polyethyleneimine Article 2 Bio-sensor platforms 2 Biosensing Techniques 2 Biosensing applications 2 Biosensors 2 Canavalia 2 Chemical sensors 2 Copper 2 Enzymes 2 Enzymes, Immobilized 2 Equipment Design 2 Field effect transistors 2 Field-effect transistors 2 Graphene 2 Graphene transistors 2 Graphite 2 Heavy metals 2 Humans 2 Hydrolysis of ureas 2 Layer-by-layer assemblies 2 Limit of Detection 2 Long term stability 2 Metabolism 2 Oxides 2 Polyelectrolyte multilayer 2 Polyelectrolytes 2 Reduced graphene oxides 2 Solutions 2 Transistors 2