Magnetized Carbon Nanotube Based Lateral Flow Immunoassay for Visual Detection of Complement Factor B.

Yan Huang,Guodong Liu,Kun Li,Lisheng Qian,Xueji Zhang,Fang Wang,Tingting Wu

doi:10.3390/molecules24152759

Abstract

The authors describe a magnetized carbon nanotube (MCNT) based lateral flow immunoassay (LFI) for visual detection of complement factor B (CFB) in blood. MCNT was prepared by decorating magnetic Fe3O4 nanoparticles on multi-walled CNT surface and used as a colored tag for LFI. Monoclonal antibody (mAb, Ab1) of CFB was covalently immobilized on the MCNT surface via diimide-activated conjugation between the carboxyl groups on the MCNT surface and amino groups of antibodies. Polyclonal antibody of CFB (Ab2) and the secondary antibody were used to prepare the lateral flow test strips. The assay involved: (1) the capture of CFB in blood with the mAb-functionalized MCNT; (2) magnetic separation of the formed CFB-mAb-MCNT and excess of mAb-MCNT from the blood with an external magnet; (3) lateral flow test to capture the CFB-mAb-MCNT complex on the test zone and the excess of mAb-MCNT on the control zone; (4) Recording the intensities of the produced the characteristic brown bands with a portable strip reader and quantitating the concentration of CFB. The proof-of-concept was demonstrated by testing CFB in the buffer, and the detection limit was 5 ng mL−1 under the optimized analytical parameters. CFB in 1 μL of human blood was detected successfully in 30 min with this LFI and the results had a high correlation with commercial ELISA kit. Thence, the MCNT-based LFI offers a rapid and low-cost tool for detecting CFB in human blood directly.

Highlights

The complement system, discovered in the late nineteenth century, includes more than 30 soluble proteins and membrane-bound proteins in serum, tissue fluid and on cell membrane surfaces, which is widely involved in the body’s microbial defense response and immune regulation, and can mediate the invasive response of immunopathology
We prepared magnetized carbon nanotube (MCNT) by coprecipitating iron and ferrous ions to form Fe3 O4 nanoparticles on the surface of the shortened multiwalled CNTs [21]
The strong peak at ~1350 cm−1 of CNT and MCNT was produced by the D band of CNT, and the other main peak at ~1576 cm−1 was due to the G band of CNT

Summary

Introduction

The complement system, discovered in the late nineteenth century, includes more than 30 soluble proteins and membrane-bound proteins in serum, tissue fluid and on cell membrane surfaces, which is widely involved in the body’s microbial defense response and immune regulation, and can mediate the invasive response of immunopathology. Complement 3 (C3) is the richest form of complement protein in plasma, which plays an important role in complement classical activation pathway and bypass activation pathway [2]. Complement factor B (CFB), mainly synthesized by the liver and macrophages, is a C3 activator precursor and an important factor in the activation pathway of the complement bypath, which participates in the body’s defense and plays a significant role in tissue and cell damage and inflammation. Sensitive and specific determination of CFB in blood would be of great significance in clinical diagnosis

Methods

Results

Conclusion