The CAM Model: An in Vivo Testbed for Molecular Communication Systems

Molecular communication (MC) research is increasingly focused on applications within the human body, such as health monitoring and drug delivery, which require testing in realistic and living environments. Thus, elevating experimental MC research to the next level requires developing realistic in vivo experimental testbeds. In this paper, we introduce the chorioallantoic membrane (CAM) model as the first versatile 3D in vivo MC testbed. The CAM itself is a highly vascularized membrane formed in fertilized chicken eggs and the CAM model has gained significance in various research fields, including bioengineering, cancer research, and drug development. Its versatility, reproducibility, and realistic biological properties make it perfectly suited for next-generation MC testbeds, facilitating the transition from proof-of-concept systems to practical applications. In this paper, we provide a comprehensive introduction to the CAM model, its properties, and its applications in experimental research. Additionally, we present a characterization of the CAM model as an MC system. As an experimental study, we investigate the distribution of fluorescent molecules in the closed-loop vascular system of the CAM model. We derive an analytical model based on the wrapped normal distribution to describe the propagation of particles in dispersive closed-loop systems, where the propagation of particles is mainly influenced by diffusion and flow. Based on this analytical model, we propose parametric models to approximate the particle propagation dynamics inside the CAM model. The model parameters are estimated via curve fitting to experimental results using a nonlinear least squares method. We provide a dataset containing experimental results for 69 regions in 25 eggs, on which we evaluate the proposed parametric models. Moreover, we discuss the estimated parameters, their relationships, and plausibility. Furthermore, we investigate and develop a parametric model for the long-term behavior of particles in the CAM model and their accumulation in the chick embryo’s liver.