Entrapment of Photon Upconversion Micelles in Anionic Nanofibrillar Cellulose Hydrogel: Study on System Stability, Upconversion Efficiency and Optimization
Löfman, Emilia (2022)
2022
Ympäristö- ja energiatekniikan DI-ohjelma - Programme in Environmental and Energy Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
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Hyväksymispäivämäärä
2022-05-23
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202205174993
https://urn.fi/URN:NBN:fi:tuni-202205174993
Tiivistelmä
Triplet fusion upconversion, TF-UC, is a photochemical process where the properties of two molecule types, sensitizer, and annihilator, are combined to produce high energy emission upon low energy excitation. The phenomenon is especially interesting in the field of targeted drug delivery, where the constraints of tissue absorption can be broken, and high energy blue light can be generated inside the tissue and used as a photocatalyst for different chemical reactions.
In this work we aimed to introduce photon upconversion via TF-UC inside anionic nanofibrillar cellulose hydrogel, non-toxic and biocompatible gel which has been studied as a drug reservoir. However, to guarantee efficient upconversion, the three different sensitizers, PdTPTBP, PtTPTBP and PtOEP paired with the annihilator TTBPer, were first loaded into micelles composed of two different surfactants, CrEL and T80 to solubilize the dyes and these micelles were then entrapped in the hydrogel. Since it was hypothesized that Coulombic interactions between the micelles and anionic nanocellulose fibres could improve the retention of the micelles inside the hydrogel, we modified the micelles using two different cationic co-surfactants, STA and DOTAP. The micelles were characterized by measuring their size, size distribution and ζ-potential, and their upconversion properties were studied by determining the power density threshold and upconversion quantum yield. The leaking of the micelles from hydrogel and the signal stability of TTBPer in the released micelles was studied up to two weeks. Finally, upconversion spectrum of entrapped micelles inside hydrogel was recorded with different excitation power densities.
It was established that the surface charge modification of micelles did not improve their retention in the hydrogel, but on the contrary made the system overall more unstable in terms of both the release rate of the micelles and TTBPer signal stability in the released micelles. CrEL based micelles performed better to T80 based micelles, and it was shown that the higher loading of micelles in hydrogel causes them to be released slower and the TTBPer signal to stay more stable. Out of the three sensitizers tested, PdTPTBP and PtOEP showed the best promise in terms of upconversion efficiency in physiological conditions. PdTPTBP loaded STA modified CrEL micelles showed upconversion quantum yield of 0.6 % in line with the previous records. The upconverted emission spectrum of PdTPTBP loaded CrEL micelles (unmodified) entrapped in hydrogel was successfully recorded although high excitation power densities had to used suggesting that the oxygen sensitivity of the studied system might be too high. PtOEP loaded micelles entrapped in hydrogel were not yet studied but they showed decent upconversion emission in oxic water solution making them an interesting system for further studies.
In this work we aimed to introduce photon upconversion via TF-UC inside anionic nanofibrillar cellulose hydrogel, non-toxic and biocompatible gel which has been studied as a drug reservoir. However, to guarantee efficient upconversion, the three different sensitizers, PdTPTBP, PtTPTBP and PtOEP paired with the annihilator TTBPer, were first loaded into micelles composed of two different surfactants, CrEL and T80 to solubilize the dyes and these micelles were then entrapped in the hydrogel. Since it was hypothesized that Coulombic interactions between the micelles and anionic nanocellulose fibres could improve the retention of the micelles inside the hydrogel, we modified the micelles using two different cationic co-surfactants, STA and DOTAP. The micelles were characterized by measuring their size, size distribution and ζ-potential, and their upconversion properties were studied by determining the power density threshold and upconversion quantum yield. The leaking of the micelles from hydrogel and the signal stability of TTBPer in the released micelles was studied up to two weeks. Finally, upconversion spectrum of entrapped micelles inside hydrogel was recorded with different excitation power densities.
It was established that the surface charge modification of micelles did not improve their retention in the hydrogel, but on the contrary made the system overall more unstable in terms of both the release rate of the micelles and TTBPer signal stability in the released micelles. CrEL based micelles performed better to T80 based micelles, and it was shown that the higher loading of micelles in hydrogel causes them to be released slower and the TTBPer signal to stay more stable. Out of the three sensitizers tested, PdTPTBP and PtOEP showed the best promise in terms of upconversion efficiency in physiological conditions. PdTPTBP loaded STA modified CrEL micelles showed upconversion quantum yield of 0.6 % in line with the previous records. The upconverted emission spectrum of PdTPTBP loaded CrEL micelles (unmodified) entrapped in hydrogel was successfully recorded although high excitation power densities had to used suggesting that the oxygen sensitivity of the studied system might be too high. PtOEP loaded micelles entrapped in hydrogel were not yet studied but they showed decent upconversion emission in oxic water solution making them an interesting system for further studies.