30th Annual Conference of the European Society for Biomaterials together with the 26th Annual Conference of the German Society for Biomaterials (DGBM)
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Bioactive glasses: from the laboratory to the clinic

Session chair: Boccaccini, Aldo, R. (University of Erlangen-Nuremberg, Institute of Biomaterials, Erlangen, Germany); Brauer, Delia (University of Jena, Jena, Germany)
 
Shortcut: I-SY1
Date: Tuesday, 10 September, 2019, 10:30 a.m.
Room: Hall 4
Session type: Symposia

The biomaterial “bioactive glass” celebrates this year its first 50 years since its invention by Prof. Larry Hench in 1969. The special symposium at ESB 2019 is organized to highlight the current status in the broad field of bioactive glasses, both from the fundamental and application viewpoints. Indeed, over the last 50 years, bioactive glasses, originally intended for applications as bone substituting materials and small orthopedic implants, have expanded in their functionalities and applications. Novel chemical compositions and advanced processing techniques pave the way to a great variety of medical applications, including biomedical coatings, dental care, scaffolds for tissue engineering, advanced drug delivery devices, wound healing, soft tissue repair and cancer treatment. Various applications of bioactive glasses will be presented and discussed in this special symposium.

Contents

Click on an contribution to preview the abstract content.

10:30 a.m. I-SY1-KL01

Bouncy Bioglass for Cartilage and Bone Regeneration (#40)

J. R. Jones1

1 Imperial College London, Department of Materials, London, United Kingdom

Introduction

Bioglass® has now been used in more than 1.5 million patients as a synthetic bone graft (e.g. NovaBone®, NovaBone Products LLC, FL). It has outperformed other bioactive ceramics in comparative in vivo studies and regulatory claims of “osteostimulaton” (NovaBone) and antimicrobial properties (BonAlive) show the acceptance that it is the ions that they release that provide added bioactivity. Bioglass’ potential for bone regeneration is limited because it is only available as a particulate or putty1. Only now are Bioglass scaffolds reaching clinical use (Bio2 Technologies), but they remain brittle. For bone regeneration, we need materials that can maintain the biological properties of Bioglass but can take cyclic loads and biodegrade at a controlled rate. No materials can currently regenerate articular cartilage.

Experimental Methods

We have developed sol-gel hybrids of covalently bonded co-networks of degradable polymers and bioactive silica. The hybrid acts as a single material with tailored mechanical properties and congruent degradation2. Sol-gel hybrids can be 3D extrusion printed to obtain porous scaffolds with regular and reproducible architecture that can be tuned in order to match the desired requirements. Herein, I will report on our covalently-linked silica/polycaprolactone (SiO2/PCL) hybrid material for regeneration of articular cartilage focal defects. The device is composed of a 3D printed porous scaffold capped with a dense thin layer of the same material: while the scaffold is intended to be fixed into the defect and promote cartilage regeneration, the cap should have optimised tribological properties to ensure low friction in contact with the opposing cartilage.

HYBRID CHALLENGES

The chemistry and processing is complex to create a successful bioactive hybrid. Challenges to overcome are: creating a porous structure while controlling degradation rate and mechanical properties. Critical to the success of the hybrids is achieving mechanical properties and controlled congruent degradation. This can only be achieved by synthesising hybrids that have covalent coupling between the co-networks.

Results and Discussion

HYBRIDS OF SYNTHETIC POLYMERS

SiO2/PCL hybrids with glycidyloxypropyltrimethoxy-silane (GTPMS) as the coupling agent have unprecedented mechanical properties, including elastic recovery and the ability to bounce or be hit by a hammer. Scaffolds can be directly printed through extrusion printing (Fig. 1). Chondrocytes seeded on 3D printed scaffolds demonstrated chondrogenic differentiation and cartilaginous matrix formation in vitro, showing positive staining for Collagen Type II, indicative of articular cartilage. Bone marrow stem cells seeded in the scaffolds also differentiate and produce Type II collagen. In vivo subcutaneous implantation in mice showed minimal inflammatory response (similar to sham).

