionally, some air bubbles were entrapped inside particles during spheroidization, causing a 2% drop in relative density of MS. However, the packing density of MS was 30% higher than that of MP. Culture of hMSCs on the particles showed significant improvement in cell spreading on MS compared to that on MP and nearly 2 times higher cell metabolic activity after 7 days of culture, suggesting that MS provided a more favorable support and geometry for hMSC attachment and growth for tissue engineering.

Formulation and in vitro characterization of rifampicin-loaded porous poly (ε-caprolactone) microspheres for sustained skeletal delivery

PURPOSE

Mycobacterium tuberculosis is a serious public health problem affecting hundreds of millions of elderly people worldwide, which is difficult to be treated by traditional methods because of the peculiarity of skeletal system and liver damage caused by high-dose administration. In this research, a porous drug release system has been attempted to encapsulate rifampicin (RIF) into poly (ε-caprolactone) (PCL) microspheres to improve the efficacy and benefit of anti-tuberculosis drug in skeletal system.

MATERIALS AND METHODS

The microspheres prepared by two different methods, oil-in-oil (o/o) emulsion solvent evaporation method and oil-in-water (o/w) method, were characterized in terms of morphology, size, encapsulation efficiency, drug distribution, degradation, and crystallinity.

RESULTS

The microspheres exhibited a porous structure with evenly drug distribution prepared by o/o emulsion solvent evaporation method, and their diameter ranged from 50.54 to 57.34 μm. The encapsulation efficiency was up to 61.86% when drug-loading content was only 1.51%, and showed a little decrease with the drug-loading content increasing. In vitro release studies revealed that the drug release from porous microspheres was controlled by non-Fickian diffusion, and almost 80% of the RIF were completely released after 10 days. The results of RIF-loaded microspheres on the antibacterial activity against Staphylococcus aureus proved that the porous microspheres had strong antibacterial ability. In addition, the polymer crystallinity had prominent influence on the degradation rate of microspheres regardless of the morphology.

CONCLUSION

It was an efficient way to entrap slightly water-soluble drug like RIF into PCL by o/o emulsion solvent evaporation method with uniform drug distribution. The RIF-loaded porous PCL microspheres showed the combination of good antimicrobial properties and excellent cytocompatibility, and it could generate gentle environment by PCL slow degradation.

Porous calcium phosphate glass microspheres for orthobiologic applications

Orthobiologics is a rapidly advancing field utilising cell-based therapies and biomaterials to enable the body to repair and regenerate musculoskeletal tissues. This paper reports on a cost-effective flame spheroidisation process for production of novel porous glass microspheres from calcium phosphate-based glasses to encapsulate and deliver stem cells. Careful selection of the glass and pore-forming agent, along with a manufacturing method with the required processing window enabled the production of porous glass microspheres via a single-stage manufacturing process. The morphological and physical characterisation revealed porous microspheres with tailored surface and interconnected porosity (up to 76 ± 5%) with average pore size of 55 ± 8 µm and surface areas ranging from 0.34 to 0.9 m² g^-1. Furthermore, simple alteration of the processing parameters produced microspheres with alternate unique morphologies, such as with solid cores and surface porosity only. The tuneable porosity enabled control over their surface area, degradation profiles and hence ion release rates. Furthermore, cytocompatibility of the microspheres was assessed using human mesenchymal stem cells via direct cell culture experiments and analysis confirmed that they had migrated to within the centre of the microspheres. The novel microspheres developed have huge potential for tissue engineering and regenerative medicine applications.

STATEMENT OF SIGNIFICANCE

This manuscript highlights a simple cost-effective one-step process for manufacturing porous calcium phosphate-based glass microspheres with varying control over surface pores and fully interconnected porosity via a flame spheroidisation process. Moreover, a simple alteration of the processing parameters can produce microspheres which have a solid core with surface pores only. The tuneable porosity enabled control over their surface area, degradation profiles and hence ion release rates. The paper also shows that stem cells not only attach and proliferate but more importantly migrate to within the core of the porous microspheres, highlighting applications for bone tissue engineering and regenerative medicine.

