Visual determination of heparin in serum utilizing surfen-induced aggregation emission enhancement of gold nanoclusters and heparin-induced fluorescence enhancement of surfen

We developed a ratiometric luminescence probe for heparin detection based on the interactions among surfen, glutathione-capped gold nanoclusters (GSH-AuNCs), and heparin. At neutral pH, surfen triggers aggregation-induced emission enhancement (AIEE) in GSH-AuNCs, forming dual-emission surfen-AuNC aggregates with fluorescence at 490 nm and 610 nm. Heparin competitively binds to surfen, displacing it from the aggregates, resulting in decreased fluorescence at 610 nm and increased emission at 490 nm, enabling both ratiometric and visual heparin detection. Investigations of the AIEE mechanism reveal that surfen reduces electrostatic repulsion and enhances van der Waals interactions, facilitating nanocluster aggregation. Theoretical models based on the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory were employed to quantify these interactions. The probe demonstrates a linear response for heparin concentrations between 0.5 and 10 μM, with a detection limit of 0.2 μM, suitable for clinical monitoring. In 10-fold diluted human plasma, the probe maintains sensitivity, allowing naked eye detection of heparin through distinct color changes. These findings highlight this ratiometric probe as a practical, sensitive, and accessible tool for heparin quantification in complex clinical samples, surpassing the limitations of single-emission probes.