<p>In this paper, the design and optimization of a dual-band THz biosensor employing a perfect metamaterial absorber (PMA) is presented. The proposed PMA configuration is evolved from a ring resonator connected to a central metallic patch through a set of connecting stub lines, thereby enhancing the effective current path and enabling structural miniaturization. The graphene-based resonator, realized on a Gallium Arsenide (GaAs) substrate, exhibits dual resonance characteristics centred at 2.5 THz and 3.0 THz with near-unity absorptivity at both operating frequencies. The proposed unit cell has a footprint of 0.25λ × 0.25λ at the lowest operating frequency, making it suitable for compact THz sensing applications. Owing to its geometrically symmetric configuration, the proposed absorber exhibits polarization-insensitive characteristics and maintains 80% absorption performance for oblique incidence angles up to 70°. To achieve rapid convergence and efficient optimization of the geometrical parameters, the proposed structure is optimized using the metaheuristic Marine Predators Algorithm (MPA). The optimization framework demonstrates good optimization accuracy with a mean squared error (MSE) below 0.1 and a mean absolute percentage error (MAPE) below 1% in comparison with traditional inbuilt optimizers in the electromagnetic solver. The suitability of the proposed THz PMA for biomedical sensing applications is investigated through refractive index-based analyte characterization. Theoretical analysis show that the PMA based biosensor offers sensitivities of 498 and 396&#xa0;GHz/RIU at 2.5 and 3.0 THz, respectively thereby demonstrating the robustness of the proposed biosensing platform for advanced biomedical detection applications.</p>