Roles of Remote and Contact Forces in Epithelial Cell Structure Formation.

Cancer cells collectively form a large-scale structure for their growth. In this article, we report that HeLa cells, epithelial-like human cervical cancer cells, aggressively migrate on Matrigel and form a large-scale structure in a cell-density-dependent manner. To explain the experimental results, we develop a simple model in which cells interact and migrate using the two fundamentally different types of force, remote and contact forces, and show how cells form a large-scale structure. We demonstrate that the simple model reproduces experimental observations, suggesting that the remote and contact forces considered in this work play a major role in large-scale structure formation of HeLa cells. This article provides important evidence that cancer cells form a large-scale structure and develops an understanding into the poorly understood mechanisms of their structure formation.

Packet Fragmentation and Reassembly in Molecular Communication.

This paper describes packet fragmentation and reassembly to achieve reliable molecular communication among bionanomachines. In the molecular communication described in this paper, a sender bionanomachine performs packet fragmentation, dividing a large molecular message into smaller pieces and embedding into smaller molecular packets, so that molecular packets have higher diffusivity to reach the receiver bionanomachine. The receiver bionanomachine then performs packet reassembly to retrieve the original molecular message from a set of molecular packets that it receives. To examine the effect of packet fragmentation and reassembly, we develop analytical models and conduct numerical experiments. Numerical results show that packet fragmentation and reassembly can improve the message delivery performance. Numerical results also indicate that packet fragmentation and reassembly may degrade the performance in the presence of drift in the environment.

Molecular communication among biological nanomachines: a layered architecture and research issues.

Molecular communication is an emerging communication paradigm for biological nanomachines. It allows biological nanomachines to communicate through exchanging molecules in an aqueous environment and to perform collaborative tasks through integrating functionalities of individual biological nanomachines. This paper develops the layered architecture of molecular communication and describes research issues that molecular communication faces at each layer of the architecture. Specifically, this paper applies a layered architecture approach, traditionally used in communication networks, to molecular communication, decomposes complex molecular communication functionality into a set of manageable layers, identifies basic functionalities of each layer, and develops a descriptive model consisting of key components of the layer for each layer. This paper also discusses open research issues that need to be addressed at each layer. In addition, this paper provides an example design of targeted drug delivery, a nanomedical application, to illustrate how the layered architecture helps design an application of molecular communication. The primary contribution of this paper is to provide an in-depth architectural view of molecular communication. Establishing a layered architecture of molecular communication helps organize various research issues and design concerns into layers that are relatively independent of each other, and thus accelerates research in each layer and facilitates the design and development of applications of molecular communication.

Cooperative target tracking by a mobile bionanosensor network.

This paper describes a mobile bionanosensor network designed for target tracking. The mobile bionanosensor network is composed of bacterium-based autonomous biosensors that coordinate their movement through the use of two types of signaling molecules, repellents and attractants. In search of a target, the bacterium-based autonomous biosensors release repellents to quickly spread over the environment, while, upon detecting a target, they release attractants to recruit other biosensors in the environment toward the location around the target. A mobility model of bacterium-based autonomous biosensors is first developed based on the rotational diffusion model of bacterial chemotaxis, and from this their collective movement to track a moving target is demonstrated. In simulation experiments, the mobile bionanosensor network is evaluated based on the mean tracking time. Simulation results show a set of parameter values that can optimize the mean tracking time, providing an insight into how bacterium-based autonomous biosensors may be designed and engineered for target tracking.