In this study, we integrated two amplification mechanisms to enhance colorimetric LFIA: analyte concentration within the sample, driven by the iron oxide core, and (2) enhanced optical brightness, achieved through the sharp spiked morphology of the outer shell of the nanoparticle system. To achieve the Fe3O4 core with a sharp-spiked shell morphology, we developed a simple and straightforward surfactant-free synthesis strategy to fabricate iron core-gold nanostar (mpGNS) structures with numerous sharp branches. Establishing a surfactant-free synthesis method is essential for maximizing spike formation and enhancing colorimetric LFIA performance. In contrast, surfactant-based methods can obstruct nucleation centers, inhibiting spike development . While previous studies have explored magnetic core-shell gold nanostars, many have relied on complex synthesis procedures involving surfactants . In this study, we present a surfactant-free approach specifically designed to optimize spike formation, achieving the highest possible number of sharp branches.