Molecular Communication Link Research Articles

Computational estimation of chemical reaction rates in extracellular vesicle signaling

The rates of chemical reactions involved in cell-to-cell communication can serve as a powerful tool for advanced theranostics and in establishing a molecular communication link between bio-transceivers. Reaction rates are usually experimentally measured by quantifying chemical products, which is challenging when several signal transduction mechanisms are involved in the signaling pathway. Without loss of generality, we focus on extracellular vesicle (EV) cell-to-cell signaling and propose a computational method to estimate the chemical reaction rates which characterize a process by which EVs are taken by cells. The method is based on measuring only the time-course of environmental EVs, and eliminates the need to measure either bound or internalized EVs which is usually essential for experimental evaluation of the rates by using advanced molecular imaging modalities. As an alternative to a proposed approximation by a linear system model, our computation exploits a nonlinear system model in which the impact of limited receptor sites on the recipient cell membrane is incorporated. The reaction rates are obtained through a suggested linear and iterative approach as well as a novel way of applying Michaelis–Menten kinetics in the frequency domain. The range of validity of each technique is evaluated by varying the number of free binding sites on the cell membrane in relation to the initial number of environmental EVs. In conclusion, the proposed methods are very effective in assessing the dynamics of the EV uptake using a simple in vitro platform.

An Integrated Molecular Communication System Based on Acoustic Tweezers.

In this work, a molecular communication link integrated with a micro-electro mechanical system (MEMS) based environment has been designed and simulated. The motivation behind this approach is to explore the possibility of merging acoustic tweezing technique with a molecular communication system to increase the accuracy and reliability of the overall communication link. The proposed design is simulated using finite element methods that mimic the actual environment for an accurate solution. We derive symbol error rate as a performance metric and further show that the proposed system outperforms the diffusion-based modulation techniques and facilitates a reliable communication in the presence of fluid flow and while being insusceptible to external factors.

Molecular Communications With Molecular Circuit-Based Transmitters and Receivers.

The performance of a communication link can be improved by maximizing the mutual information between the input and output signals. This paper considers this maximization problem in a molecular communication link where both the transmitter and the receiver are molecular circuit. This general optimization is hard to solve. We simplify the problem by limiting to reactions with linear reaction rates and molecular circuits with a limited number of species. We derive an expression of mutual information and use it for numerical maximization. We show that our parameterized transmitter circuit is able to give mutual information that is close to upper bound obtained in our earlier work.

Secrecy Capacity and Secure Distance for Diffusion-Based Molecular Communication Systems

The biocompatibility and nanoscale features of Molecular Communication (MC) make this paradigm, based on molecules and chemical reactions, an enabler for communication theory applications in the healthcare at its biological level ( e.g. , bimolecular disease detection/monitoring and intelligent drug delivery). However, the adoption of MC-based innovative solutions into privacy and security-sensitive areas is opening new challenges for this research field. Despite fundamentals of information theory applied to MC have been established in the last decade, research work on security in MC systems is still limited. In contrast to previous literature focused on challenges, and potential roadmaps to secure MC, this paper presents the preliminary elements of a systematic approach to quantifying information security as it propagates through an MC link. In particular, a closed-form mathematical expression for the secrecy capacity of an MC system based on free molecule diffusion is provided. Numerical results highlight the dependence of the secrecy capacity on the average thermodynamic transmit power, the eavesdropper’s distance, the transmitted signal bandwidth, and the receiver radius. In addition, the concept of secure distance in an MC system is introduced and investigated for two different techniques of signal detection, i.e. , based on energy and amplitude. The secrecy capacity can be used to determine how much secure information (bit/sec/Hz) can be exchanged and within which operative range, while the secure distance can be used to set the transmit power to obtain a secure channel at a given distance. We envision these metrics will be of utmost importance for a future design framework tailored to MC systems and their practical applications.

Coexistence in molecular communications

Molecular communications is emerging as a technique to support coordination in nanonetworking, particularly in biochemical systems. In complex biochemical systems such as in the human body, it is not always possible to view the molecular communication link in isolation as chemicals in the system may react with chemicals used for the purpose of communication. There are two consequences: either the performance of the molecular communication link is reduced; or the molecular link disrupts the function of the biochemical system. As such, it is important to establish conditions when the molecular communication link can coexist with a biochemical system. In this paper, we develop a framework to establish coexistence conditions based on the theory of chemical reaction networks. We then specialize our framework in two settings: an enzyme-aided molecular communication system; and a low-rate molecular communication system near a biochemical system. In each case, we prove sufficient conditions to ensure coexistence.

Improving the Capacity of Molecular Communication Using Enzymatic Reaction Cycles.

This paper considers the capacity of a diffusion-based molecular communication link assuming the receiver uses chemical reactions. The key contribution is we show that enzymatic reaction cycles, which is a class of chemical reactions commonly found in cells consisting of a forward and a backward enzymatic reaction, can improve the capacity of the communication link. The technical difficulty in analyzing enzymatic reaction cycles is that their reaction rates are nonlinear. We deal with this by assuming that the amount of certain chemicals in the enzymatic reaction cycle is large. In order to simplify the problem further, we use singular perturbation to study a particular operating regime of the enzymatic reaction cycles. This allows us to derive a closed-form expression of the channel gain. This expression suggests that we can improve the channel gain by increasing the total amount of substrate in the enzymatic reaction cycle. By using numerical calculations, we show that the effect of the enzymatic reaction cycle is to increase the channel gain and to reduce the noise, which results in a better signal-to-noise ratio and in turn a higher communication capacity. Furthermore, we show that we can increase the capacity by increasing the total amount of substrate in the enzymatic reaction cycle.