Bespoke synthetic polymers can be synthesised with the coupling agents built in through controlled polymerisation, e.g. acrylate based polymers containing links of TMSPMA, spacer monomers and biodegradable linkers. Degree of branching and architecture (star v linear v branched) has a large effect on mechanical properties.

Conclusion

Hybrids have the potential to combine bioactivity of bioactive glasses with controlled degradation and mechanical properties. They have potential in bone and cartilage regeneration.

References

1. Jones J.R. Brauer D.S. Hupa L. Greenspan D.S. Int J Appl Glasses: 2016:7: 423-434.

2. Jones J.R., Acta Biomater. 9:4457-4486, 2013.

3. Tallia F. et al. Materials Horizons, 2018, 5, 849-860.

4. Chung J. et al. Acta Biomaterialia, 2017: 54: 411-418

Bouncy bioglass can be printed and stimulate type II collagen production
Clockwise: Flexible silica/PCL hybrids; SEM & photo of a 3D printed hybrid; Col II matrix in a pore produced by chondrocytes
Keywords: A-01 h - Composites and nanocomposites, A-05 a - Biomaterials for extrusion printing, A-07 e - Cartilage and osteochondral
11:00 a.m. I-SY1-KL02

Bioactive glass: from the laboratory to the clinic (#1012)

N. Lindfors1, R. Björkenheim1, G. Strömberg1, J. Pajarinen1, E. Eriksson1

1 Helsinki University, Helsinki University Hospital, Helsinki, Finland

Introduction

Bioactive glasses (BAGs) are bone substitutes with proven osteoconductive, osteostimulative, angiogenetic and antibacterial properties. Implanted in the body a rapid exchange of Na+ from the glass and H+ and H3O- from the solution takes place, forming silanol groups and a SiO2-layer at the glass surface. Migration of Ca2+ and PO43- to the surface of the BAG results in a CaO-P2O5-rich layer on top of the silica-layer. Subsequent protein adsorption and chemical bonding of apatite crystallites around collagen fibrils finally then form a bond between the BAG and the surrounding bone.

Bone formation and fracture healing is a highly regulated process involving several factors e.g. the mechanical environment, inflammatory and osteogenic cells, vascular and inflammatory mediators and when needed an osteogenic scaffold.

Experimental Methods

Clinically e.g. BAG-S53P4 granules have been used in benign tumor surgery, head and neck- spine and neurosurgery and in the treatment of osteomyelitis.  Osteomyelitis is an infectious process that leads to bone destruction. Surgical procedures are often performed in combination with systemic and local antibiotics using a two-stage procedure, in which autograft or synthetic bone is used for filling the bone defect. In a multinational study involving six countries and eleven centers, 116 patients with verified chronic osteomyelitis were treated using antibacterial BAG-S53P4 granules as part of the treatment. The success rate was 90%. The study showed that BAG-S53P4 granules could be used in a one-stage procedure with excellent results.

Results and Discussion

The iv-vivo behavior of BAGs is also dependent on the manufacturing process. By developing the sintering process of BAG-S53P4, new stable scaffolds have been manufactured and designed for a single-stage induced membrane technique.  Expressions of BMP and VEGF induced by BAG-S53P4 and PLGA coating, as well as, new bone formation have been observed iv-vivo, implying promising preclinical results.

Conclusion

Preclinical and clinical results of BAG-S53P4 support the use of BAG-S53P4 as bone graft subsitute in the treatment of bone defects, as well as in the treatment of infected bone. 

References

1. Hench LL. The story of Bioglass. J Mater Sci: Mater Med 2006;17:967–978.

2. Lindfors NC, Heikkilä J, Koski I, Mattila K, Aho J. Bioactive glass and autogenous bone as bone graft substitutes in benign bone tumors. J Biomed Mater Res 2008;90B:131-136.

3. Rantakokko J, Frantzen J, Heinänen J, Kajander S, Kotilainen E, Gullichsen E, Lindfors NC. Posterolateral spondylodesis using bioactive glass S53P4 and autogenous bone in instrumented unstable lumbar spine burst fracture – A prospective 10-year follow-up study. Scand J Surg 2012;101:66-71.

