Biophotonic scaffolds for drug release using NIR excitation
Alvarez Morales, Gonzalo (2020)
2020
Materiaalitekniikan DI-tutkinto-ohjelma - Degree Programme in Materials Engineering, MSc (Tech)
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2020-04-24
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202004243663
https://urn.fi/URN:NBN:fi:tuni-202004243663
Tiivistelmä
Drug delivery systems (DDS) allow for precise control of the concentration of a drug in the organism over space and/or time. If loaded with the drugs before implantation, DDS could be engineered to release the drug under external stimulus. This stimulus could be light at 980nm which can penetrate the skin. This biophotonic DDS could then fight infections locally. Such DDS need to be fabricated from bioactive glasses which react when pumped at 980nm. Such glasses are capable of firm bonding with the surrounding tissues by developing bone-like hydroxyapatite (HA) layers when reacting with physiological fluids.
This thesis is focused on the development of the glass which will be used for the fabrication of the DDS: The glass of investigation is glass S53P4 (commercially available as BonAlive®) derivative from 50% SiO2 substitution (B50), which shows a faster dissolution, and faster conversion into HA than S53P4 glass. Er3+ & Yb3+ ions and NaYF4:Er3+,Yb3+ nanocrystals (NCs) were added in the bioactive glass so it can exhibit upconversion luminescence properties under 980nm pumping.
The development of upconverting glasses with the possibility to be sintered into highly porous scaffolds with high upconversion is first discussed. The glasses with the composition 95.5B50-0.5Er2O3-4Yb2O3 (in mole %) and with the composition 98%B50-2% NaYF4:Er3+,Yb3+ (wt.%) were found to be the most promising glasses for the fabrication of the scaffolds which are not only bioactive but also exhibit green light under 980nm pumping. Scaffolds were processed using the burn off method. They possess the appropriate level of porosity and exhibit upconversion. However, crystallization occurred during the sintering leading to some changes in the shape and intensity of the upconversion. The mechanical properties of the modified scaffolds were comparable to those of the B50 scaffold.
Scaffolds with 60-75% porosity were immersed in SBF for up to 336h. We found that they have a slower dissolution rate than the base glass but maintained an acceptable dissolution rate. The possibility to use the developed scaffolds in DDS using external near infrared excitation as a control signal is finally discussed in this thesis.
This thesis is focused on the development of the glass which will be used for the fabrication of the DDS: The glass of investigation is glass S53P4 (commercially available as BonAlive®) derivative from 50% SiO2 substitution (B50), which shows a faster dissolution, and faster conversion into HA than S53P4 glass. Er3+ & Yb3+ ions and NaYF4:Er3+,Yb3+ nanocrystals (NCs) were added in the bioactive glass so it can exhibit upconversion luminescence properties under 980nm pumping.
The development of upconverting glasses with the possibility to be sintered into highly porous scaffolds with high upconversion is first discussed. The glasses with the composition 95.5B50-0.5Er2O3-4Yb2O3 (in mole %) and with the composition 98%B50-2% NaYF4:Er3+,Yb3+ (wt.%) were found to be the most promising glasses for the fabrication of the scaffolds which are not only bioactive but also exhibit green light under 980nm pumping. Scaffolds were processed using the burn off method. They possess the appropriate level of porosity and exhibit upconversion. However, crystallization occurred during the sintering leading to some changes in the shape and intensity of the upconversion. The mechanical properties of the modified scaffolds were comparable to those of the B50 scaffold.
Scaffolds with 60-75% porosity were immersed in SBF for up to 336h. We found that they have a slower dissolution rate than the base glass but maintained an acceptable dissolution rate. The possibility to use the developed scaffolds in DDS using external near infrared excitation as a control signal is finally discussed in this thesis.