Contents of Supplemental Information.Scheme S1. Synthetic route used to produce 3, I = ferrocenecarboxylic acid. Scheme S2. Synthetic methods used to produce 5 and 6 (II = 1'-Fmoc-amino-ferrocene carboxylic acid).

Early detection is a key to successful treatment of most diseases, and is particularly imperative for the diagnosis and treatment of many types of cancer. The most common techniques utilized are imaging modalities such as Magnetic Resonance Imaging (MRI), Positron Emission Topography (PET), and Computed Topography (CT) and are optimal for understanding the physical structure of the disease but can only be performed once every four to six weeks due to the use of imaging agents and overall cost. With this in mind, the development of "point of care" techniques, such as biosensors, which evaluate the stage of disease and/or efficacy of treatment in the clinician's office and do so in a timely manner, would revolutionize treatment protocols.1 As a means to exploring ferrocene based biosensors for the detection of biologically relevant molecules 2 , methods were developed to produce ferrocene-biotin bio-conjugates described herein. This report will focus on a biotin-ferrocenecysteine system that can be immobilized on a gold surface. Video LinkThe video component of this article can be found at

Early detection is a key to successful treatment of most diseases, and is particularly imperative for the diagnosis and treatment of many types of cancer. The most common techniques utilized are imaging modalities such as Magnetic Resonance Imaging (MRI), Positron Emission Topography (PET), and Computed Topography (CT) and are optimal for understanding the physical structure of the disease but can only be performed once every four to six weeks due to the use of imaging agents and overall cost. With this in mind, the development of "point of care" techniques, such as biosensors, which evaluate the stage of disease and/or efficacy of treatment in the clinician's office and do so in a timely manner, would revolutionize treatment protocols.1 As a means to exploring ferrocene based biosensors for the detection of biologically relevant molecules 2 , methods were developed to produce ferrocene-biotin bio-conjugates described herein. This report will focus on a biotin-ferrocenecysteine system that can be immobilized on a gold surface.