Photoluminescent Lanthanocholate Gel-Based Sensors for Human Well-Being

Abstract

Lanthanide-based luminescent materials have emerged as highly promising in biosensing, primarily owing to the long lifetimes of lanthanides, which enable the efficient elimination of background signals during time-delayed measurements. Maitra and coworkers were the first to demonstrate the lanthanide-induced supramolecular gelation of the sodium salt of cholic acid, creating lanthanocholate (LnCh) gels. When these gels were doped with sensitizers, they exhibited significant photoluminescence enhancement. However, the LnCh gels doped with pro-sensitizers (covalently modified sensitizers) showed only weaker photoluminescence, highlighting the potential for biosensing, which forms the basis of the work presented in this thesis. The first chapter of the thesis introduces the research themes, emphasizing the significance of sensing and lanthanide luminescence, focusing on lanthanide-induced bile-salt-derived gels. Chapter 2 details a paper-based sensor for fluoride detection, utilizing the photoluminescence of Tb(III) within a TbCh gel matrix. The sensor operates via fluoride-triggered desilylation of pro-sensitizer, which releases sensitizer 2,3-dihydroxynaphthalene (DHN), thereby enhancing the luminescence. Chapter 3 outlines a TbCh hydrogel-based protocol for detecting α-galactosidase, which is valuable for screening potential drugs through enzyme-induced release of the sensitizer DHN from a pro-sensitizer. Chapter 4 presents a neuraminidase-based Influenza detection protocol, leveraging the sensitized Eu(III) luminescence. The pro-sensitizer synthesized by the conjugation of one of the Eu(III) sensitizer 1-hydroxypyrene (1HP) with N-acetylneuraminic acid liberated 1HP upon reaction with the influenza virus, exhibiting PL enhancement while incorporated in the EuCh hydrogel. The developed sensor demonstrated comparable sensitivity to the gold standard RT-PCR method while minimizing the cost and assay time. Finally, the Appendix summarizes the synthesis of various arylglycosides designed to explore the investigation of the glucosidase activity of alkaline phosphatase from the bovine intestine. Overall, the thesis highlights the versatile and impactful potential of lanthanocholate hydrogels as sensitive and efficient platforms for a wide range of biosensing applications.