Highly Specific and Ultrasensitive Graphene-Enhanced Electrochemical Detection of Low-Abundance Tumor Cells Using Silica Nanoparticles Coated with Antibody-Conjugated Quantum Dots

Abstract

A dual signal amplification immunosensing strategy that offers high sensitivity and specificity for the detection of low-abundance tumor cells was designed. High sensitivity was achieved by using graphene to modify the immunosensor surface to accelerate electron transfer and quantum dot (QD)-coated silica nanoparticles as tracing tags. High specificity was further obtained by the simultaneous measurement of two disease-specific biomarkers on the cell surface using different QD-coated silica nanoparticle tracers. The immunosensor was constructed by covalently immobilized capture antibodies on a chitosan/electrochemically reduced graphene oxide film-modified glass carbon electrode. Cells were captured with a sandwich-type immunoreaction and the different QD-coated silica nanoparticle tracers were captured on the surface of the cells. Each biorecognition event yields a distinct voltammetric peak, which position and size reflects the corresponding identity and amount of the respective antigen. This strategy was vividly demonstrated by the simultaneous immunoassay of EpCAM and GPC3 antigens on the surface of the human liver cancer cell line Hep3B using anti-EpCAM-CdTe- and anti-GPC3-ZnSe-coated silica nanoparticle tracers. The two tracers gave comparable sensitivity, and the immunosensor exhibited high sensitivity and specificity with excellent stability, reproducibility, and accuracy, indicating its wide range of potential applications in clinical and molecular diagnostics.

Real‐Time Cellular Cytochrome C Monitoring through an Optical Microfiber: Enabled by a Silver‐Decorated Graphene Nanointerface

“…As widely employed in many electrochemical sensors,15, 16, 17, 42, 43, 44, 45 RGO with a partial planar structure and abundant oxygen‐containing functional groups provided a suitable platform (high surface area43 and more binding sites45) for aptamer immobilization by π–π interactions in this work 30. Simultaneously, slight changes in the charge environment of the RGO sheet arising from the binding of cyt c may result in an improved change in electronic characteristics,46 which sharpened the sensitivity of sensor.…”

“…To improve the sensitivity and lower the LOD to meet the requirement of in situ cell monitoring, we have constructed a nanointerface with Ag NP‐functionalized reduced graphene oxide (Ag@RGO) between silica microfiber and aptamers (Figure 1a). As a result of the plasmonic electromagnetic field enhancement of Ag NPs,14 as well as the accelerated electron transformation15, 16 and electronic characteristics17 of reduced graphene oxide (RGO), the LOD of the as‐prepared sensor achieved is 6.82 × 10 −17 m , which is five orders of magnitude lower than those of existing electrochemical methods (5.0 × 10 −12 m ),18 six orders of magnitude than those of surface plasmon resonance arrays (5.0 × 10 −11 m ),19 and nine orders of magnitude than both fluorescence methods (2.0 × 10 −8 m )20 and optical microfiber methods without Ag@RGO nanointerface. Such a low LOD meets the requirement of in situ monitoring of the ultralow concentrations of cyt c present outside the cells during the initial step of apoptosis.…”

Recent Advances in the Generation of Antibody–Nanomaterial Conjugates

“…This immunosenser showed high sensitivity with a detection limit of at least 10 cells mL −1 at the same time exhibiting high accuracy and precision with good stability, and could be used for clinical and molecular diagnostics. [31] Such examples highlight the broad applicability of simple covalent chemistries and indicate how complex sensors and nanomedicines can be developed by utilizing amide-coupling chemistries.…”

Metallic nanocrystallites-incorporated ordered mesoporous carbon as labels for a sensitive simultaneous multianalyte electrochemical immunoassay

“…Various signal amplification technologies using nanomaterials including colloidal gold nanoparticles Lu et al, 2012), carbon nanotubes (Li et al, 2012b;Wan et al, 2011), quantum dots (QD) (Kokkinos et al, 2013;Wu et al, 2013) and silica nanoparticles (Tang and Liu. 2013;Eum et al, 2014;Yang et al, 2010) and magnetic beads (Tang et al, 2012;Zarei et al, 2012;Weizmann et al, 2003) have been developed, the prepared labels can greatly amplify the transduction signal of a recognition event in bioassays and simplify the detection steps.…”