Engineering Fe-doped carbon-based nanozyme from novel source for chemiluminescence/colorimetric dual-mode microplate sensing of the anticancer drug raloxifene in different matrices.

A novel carbon-based nanozyme has been designed and synthesized via upcycling expired pharmaceutical; gabapentin (GABA) into Fe, N, S-doped carbon dots within 3 min of microwave irradiation. The engineered nanozyme exhibits unique dual oxidase/peroxidase-mimicking activities. Thus, a dual-mode sensing microplate-based platform was introduced. The new nanozyme presents peroxidase-like properties that can catalyze HO to produce O species, triggering long-lasting glow-type chemiluminescence (CL) of luminol. The oxidase-mimic activity of the nanozyme was evidenced using 3,3',5,5'-tetramethylbenzidine (TMB) as substrate in the absence of HO, which turned blue (oxTMB) in acidic pH (λ = 655 nm). This innovative dual-signal platform was utilized for the analysis of raloxifene (RLX), which is an estrogen receptor modulator used as an anticancer and anti-osteoporosis drug, in multiple matrices. RLX acts as an inhibitor of nanozyme action, resulting in quenching of the CL signal and fading of the oxTMB blue color. Consequently, the nano-sensing strategy showed excellent ultrasensitive linear ranges of 10.0-2000.0 and 10.0-200.0 ng mL with remarkably low detection limits of 3.03 and 3.30 ng mL for the CL and colorimetric methods, respectively. The designed nanosensor was successfully applied for RLX assay in various matrices, involving hospital effluent, tap and river waters, pharmaceuticals, and human urine, with excellent % recovery from 95.20 to 102.10 % in CL and 96.46-104.63 % in colorimetry. The dual-mode signal system performs self-inspection by comparing the detection outcomes of each mode; thus, it grants sensitivity, accuracy, and fidelity. Notably, this strategy eliminates the need for pyrolysis at high temperature, lengthy multistep, and high energy, which distinguishes it from traditional procedures for nanozyme synthesis. It offers an effective new avenue for furnishing sensing platforms from waste used for clinical diagnosis, environmental pollution control, and pharmaceutical monitoring.