The present invention is directed to a system, device and method for measuring the concentration of an analyte in a fluid or matrix. A thermodynamically stabilized analyte binding ligand for use in the system, device and method is disclosed. The thermodynamically stabilized analyte binding ligand is resistant to degradation at physiological temperatures and its use within the device provides a minimally invasive sensor for monitoring the concentration of an analyte in a fluid or matrix as are present in the body of an animal.