Browsing by Author "Wu, Hsuan-Chen"
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Item Chitosan to Connect Biology to Electronics: Fabricating the Bio-Device Interface and Communicating Across This Interface(MDPI, 2014-12-24) Kim, Eunkyoung; Xiong, Yuan; Cheng, Yi; Wu, Hsuan-Chen; Liu, Yi; Morrow, Brian H.; Ben-Yoav, Hadar; Ghodssi, Reza; Rubloff, Gary W.; Shen, Jana; Bentley, William E.; Shi, Xiaowen; Payne, Gregory F.Individually, advances in microelectronics and biology transformed the way we live our lives. However, there remain few examples in which biology and electronics have been interfaced to create synergistic capabilities. We believe there are two major challenges to the integration of biological components into microelectronic systems: (i) assembly of the biological components at an electrode address, and (ii) communication between the assembled biological components and the underlying electrode. Chitosan possesses a unique combination of properties to meet these challenges and serve as an effective bio-device interface material. For assembly, chitosan’s pH-responsive film-forming properties allow it to “recognize” electrode-imposed signals and respond by self-assembling as a stable hydrogel film through a cathodic electrodeposition mechanism. A separate anodic electrodeposition mechanism was recently reported and this also allows chitosan hydrogel films to be assembled at an electrode address. Protein-based biofunctionality can be conferred to electrodeposited films through a variety of physical, chemical and biological methods. For communication, we are investigating redox-active catechol-modified chitosan films as an interface to bridge redox-based communication between biology and an electrode. Despite significant progress over the last decade, many questions still remain which warrants even deeper study of chitosan’s structure, properties, and functions.Item Effect of electrical energy on the efficacy of biofilm treatment using the bioelectric effect(Nature Publishing Group, 2015-09-23) Kim, Young Wook; Subramanian, Sowmya; Gerasopoulos, Konstantinos; Ben-Yoav, Hadar; Wu, Hsuan-Chen; Quan, David; Carter, Karen; Meyer, Mariana T.; Bentley, William E.; Ghodssi, RezaBACKGROUND/OBJECTIVES: The use of electric fields in combination with small doses of antibiotics for enhanced treatment of biofilms is termed the ‘bioelectric effect’ (BE). Different mechanisms of action for the AC and DC fields have been reported in the literature over the last two decades. In this work, we conduct the first study on the correlation between the electrical energy and the treatment efficacy of the bioelectric effect on Escherichia coli K-12 W3110 biofilms. METHODS: A thorough study was performed through the application of alternating (AC), direct (DC) and superimposed (SP) potentials of different amplitudes on mature E. coli biofilms. The electric fields were applied in combination with the antibiotic gentamicin (10 μg/ml) over a course of 24 h, after the biofilms had matured for 24 h. The biofilms were analysed using the crystal violet assay, the colony-forming unit method and fluorescence microscopy. RESULTS: Results show that there is no statistical difference in treatment efficacy between the DC-, AC- and SP-based BE treatment of equivalent energies (analysis of variance (ANOVA) P > 0.05) for voltages < 1 V. We also demonstrate that the efficacy of the BE treatment as measured by the crystal violet staining method and colony-forming unit assay is proportional to the electrical energy applied (ANOVA P < 0.05). We further verify that the treatment efficacy varies linearly with the energy of the BE treatment (r2 = 0.984). Our results thus suggest that the energy of the electrical signal is the primary factor in determining the efficacy of the BE treatment, at potentials less than the media electrolysis voltage. CONCLUSIONS: Our results demonstrate that the energy of the electrical signal, and not the type of electrical signal (AC or DC or SP), is the key to determine the efficacy of the BE treatment. We anticipate that this observation will pave the way for further understanding of the mechanism of action of the BE treatment method and may open new doors to the use of electric fields in the treatment of bacterial biofilms.Item INCORPORATION OF BACTERIAL QUORUM SENSING IN SYNTHETIC BIOLOGY(2012) Wu, Hsuan-Chen; Bentley, William E; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The global objective of this research is to develop a synthetic biology toolkit consisting of molecules, cells, and devices that provide flexible, yet selective targeting, sensing, and switching capabilities, that in turn guide biological behavior in user-specified manner. We employ bacteria as "smart" programmable devices. We envision creating bacteria that autonomously move to specific areas, synthesize a drug, deliver the drug, and move on to new sites. "Targeting" endows bacterial cells the means to dock onto specific surfaces with antibody-antigen specificity. Sensing and switching capability allows bacteria to sense and, after making a "decision", respond by synthesizing and delivering cargo to molecular scale features displayed on target surfaces. Relevant surface features may include an overexpressed receptor on a tumor cell, glucagon-like peptide-1 receptor on pancreatic beta cells, or even other bacterial cells resident in a recalcitrant biofilm. Towards the realization of this goal, we employed an antibody-binding protein G display strategy to complex target-binding antibodies with bacteria. We characterized the assembly and efficacy of this complex by binding to well-defined surfaces decorated with specific antigens. For sensing and switching we made use of the genetic circuitry of bacterial quorum sensing (QS) that coordinates multicellular responses. In particular, we hypothesized the creation of a biological "switch" that would take action only after a certain threshold "feature" density had been detected. Specifically, in our most significant demonstration we designed and implemented QS based sensing and actuating based on the surface density of cancer-indicating EGFR receptors displayed on epithelial cancer cell lines. Because recent reports have demonstrated bacterial placement of a molecular "cargo" or "payload" in unrelated studies involving vaccination or direct attack on bacterial pathogens, we turned to developing innovative RNA-based drug syntheses concepts for eventual use in cancer therapy. That is, we designed RNA interfering (RNAi) technology to arrest the progression of the eukaryotic cell cycle by silencing gateway genes that serve to guide cell division and proliferation. Thus, our strategy serves to inhibit cell growth and promote cell death - actions that could find utility in treating metastatic cancer. Through a different lens, this same concept, the molecularly "programmed" manipulation of cell cycle status and cell growth via synthetic biology can serve to promote recombinant protein production in an industrially relevant eukaryotic insect cell line. In summary, we envision the exploitation of bacterial cells as programmable smart devices that can target, dock and deliver cargoes that are synthesized and delivered only after a set of predetermined parameters are met. We also envision a new biological "switch" that is based on the area-based density of a molecular feature - this will dramatically expand the capabilities and reach of synthetic biology. Our concepts embrace the notion that the individual cell may be the product of synthetic biology, as opposed to a synthesized molecule which is the prevailing product of choice.