We have designed and fabricated a low-cost modular electrical and fluidic integration platform for microelectromechanical systems (MEMS) based biosensors, paving the way for a disposable, low-cost Lab-on-a-Chip. We demonstrate seamless integration using an additive manufacturing enabled "plug-and-play" platform that does not require permanent electronic or fluidic integration. This paper describes the fabrication steps and assembly of the method and highlights its advantages over the more traditional methods, such as `wire bonding' and `flip chip'. We also provide design guidelines for improved biosensing, taking transport and binding kinetics into consideration in the context of prostate cancer diagnosis. Our novel approach combined with the design guidelines, opens up new opportunities for low-cost disposable high-density MEMS-based lab-on-a-chips for biosensing applications.