Boron, Titanium, and Calcium Doped Graphene Monolayers for Alzheimer’s Disease Biomarker Detection: A Density Functional Theory Study

Alzheimer's disease remains a critical public health concern, with early detection hindered by the limited sensitivity and invasiveness of conventional diagnostic techniques. Two-dimensional monolayer materials offer a promising alternative by enabling label-free, real-time, and noninvasive detection of disease-specific biomarkers. In this study, we analyzed the effectiveness of doped graphene monolayers as biosensing platforms for two emerging biomarkers of Alzheimer's disease: glycine and d-serine. Using density functional theory, we investigated the adsorption behavior of these biomarkers on pristine graphene as well as boron-, titanium-, and calcium-doped graphene monolayers. Our results showed that calcium-doped graphene exhibits the most favorable sensing characteristics across multiple criteria. Glycine adsorption on calcium-doped graphene resulted in a recovery time of 0.170 s, indicating a rapid sensor response and high reversibility. Both biomarkers induced a semiconductor-to-metal transition, significantly enhancing electrical conductivity. Charge density and band structure analyses further revealed strong orbital interactions and substantial electronic modulation upon adsorption. These findings demonstrate that calcium-doped graphene is a promising candidate for the development of highly sensitive, reversible, and real-time biosensors for the early stage detection of Alzheimer's disease.