Multifunctional DNA mediated spatially confined assembly for antibody orientation: surpassing sensitivity and accuracy for rituximab detection

Abstract The sensitive, accurate and fast monitoring of therapeutic drugs plays an important role in guiding clinical medication or individualized treatment. Inspired by the highly efficient interactions of ordered structures in living organisms, a multifunctional DNA mediated spatially confined assembly (SCA) based antibody orientation strategy was proposed in this work. The multifunctional DNA containing a signaling molecule labeled on the head and a poly adenine tail (20 bases), can not only direct the ordered immobilization of antibodies on gold nanoparticles, but can also enrich electrochemical signal molecules. Compared with a randomly arranged antibody immobilization strategy, the SCA based antibody orientation strategy can produce nearly 200% of peak current signal. Moreover, MoS2/gold nanoparticles were used to modify electrodes in this study in order to improve the electrochemically active surface area and electron transfer of the electrode as well as the spatial regulation of thiol peptides. By using a highly specific CD20 epitope mimetic peptide this proposed biosensor exhibits high sensitivity for rituximab detection (LOD 56.4 fM) as well as good selectivity, stability and satisfactory accuracy. When applying it for detecting rituximab in lymphoma patients’ plasma, comparable results to commercial ELISA were obtained with a low RSD (＜6.5%). The proposed signal tag fabrication strategy could easily be extended to analyze other targets by changing the sensing platform, which has a potential application in the fields of biological analysis and medical diagnosis.