<p>The diagnostic method for Alzheimer’s disease (AD) is moving towards non-invasive approaches and miRNAs in biofluids are being considered as potential early biomarkers. Among all the miRNAs, the elevated levels of miRNA-128 in the serum may serve as potential diagnostic biomarker for AD. We report an electrochemical sensing platform based on a reusable fluorine-doped tin oxide (FTO) electrode, modified with citrate-capped silver nanoparticles (Ag-Cit NPs) synthesized using the <i>Bryophyllum pinnatum</i> leaf extract. Initially, the FTO were treated with (3-aminopropyl) triethoxysilane (APTES) to achieve the amine groups interaction with Ag-Cit NPs (Ag-Cit/APTES/FTO electrode). The biotinylated-cDNA (Btn-cDNA) was conjugated on Ag-Cit/APTES/FTO electrode with the help of streptavidin (SV) and the possible vacant electrode surface was blocked with the help of 6-mercapto-1-hexanol (MCH). The fabricated biosensing electrode (MCH/Btn-cDNA/SV/Ag-Cit/APTES/FTO) showed the low detection limit of 0.024 fM for miRNA-128 detection using electrochemical impedance spectroscopy. With the limit of quantification of 0.080 fM and a sensitivity of 402.48 Ω fM⁻¹cm^− 1, this nanoplatform achieved recoveries of 99% to 101.9%. The selective signal for miRNA-128 was obtained when compared with the mismatch and single mismatch miRNAs. Furthermore, the reliable performance in the real serum samples of AD patients, recommends this nano-sensor platform for future non-invasive detection tool in early diagnosis of AD.</p> Graphical Abstract <p></p>