1558-1748 (c) 2018 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/JSEN.2018.2869071, IEEE Sensors Journal > REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLE-CLICK HERE TO EDIT) < 1 Abstract— Controlling the arrangement and organization of the self-assembled material is a crucial step in development of biosensor devices. Here, we have described a sensitive electrochemical immune-biosensor based on a simple and biocompatible self-assembly method which provide flower-like diphenylalanine peptide nanostructures (FPNSs) on to the glassy carbon electrode (GCE). Then, human growth hormone (hGH) antibody was immobilized onto the surfaces of FPNSs through the amide bonds formation between the amino groups of diphenylalanine peptide and the carboxylic groups of hGH antibody. This immune-biosensor was applied for the sensitive detection of human growth hormone. The Cyclic voltammetry and electrochemical impedance spectroscopy techniques were employed for the characterization of various coating layers on the glassy carbon electrode. The relative charge transfer resistance of the hGH antibody/FPNSs modified glassy carbon electrode was found to be changed linearly with the concentration of the hGH. This electrochemical biosensor exhibited a linear detection range of 1 – 100 pgmL -1 of hGH. This proposed immune-biosensor could be used as paraclinical test for the determination of hGH. Index Terms: Peptide nanostructures, Impedance, Immuno- biosensor, human growth hormone antibody. I. INTRODUCTION uman growth hormone (hGH) is the most prominent peptide hormone in the human body, raising motivation levels in the blood. The secretion of this hormone in stress condition causes increase of protein, lipid and carbohydrate metabolism [1]. It is normally applied to medically treat children's growth disorders [2]. Also, hGH has been banned by the IOC and NCAA in sports since at least 40 years ago [3]. Thus, introduction of a selective and specific probe for detection and determination of hGH in biological fluid such as human serum is important. To date, numerous methods have been reported for the analysis of hGH using different analytical methods, such as Reverse Transcription Polymerase Chain Reaction [4], Enzyme-linked Immunosorbent Assays[5], Transcription Polymerase Chain Reaction [6] and surface plasmon resonance [7]. *Corresponding author e-mail: allafchian@cc.iut.ac.ir a Research Institute for Nanotechnology and Advanced Materials, Isfahan University of Technology, Isfahan 84156–83111, Iran. b Department of Molecular Biotechnology, Cell Science Research Center, Royan Institute for Biotechnology, ACECR, Isfahan, Iran. However, these methods require costly and large laboratory facilities, tedious analytical procedures, specially trained workers, and long assay time [8]. Electrochemical biosensors based on nanomaterials have received much attention for the measurement of biomaterials as their sensing performances are not affected by the turbidity or absorbance of the sample [9- 13]. Also, electrochemical biosensors offer the advantages of being highly sensitive, fast in signal generation and readout, suitable for miniaturization, and simple in terms of pretreatment procedures [14]. Among the electrochemical biosensors, probes based on self-assemble peptides which are functionalized with antibodies for the sensitive detection of antigen are known as a sensitive immune-biosensor. Such systems have the ability to detect concentrations of antigen with higher sensitivity, as compared to the existing methods [15]. The significant thermal and chemical stability of diphenylalanine peptide nanostructures has been demonstrated in practical nanodevices [16]. When a diphenylalanine peptide nanostructure is formed, a very high surface area to volume ratio is created, leading to a substantial increase in the loading of antigen on the electrodes and the enhancement of the sensitivity of the biosensors [17]. Since in self-assembly techniques, the ability to design and control of assembled layer base on intramolecular binding is very important. Herein, we report for first time a self- assembled flower-like diphenylalanine peptide nanostructures electrode has been immobilized with hGH antibody. This report potentially provides the ability to manipulate surfaces in unconventional forms. In addition, the electrochemical performance of this immune-biosensor was evaluated in the measurement of hGH in human serum samples. II. MATERIALS AND METHODS A. Materials Diphenylalanine peptide in a lyophilized form and EDC: 1- Ethyl-3-(3-dimethylaminopropyl) carbodiimide were obtained from Sigma-Aldrich. 1,1,1,3,3,3 Hexafluoro-2-propanol (HFP), potassium ferricyanide, and potassium ferrocyanide, was purchased from Merck. Monoclonal hGH antibody and human growth hormone were obtained from Cytomatingene company. B. Self-assembly of diphenylalanine peptide nanostructures 100 mg of diphenylalanine peptide was completely dissolved in 1ml HFP in a sample tube in order to form a Flower-Like Self-Assembly of Diphenylalanine for Electrochemical Human Growth Hormone Biosensor Ali Reza Allafchian* a , Ehsan Moini a , Seyede Zohreh Mirahmadi-Zare b H