A highly sensitive magnetic nano-fluorescent probe for singlet oxygen detection and screening of natural photosensitizers

Abstract

In this study, a magnetic nano-fluorescent probe was designed and synthesized. The probe has a high sensitivity and good selectivity for singlet oxygen (1O2), and it was successfully used to screen natural photosensitizers (TSF-OH, TSF-CHO, and TSF-COOH) isolated and purified from the traditional Chinese medicine Eclipta herba when combined with chromatography. The photosensitivity was confirmed by the 1O2 generation ability of the compound and photodynamic antibacterial experiments. To improve the absorption wavelength and 1O2 generation efficiency, five derivatives (L-A to L-E) with lower energy gaps, longer wavelengths, and higher 1O2-generation ability were designed and synthesized using a LUMO-HOMO energy gap (ΔEL-H) and singlet–triplet energy gap (ΔEST) as design strategies and TSF-CHO as skeleton by Gaussian calculation. The minimum bactericidal concentration of the L-E compound to Pseudomonas aeruginosa was 6.6 × 10−6 M, and the minimum bactericidal concentration of TSF-CHO was 4.5 × 10−5 M. The NMF-RP probe offers a new strategy for screening natural photosensitizers from plants, and the design of derivatives offers directions for the modification of photosensitizers.