Iridium–Schiff base complex-based fluorimetric turn-off sensor and HPLC-DAD analytical approaches for quantitation of 8-hydroxy-2′-deoxyguanosine as an oxidative DNA damage biomarker in biofluids of healthy and diabetic subjects

Abstract

8-Hydroxy-2′-deoxyguanosine (8-OHdG) is a well-established biomarker of oxidative DNA damage formed through reactive oxygen species-mediated oxidation of guanosine residues. It is widely recognized as a laboratory biomarker of oxidative DNA damage and has been associated with carcinogenic progression. In this study, a novel, rapid, and highly selective spectrofluorometric platform was developed based on quenching of the fluorescence of a newly synthesized iridium–Schiff base complex by 8-OHdG; an HPLC-DAD method was also developed for confirmatory quantification. The iridium–Schiff complex exhibited intrinsic green fluorescence at λ_em = 500 nm upon excitation at λ_ex = 292 nm. The optimal fluorescence intensity and pronounced quenching effect of 8-OHdG were achieved in an acetate buffer solution with pH 3.6. Both methods exhibited wide linearity ranges: 0.025–20 µg mL⁻¹ for spectrofluorimetry and 0.005–50 µg mL⁻¹ for HPLC-DAD. The limits of detection (LODs) were 0.0179 µg mL⁻¹ and 0.0013 µg mL⁻¹, respectively. High accuracy and precision were confirmed with recovery percentages ranging from 97.142% to 100.006% for the spectrofluorimetric method and 95.321% to 99.399% for HPLC-DAD. Moreover, relative standard deviation values (RSD%) ranges did not exceed 0.266–2.05% and 0.604–1.984%, respectively confirming the high reproducibility of the developed approaches. For minimizing matrix interference from endogenous substances such as creatinine and uric acid, samples were pretreated using Strata C18-E solid-phase extraction cartridges prior to analysis. The novel methods coupled with Strata C18-E (SPE) were successfully validated and applied to the analysis of 8-OHdG in 40 human urine and serum samples obtained from healthy and diabetic patient volunteers. Detectable levels of 8-OHdG were found in 36 out of 40 samples, ranging from 0.013 to 15.766 µg mL⁻¹. Furthermore, both analytical approaches for the detection of 8-OHdG are in alignment with the principles of white and green analytical chemistry, offering environmentally friendly, efficient, and straightforward analytical procedures. Accordingly, the proposed methods exhibit considerable promise for the determination of urinary 8-OHdG, which serves as a reliable biomarker of oxidative stress in a range of pathological conditions owing to its diagnostic relevance as an oxidative DNA damage biomarker.