4. Frantzen J, Rantakokko J, Aro HT, Kajander S, Koski I, Gullichsen E, Kotilainen E, Lindfors NC. Instrumented spondylodesis in degenerative spondylolisthesis with bioactive glass and autologous bone – A prospective 11-year follow-up. J Spinal Disord Tech 2011;24:455-461.

5. Lindfors NC, Hyvönen P, Nyyssönen M, Kirjavainen M, Kankare J, Gullichsen E, Salo J. Bioactive glass S53P4 as bone graft substitute in treatment of osteomyelitis. Bone 2010;47:212-218.

6. Lindfors NC, Geurts J, Drago L, Arts JJ, Juutilainen V, Hyvönen P, Suda AJ, Aloj, D, Artiaco S, Alizadeh Ch, Brychcy A, Bialecki J, Romano` C.. Bioactive glass S53P4 in the treatment of osteomyelitis – a multinational study. Adv Exp Med Biol 2017;971:81-92.

7. Björkenheim R, Strömberg G, Pajarinen J, Ainola M, Uppstu P, Hupa L, Böhling TO, Lindfors NC. Polymer coated bioactive glass S53P4 increases VEGF and TNF expression in an induced membrane model in vivo. J Mater Sci 2017;52:9055-9065.

8. Björkenheim R, Strömberg G, Ainola M, Uppstu P, Aalto-Setälä L, Hupa L, Pajarinen J, Lindfors NC. BMP expression and bone formation are induced by bioactive glass S53P4 scaffolds in vivo. J Biomed Mater Res Part B Appl B 2018;11:45

Keywords: A-01 e - Bioglasses & silicates, A-11 a - Clinical trials, A-07 b - Antibacterial
11:30 a.m. I-SY1-03

Development and characterization of B and Co ions co-doped 45S5 bioactive glass for possible use in angiogenesis (#134)

S. Chen1, M. Michálek1, D. Galusková2, M. Michálková2, P. Švančárek2, A. Talimian2, H. Kaňková1, J. Kraxner1, L. Liverani3, D. Galusek2, A. R. Boccaccini3

1 TnU AD, Centre for Functional and Surface Functionalized Glass, Trenčín, Slovakia
2 TnU AD, Joint Glass Centre of the IIC SAS, TnU AD and FChFT STU, Centre for Functional and Surface Functionalized Glass, Trenčín, Slovakia
3 University of Erlangen-Nuremberg, Institute of Biomaterials, Erlangen, Germany

Introduction

In the past decade, boron (B) has been increasingly used in bioactive materials to promote angiogenesis, exhibiting positive effect on neovascularization [1]. B potently activates the MAPK signaling pathway and borate co-transporter to markedly increase vascular endothelial cells (VECs) proliferation and migration. Addition of B also enhances VECs tubule formation and secretion of IL-6 and bFGF, which also stimulate the angiogenic response.
Cobalt (Co) as an essential element in human physiology can also promote angiogenesis, albeit in a different way [2]. Hypoxia (low oxygen pressure) in vivo plays a pivotal role in coupling angiogenesis with osteogenesis via progenitor cell recruitment, differentiation and angiogenesis. Hypoxia activates a series of angiogenic processes mediated by the hypoxia inducing factor-1α (HIF-1α). Hypoxia can be mimicked by stabilizing HIF-1α expression. Co2+ ion is a well-established chemical inducer of HIF-1α, which elicits a significant hypoxic cascade including VEGF secretion, identified as a key regulator in angiogenesis.
The incorporation of biologically active ions in bioactive glasses is being increasingly considered to enhance the angiogenic effect of these materials [3]. In this study, both B and Co were used as dopants in a 45S5 bioactive glass in order to promote angiogenesis by two different mechanisms (Fig. 1).