Interrelationships among hydrogen permeation, physiochemical properties and early adsorption abilities of titanium

This study aimed to investigate if the titanium samples with low hydrogen permeation which treated with a novel etching combination: phosphoric acid and sodium fluoride could influence the surface physiochemical properties and early adsorption ability. Titanium samples were treated with three different concentrations of the new formula, as groups A, B and C, and treated with the traditional etching formula, as group T. Zeta potential, contact angle, X-ray photoelectron spectroscopy (XPS) and fibronectin (FN)/vitronectin (VN) adsorption of Sprague-Dawley (SD) rat tibial osteotomies in the initial 30min and MG-63 adsorption in the initial 24 h were detected. Basing on the results of trails and pearson correlation analysis, the low hydrogen permeation into titanium didn't exert an impact on the surface morphology and surface stability. The adsorptions of F, P, S, acid hydroxyl and basic hydroxyl on the surfaces brought no bear on them as well. Surface concave depth and surface skewness showed highly positive correlation and moderate negative correlation with adsorption ability, respectively. Therefore, the surface morphology of titanium treated with the novel etching formula plays the only and primary role on the early adsorption. Because of its specific surface topography, group C showed the best performance which possessed slightly superiority than those of group B and group T, and with the lowest being group A. The low hydrogen permeation into titanium substrate was just benefit for improving the titanium mechanical properties, but not for the surface biochemical traits.

Zinc and strontium based phosphate glass beads: a novel material for bone tissue engineering

Degradable phosphate-based glasses that contain strontium, zinc and calcium were investigated to examine their function as an osteoconductive material. Glass beads of the general formula of (P₂O₅)-(Na₂O)-(TiO₂)-(CaO)-(SrO) or (ZnO) were prepared by a melt quench technique followed by milling and spheroidisation. After performing x-ray diffraction on all the samples for glass structure evaluation, glass bead size distribution was initially measured by a scanning electron microscope (SEM). Then, some of these samples were immersed in deionised water to evaluate both the surface changes and measure the ion release rate, whereas other samples of glass beads were incubated in culture media to determine pH changes. Furthermore, human osteoblast-like osteosarcoma cells MG63 and human mesenchymal stem cells were seeded on the glass beads to determine their cytocompatibility via applying CCK assay, ALP assay and Ca assay. SEM images and fluorescence images of confocal microscopy were performed for the cellular studies. While mass degradation and ion release results displayed a significant increase with zinc and strontium incorporation within time, pH results showed an initial increase in pH followed by a decrease. Cellular studies emphasised that all formulations enhanced cellular proliferation. Phosphate glass beads with zinc content 5 mol% and strontium content of 17.5 mol%, (ZnO5) and (SrO17.5) respectively displayed more promising results although they were insignificantly different from that of control (p > 0.05). This may suggest their applicability in hard tissue engineering.

Biomineralization of Fucoidan-Peptide Blends and Their Potential Applications in Bone Tissue Regeneration

Fucoidan (Fuc), a natural polysaccharide derived from brown seaweed algae, and gelatin (Gel) were conjugated to form a template for preparation of biomimetic scaffolds for potential applications in bone tissue regeneration. To the Fuc-Gel we then incorporated the peptide sequence MTNYDEAAMAIASLN (MTN) derived from the E-F hand domain, known for its calcium binding properties. To mimic the components of the extracellular matrix of bone tissue, the Fuc-Gel-MTN assemblies were incubated in simulated body fluid (SBF) to induce biomineralization, resulting in the formation of β-tricalcium phosphate, and hydroxyapatite (HAp). The formed Fuc-Gel-MTN-beta-TCP/HAP scaffolds were found to display an average Young's Modulus value of 0.32 GPa (n = 5) with an average surface roughness of 91 nm. Rheological studies show that the biomineralized scaffold exhibited higher storage and loss modulus compared to the composites formed before biomineralization. Thermal phase changes were studied through DSC and TGA analysis. XRD and EDS analyses indicated a biphasic mixture of β-tricalcium phosphate and hydroxyapatite and the composition of the scaffold. The scaffold promoted cell proliferation, differentiation and displayed actin stress fibers indicating the formation of cell-scaffold matrices in the presence of MT3C3-E1 mouse preosteoblasts. Osteogenesis and mineralization were found to increase with Fuc-Gel-MTN-beta-TCP/HAP scaffolds. Thus, we have developed a novel scaffold for possible applications in bone tissue engineering.

