Ratiometric fluorescent detection of sarcosine in prostate cancer cell lysates based on a CdTe QDs/Ag⁺ turn-on system

Prostate cancer (PCa) is one of the most common malignancies in men, and sarcosine has been identified as a potential metabolic biomarker for PCa progression. Herein, we develop a ratiometric CdTe quantum dots (R-QDs)/Ag⁺ switch-on fluorescent sensing platform for sensitive and specific detection of sarcosine in prostate cancer cells. In this ratiometric design, the 640 nm emission of R-QDs serves as the internal reference signal, while the 520 nm emission is the responsive signal. The sensing strategy is based on Ag⁺-induced quenching of the 520 nm emission (turn-off state), followed by enzymatic recovery of the 520 nm emission via H₂O₂ generated from sarcosine oxidase-catalyzed oxidation of sarcosine (turn-on state), while the 640 nm reference emission remains essentially unchanged. Under optimal conditions, the nanosensor exhibits a linear response to sarcosine concentration in the range of 0-20 µM with a detection limit of 1.2 µM. The platform demonstrates excellent selectivity toward sarcosine over other interfering substances. Moreover, the nanosensor successfully detects endogenous sarcosine in prostate cancer cell lysates (PC-3 and LNCaP) with significantly higher FL₅₂₀/FL₆₄₀ ratio recovery compared to benign prostate epithelial cells (BPH-1). This work provides a cost-effective and reliable tool for sarcosine detection in prostate cancer research.