A highly sensitive and self-powered cholesterol biosensor

• Blood cholesterol is a very important parameter for the assessment of atherosclerosis and other lipid disorders. The total cholesterol concentration in human blood should be less than 5.17 mM. Concentrations in the range 5.17 – 6.18 mM are considered borderline high risk and levels above 6.21 mM, high risk. Cholesterol determination with high accuracy is therefore necessary in order to differentiate these levels for medical screening or diagnosis. Several attempts to develop highly sensitive cholesterol biosensors have been described, but, to the best of our knowledge, this is the first report of a self-powered cholesterol biosensor, i.e. a device delivering the analytical information from the current output of the energy of the biocatalytic conversion of cholesterol, without any external power source. This is particularly relevant to the development of inexpensive screening devices based on printed electronics. We present two complementary bioelectrocatalytic platforms suitable for the fabrication of a self-powered biosensor. Both are based on cholesterol oxidase (ChOx) immobilisation in a sol-gel matrix, as illustrated in Fig. 1 [1]. Mediated biocatalytic cholesterol oxidation [2] was used as the anodic reaction and electrocatalytic reduction of hydrogen peroxide on Prussian Blue (PB) as the cathodic reaction. Due to a synergistic effect in the self-powered cholesterol biosensor, the analytical parameters of the overall device exceeded those of the individual component half-cells, yielding a sensitivity of 0.19 A M-1 cm-2 and a dynamic range that embraces the free cholesterol concentrations found in human blood. Thus, we have demonstrated the novel concept of highly sensitive cholesterol determination using the first self-powered cholesterol biosensor. This configuration is particularly promising for incorporation in emerging plastic- and paper-based analytical instruments for decentralised diagnostics and mobile health. 

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