A Three-Dimensional Electrochemiluminescence Sensor Integrated with Peptide Hydrogel for Detection of H2O2 Released from Different Subtypes of Breast Cancer Cells

Breast cancer is a malignant tumor, with various subtypes showing different behaviors. Endogenous H2O2 is an important marker of tumor progression, which makes it important to study the relationship between breast cancer subtypes and H2O2 for pathogenesis and treatment strategies, but this has rarely been reported so far. In this work, we constructed a three-dimensional (3D) electrochemiluminescence (ECL) sensing platform for the detection of H2O2 released from two typical subtypes of breast cancer cells (MCF-7 cells for luminal A-type and MDA-MB-231 cells for three negative breast cancers, TNBCs). To adequately replicate the tumor microenvironment, the peptide hydrogel was introduced as a scaffold for 3D cell culture. The titanium foam (TF) was used as a 3D electrode to better match the 3D culture substrate. N-(4-Aminobutyl)-N-ethylisoluminol (ABEI) was selected as the ECL emitter and assembled into the peptide hydrogel by hydrogen bonding and π-stacking, which resulted in a stable and homogeneous distribution of ABEI along the hydrogel fibers. Furthermore, basic amino acids were introduced to provide alkaline microenvironment for ABEI. Therefore, ABEI exhibited high ECL efficiency, resulting in a high sensitivity with an ultralow detection limit of 0.023 nM (S/N = 3) for H2O2 of the proposed ECL biosensor. MCF-7 and MDA-MB-231 cells were cultured in a 3D peptide hydrogel/ABEI/TF electrode, respectively, and endogenous H2O2 was successfully monitored. A notably significant difference of H2O2 released between MDA-MB-231 cells and MCF-7 cells without stimulation but similar extra release with stimulation were observed. These findings may help understand the physiological mechanisms behind the various subtypes and reactive oxygen species (ROS)-related treatment for breast cancer.