Biomimetically grown apatite spheres from aggregated bioglass nanoparticles with ultrahigh porosity and surface area imply potential drug delivery and cell engineering applications

Here we communicate the generation of biomimetically grown apatite spheres from aggregated bioglass nanoparticles and the potential properties applicable for drug delivery and cell/tissue engineering. Ion releasing nanoparticulates of bioglass (85%SiO₂-15%CaO) in a mineralizing medium show an intriguing dynamic phenomenon - aggregation, mineralization to apatite, integration and growth into micron-sized (1.5-3μm) spheres. During the progressive ionic dissolution/precipitation reactions, nano-to-micro-morphology, glass-to-crystal composition, and the physico-chemical properties (porosity, surface area, and charge) change dynamically. With increasing reaction period, the apatite becomes more crystallized with increased crystallinity and crystal size, and gets a composition closer to the stoichiometry. The developed microspheres exhibit hierarchical surface nanostructure, negative charge (ς-potential of -20mV), and ultrahigh mesoporosity (mesopore size of 6.1nm, and the resultant surface area of 63.7m²/g and pore volume of 0.153cm³/g) at 14days of mineralization, which are even higher than those of its precursor bioglass nanoparticles. Thanks to these properties, the biomimetic mineral microspheres take up biological molecules effectively, i.e., loading capacity of positive-charged protein is over 10%. Of note, the release is highly sustainable at a constant rate, i.e., profiling almost 'zero-order' kinetics for 4weeks, suggesting the potential usefulness as protein delivery systems. The biomimetic mineral microspheres hold some remnant Si in the core region, and release calcium, phosphate, and silicate ions over the test period, implying the long-term ionic-related therapeutic functions. The mesenchymal stem cells favour the biomimetic spheres with an excellent viability. Due to the merit of sizes (a few micrometers), the spheres can be intercalated into cells, mediating cellular interactions in 3D cell-spheroid engineering, and also can stimulate osteogenic differentiation of cells when incorporated into cell-laden gels. The intriguing properties observed in this study, including biomimetic composition, high mesoporosity, release of therapeutic ions, effective loading and long-term release of proteins, and diverse yet favorable 3D cellular interactions, suggest great potential of the newly developed biomimetic microspheres in biomedical applications, such as drug delivery and cell/tissue engineering.

STATEMENT OF SIGNIFICANCE

This work reports the generation of apatite spheres with a few micrometers in size biomimetically grown from bioactive glass nanoparticles, through a series of intriguing yet unprecedented phenomenon involving aggregation of nanoparticles, mineralization and sphere growth. The mineral microspheres possess some unique physico-chemical properties including mesoporosity, ultrahigh surface area, and therapeutic ionic release. Furthermore, the spheres show excellent loading and delivery capacity of protein molecules, and mediate favorable cellular interactions in 2D and 3D culture conditions, demonstrating a future multifunctional microcarrier platform for the therapeutics delivery and cell/tissue engineering.

Towards modular bone tissue engineering using Ti–Co-doped phosphate glass microspheres: cytocompatibility and dynamic culture studies

The production of large quantities of functional vascularized bone tissue ex vivo still represent an unmet clinical challenge. Microcarriers offer a potential solution to scalable manufacture of bone tissue due to their high surface area-to-volume ratio and the capacity to be assembled using a modular approach. Microcarriers made of phosphate bioactive glass doped with titanium dioxide have been previously shown to enhance proliferation of osteoblast progenitors and maturation towards functional osteoblasts. Furthemore, doping with cobalt appears to mimic hypoxic conditions that have a key role in promoting angiogenesis. This characteristic could be exploited to meet the clinical requirement of producing vascularized units of bone tissue. In the current study, the human osteosarcoma cell line MG-63 was cultured on phosphate glass microspheres doped with 5% mol titanium dioxide and different concentrations of cobalt oxide (0%, 2% and 5% mol), under static and dynamic conditions (150 and 300 rpm on an orbital shaker). Cell proliferation and the formation of aggregates of cells and microspheres were observed over a period of two weeks in all glass compositions, thus confirming the biocompatibility of the substrate and the suitability of this system for the formation of compact micro-units of tissue. At the concentrations tested, cobalt was not found to be cytotoxic and did not alter cell metabolism. On the other hand, the dynamic environment played a key role, with moderate agitation having a positive effect on cell proliferation while higher agitation resulting in impaired cell growth. Finally, in static culture assays, the capacity of cobalt doping to induce vascular endothelial growth factor (VEGF) upregulation by osteoblastic cells was observed, but was not found to increase linearly with cobalt oxide content. In conclusion, Ti–Co phosphate glasses were found to support osteoblastic cell growth and aggregate formation that is a necessary precursor to tissue formation and the upregaulation of VEGF production can potentially support vascularization.

