Bone grafting is a common procedure in orthopaedic, traumatology, and maxillofacial surgery. In the United States and Europe, half a million patients require bone grafts annually. However, there is a high risk for the patient to be infected (with over half of the hospital-acquired infections related to implants). One should not forget that bacteria colonizing on implants can form biofilms which are highly resistant to antibiotics and the host’s immune system.
Implants used in bone regeneration can be prepared from bioactive glass (BAG), a non-crystalline ceramic pertaining to its high bioactivity and high versatility. The glass with the composition 26.93SiO₂ - 26.93B₂O₃ - 22.66Na₂O - 1.72P₂O₅ - 21.77CaO (in mol%) was reported to be a good candidate based on its ability to not only promote bone regeneration (osteopromotion) but also vasculature (angiogenesis).¹ Due to its good thermal stability against crystallization, 3D porous scaffolds were successfully prepared from this glass.² Hydroxyapatite layer was found to precipitate on the borosilicate glass scaffolds confirming the great potential of this glass composition as bioactive glass.
Porous scaffolds could find application as a local drug delivery system. For example, a new bioactive scaffold was reported to deliver antibacterial or antifungal drugs for 6 weeks in vitro. However, it would be more beneficial to have a drug release on-demand. Nitric oxide is both antimicrobial and osteogenic. To the best of our knowledge, there has been no study reported on NO release from bioactive porous scaffolds using light. For this application, the scaffold should be prepared with specific porosity (at least 60%) and should emit light at a specific wavelength. The porosity will be obtained by preparing the scaffold using the porogen technique and the light emission will be by incorporating rare-earth ions (RE) doped crystals into the glass matrix
In this presentation, we will explain how biophotonic porous scaffolds can be prepared with upconversion properties using Yb³⁺ and Er³⁺ codoped CaWO₄ crystals. We will demonstrate that the scaffold emits green light under 980 nm pumping due to the upconversion process which is strong enough to release NO drugs.
Acknowledgments
This work was supported by the Academy of Finland [Flagship Programme, Photonics Research and Innovation PREIN-320165]. SG would like to thank the Academy of Finland for financial support through the UNIBIO project (#331924)
References
(1)           Ojansivu, M.; Mishra, A.; Vanhatupa, S.; Juntunen, M.; Larionova, A.; Massera, J.; Miettinen, S. The Effect of S53P4-Based Borosilicate Glasses and Glass Dissolution Products on the Osteogenic Commitment of Human Adipose Stem Cells. PLOS ONE 2018, 13 (8), e0202740. https://doi.org/10.1371/journal.pone.0202740.
(2)           Erasmus, E. P.; Sule, R.; Johnson, O. T.; Massera, J.; Sigalas, I. In Vitro Evaluation of Porous Borosilicate, Borophosphate and Phosphate Bioactive Glasses Scaffolds Fabricated Using Foaming Agent for Bone Regeneration. Sci Rep 2018, 8 (1), 3699. https://doi.org/10.1038/s41598-018-22032-2.