An anthracenecarboximide-guanidine fluorescent probe for selective detection of glyoxals under weak acidic conditions

Abstract

An anthracenecarboximide-guanidine based turn-on fluorescent probe ANC-DCP-1 for selective detection of glyoxals (methylglyoxal and glyoxal, GOS) over formaldehyde under weak acidic conditions around pH 6.0 was reported. The probe showed great potential in studying relative GOS levels in weak acidic biological fluids such as in urine for diabetic diagnosis and prognosis, and also found application in the food industry such as for fast unique manuka factor (UMF) scale determination of Manuka honey.

Fig. 1. Probe design: (a) common reactive groups used in GOS fluorescent probes; (b) NAP-DCP series of probes adopting 1,8-naphathalimide as the fluorophore; (c) this work: 1,9-anthracenedicarboximide based fluorescent probe ANC-DCP-1. The extension of conjugation system lowered pK_a and pH required for full protonation of the probe.

Fig. 2. (a and b) Time-dependent UV-Vis spectra of ANC-DCP-1 (20 μM) upon addition of 200 equiv. MGO (a) or GO (b); (c) fluorescence emission spectra (λ_ex = 525 nm) of ANC-DCP-1 (5 μM) before and after addition of 200 equiv. MGO or GO for 2 h; (d) fluorescence intensity of ANC-DCP-1 (5 μM) at 615 nm (λ_ex = 525 nm) upon addition of various species (1 mM): (1) blank, (2) GO, (3) MGO, (4) formaldehyde, (5) benzaldehyde, (6) glyoxylic acid, (7) acetaldehyde, (8) o-phthalaldehyde, (9) H₂O₂, (10) glutathione, (11) cysteine, (12) homocysteine, (13) glucose, (14) Na⁺, (15) Ca²⁺, (16) Al³⁺, (17) K⁺, (18) Cu²⁺, (19) Zn²⁺, (20) blank (5% DMSO); (21) NOC-18 (5% DMSO).

Fig. 3. (a) Fluorescence intensities of different urine samples at 615 nm (λ_ex = 525 nm) observed immediately (black columns) after addition of ANC-DCP-1 (10 μM) versus observed after 2 h incubation at 37 °C and pH 6.0 (red columns); (b) comparison of fluorescence intensity increases at 615 nm (λ_ex = 525 nm) after 2 h incubation at 37 °C and pH 6.0 for normal urine samples, diabetic urine samples not being chylous, and diabetic urine samples being chylous; (c) nonlinear regression of the measured fluorescence intensity increases at 615 nm (λ_ex = 525 nm) in the urine specimen and the corresponding blood glucose concentrations (mmol L⁻¹) of the five diabetic patients.

Fig. 4. (a) Linear regression of fluorescence intensity at 615 nm (λ_ex = 525 nm) of the probe ANC-DCP-1 (10 μM) in diluted acacia honey (pH 6.0) incubated at 37 °C for 1 h versus the concentrations (0–1000 μM) of MGO added; (b) measured fluorescence intensity at 615 nm (λ_ex = 525 nm) of the probe ANC-DCP-1 (10 μM) in the two diluted Manuka honey samples (pH 6.0) incubated at 37 °C for 1 h.