Experimental Methods

B (2 wt% and 10 wt% B2O3) and Co (2 wt% and 4 wt% CoO) were added into 45S5 bioactive glass, either alone, or in conjunction, replacing Si partially. The glass was prepared by conventional melt quenching method. The samples with different compositions were respectively denoted as BG, BG.2B, BG.10B, BG.2Co, BG.4Co, BG.2B2Co, BG.2B4Co, BG.10B2Co and BG.10B4Co.
The composition of the bioactive glasses (BGs) was characterized by Fourier transform infrared spectroscopy (FTIR, Shimadzu IRAffinity-1S), energy-dispersive X-ray spectroscopy (EDX; Scanning Electron Microscope JEOL JSM-7600 F/EDS/WDS/EBSD) and inductively coupled plasma-optical emission spectrometry (ICP-OES; Agilent 5100 SVDV ICP OES). The release of Si, P, Ca, B and Co ions from the BGs powder (less than 25 μm) was also determined by ICP-OES using simulated body fluid (SBF) as immersion medium for 1, 3 and 7 days. Afterwards, the solution was centrifugated and filtrated, and the ionic dissolution products (IDPs) were measured by ICP-OES. After immersion, the samples were examined by scanning electron microscopy (SEM; Scanning Electron Microscope JEOL JSM-7600 F/EDS/WDS/EBSD) and X-ray diffraction (XRD; X-ray powder diffractometer Panalytical Empyrean DY1098).

Results and Discussion

The results of BG.2B2Co and BG.10B4Co were selected to demonstrate B and Co doping in the 45S5 BG. Fig. 2A confirms the presence and homogeneous distribution of all elements (Si, Na, P, Ca, B and Co) in the BG.2B2Co and BG.10B4Co samples. The compositions determined by ICP were almost identical to the designed compositions (Fig. 2B). FTIR spectra of BGs before/after immersion in SBF are shown in Fig. 2C. The main absorption bands of BGs before immersion are assigned to: 1479 cm-1 (CO32- ν3), 1396 cm-1 (νB-O of BO3), 1188 cm-1 (νB-O of BO4), 1100-900 cm-1 (Si-O-Si and phosphate), 866 cm-1 (CO32- ν2), 732 cm-1(O-P-O), 472 cm-1 (Si-O-Si). After immersion in SBF for 7 days, four feature absorption bands of hydroxyapatite (HA) at 962 cm-1 (PO43- ν1), 447 cm-1 (PO43- ν2), 1022 cm-1 (PO43- ν3) and 560-600 cm-1 (PO43- ν4) were identified. The results of XRD (Fig. 2D) also confirmed the presence of HA through two observed diffraction lines attributed to HA phase at 2θ=32° (khl=211) and 2θ=26° (khl=002). Before immersion both tested glasses were amorphous. The crystals of HA can be directly observed in Fig. 2E. A burst release of all measured elements during the first day is indicated in Fig. 2F, which almost levelled out afterwards. And it can be observed that different composite of B and Co successfully caused significant different release of B and Co.

Conclusion

In this study, B and Co ions were successfully and homogeneously doped into 45S5 bioactive glass. The compositions measured by ICP were almost identical to the designed compositions, and different release behaviour of B and Co was found. Both BG.2B2Co and BG.10B4Co could induce the production of HA on the surface of BG particles upon immersion in SBF.​ Presented results would lead to better understanding of the possible synergistic effect of B and Co on angiogenesis.

References

[1] Durand L A H, Vargas G E, Romero N M, et al. Angiogenic effects of ionic dissolution products released from a boron-doped 45S5 bioactive glass[J]. Journal of Materials Chemistry B, 2015, 3(6): 1142-1148.
[2] Hu X, Yu S P, Fraser J L, et al. Transplantation of hypoxia-preconditioned mesenchymal stem cells improves infarcted heart function via enhanced survival of implanted cells and angiogenesis[J]. The Journal of thoracic and cardiovascular surgery, 2008, 135(4): 799-808.
[3] Hoppe A, Güldal N S, Boccaccini A R. A review of the biological response to ionic dissolution products from bioactive glasses and glass-ceramics[J]. Biomaterials, 2011, 32(11): 2757-2774.

Acknowledgement

This paper is created in the frame of the project FunGlass that has received funding from the European Union´s Horizon 2020 research and innovation programme under grant agreement No 739566. And the financial support of this work by the funding from the grant VEGA 2/0026/17 and APVV 15/0014 are gratefully acknowledged.

