Generating luminescent Graphene quantum Dots from Tryptophan: Fluorosensors for hydrogen peroxide in cancer cells.

Herein, we report a single step synthesis of highly fluorescent Graphene Quantum Dots (GQDs) using tryptophan and glycerol as precursors via pyrolysis. The morphological and functional characterization of the prepared GQDs was performed using PXRD, FTIR, TEM, XPS and zeta potential measurements. The prepared GQDs found their practical application in ultrasensitive detection of an emerging potential cancer biomarker, H2O2, by exploiting the fluorescence quenching behaviour of H2O2. To evaluate the detection sensitivity, a series of various concentrations of H2O2 was spiked to biomatrices like, serum and MCF-7 (human breast cancer cell line) cell lysate medium. A remarkably low limit of detection (LOD) was found in serum medium (139.5 pM) which further improved in MCF-7 cell lysate medium (LOD 61.43 pM). Moreover, the sensing capacity of the GQDs was further validated in presence of various physiological variables such as glucose, cholesterol, insulin and nitrite. Sensing assay was also carried out in HaCaT (human keratinocyte cell line) cell lysate medium to compare the performance of our prepared sensor but the non-linearity of the F0/F versus H2O2 concentration plot pointed towards the conduciveness of the MCF-7 cell lysate medium for sensitive detection of H2O2.The mechanism behind the sensing was also explored using spectroscopic methods.

A multispectroscopic approach for ultra-trace sensing of prostate specific antigen (PSA) by iron nanocomposite fabricated on graphene nanoplatelet.

Herein we report an easy, rapid and cost-effective method for spectroscopic sensing of a prostate cancer biomarker prostate specific antigen (PSA) using a novel nanocomposite. The material is a synthetic quinoxaline derivative-based iron nanocomposite fabricated on graphene nanoplatelet surface (1d-Fe-Gr). Presence of graphene enhanced the efficacy of synthesized 1d-Fe-Gr to sense PSA in serum medium with an impressive limit of detection (LOD) value of 0.878 pg/mL compared to 1d-Fe alone (LOD 17.619 pg/mL) using UV-visible absorption spectroscopy. LOD of PSA by 1d-Fe-Gr using Raman spectroscopy is even more impressive (0.410 pg/mL). Moreover, presence of interfering biomolecules like glucose, cholesterol, bilirubin and insulin in serum improves the detection threshold significantly in presence of 1d-Fe-Gr which otherwise cause LOD values of PSA to elevate in control sets. In presence of these biomolecules, the LOD values improve significantly as compared to healthy conditions in the range 0.623-3.499 pg/mL. Thus, this proposed detection method could also be applied efficiently to the patients suffering from different pathophysiological disorders. These biomolecules may also be added externally during analyses to improve the sensing ability. Fluorescence, Raman and circular dichroism spectroscopy were used to study the underlying mechanism of PSA sensing by 1d-Fe-Gr. Molecular docking studies confirm the selective interaction of 1d-Fe-Gr with PSA over other cancer biomarkers.