Emissive nanoaggregate-based dual sensing of heparin and protamine sulphate.

Heparin (Hep), a widely used blood thinner, requires continuous monitoring upon administration, as both under- and overdosing can lead to complications such as thrombosis or haemorrhage. At the same time, protamine sulfate (PS) serves as the clinical antidote for Hep via electrostatic interactions. Inspired by the need to continuously monitor this clinically relevant Hep-PS pair, we have designed a simple tetraphenylethylene (TPE)-based tetracationic sensor to detect these analytes via a fluorescence switch-on/off mechanism. Hep binding induces strong electrostatic interactions between highly negative functional groups and the positively charged probe, leading to fluorescence enhancement due to the aggregation-induced emission (AIE) effect, whereas subsequent addition of PS competitively extracts Hep, restoring the quenched state. The probe exhibits good sensitivity and selectivity towards both Hep and PS with comparatively low LOD and LOQ, enabling detection in clinically optimum concentration. Practical applicability was further evaluated in complex biological matrices. In addition, fluorescence results with clinical Hep and the probe showed good agreement with the conventional apTT assay. This simple, reversible platform enables rapid dual detection of the Hep-PS pair and has potential for anticoagulation monitoring.