We have designed a novel nanobiosensor for in silico detecting proteins based on leucine/Pd-loaded single-walled carbon nanotube matrix. Density functional theory at the B3LYP/6-31G (d) level of theory was realized to analyze the geometrical and electronic structure of the proposed nanobiosensor. The solvent effects were investigated using the Tomasi's polarized continuum model. Atoms-in-molecules theory was used to study the nature of interactions by calculating the electron density ρ(r) and Laplacian at the bond critical points. Natural bond orbital analysis was performed to achieve a deep understanding of the nature of the interactions. The biosensor has potential application for high sensitive and rapid response to protein due to the chemical adsorption of L-leucine amino acid onto Pd-loaded single-walled carbon nanotube and reactive functional groups that can incorporate in hydrogen binding, hydrophobic interactions and van der Waals forces with the protein surface in detection process.