Surface modification of SU-8 for enhanced cell attachment and proliferation within microfluidic chips Qudus Hamid, 1 Chengyang Wang, 1 Jessica Snyder, 1 Wei Sun 1,2,3 1 Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, Pennsylvania 2 Mechanical Engineering and Biomanufacturing Research Institute, Tsinghua University, Beijing, China 3 Shenzhen Biomanufacturing Engineering Laboratory, Shenzhen, Guangdong, China Received 5 February 2014; revised 9 May 2014; accepted 17 May 2014 Published online 00 Month 2014 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jbm.b.33223 Abstract: Advances in micro-electro-mechanical systems (MEMS) have led to an increased fabrication of micro- channels. Microfabrication techniques are utilized to develop microfluidic channels for continuous nutrition supply to cells inside a micro-environment. The ability of cells to build tis- sues and maintain tissue-specific functions depends on the interaction between cells and the extracellular matrix (ECM). SU-8 is a popular photosensitive epoxy-based polymer in MEMS. The patterning of bare SU-8 alone does not provide the appropriate ECM necessary to develop microsystems for biological applications. Manipulating the chemical composi- tion of SU-8 will enhance the biological compatibility, giving the fabricated constructs the appropriate ECM needed to pro- mote a functional tissue array. This article investigates three frequently used surface treatment techniques: (1) plasma treatment, (2) chemical reaction, and (3) deposition treatment to determine which surface treatment is the most beneficial for enhancing the biological properties of SU-8. The investi- gations presented in this article demonstrated that the plasma, gelatin, and sulfuric acid treatments have a potential to enhance SU-8’s surface for biological application. Of course each treatment has their advantages and disadvan- tages (application dependent). Cell proliferation was studied with the use of the dye Almar Blue, and a micro-plate reader. After 14 days, cell proliferation to plasma treated surfaces was statistically significantly enhanced (p < 0.00001), com- pared to untreated surfaces. The plasma treated surface is suggested to be the better of the three treatments for biologi- cal enhancement followed by gelatin and sulfuric acid treat- ments, respectively. V C 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 00B: 000–000, 2014. Key Words: surface modification, biosensors/biochips, bioma- terials availability, microfluidic, SU-8 How to cite this article: Hamid Q, Wang C, Snyder J, Sun W. 2014. Surface modification of SU-8 for enhanced cell attachment and proliferation within microfluidic chips. J Biomed Mater Res Part B 2014:00B:000–000. INTRODUCTION Micro-electro-mechanical systems (MEMS) technology was first introduced in the semiconductor industry where con- ventional techniques were utilized to develop integrated cir- cuits. 1 Conventional MEMS technologies are developed for the fabrication of integrated circuits (ICs) on silicon wafers. Conventional MEMS technologies are very expensive and are not developed for biological applications. However, advances in recent decades have led to the development of biological platforms which investigates, but are not limited to, mimicry of in vivo conditions, behaviors within microfluidic environ- ment, and cell–cell interaction. 2–5 Micro-molding, etching, and deposition of features on or in materials are frequently referred to as microfabrication. 1,6–9 These techniques enable the creation of biologically inspired systems. Microfabricated constructs often possess a combination of structural and mechanical features that aid, but are not limited to, the development of micro-scale devices for pharmaceutical applications. 10,11 There is a paradigm shift in the field of tis- sue engineering and regenerative medicine where microfab- rication techniques have become an integrative part of developing tissue constructs. 12 The ability to control surface microarchitecture, topography, and feature size makes microfabrication techniques an ideal manufacturing process to develop tissue arrays that aims at restoring, maintaining, or improving tissue function. 13–16 In the late 1900s, the field of tissue engineering and regenerative medicine was established to address the limita- tions of tissue grafting and tissue repair. 17–23 A major chal- lenge of this is the ability to find materials and techniques that promote cell attachment, proliferation, differentiation, and have specific architecture that enables the development of an extracellular matrix (ECM). 13,16,24–26 The ECM plays a critical role in the initial development of a tissue array as it serves as the platform for which the architecture, topology, chemical composition, and functional groups provide the proper environment for cells to attach and proliferate into functional tissue construct. 27–33 Given that the success of a Correspondence to: W. Sun (e-mail: sunwei@drexel.edu) Contract grant sponsor: National Science Foundation; contract grant number: 1209517 V C 2014 WILEY PERIODICALS, INC. 1