A biocompatible cerasome based platform for direct electrochemistry of cholesterol oxidase and cholesterol sensing

Cerasomes are a novel organic-inorganic hybrid material composed of spherical lipid bilayer vesicles with an internal aqueous compartment, which are similar to liposomes formed from phospholipids, with an inorganic silicate framework covering the vesicular surface. In this research, an anionic cerasome formed from N,N-dihexadecyl-N′-[(3-triethoxysilyl)propyl]urea was successfully prepared, and the cerasomes were characterized by scanning electron microscopy (SEM), behaving as a spherical-like structure. An electrochemical platform was constructed using a combination of the cerasomes and cholesterol oxidase (ChOx) on a glassy carbon electrode. Ultraviolet-visible (UV-vis) spectroscopy was used to monitor the assembly process and the electrochemical impedance spectroscopy (EIS) results demonstrated that ChOx had been successfully immobilized. The obtained enzyme-modified electrode exhibited both the effective direct electron transfer between the enzyme and electrode surface and the excellent electrochemical catalytic activity towards cholesterol with a wide linear range from 5.0 × 10^-6 to 3.0 × 10^-3 mol L^-1 and a low detection limit 1.7 × 10^-6 mol L^-1 (S/N 3). The excellent catalytic performance of the modified electrode is attributed to the good biocompatibility of the cerasomes, which can provide a soft and morphologically stable interface for enzymatic immobilization, allowing the enzyme to retain its catalytic activity, along with their specific affinity (K_m 0.139 mmol L^-1) for water-insoluble cholesterol. The results indicate that cerasomes are useful as a platform for electrochemical sensing of cholesterol and have the potential to immobilize enzymes for bioelectrochemical applications.