Review of the Development of Methods for Characterization of Microspheres for Use in Embolotherapy: Translating Bench to Cathlab

Therapeutic embolotherapy is the deliberate occlusion of a blood vessel within the body, which can be for the prevention of internal bleeding, stemming of flow through an arteriovenous malformation, or occlusion of blood vessels feeding a tumor. This is achieved using a wide selection of embolic devices such as balloons, coils, gels, glues, and particles. Particulate embolization is often favored for blocking smaller vessels, particularly within hypervascularized tumors, as they are available in calibrated sizes and can be delivered distally via microcatheters for precise occlusion with associated locoregional drug delivery. Embolic performance has been traditionally evaluated using animal models, but with increasing interest in the 3R's (replacement, reduction, refinement), manufacturers, regulators, and clinicians have shown interest in the development of more sophisticated in vitro methods for evaluation and prediction of in vivo performance. Herein the current progress in developing bespoke techniques incorporating physical handling, fluid dynamics, occlusive behavior, and sustained drug elution kinetics within vascular systems is reviewed. While it is necessary to continue to validate the safety of such devices in vivo, great strides have been made in the development of bench tests that better predict the behavior of these products aligned with the principles of the 3R's.

Bioactive calcium phosphate-based glasses and ceramics and their biomedical applications: A review

An overview of the formation of calcium phosphate under in vitro environment on the surface of a range of bioactive materials (e.g. from silicate, borate, and phosphate glasses, glass-ceramics, bioceramics to metals) based on recent literature is presented in this review. The mechanism of bone-like calcium phosphate (i.e. hydroxyapatite) formation and the test protocols that are either already in use or currently being investigated for the evaluation of the bioactivity of biomaterials are discussed. This review also highlights the effect of chemical composition and surface charge of materials, types of medium (e.g. simulated body fluid, phosphate-buffered saline and cell culture medium) and test parameters on their bioactivity performance. Finally, a brief summary of the biomedical applications of these newly formed calcium phosphate (either in the form of amorphous or apatite) is presented.

Degradation of zinc containing phosphate-based glass as a material for orthopedic tissue engineering

Phosphate-based glasses have been examined in many studies as a potential biomaterial for bone repair because of its degradation properties, which can be controlled and allow the release of various elements to promote osteogenic tissue growth. However most of these experiments studied either tertiary or quaternary glass systems. This study investigated a qinternary system that included titanium dioxide for degradation rate control and zinc that is considered to have a role in bone formation. Zinc and titanium phosphate glass discs of different compositions were melt synthesized and samples of each composition was tested for different physical, chemical and biological characteristics via density measurement, X-ray diffraction, differential thermal analysis, mass loss, ion release, scanning electron microscopy, biocompatibility studies via live/dead assays at three time points (day 1, 4, and 7). The results showed that the glass was amorphous and that the all thermal variables decreased as zinc oxide amount raised, mass loss as well as ion release increased as zinc oxide increased, and the maximum rise was with ZnO15. The cellular studies showed that all the formulation showed similar cytocompatibility properties with MG63 except ZnO15, which displayed cytotoxic properties and this was confirmed also by the scanning electron microscope images. In conclusion, replacing calcium oxide with zinc oxide in proportion less than 10 % can have a positive effect on bone forming cells.

A novel hybrid nanofibrous strategy to target progenitor cells for cost-effective in situ angiogenesis

Ti-doped calcium phosphate ormoglasses combined with biodegradable PLA promote an efficient and low-cost angiogenesis by the generation of high Ca²⁺concentrated interfaces that induce a high yield of tubulogenesis, with the gain in interface–cell interaction and instructivity.

