The aggregation of cytotoxic amyloid peptides (Aβ1-42) is widely recognised as the cause of brain tissue degeneration in Alzheimer’s disease (AD). Indeed, evidence indicates that the deposition of cytotoxic Aβ1-42 plaques formed through the gradual aggregation of Aβ1-42 monomers into fibrils determines the onset of AD. Thus, distinct Aβ1-42 inhibitors have been developed, and only recently, the use of short linear peptides has shown promising results by either preventing or reversing the process of Aβ1-42 aggregation. Among them, the KLVFF peptide sequence, which interacts with the hydrophobic region of Aβ16-20, has received widespread attention due to its ability to inhibit fibril formation of full-length Aβ1-42. In this study, hyperbranched poly-L-lysine dendrons presenting sixteen KLVFF at their uppermost molecular branches were designed with the aim of providing the KLVFF sequence with a molecular scaffold able to increase its stability and of improving Aβ1-42 fibril formation inhibitory effect. These high-purity branched KLVFF were used to functionalise the surface of the metal oxide chip of the optical waveguide lightmode spectroscopy sensor showing the more specific, accurate and rapid measurement of Aβ1-42 than that detected by linear KLVFF peptides.