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Investigating Host-guest Complexation of Chemical UV filters for Improving Photostability

Pajoubpong, Jinnipha
http://orcid.org/0000-0001-7004-5210
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1712914538893362

Abstract Details

2024, PhD, University of Cincinnati, Pharmacy: Pharmaceutical Sciences.
Among chemical UV filters approved by the US FDA, avobenzone (AVO) is the most efficient and commonly used UVA filter in broad-spectrum sun care products. However, one pitfall of AVO is a lack of photostability leading to a decrease in its UV protection capacity. Its photostability primarily depends on the solvent system (solvents, emollients, and UV filters) and excipients in its vicinity (i.e., other UV filter molecules, and triplet or single quenchers). Moreover, when AVO and octinoxate (OCT), a UVB filter, are used in combination, it appears that the photo-instability of AVO can cause the photolysis of OCT. It has been reported that forming inclusion complexes with ß-cyclodextrins (ß-CD) enhanced the photoactive performance of AVO and OCT by improving their photostability and reducing skin permeation. However, most studies have investigated the complexes in solvents unintended for cosmetic formulations. Most importantly, the mechanism of host-guest complexation and photo-stabilization by ß-CD has not yet been revealed. Therefore, this dissertation aims to investigate the effect of macrocyclic compounds (ß-CD vs Cucurbit[7]uril (CB[7]) on the photostability of AVO and OCT in aqueous environment, which is motivated by three research questions. What are the differences in the complexation of AVO and OCT with ß-CD and CB[7]? How do forming complexes with ß-CD and with CB[7] affect the photostability, skin permeation, and efficacy of AVO and OCT? Finally, what is the impact of ethanol as a cosolvent on the complexation and photostability of AVO and OCT? To examine these questions, we prepared complexes of AVO-ß-CD, AVO-CB[7], OCT-ßCD, and OCT-CB[7] and characterized the complexes both in solution phase and solid state using several analytical techniques. We also conducted photostability studies for all complexes, skin permeation tests for AVO complexes, and evaluated the efficacy for all complexes. The findings from the research show that ß-CD and CB[7] have similar mechanisms of host-guest complexation with AVO and OCT. However, CB[7] interacts with AVO stronger than ß-CD does and vice versa with OCT. As for ethanol as a cosolvent, it plays an important role in both complexation and photostability. In most tested complexes, we found that low content of ethanol in solutions strengthens the interaction between the guests and the hosts. Higher content of ethanol weakens the interaction although it significantly increases photostability of AVO and OCT. The concentration of hosts contributes to the bound guest concentration, resulting in a degree of photostability and skin permeation. We conclude that ß-CD and CB[7] increase the photostability of AVO in an aqueous environment by stabilizing its keto tautomer. They also enhance the photostability of OCT, although the mechanism remains unclear. Moreover, the in vitro SPF values of complexes exhibit an increasing trend with higher host concentrations, attributed to enhanced water solubility and subsequent UV absorbance. Additionally, ß-CD complexes, compared to CB[7] complexes, can self-assemble leading to the formation of microparticles (300 nm to 500 nm in diameter). These microparticles acquire the capacity for UV radiation reflection and scattering, thereby further boosting the SPF values.
Harshita Kumari, Ph.D. (Committee Chair)
Frank Heinrich, PhD (Committee Member)
Kevin Li, Ph.D. (Committee Member)
Gerald Kasting, Ph.D. (Committee Member)
Kavssery Ananthapadmanabhan (Committee Member)
David Moore, Ph.D. (Committee Member)
169 p.
Pharmaceuticals
Avobenzone; Photostability; Host-guest complexation; Octinoxate; Cucurbituril; Cyclodextrins

Recommended Citations

Citations

  • Pajoubpong, J. (2024). Investigating Host-guest Complexation of Chemical UV filters for Improving Photostability [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1712914538893362

    APA Style (7th edition)

  • Pajoubpong, Jinnipha. Investigating Host-guest Complexation of Chemical UV filters for Improving Photostability. 2024. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1712914538893362.

    MLA Style (8th edition)

  • Pajoubpong, Jinnipha. "Investigating Host-guest Complexation of Chemical UV filters for Improving Photostability." Doctoral dissertation, University of Cincinnati, 2024. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1712914538893362

    Chicago Manual of Style (17th edition)

ucin1712914538893362
© 2024, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.
Release 3.2.12