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3D Printing Bioactive Glass Scaffolds for Tissue Regeneration

Krista Grayson

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3D printing, also known as additive manufacturing, is already widely utilized in the medical industry. Hearing aids are routinely 3D printed, and there have been numerous reports of 3D printers producing patient-specific implants made from plastic or metal.1-4

Researchers are now combining advanced materials like bioactive glasses and 3D printing techniques to create custom scaffolds and implants that dissolve in the body and are replaced with new tissues.

What is bioactive glass?

Bioactive glasses provide the ideal synthetic materials for regenerative procedures such as bone grafting (Figure 1). Bioactive glasses are phosphosilicate materials that contain sodium and calcium. In the body, the glasses bind strongly to tissues and provide surfaces for new cell and tissue growth.

The glass eventually dissolves and releases calcium into the blood, which reacts to make hydroxylapatite, a hard and rigid mineral that is a key component of bone. In this way, bioactive glasses can aid the regeneration of bone. The composition of bioactive glasses can be tailored to give the glasses therapeutic, antimicrobial, and cell recruiting effects. Furthermore, bioactive glasses can be combined with other materials to create composites with a variety of properties, resulting in a wide range of medical applications.8,9

Steve Jung, CTO at Mo-Sci Corporation, described the advantageous properties of bioactive glass “Since its inorganic, it’s essentially a limitless supply; you can always make more, whereas bone or other types of materials used in medical applications you need cadaver or patient supplied bone, and sometimes there’s not enough”.

As bioactive glass grafts are man-made, they are also relatively inexpensive and provide no potential for disease transmission.8

Figure 1. Features that make bioactive glasses optimum candidates for bone tissue engineering.10

3D printing bioactive glass

The use of particles and putties of bioactive glass in clinical practice to support bone regeneration is widespread and has been used in more than a million patients.9,11 Bioactive glasses can also be used to make scaffolds to support tissue regeneration in larger areas. Bioactive glass scaffolds can be produced using foaming methods, resulting in scaffolds with pore structures that mimic the structure of bone (Figure 2).

However, it can be difficult to control the pore architectures of scaffolds produced by foaming, and the resulting scaffolds are relatively brittle. Surgeons often require scaffolds for bone grafts that have precise pore architectures and can be load bearing. 3D printing can produce bioactive glass structures with finely controlled pore structures (Figure 2) and increased mechanical strength.9,12

Figure 2. X-ray microtomography images of a bioactive glass scaffold produced using sol-gel foaming (a) and 3D printing (b,c).12

3D printing is a process that produces 3D structures from a digital model by laying down many layers of a material. Typically, 3D printing uses polymers or metals to produce structures, but researchers are now able to 3D print bioactive glass materials and composites. This enables bioactive glass scaffolds to be precisely designed in terms of their pore architecture and the final shape of the scaffold.13-15 3D printed structures made from bioactive glass could be used for novel solutions in medical implants, dental implants, surgery, and tissue scaffolding. The use of 3D printing means that a patient can be scanned, and then a unique implant or scaffold can be designed and printed with the correct size and properties for them.9,16

Although the use of 3D printed bioactive glasses is not yet widespread, there have been numerous investigations into their use in both animal models and human patients requiring unique, custom solutions (Figure 3). Research into the potential of 3D printed bioactive glasses and composites is ongoing, and the process of 3D printing bioactive glass structures is still being optimized, particularly with regards to optimizing the porosity and mechanical strength of the resulting scaffolds, and selecting the most appropriate binder materials and post processing techniques.16-18

There is also ongoing research into incorporating live cells, growth factors, and drugs into bioactive glass scaffolds using 3D printing.16,19

Figure 3. Photos of a tailor-made bioactive glass composite implant before operation (above, left), and during surgery (below, left). A CT scan image 2 years after reconstruction (right). New bone formation between the implant and surrounding bone is seen (white arrows).20

Bioactive Glass from Mo-Sci

3D printing bioactive glass scaffolds can produce precisely designed, custom scaffolds for bone grafting. However, the process of printing bioactive glasses is still under optimization.