Structure and solubility behaviour of zinc containing phosphate glasses

The structure of phosphate glasses of general composition 10Na₂O : (20 + x/2)ZnO : (20 + x/2)CaO : (50 -x)P₂O₅ (0 ≤x≤ 20) has been investigated using IR spectroscopy, 1D ³¹P and ⁴³Ca MAS Bloch decay, ³¹P-³¹P double quantum MAS-NMR and ⁴³Ca and ⁶⁷Zn static NMR techniques, as well as neutron diffraction analysis. Zinc is shown to aid glass formation in this system. Glass transition temperature and density increase with increasing cation : phosphate ratio. However, free volume calculations show structures becoming significantly more compact from x = 5 to x = 10. The structural data confirm depolymerisation of the glasses with increasing cation : phosphate ratio. Zinc oxide is found to act in a network forming role in the system, with ⁶⁷Zn NMR and neutron diffraction analysis confirming zinc exhibits predominantly four-coordinate geometry. Solubility in deionised water and tris/HCl buffer solution is seen to decrease significantly with increasing x-value. This is discussed in terms of water ingress and the degree of structural openness, associated with increased cross-linking and a decrease in concentration of P-O-P linkages. pH measurements confirm invert phosphate compositions maintain physiological pH levels on immersion in water and buffer solutions for up to four weeks.

Titanium phosphate glass microcarriers induce enhanced osteogenic cell proliferation and human mesenchymal stem cell protein expression

In this study, we have developed 50- to 100-µm-sized titanium phosphate glass microcarriers (denoted as Ti5) that show enhanced proliferation of human mesenchymal stem cells and MG63 osteosarcoma cells, as well as enhanced human mesenchymal stem cell expression of bone differentiation markers, in comparison with commercially available glass microspheres at all time points. We also demonstrate that these microcarriers provide superior human mesenchymal stem cell proliferation with conventional Dulbecco’s Modified Eagle medium than with a specially developed commercial stem cell medium. The microcarrier proliferative capacity is revealed by a 24-fold increase in MG63 cell numbers in spinner flask bioreactor studies performed over a 7-day period, versus only a 6-fold increase in control microspheres under the same conditions; the corresponding values of Ti5 and control microspheres under static culture are 8-fold and 7-fold, respectively. The capability of guided osteogenic differentiation is confirmed by ELISAs for bone morphogenetic protein-2 and osteopontin, which reveal significantly greater expression of these markers, especially osteopontin, by human mesenchymal stem cells on the Ti5 microspheres than on the control. Scanning electron microscopy and confocal laser scanning microscopy images reveal favorable MG63 and human mesenchymal stem cell adhesion on the Ti5 microsphere surfaces. Thus, the results demonstrate the suitability of the developed microspheres for use as microcarriers in bone tissue engineering applications.

Preparation and characterization of vanillin-crosslinked chitosan therapeutic bioactive microcarriers

Chitosan microspheres with diameter of 14.3-48.5 μm were prepared by emulsion method and using natural vanillin as cross-linking agent. The surface morphology and microstructure of the microspheres were characterized by scanning electron microscopy, X-ray diffraction and Fourier-transform infrared spectroscopy, etc. The hollow microspheres showed a well-defined spherical shape with median diameter of 30.3 μm and possessed a uniform surface with micro-wrinkles, which is in favor of the drug release. Interpenetrating network cross-linking mechanism might result from the Schiff base reaction and the acetalization of hydroxyl and carbonyl between chitosan and vanillin. Berberine, as a model drug, was loaded in the microspheres and released in a sustainable manner. The drug loading ratio could change from 9.16% to 29.70% corresponding to the entrapment efficiency of 91.61% to 74.25%. In vitro cell culture study using MG63 cells and in vivo implantation clearly showed that the microspheres could provide favorable cell attachment and biocompatibility. The results confirm that the drug-loaded vanillin-crosslinked chitosan microspheres could be a worthy candidate either as carriers of drugs and cells, or as therapeutic matrix for bone repair and regeneration.

