Ultrasensitive aptasensor for arsenic detection using quantum dots and guanylated Poly(methacrylamide).

The present study demonstrate the first time usage of poly (HPMA-s-GPMA) copolymer for the fabrication of three-component based aptasensor for simple, selective, rapid and label free detection of arsenite (As). For this purpose, guanidinium bearing poly (HPMA-s-GPMA) copolymer and MPA-CdTe@CdS quantum dots (QDs) was employed in conjunction with As specific aptamer. This protocol utilizes the quenching phenomena displayed by QDs due to the competitive binding of As ions and cationic copolymer to the aptamer. In particular, the As bind to the specific aptamer, leaving poly (HPMA-s-GPMA) freely available for its electrostatic intercations with QDs, which quenches the fluorescent signal. Contrarily, in the absence of As ions, the aptamer can electrostatically bind to poly (HPMA-s-GPMA); making copolymer inactive to affect the fluorescence signal of the QDs. The efficiency of the proposed fluorescence nanoprobe was further tested using linear calibration curves. The obtained data in the range of 0.01-100 nM showed excellent specificity for As ions with the limit of detection (LOD) of 246.77 pM. Moreover, the "on-off" fluorescent aptasensor is highly selective for As ions in the presence of other interfering metal ions by utilizing As specific aptamer. Furthermore, the reported study showed outstanding applicability in the real-world samples (water, food and soil) containing preservatives, metal ions, minerals, and other moieties. The proposed sensing platform not only exhibits the trace level detection of As ions in cost-effective manner but also opens a pathway for the development of state-of-art device fabrication for on-site detection of arsenic.