▎ 摘　　要

NOVELTY - The biosensor (100) has a graphene-based screen-printed electrodes (SPEs) (12) arranged on a biosensor substrate (11). The primary amine (NH2) linkers (10) are attached to the SPEs. The bioreceptor molecules (13) covalently bound to primary amine linkers. The blocking layer (14) is deposited on SPEs. The graphene-based SPEs are either reduced graphene oxide (rGO) SPEs or a micro-fabricated graphene field effect transistors (GFET). The primary amine linkers are covalently bonded to SPEs surface through chemisorption mechanism. The chemisorption mechanism of primary amine linkers take place during the immersion of said SPEs in ammonia solution at room temperature. The bioreceptor molecules are antibody molecules. The blocking layer is Bovine serum albumin (BSA). USE - Label-free electrochemical biosensor used for detection of body-fluid based biomarkers for diagnosis of chronic diseases, and applied to printed graphene electrodes and micro-fabricated graphene field effect transistors (GFET). ADVANTAGE - The improved label-free graphene-based electrochemical biosensor provides a method for the rGO SPEs surface modification with linker molecules for effective immobilisation of bioreceptors and for improving the performance of biosensors. The graphene or rGO based label-free biosensor has the ability to detect biomarkers in a cost and time efficient way. The graphene-based biosensor performance in term of sensitivity is far most important to increase the probability of attaching higher number of bio-receptors to capture the target biomarker. The increased performance of the biosensor is achieved by implementing a small NH2 linker. The molecules effectively attach more target-receptor molecules on the electrode surface, leading to remarkable performance in limit of detection and linear dynamic sensing range of rGO electrodes. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) a method for using the label-free electrochemical biosensor; and (2) a method of fabrication of a label-free electrochemical biosensor. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic illustration of the detection process of modification of rGO electrode by NH2 linkers through ammonia chemisorption. Primary amine linkers (10) Biosensor substrate (11) SPEs (12) Bioreceptor molecule (13) Blocking layer (14) Label-free electrochemical biosensor (100)