Development of microspheres for biomedical applications: a review

An overview of microspheres manufactured for use in biomedical applications based on recent literature is presented in this review. Different types of glasses (i.e. silicate, borate, and phosphates), ceramics and polymer-based microspheres (both natural and synthetic) in the form of porous , non-porous and hollow structures that are either already in use or are currently being investigated within the biomedical area are discussed. The advantages of using microspheres in applications such as drug delivery, bone tissue engineering and regeneration, absorption and desorption of substances, kinetic release of the loaded drug components are also presented. This review also reports on the preparation and characterisation methodologies used for the manufacture of these microspheres. Finally, a brief summary of the existing challenges associated with processing these microspheres which requires further research and development are presented.

In vitro bioactivity of titanium-doped bioglass

Previous studies have suggested that incorporating relatively small quantities of titanium dioxide into bioactive glasses may result in an increase in bioactivity and hydroxyapatite formation. The present work therefore investigated the in vitro bioactivity of a titanium doped bioglass and compared the results with 45S5 bioglass. Apatite formation was evaluated for bioglass and Ti-bioglass in the presence and absence of foetal calf serum. Scanning electron microscopy (SEM) images were used to evaluate the surface development and energy dispersive X-ray measurements provided information on the elemental ratios. X-ray diffraction spectra confirmed the presence of apatite formation. Cell viability was assessed for bone marrow stromal cells under direct and indirect contact conditions and cell adhesion was assessed using SEM.

Temporal analysis of dissolution by-products and genotoxic potential of spherical zinc-silicate bioglass: "imageable beads" for transarterial embolization

Embolization of vascular tumors is an important tool in minimally invasive surgical intervention. Radiopaque, non-degradable, and non-deformable spherical zinc-silicate glass particles were produced in a range of 45-500 μm. Three size ranges (45-150, 150-300, and 300-500 μm) were used in the current study. The glass microspheres were eluted in polar (saline solution) and non-polar (dimethyl sulfoxide) medium, and ion release profiles were recorded using inductively coupled plasma atomic emission spectroscopy. Approximately 80% of Gaussian distribution was achieved by simple sieving. The ions released from the microspheres were dependent upon surface area to volume ratio as well as the nature of elution media. Greater ions were released from smaller particles (45-150 μm) having largest surface area in polar medium. For the genotoxicity bacterial mutation Ames assay, the concentrations of all the ions were well below their therapeutic concentration reported in the literature. No mutagenic effect was observed in the bacterial mutation Ames test. Hence, it can be concluded that the glass microspheres produced herein are non-mutagenic further supporting the materials potential as a suitable embolic agent.

Osteoblastic differentiation under controlled bioactive ion release by silica and titania doped sodium-free calcium phosphate-based glass

Sodium-free phosphate-based glasses (PGs) doped with both SiO2 and TiO2 (50P2O5-40CaO-xSiO2-(10-x)TiO2, where x=10, 7, 5, 3, and 0mol%) were developed and characterised for controlled ion release applications in bone tissue engineering. Substituting SiO2 with TiO2 directly increased PG density and glass transition temperature, indicating a cross-linking effect of Ti on the glass network which was reflected by significantly reduced degradation rates in an aqueous environment. X-ray diffraction confirmed the presence of Ti(P2O7) in crystallised TiO2-containing PGs, and nuclear magnetic resonance showed an increase in Q(1) phosphate species with increasing TiO2 content. Substitution of SiO2 with TiO2 also reduced hydrophilicity and surface energy. In biological assays, MC3T3-E1 pre-osteoblasts effectively adhered to the surface of PG discs and the incorporation of TiO2, and hence higher stability of the PG network, significantly increased cell viability and metabolic activity indicating the biocompatibility of the PGs. Addition of SiO2 increased ionic release from the PG, which stimulated alkaline phosphatase (ALP) activity in MC3T3-E1 cells upon ion exposure. The incorporation of 3mol% TiO2 was required to stabilise the PG network against unfavourable rapid degradation in aqueous environments. However, ALP activity was greatest in PGs doped with 5-7mol% SiO2 due to up-regulation of ionic concentrations. Thus, the properties of PGs can be readily controlled by modifying the extent of Si and Ti doping in order to optimise ion release and osteoblastic differentiation for bone tissue engineering applications.