Figure 1.
The mechanisms of promoting angiogenesis through addition of boron and cobalt to bioactive glasses.
Figure 2.
The results of material characterization of BG.2B2Co and BG.10B4Co.
Keywords: A-01 e - Bioglasses & silicates, A-07 d - Bone , A-07 r - Wound healing and tissue adhesives
11:45 a.m. I-SY1-04

Oxyfluorophosphate bioactive glasses and glass-ceramics (#1015)

A. Nommeots-Nomm1, A. Houaoui2, L. Petit3, E. Pauthe2, M. Boissière2, J. Massera1

1 Tampere University, Faculty of Medicine and Health Technology, Tampere, Finland
2 Université de Cergy-Pontoise, Equipe de Recherche sur les Relations Matrice Extracellulaire-Cellules , Cergy, France
3 Tampere University, Photonics Laboratory, Tamnpere, Finland

Introduction

Fluoride containing bioactive glasses have attracted much interest in dental and orthopedic application, pertaining to their ability to precipitate fluorapatite rather than hydroxyapatite. Indeed, fluorapatite is more stable and chemically resistant than hydroxyapatite and is less sensitive to resorption in-vivo. However, introducing fluoride in silicate based bioactive glasses was found to lead to an increase in the silica network connectivity and lack of Si-F bonds, in turns leading to a decrease in the glass bioactivity. The consequence of a lower bioactivity is the formation of inhomogeneous hydroxyapatite and silica-rich layer at the glass particle surface. Alternatives are the phosphate glasses. Invert phosphate glasses (up to the metaphosphate) have been found to be bioactive. However, little is known on the impact of Fluorine on the in-vitro dissolution properties and their interaction with cells.

Experimental Methods

Glass within the 75NaPO3-(25-x)CaO-xCaF2, with from 0 to 20, were processed by melt quenching. The structure of the glasses was investigated by Raman, FTIR and NMR in order to assess the role played by the F ions in the glass network. The thermal properties were measured using a DTA. Based on the DTA measurement, a series of heat treatment were performed to produce glass-ceramics. The in-vitro dissolution of the glasses and glass-ceramics produced was tested in TRIS buffer solution. Ion released in solution was quantified by ICP-OES. The index of cytotoxicity (IC50) was assessed using MC3T3-E1 cells cultured in extract. Live/dead, cytoplasmic nuclear ratios as well as cell proliferation, upon cell exposure to the glass extract was also evaluated

Results and Discussion

With increasing fluorine content an increase of the P-F bond is reported. The structural changes, associated to the increase in F ions, leads to an increase in dissolution rate. The thermal properties were measured using DTA and a crystallization study revealed that upon substitution of CaO for CaF2 a progressive change from surface to bulk crystallization occurred. This is of particular interest as, typically, bioactive glass crystallize from the surface limiting their application as glass-ceramics. An increase in F content leads to a decrease in the IC50, however the glass ceramics containing CaF2 was found to have a higher IC50 than its glass counterpart. Furthermore, crystallization of the glasses into glass ceramics, was also found to lead to an increase in the cytoplasmic nuclear ratio.  

Conclusion

Overall, the developed glass were found, as expected to favor the precipitation of a fluoroapatite layer. The presence of F increase the dissolution rate and leads to a decrease in the glass concentration that can be used, in order to maintain over 50% cell viability. The developed F-containing glasses can be processed into glass-ceramics through control CaF2 crystal growth. The presence of nanocrystals leads to an increase in the IC50 greater than those reported for the glass counterpart, indicating that the glass-ceramic is less cytotoxic. The developed glasses were found to have thermal, in-vitro dissolution and cell bioresponse promising for orthopedic and dental application

Acknowledgement

The authors would like to acknowledge the Academy of Finland for financial support. Tamper University of Technology foundation is also gratefully acknowledge for the salary of A. N-N. Finally, IAS (Institute for Advanced Studies) is acknowledge for supporting visits between the partners.

Keywords: A-01 a - Metallic biomaterials/implants