Biological nanosensors consist of a bio-receptor and a transducer. The transduction method of choice is currently fluorescence because of the high sensitivity and relative ease of measurement. The measurement can be achieved by using the following methods: binding active nanoparticles to active proteins within the cell, using site-directed mutagenesis to produce indicator proteins, allowing for real-time measurements, or by creating a nanomaterial (e.g. nanofibers) with attachment sites for the bio-receptors. Even though electrochemical nanosensors can be used to measure intracellular properties, they are typically less selective for biological measurements, as they lack the high specificity of bio-receptors (e.g. antibody, DNA).