Intellectual Merits: Recent advances in signal processing with cascades of enzymatic reactions realizing logic gates, such as AND, OR, etc., as well as progress in networking these gates and coupling of the resulting systems to signal-responsive electrodes for output readout, have opened new biosensing opportunities. The goal of the proposed collaborative research program is to develop a new paradigm of digitally operating biosensors logically processing multiple biochemical signals through Boolean logic networks composed of biomolecular systems, yielding the final output signal as YES/NO responses. This activity will thus lead to high-fidelity biosensing compared to common single or parallel sensing devices. We will develop biochemical signal processing systems for novel biosensor concepts, with multiple input signals being processed via enzymatic or immune-recognition processes, in combination with electrochemical transduction of the output signal. To demonstrate the new concept of digital multi-signal processing biosensors, we will, for instance, design a model multi-enzyme sensing system aimed at rapid identification of the complex biomarker changes from a healthy person to the conditions of various pathophysiological dysfunctions. These experimental developments will be facilitated by theoretical modeling and design of new low-noise, scalable, multi-stage signal processing networks with digital logic gates, as well as non-Boolean network elements carried out by biochemical reactions. We will develop a comprehensive approach for optimization of networks for biosensing, incorporating components for analog/digital error suppression for larger networks. Specifically, for multiinput systems we will advance a novel strategy including modular network analysis, detailed network representation and adjustment of relative component activities, gate function optimization for the key gates in the network, and exploration of the role of non-Boolean network elements, e.g., filters. An important component of our research will be in interfacing of the biosensing logic systems with electrochemical transducers and chemical actuators, towards the development of practical logic gate biosensors and feedback-loop systems. Fundamental studies aimed at addressing the distinct challenges associated with the new biosensing paradigm will be carried out. Particular attention will be given to the surface confinement of the biomolecular "machinery" components, to the role of the system scalability, and to the efficient transduction of the output signals. We will also interface directly the new biochemical signal-processing assemblies with signal-responsive chemical actuators to yield "smart" feedback-loop systems, responding reversibly to inputs from the biochemical environment. This research is transformative since the improved understanding of the novel biomolecular logic systems will lead to powerful multi-analyte sensing devices and intelligent "Sense/Act" systems. Our collaborative, interdisciplinary program will require a coordinated effort at two institutions, and will utilize the state-ofthe-art bioelectronics and bionanotechnology advances recently developed by the participating teams. We offer the necessary complementary expertise and an established track record, as well as successful ongoing collaboration evidenced by joint high-quality publications and patent applications.
Broader Impacts and Outreach: Novel biosensor systems with built-in logic hold great promise to benefit a wide range of applications ranging from environmental and health monitoring to national defense and food safety. Logic biosensor systems of even moderate complexity will allow realizations of closed-loop ("Sense/Act/Treat") assemblies for security or biomedical applications, e.g., patient-tailored therapy. Our program will contribute to education and to ensuring national leadership in advanced science and technology. These impacts will be realized through training of the next generation of scientists, graduate students, and postdocs, and the introduction of new Nanobioelectronics and Nanobiotechnology classes. Inspiring high school and undergraduate students for scientific careers is a key element of our outreach. Outreach K-12 activities in both universities will thus include extensive pre-college mentorships and community activities.
Novel biosensors digitally process multiple biochemical signals through Boolean logic networks of coupled biomolecular reactions and produce output in the form of YES/NO response. Compared to traditional single-analyte sensing devices, biocomputing approach enables a high-fidelity multi-analyte biosensing, particularly beneficial for biomedical applications. Multisignal digital biosensors thus promise advances in rapid diagnosis and treatment of diseases by processing complex patterns of physiological biomarkers. Specifically, they can provide timely detection and alert to medical emergencies, along with an immediate therapeutic intervention. Application of biocomputing concepts has been successfully demonstrated for systems for logic analysis of biomarkers of different injuries, particularly exemplified for liver injury.The developed approach to the logic analysis of biomarkers was also applied to forensic applications, thus allowing to determine the race and gender of possible suspects. Integration of binary YES/NO analysis of various combinations of biomarkers with signal stimulated drug release resulted in novel systems which can autonomously operate analyzing biomedical problems and releasing drugs to compensate them. The signals resulting in the drug release range from small biomolecules to bacterial cells. This approach represents a new step to theranostics (combination of diagnostics with therapy). Wide-ranging applications of multi-analyte digital biosensors in medicine, environmental monitoring and homeland security are anticipated.
