چكيده به لاتين
The challenges remain to develop nanocomposites with a broad range of conductivity, sensitivity, selectivity and linear response for electrochemical biosensing applications. A scalable nanocomposite-based sandwich arrangement of metal nanoparticles-grafted functionalized graphene nanostructured polyaniline was demonstrated to address this challenge. Among different metal nanoparticles tested in this work (gold, silver, and copper), silver nanoparticles were selected owing to its higher charge transfer conductivity, easier access and relatively lower cost. The critical modification of the AgNPs grafted NFG-PANI coated on very low-cost fluorine doped tin oxide electrode increased the charge transfer conductivity of the electrode (the resistance drops down from 11,000 Ω to 6 Ω). The designed nano-sensor was used for non-enzymatic, rapid, stable and highly reproducible detection of ascorbic acid with a simple structure in the presence of electroactive interferences and also to accurately and practically detect this biomolecule as in vitamin C tablets with the recovery of 98%. The enhanced ascorbic acid electrochemical properties of this nanocomposite is attributed to the superior charge transfer conductivity of the graphene/polyaniline and the excellent catalytic activity of silver nanoparticles. The results demonstrate that this nanocomposite can be a promising candidate for rapid and selective detection of AA in practical clinical samples.
However, the detection of cancer cells at a single cell level requires a new class of nanocomposite-coated electrodes with exceptional sensitivity and specificity. The presented nanocomposite was modified with a specific antibody for highly sensitive detection of SK-BR3 breast cancer cells and the obtained immunosensor showed a fast response time of 30 min within a wide dynamic range of 10−5×106 cells mL−1, a very low detection limit of 2 cells mL−1, and high efficiency of >90% for the label-free detection of cancer cells in whole blood sample without any need for sample preparation and cell staining.
MicroRNAs are small and noncoding RNAs, shown to be expressed abnormally in many tumors and identified as predictive biomarkers for early diagnosis of several cancers including the breast. Therefore, the label-free and highly sensitive detection of miRNAs is of critical significance. The highly sensitive and label-free nano-genosensor was developed for the detection of miR-21, a known breast cancer biomarker, based on high performance fabricated nanocomposite. Applying this selective and specific nano-biosensor with high sensitivity resulted in detection of a wide dynamic range of 10 fM - 10 μM with a sensitivity of 2.5 μA cm-2 and a low detection limit of 0.2 fM. This nano-biosensor also demonstrated highly reproducible results in the analysis of blood samples, with recoveries between 94 to 107%, and could be used for early detection of breast cancer by direct detection of the miRNA-21 in real clinical samples without any need to sample preparation, RNA extraction and/or amplification.
Ultimately, for the first time, a microchip with a replaceable electrode was designed to create electrodes with high reproducibility, miniturizability, automatic sensing and fabricating point-of-care devices. The proposed microfluidic system has the ability to make stable, cost effective, and repeatable sensors that open the avenue to continuously monitor the changes in biomarkers activity during the drug treatment period.
