Construction and investigation of all-in-one microneedles complexed with functionalized polydiacetylene liposomes for improved in situ detection sensitivity

Polydiacetylene (PDA) liposomes have been widely applied for detection due to their distinctive optical properties. However, the liquid phase in which PDA liposomes are dispersed generates several drawbacks, for instance, instability, compromise of detection sensitivity induced by dilution, and separation of target sampling and detection, making it inconvenient for application. In this paper, various functionalized PDA liposomes for detecting target were prepared, which were also immobilized into swelling microneedles to construct a solid-phase detection system. The PDA liposomes-complexed microneedles (PDA/MNs) enable the integration of target sampling and detection in one platform. The effects of the dispersing matrix phase on the detection sensitivity of PDA liposomes were systematically investigated from both environmental and chemical perspectives. PDA/MNs exhibited higher sensitivity than their counterparts in liquid phase. PDA/MNs were optimized and validated for lead ion (Pb²⁺) and sialic acid (SA) detections. For Pb²⁺ detection, the limit of detection (LOD) of the PDA/MNs was 13.7 μM and 2.5 times lower than the liquid phase. For SA detection, the LOD of the PDA/MNs was 0.83 μM and 1.7 times lower than the liquid phase. The results suggested that such PDA/MNs were validated to provide a label-free, stable, sensitive, and convenient tool in an all-in-one manner for physiologic target detection.