Optical Determination of Tryptophan Using Persistent Luminescence Nanoparticles (PLNPs)

Abstract

Tryptophan is an essential amino acid that is an important part of the human diet. In this work, label-free photoluminescence sensing based upon persistent luminescent nanoparticles (PLNPs) Zn_0.8Ga₂O₄: Cr³⁺ is reported to determine tryptophan. Following 254 nm excitation, the PLNPs released luminescence after storing the absorbed light. Compared to the standard fluorescence, the persistent afterglow of the PLNPs was used for detection and imaging without external illumination, thereby eliminating autofluorescence and scattered light generated by biological substrates. For tryptophan concentrations from 4 to 240 µM, a linear relationship was described by F/F₀ = 0.9416 − 0.0024 [Trp] with a correlation coefficient of 0.9911 and a detection limit of 0.19 µM. The recoveries of analyzed samples were between 97.9 and 101.9% providing good accuracy and simple methodology.

Keywords:

• Fluorescent sensor
• persistent luminescence nanoparticles (PLNPs)
• photoluminescence
• tryptophan
• Zn_0.8Ga₂O₄: Cr³⁺

Acknowledgement

The authors are grateful to the Analysis and Testing Center of Shanxi Normal University.

Authors’ Contributions

Zhenmin Zhai: methodology, conceptualization validation, investigation, writing – original draft; Zhefeng Fan: investigation, conceptualization, methodology, supervision.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that influenced the work reported in this article.

Funding

This work did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.