1. System Design of a Molecular Communication Network Christina Wong 1,Tatsuya Suda 2 (Faculty Mentor) 1 Department of Biomedical Engineering, 2 School of Information and Computer Sciences, University of California, Irvine Introduction http://netresearch.ics.uci.edu/ · www.research.calit2.net/students/surf-it2006 · www.calit2.net S ummer U ndergraduate 2 R esearch 0 F ellowship in 0 I nformation 6 T echnology 2. Chemical Modification of Au/SiO 2 Substrate Two chemical groups, thiols and silanes, were used to modify the Au/SiO 2 substrate surfaces. Thiols attach to Au through S atoms and silanes attach to SiO 2 via O atoms. Different functional groups (CH3-, OH-) can be linked onto thiols and silanes to govern cell adhesion. The silanes and thiols used in this study were octadecyltrichlorosilane (OTS, hydrophobic); hexadecanethiol (HDT, hydrophobic) and PEG-5000’ thiol (hydrophilic). The chemicals formed self assembled monolayers (SAMS) on the Au/SiO 2 surfaces when the substrates were immersed for 48 hours in 1 mM (HDT and OTS) or 0.01 mM (PEG-5000’ thiol) dilutions in ethanol. Results Experimental Procedures 1. Fabrication of Substrate Surfaces A thin layer of gold (Au) is deposited onto glass (SiO 2 ) slides using titanium (Ti) as an adhesion layer. The Au layer is etched off to yield sets of 5 gold or glass lines with widths of 30, 45, 60, 75, and 90 μm. HeLa cells attached and grew freely on surfaces modified with OTS and HDT. On PEG-5000’ thiolated surfaces, >90% of the cells grew only on the cell-adhesive regions of the substrate. However, at 44 hours, cells began to penetrate the cell-resistant regions (Figure 4d). Conclusions PEG-5000’ thiol was able to control HeLa cell adhesion on Au/SiO 2 substrates, allowing a network of cells to be established. After long incubation times (44 hours), cells began to migrate into cell-resistant areas (Figure 4d), indicating cell-cell communication between cells on the pattern. The characteristics of communication through the cellular network will be further studied with a confocal microscope. Acknowledgements This project was supported by Calit2 and UROP. Many thanks are extended for the resources and guidance provided by faculty mentors Professor Tatsuya Suda, Dr. Tadashi Nakano, Professor Diane Lin, and Professor William Tang's Microbiomechanics Laboratory Group members: Yu-Hsiang Hsu, John Lin, and Andrew Kang. SiO 2 Au OH CH 3 Collagen Cell OH PEG-thiol Collagen PEG-thiol Molecular Communication is a new and interdisciplinary area of research that encompasses nano-, biological, and communication technologies. Biological nanomachines, or nano-scale devices capable of performing simple computational, sensing, or actuation activities, are an important focus of this field because there is a need to advance the communication aspects of these machines. By using molecules as carriers of information, molecular communication provides a mechanism for short distance information exchange between nanomachines. Successful control of nanomachine communication will open the way for a wide range of nano-scale applications, including distributed computing and sensing systems. The purpose of this project is to establish a communication network of HeLa (Human epithelial carcinoma) cells expressing cell-cell gap junction channels. The network will be created using chemical means to construct specific patterns of cells on gold and glass substrates. Due to their highly proliferative and adhesive nature, it is significantly more difficult to achieve patterns with HeLa cells than with other cell types. 3. Using ECM Proteins to Construct a HeLa Cell Network Cells adhere to surfaces coated with extracellular matrix (ECM) proteins, such as fibronectin and collagen. Proteins generally adhere to hydrophobic groups (CH3-) and cannot adhere to hydrophilic groups (OH-). Patterns of cells can be formed using this principle since cells should grow only on regions where ECM proteins are attached. SiO 2 Au Ti SiO 2 Au SiO 2 Au SiO 2 Au Au is etched off to create gold or glass lines on the substrate surface Au/SiO 2 substrates immersed in either HDT, OTS, or PEG-5000’ thiol for 48 hours SAM of a) OTS formed on SiO 2 (top), b) HDT formed on Au (X = CH 3, bottom), c) PEG-5000’ thiol formed on Au (X = OH, bottom) Network of Biological Cells Engineering the network components using cells Figure 1. A communication network of cells. Figure 2. Schematic of chemical modification of Au/SiO 2 substrate. Figure 3. ECM protein regulation of cell adhesion. Figure 4. View through a light microscope of HeLa cells on a) substrate with gold lines modified with HDT and b) OTS; c) substrate with glass lines modified with PEG-5000’ thiol at 29 hours and d) 44 hours. c)d) a)b) c)d)