Aptamer-conjugated magnetic nanoparticles for the efficient capture of cancer biomarker proteins

Abstract

Breast cancer tests are costly, requiring specialized instruments and highly trained operators. Serum protein biomarkers are ideal targets for the development of low cost and non-invasive point-of-care (POC) diagnostic assays such as the lateral flow immunoassay (LFIA). However, these proteins are often present at very low levels relative to other serum proteins, making it very difficult to detect the presence of the cancer biomarker proteins. There is, therefore, a need to improve the sensitivity of LFIAs. In this study, we demonstrate the functionalization of iron oxide magnetic nanoparticles using l-cysteine and conjugated to streptavidin. The functionalized MNPs-streptavidin was in turn conjugated to biotin containing an aptamer with specificity to a breast cancer biomarker protein. The complex was used to isolate MUC 1 proteins from lysates extracted from MCF-7 cells. Characterization was done to ascertain the changes in morphology before and after conjugation of the molecules to the MNPs using high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR), superconducting quantum interference device (SQUID), QUBIT fluorimeter and Matrix-assisted laser desorption ionization/time-of-flight mass spectrometry (MALDI-TOF-MS). The XRD pattern matched JCPDS no.00-039-1346 suggesting that the iron oxide synthesized is maghemite (α-Fe2O3). We quantified the isolated proteins using Qubit fluorimeter and identified them using MALDI-TOF-MS. The concentration of isolated proteins that were isolated from 6 µL of lysate and dispersed in 20 µL of PBS was determined to be 15.63 µg/mL. The concentration was determined after 3 cycles of thorough washing. The application of these MNPs in the design of LFIAs can significantly increase the sensitivity of these diagnostic devices.