Practical Transmitters for Molecular Communication: Functionalized Nanodevices Employing Cooperative Transmembrane Transport Proteins

Abstract: This paper introduces a novel optically controllable molecular communication (MC) transmitter (TX) design based on vesicular nanodevices (NDs). The NDs are functionalized for the controlled release of signaling molecules (SMs) via transmembrane proteins. The proposed design contributes to overcoming the current barrier between MC theory and practical implementation, as all components of the system are chemically realizable. The NDs possess an optical-to-chemical conversion capability, therefore, the proposed NDs can be employed as externally controllable TXs in various MC systems. The proposed ND design comprises two cooperating modules, namely an energizing module and a release module, and, depending on the specific choices for the modules, allows for the release of different types of SMs. After introducing the general system model for the proposed realistic TX design, we provide a detailed mathematical analysis of a specific TX realization. In particular, we derive both an exact and a closed-form approximate analytical solution for the concentration of the released SMs and validate our results by comparison with a numerical solution. Moreover, we model the impact of a buffering medium, which is typically present in liquid environments, e.g., in experimental settings or in in-body applications. This allows the evaluation of the feasibility of our proposed TX design in practical chemical implementations. We consider various forms of parameter randomness occurring during vesicle synthesis, i.e., deviations which are unavoidable during experiments. We show that considering random distributions of the parameter values, such as the ND size, the number of incorporated proteins on the vesicle surface, and the vesicle membrane permeability, is crucial for an adequate kinetic analysis of the system.