The present application is directed to methods of performing chemical reactions, including multi-step chemical reactions in which two or more of the reagents in the chemical reaction are incorporated or entrapped in a solid polymeric structure comprising pullulan. In certain embodiments, the chemical reaction or multi-step reaction serves as a sensor. Accordingly the present application is also directed to sensors for performing the methods of the application. In certain embodiments, at least one of the reagents is a biomolecule and the sensor is a biosensor. In certain other embodiments, the solid polymeric structure comprising pullulan and the reagents for performing a chemical reaction form a convenient device for performing a chemical reaction.