Cholesterol biosensors based on oxygen sensing alginate-silica microspheres

Cholesterol determination in body is important in diagnosis of diseases like coronary heart disease, arteriosclerosis, diabetes, and obstructive jaundice. This research aims at developing fluorimetric cholesterol biosensors based on self‐assembled mesoporous alginate‐silica (Algilica) microspheres. For preparing the biosensor, Pt‐(II)‐octaethylporphine (PtOEP; oxygen sensitive metalloporphyrin) dye has been loaded in the Algilica microspheres using the solvent‐mediated precipitation method. Cholesterol oxidase (ChOx) was then covalently conjugated to PtOEP/Algilica microspheres using EDC and NHS reagents. PtOEP dye and enzyme encapsulation, activity and stability were then analyzed. Layer‐by‐layer self‐assembly was finally performed using PAH and PSS polyelectrolytes to minimize leaching of the biosensor components. The prepared biosensor exhibited linearity over a range of 0.77–2.5 mM O2 (KSV: 0.097/mM of O2) obtained using from Stern–Volmer plots. The biosensor response to standard cholesterol displayed a linear analytical range from 1.25 to 10 mM of cholesterol with regression coefficient of 0.996 (1.25–3.75 mM), 0.976 (1.25–6 mM), and 0.959 (1.25–10 mM) and response time of 10 min. Thus, the prepared cholesterol biosensor shows great potential in the diagnosis of hypercholesterolemia. Biotechnol. Bioeng. 2011;108:2011–2021. © 2011 Wiley Periodicals, Inc.