ESIPT-active hydroxybenzothiazole-picolinium@CB[7]-HAp NPs based supramolecular sensing assembly for spermine, spermidine and cadaverine: Application in monitoring cancer biomarkers and food spoilage

Abstract

A three-component supramolecular sensing platform has been developed involving a water-soluble, ESIPT-active benzothiazole based probe (BTPICO), cucurbit[7]uril (CB[7]), and citrate-stabilized hydroxyapatite nanoparticles (HAp NPs) for the rapid and sensitive detection of spermine, spermidine, and cadaverine in aqueous media. Spermine, and spermidine act as biomarkers for early-stage diagnosis of cancer in humans and cadaverine mainly acts as a marker for food spoilage. As per the strategy, BTPICO spontaneously forms a conjugate by electrostatic interaction with the negatively charged surface of HAp NPs and goes to a non-emissive state due to the loss of ESIPT property. In the presence of CB[7], the dye interacts with CB[7] portal and in its shield, the dye turns on its emission. The partially positively charged complex further interacts with the negatively charged surface of HAp NPs to form a strongly emissive three-component sensing assembly. Upon addition of spermine, spermidine or cadaverine, the dye is quickly displaced from CB[7] portal by the much stronger interaction with the biogenic amines and fluorescence is again turned off by forming the non-emissive conjugate (BTPICO-HAp NP). The sensing mechanism was established by DLS, microscopic studies, time-resolved spectroscopy, etc. The supramolecular sensing assembly showed nominal interference from various metal ions, anions, amino acids, and other biogenic amines, and low limits of detection (LODs) of 1.4, 3.3, and 17.2 ppb for spermine, spermidine, and cadaverine, respectively. The practical applicability of this sensing system was demonstrated by spiking spermine and spermidine in human urine, blood serum, and cadaverine in different food samples with very good %recovery, thereby, making this sensing platform suitable for real-time, low-level measurement of spermine, spermidine, and cadaverine.