Silicon (2013) 5:241–246 DOI 10.1007/s12633-013-9165-z ORIGINAL PAPER Immobilization of a Polyphenol Oxidase Extract from Terfezia leonis Tul. Desert Truffle in Multilayered Silica Films for Dopamine Biosensing Hicham Gouzi · Thomas Moreau · Christophe Depagne · Thibaud Coradin Received: 2 July 2013 / Accepted: 18 July 2013 / Published online: 5 September 2013 © Springer Science+Business Media Dordrecht 2013 Abstract An optical biosensor based on the immobiliza- tion of a crude extract from Terfezia leonis Tul. Desert truf- fle in silica films was developed for dopamine detection. The polyphenol oxidase activity of the extract was first compared with commercial tyrosinase, showing better sta- bility in slightly acidic conditions and under mild heating conditions. The sol-gel encapsulation process was found favourable for the stability and preservation of the enzyma- tic conversion of dopamine into dopachrome. The range of linear detection of dopamine was 0.1 mM–1.5 mM with a two minutes response time. These results demonstrate the be- nefits of associating a cost-effective enzymatically-active ex- tract with water-based robust silica hosts for biosensor design. Keywords Silica · Enzymes · Biosensors · Polyphenol oxidase · Dopamine 1 Introduction Phenolic compounds determination is becoming important in the area of medicine, since some of these compounds H. Gouzi · T. Moreau · C. Depagne · T. Coradin () UPMC Univ Paris 06; CNRS, Chimie de la Mati` ere Condens´ ee de Paris, Coll` ege de France, 11, place Marcelin Berthelot, 75231 Paris cedex 05, France e-mail: thibaud.coradin@upmc.fr H. Gouzi Laboratoire de Chimie Organique, Substances Naturelles et Analyse (COSNA), D´ epartement de Chimie, Facult´ e des Sciences, Universit´ e Abou Bekr Belkaid, Tlemcen 13000, Algeria belong to the neurotransmitter class. Dopamine, epinephrine (adrenalin), and seretonin are compounds called cathe- cholamines, having great clinical and pharmaceutical interest [1]. 3,4-dihydroxyphenyl ethylamine, known as dopamine (DOPA), is an important neurotransmitter in the mammalian central nervous system and plays a vital role in the function of central nervous, renal, hormonal and car- diovascular system [2]. The abnormal levels of DOPA may result in several diseases and neurological disorders such as schizophrenia, Parkinson’s and Alzheimer’s diseases. For this reason, monitoring the concentration fluctua- tions of this neurotransmitter is of great importance, and consequently, the development of simple, rapid, sensitive, and selective detection methods for DOPA has received much interest over the past two decades [3]. However these methods often require sophisticated preparation, expensive instrumentation, and need skillful operators. In many situations, biosensors represent an interesting alternative for the detection of biological substrates because of their many advantages such as selectivity, low cost, fast and cheap screening of samples [4]. For dopamine detection, polyphenol oxidase (PPO) (monophenol, o- diphenol:oxygen oxidoreductase, EC 1.14.18.1) enzymes are of particular interest [5]. PPO is a copper-enzyme which in the presence of oxygen catalyzes two different reactions: the o-hydroxylation of monophenols (cresolase activity) and the oxidation of o-diphenols into reactive o-quinones (cate- cholase activity) [6]. Subsequently, the o-quinones undergo non-enzymatic reactions, producing intermediates which associate spontaneously into dark, red or brown pigments. In animals, plants and lower organisms, PPOs are responsi- ble for the first step of the melanin pathway, starting from L-tyrosine as substrate or DOPA leading to the formation of