Phosphoric acid and sodium fluoride: a novel etching combination on titanium

We investigate whether a novel and inexpensive etching method, H3PO4 + NaF, on titanium could obtain both a lower hydrogen content and superior calcium phosphate deposition performance, while achieving similar surface roughness in comparison with the traditional etching method. Pure titanium samples were treated with different concentrations of H3PO4 + NaF at ambient temperature without auxiliary implementations (groups A, B and C), and were treated using the traditional method (group T). The samples were then maintained in simulated body fluid for 10 and 20 days. The surface morphology and chemistry, as well as the hydrogen content and distribution, were studied. The hydrogen content of the new groups are in the range of 31 (3.6)-86.9 (7.2) ppm, and that of group T is 287 (13.5) ppm. The amount of deposited calcium phosphates increases as the hydrogen content approaches 90 ppm; however, this trend does not apply as the hydrogen content exceeds 90 ppm. The surface roughnesses of groups A, B and C are in the range of 0.47 (0.01)-0.92 (0.05) µm. The new surface topography regularly transforms, and the surfaces with round pits exert a better effect on the deposition of calcium phosphates than the surfaces with sharp cusps.

Application of Titanium Metal Materials and Bone Tissue Engineering in Exercise-Induced Bone Injury Repair

Find a good biological characteristic of repair material of bone tissue engineering has been a hot research in the Department of orthopedics. Although there are various kinds of bone repair materials and methods, but no one can perfectly replace the human bone. Especially in the sports competition fierce, sports injury is one of the most common damages. Repair the damage of the traditional method of bone often because of their poor biocompatibility, lack of materials, not with the individual growth and other problems. It greatly reduced the effects of restoration. And titanium mesh and bone graft has the advantages of simple operation, low rejection, shapeable, implantation can close bone combined with host bone formation, and have fixed a support function, bone defect repair and can obtain satisfactory.

Biological performance of titania containing phosphate-based glasses for bone tissue engineering applications

The interplay between glass chemistry, structure, degradation kinetics, and biological activity provides flexibility for the development of scaffolds with highly specific cellular response. The aim of this study was therefore to investigate the role of titania inclusion into the phosphate-based glass on its ability to stimulate osteoblast-like human osteosarcoma (HOS) cells to adhere, proliferate and differentiate. In depth morphological and biochemical characterisation was performed on HOS cells cultured on the surface of glass discs. Cell proliferation was also studied in the presence of the glass extract. Cell differentiation, through osteoblast phenotype genes, alkaline phosphatase (ALP) activity and osteocalcin production, was carried out using normal or osteogenic media. Both Thermanox® and titania free glass were used as controls. The data demonstrated that titania inclusion provides desired cytocompatible surface that supported initial cell attachment, sustained viability, and increased cell proliferation similar or significantly higher than Thermanox®. The modified glasses regulated osteoblastic cell differentiation as detected by osteoblast phenotype gene transcription and upregulated ALP and osteocalcin expression. Using osteogenic media had no significant effect on ALP activity and osteocalcin expression. Therefore, titania modified phosphate glasses may have future use as bone tissue engineering scaffolds.

TiO₂-doped phosphate glass microcarriers: a stable bioactive substrate for expansion of adherent mammalian cells

Scalable expansion of cells for regenerative cell therapy or to produce large quantities for high-throughput screening remains a challenge for bioprocess engineers. Laboratory scale cell expansion using t-flasks requires frequent passaging that exposes cells to many poorly defined bioprocess forces that can cause damage or alter their phenotype. Microcarriers offer a potential solution to scalable production, lending themselves to cell culture processes more akin to fermentation, removing the need for frequent passaging throughout the expansion period. One main problem with microcarrier expansion, however, is the difficulty in harvesting cells at the end of the process. Therefore, therapies that rely on cell delivery using biomaterial scaffolds could benefit from a microcarrier expansion system whereby the cells and microcarriers are transplanted together. In the current study, we used bioactive glass microcarriers doped with 5% TiO₂ that display a controlled rate of degradation and conducted experiments to assess biocompatibility and growth of primary fibroblast cells as a model for cell therapy products. We found that the microcarriers are highly biocompatible and facilitate cell growth in a gradual controlled manner. Therefore, even without additional biofunctionalization methods, Ti-doped bioactive glass microcarriers offer potential as a cell expansion platform.