An optical biosensor based on the immobilization of a crude extract from Terfezia leonis Tul. Desert truffle in silica films was developed for dopamine detection. The polyphenol oxidase activity of the extract was first compared with commercial tyrosinase, showing better stability in slightly acidic conditions and under mild heating conditions. The sol-gel encapsulation process was found favourable for the stability and preservation of the enzymatic 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 benefits of associating a cost-effective enzymatically-active extract with water-based robust silica hosts for biosensor design.