Mo-Sci offers a wide variety of bioactive glasses for both research and medical applications, with custom compositions available upon request.21

References

  1. http://www.bbc.co.uk/news/uk-wales-2653440 Accessed May 11th, 2017.
  2. http://www.bbc.co.uk/news/technology-16907104 Accessed May 11th, 2017.
  3. http://www.nature.com/news/3-d-printed-windpipe-gives-infant-breath-of-life-1.13085 Accessed May 11th, 2017.
  4. https://www.forbes.com/sites/rakeshsharma/2013/07/08/the-3d-printing-revolution-you-have-not-heard-about/#19e1ce321a6b Accessed May 11th, 2017.
  5. “3D printing & medical applications” Carsten Engel at TEDxLiege, 2014. Available from: https://www.youtube.com/watch?v=y87RmyBxKic Accessed May 11th, 2017.
  6. Gross BC, Erkal JL, Lockwood SY, Chen C, Spence DM, “Evaluation of 3D Printing and Its Potential Impact on Biotechnology and the Chemical Sciences” Analytical Chemistry 86(70):3240-2253, 2014.
  7. Trombetta R, Inzana JA, Schwartz EM, Kates SL, Awad HA, “3D Printing of Calcium Phosphate Ceramics for Bone Tissue Engineering and Drug Delivery” Anals of Biomedical Engineering 45(1):23-44, 2017.
  8. “The benefits of bioactive glass” MoSci, 2016. Available from: https://vimeo.com/157284843 Accessed May 11th, 2017.
  9. “Julian Jones’ Inaugural Lecture at Imperial College London 2016” Julian Jones, 2016. Available from: https://www.youtube.com/watch?v=Kr0FKozsj88 Accessed May 11th, 2017.
  10. Montazerian M, Zantto ED, “History and trends of bioactive glass-ceramics” Journal of Biomedical Materials Research Part A 104A:1231-1249, 2016
  11. Van Gestel NAP, Geurts J, Hulsen DJW., van Rietbergen B, Hofmann S, Arts JJ, “Clinical Applications of S53P4 Bioactive Glass in Bone Healing and Osteomyelitic Treatment: A Literature Review” BioMed Research International 2015:684826, 2015.
  12. Hench LL, Jones JR, “Bioactive Glasses: Frontiers and Challenges” Frontiers in Bioengineering and Biotechnology 3:194, 2015.
  13. Qi X, Pei P, Zhu M, Du X, Xin C, Zhao S, Li X, Zhu Y, “Three dimensional printing of calcium sulfate and mesoporous bioactive glass scaffolds for improving bone regeneration in vitro and in vivo” Scientific Reports 7:42556, 2017.
  14. Wu C, Luo Y, Cuniberti G, Xiao Y, Gelinsky M, “Three-dimensional printing of hierarchical and tough mesoporous bioactive glass scaffolds with a controllable pore architecture, excellent mechanical strength and mineralization ability.” Acta Biomaterialia 7(6):2644-2650, 2011.
  15. Profeta AC, Huppa C, “Bioactive-glass in Oral and Maxillofacial Surgery” Craniomaxillofacial Trauma & Reconstruction 9(1):1-14, 2016.
  16. Bose S, Vahabzadeh S, Bandyopadhyay A, “Bone tissue engineering using 3D printing” Materials Today 16(12):496-504, 2013.
  17. Murphy C, Kolan KCR, Long M, Li W, Leu MC, Semon JA, Day DE, “3D printing of a polymer bioactive glass composite for bone repair” Solid Freedom Fabrication 2016: Proceedings of the 27th Annual International Solid Freedom Fabrication Symposium, 2016.
  18. Bergmann C, Lindner M, Zhang W, Koczur K, Kirsten A, Telle R, Fischer H, “3D printing of bone substitute implants using calcium phosphate and bioactive glasses” Journal of the European Ceramic Society 30(12):2563-2567, 2010.
  19. Murphy C, Kolan K, Li W, Semon J, Day D, Leu MC “3D bioprinting of stem cells and polymer/bioactive glass composite scaffolds for bone tissue engineering” International Journal of Bioprinting 3(1):1-11, 2017.
  20. Petola M, Vallittu PK, Vuorinen V, Aho AAJ, Aitasalo KM, “Novel composite implant in craniofacial bone reconstruction” European Archives of Otorhinolaryngology 269(2):623-628, 2011.
  21. http://www.mo-sci.com/bioactive-glass/ Accessed May 11th, 2017.