Hemozoin anchored MWCNTs for mediated reduction of hydrogen peroxide and real-time intracellular oxidative stress monitoring in colon cancer cells

Hemozoin (HZ, a malarial pigment) is an insoluble crystalline byproduct formed during the intraerythrocytic breakdown of hemoglobin by some blood-feeding parasites, such as <i>Plasmodium falciparum</i>. It consists of polymerized iron-porphyrin molecular units linked by carboxylic bonds. Due to the rigid molecular structure, studying the electron transfer activity of HZ is challenging. In this work, we report the development of a redox-active HZ-functionalized multi-walled carbon nanotube (MWCNT) modified glassy carbon electrode (GCE/MWCNT@HZ-redox). Here, HZ-redox refers to the redox-active form of hemozoin. This electrode is designed to study the electron transfer activity and mimic the peroxidase enzyme's ability to mediate hydrogen peroxide reduction in a neutral pH solution. The modified electrode exhibited a stable and well-defined redox peak at -0.385 V <i>vs.</i> Ag/AgCl in N₂-purged PBS (pH 7.0) with a surface excess value of 1.64 × 10^-9 mol cm^-2. The MWCNT@HZ-redox was characterized using Raman spectroscopy, FT-IR, and FESEM techniques. This biomimicking electrode showed excellent electrocatalytic reduction of H₂O₂ using cyclic voltammetry. Batch-injection analysis coupled with a screen-printed electrode demonstrated the electroanalytical performance for H₂O₂ sensing. The electrode exhibited a linear concentration range of 50-300 μM, with a sensitivity of 21 μA μM^-1 and a detection limit of 220 nM. As a bioanalytical application, we successfully demonstrated the <i>in situ</i> monitoring of H₂O₂ within the reactive oxygen species of HCT-116 colon cancer cells under stimulated conditions.