In this work, we have made and characterized a pair of immunobiosensors for detecting the green fluorescent protein (GFP) in an aqueous matrix. An anti-GFP antibody-based biosensor was assembled to detect GFP, while a novel peptoid (N-substituted oligomers of glycine designated as IOS-1) biosensor was also assembled for GFP detection. A quartz crystal microbalance (QCM) gold sensor was used as the supporting substrate for self-assembly of the immunobiosensors. Gravimetric measurements of the QCM gold sensor during immunobiosensor construction and operation were available in real-time using a QCM instrument. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and Fluorescence microscopy were used to characterize the immunobiosensors. Dose-dependent calibration curves were developed to contrast the performance of the peptoid immunobiosensor and the antibody-based immunobiosensor. The sensitivity of the biosensors shows that the peptoid could detect GFP at 8 nM, unlike the antibody immunobiosensor, which starts to measurably detect GFP at 40 nM. IOS-1 peptoid immunobiosensor had more adsorption capacity for GFP than the antibody-based immunobiosensor and could be reused through multiple adsorption/ desorption cycles. The peptoid immunobiosensor had a binding constant of 2.197 x 10(7) M(-1) with GFP
