Viologen-functionalized single-walled carbon nanotubes as carrier nanotags for electrochemical immunosensing. Application to TGF-β1 cytokine

Abstract

Viologen-SWCNT hybrids are synthesized by aryl-diazonium chemistry in the presence of isoamyl nitrite followed by condensation reaction of the resulting HOOC-Phe-SWCNT with 1-(3-aminoethyl)-4,4'-bipyridinium bromine and N-alkylation with 2-bromoethylamine. The V-Phe-SWCNT hybrids were characterized by using different spectroscopic techniques (FT-IR, Raman, UV-vis), TGA and Kaiser test. Viologen-SWCNTs were used for the preparation of an electrochemical immunosensor for the determination of the transforming growth factor β1 (TGF-β1) cytokine considered as a reliable biomarker in several human diseases. The methodology involved preparation of V-Phe-SWCNT(-HRP)-anti-TGF conjugates by covalent linkage of HRP and anti-TGF onto V-Phe-SWCNT hybrids. Biotinylated anti-TGF antibodies were immobilized onto 4-carboxyphenyl-functionalized SPCEs modified with streptavidin and a sandwich type immunoassay was implemented for TGF-β1 with signal amplification using V-Phe-SWCNT(-HRP)-anti-TGF conjugates as carrier tags. The analytical characteristics exhibited by the as prepared immunosensor (range of linearity between 2.5 and 1000pgmL TGF-β1; detection limit of 0.95pgmL) improve notably those reported with other previous immunosensors or ELISA kits. A great selectivity against other proteins was also found. The prepared immunosensor was validated by determining TGF-β1 in real saliva samples. Minimal sample treatment was required and the obtained results were in excellent agreement with those obtained by using a commercial ELISA kit.

Nanobioconjugates for Signal Amplification in Electrochemical Biosensing

“…Finally, a solution containing the antigen TGF-β1 was dropped onto the electrode surface, followed by the addition of the anti-TGF-β1-v-SWCNT/HRP nanobioconjugate, and the signal response was interrogated by amperometry. The results showed a target-dependent concentration linear in the range from 2.5 to 1000 pg/mL, with a LOD of 0.95 pg/mL [ 54 ].…”

Construction and Potential Applications of Biosensors for Proteins in Clinical Laboratory Diagnosis

“…Nanomaterial-based EC immunosensors have shown extensive advantages, leading to a greater loading amount of MREs, a faster electron transfer speed, and a more convenient combination of signal amplification strategies [ 2 ]. For example, Au nanoparticles (NPs) [ 43 , 44 ], carbon nanotubes (CNTs) [ 21 ], and graphene [ 36 ] have been widely used to preserve the activity of biomolecules and to enhance the electron transfer between redox species, increasing sensitivity. In addition, modern EC immunosensors exhibit an excellent detection performance for whole blood tests in a fast and simple way [ 31 , 45 ], with remarkable sensitivity and selectivity, offering EC biosensors with a benefit for transition toward POC application [ 34 ].…”

“…Recently, viologen-single-walled CNTs (SWCNTs) hybrids were synthesized for an enrichment in antibodies and enzymes and for an increase in electron transfer between transducer and electroactive materials. Based on the dual amplification efficiencies, only a trace sample was needed, and dramatically enhanced sensitivity for TGF-β1 cytokine detection was achieved, with a linear range of 2.5~1000 pg mL −1 and an LOD of 0.95 pg mL −1 [ 21 ]. An immunosensor for POC enterovirus 71 detection was proposed for both colorimetric and EC measurements, which was proved to possess good performance for early diagnosis and control of the related epidemics [ 22 ].…”

“…To enhance detection sensitivity, various signal amplification strategies have been combined with biosensing platforms [ 2 , 21 , 32 , 33 , 43 , 44 ]. For example, a dual signal amplification strategy was employed in fabricating ultrasensitive EC immunosensor for alpha fetoprotein (AFP) detection [ 32 ].…”

“…Biosensors are bioanalytical devices integrating biorecognition elements and suitable transducers, which could be further designed with various signal amplification strategies to obtain extremely high sensitivity [ 2 ]. With plenty of advantages, such as strong specificity to targets, rapid analysis, high accuracy, easy operation, and low cost, biosensors have expansive applications for diverse targets, including cyclic drugs [ 20 ], proteins [ 21 , 22 , 23 ], nucleic acids [ 24 , 25 , 26 , 27 ], and cyclic tumor cells [ 28 , 29 , 30 ]. Immunosensors have played a crucial role in the determination of tumor markers [ 31 , 32 , 33 ], significantly improving early diagnosis and prognosis of various cancers.…”