A dual channel NIR-fluorescence probe for simultaneous and independent sensing of SO2 and HSA

To address the limitations of existing NIR-fluorescent probes that only detect either SO₂ or HSA individually, we have developed a NIR-fluorescent probe (AHN) capable of detecting both SO₂ and HSA independently and concurrently in PBS buffer (pH 7.4, 10 mM). AHN detects HSO₃⁻/SO₃²⁻ via nucleophilic addition to a carbon-carbon double bond and HSA via binding to a hydrophobic pocket of HSA. The probe emits distinct fluorescence signals to differentiate between SO₂ (λ_em = 488 nm) and HSA (λ_em = 720 nm). It also distinguishes between nucleophilic attacks by HSO₃⁻/SO₃²⁻ on free AHN probe (λ_em = 488 nm) and HSA-bound AHN (λ_em = 465 nm). The detection limits for SO₂ and HSA are 124 nM and 20.5 nM, respectively, and a detection limit of 22.4 nM for SO₂ in the presence of HSA. Drug competition studies reveal that AHN specifically targets the site-I of the HSA protein. The probe also successfully detects HSA in artificial urine and HSO₃⁻ in real samples, such as water, sugar, non-alcoholic wine, and biscuits. Furthermore, HSO₃⁻ can be detected by using simple cotton wool or filter paper.