Person: Aizenberg, Michael
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Aizenberg
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Michael
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Aizenberg, Michael
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Publication Synthetic homeostatic materials with chemo-mechano-chemical self-regulation(Springer Nature, 2012) He, Ximin; Aizenberg, Michael; Kuksenok, Olga; Zarzar, Lauren D.; Shastri, Ankita; Balazs, Anna C.; Aizenberg, JoannaLiving organisms have unique homeostatic abilities, maintaining tight control of their local environment through interconversions of chemical and mechanical energy and self-regulating feedback loops organized hierarchically across many length scales. In contrast, most synthetic materials are incapable of continuous self-monitoring and self-regulating behaviour owing to their limited single-directional chemomechanical or mechanochemical modes. Applying the concept of homeostasis to the design of autonomous materials would have substantial impacts in areas ranging from medical implants that help stabilize bodily functions to 'smart' materials that regulate energy usage. Here we present a versatile strategy for creating self-regulating, self-powered, homeostatic materials capable of precisely tailored chemo-mechano-chemical feedback loops on the nano- or microscale. We design a bilayer system with hydrogel-supported, catalyst-bearing microstructures, which are separated from a reactant-containing 'nutrient' layer. Reconfiguration of the gel in response to a stimulus induces the reversible actuation of the microstructures into and out of the nutrient layer, and serves as a highly precise 'on/off' switch for chemical reactions. We apply this design to trigger organic, inorganic and biochemical reactions that undergo reversible, repeatable cycles synchronized with the motion of the microstructures and the driving external chemical stimulus. By exploiting a continuous feedback loop between various exothermic catalytic reactions in the nutrient layer and the mechanical action of the temperature-responsive gel, we then create exemplary autonomous, self-sustained homeostatic systems that maintain a user-defined parameter--temperature--in a narrow range. The experimental results are validated using computational modelling that qualitatively captures the essential features of the self-regulating behaviour and provides additional criteria for the optimization of the homeostatic function, subsequently confirmed experimentally. This design is highly customizable owing to the broad choice of chemistries, tunable mechanics and its physical simplicity, and may lead to a variety of applications in autonomous systems with chemo-mechano-chemical transduction at their core.Publication Harnessing Cooperative Interactions between Thermoresponsive Aptamers and Gels To Trap and Release Nanoparticles(American Chemical Society (ACS), 2016) Liu, Ya; Kuksenok, Olga; He, Ximin; Aizenberg, Michael; Aizenberg, Joanna; Balazs, Anna C.We use computational modeling to design a device that can controllably trap and release particles in solution in response to variations in temperature. The system exploits the thermo- responsive properties of end-grafted fibers and the underlying gel substrate. The fibers mimic the temperature-dependent behavior of biological aptamers, which form a hairpin structure at low temperatures (T) and unfold at higher T, consequently losing their binding affinity. The gel substrate exhibits a lower critical solution temperature (LCST) and thus, expands at low temperatures and contracts at higher T. By developing a new dissipative particle dynamics (DPD) simulation, we examine the behavior of this hybrid system in a flowing fluid that contains buoyant nanoparticles. At low T, the expansion of the gel causes the hairpin-shaped fibers to extend into the path of the fluid-driven particle. Exhibiting a high binding affinity for these particles at low temperature, the fibers effectively trap and extract the particles from the surrounding solution. When the temperature is increased, the unfolding of the fiber and collapse of the supporting gel layer cause the particles to be released and transported away from the layer by the applied shear flow. Since the temperature-induced conformational changes of the fiber and polymer gel are reversible, the system can be used repeatedly to “catch and release” particles in solution. Our findings provide guidelines for creating fluidic devices that are effective at purifying contaminated solutions or trapping cells for biological assays.Publication Computational modeling of oscillating fins that “catch and release” targeted nanoparticles in bilayer flows(Royal Society of Chemistry (RSC), 2016) Liu, Ya; Bhattacharya, Amitabh; Kuksenok, Olga; He, Ximin; Aizenberg, Michael; Aizenberg, Joanna; Balazs, Anna C.A number of physiological processes in living organisms involve the selective ‘‘catch and release’’ of biomolecules. Inspired by these biological processes, we use computational modeling to design synthetic systems that can controllably catch, transport, and release specific molecules within the surrounding solution, and, thus, could be harnessed for eÄective separation processes within microfluidic devices. Our system consists of an array of oscillating, microscopic fins that are anchored onto the floor of a microchannel and immersed in a flowing bilayer fluid. The oscillations drive the fins to repeatedly extend into the upper fluid and then tilt into the lower stream. The fins exhibit a specified wetting interaction with the fluids and specific adhesive interactions with nanoparticles in the solution. With this setup, we determine conditions where the oscillating fins can selectively bind, and thus, ‘‘catch’’ target nanoparticles within the upper fluid stream and then release these particles into the lower stream. We isolate the eÄects of varying the wetting interaction and the fins’ oscillation modes on the eÄective extraction of target species from the upper stream. Our findings provide fundamental insights into the system’s complex dynamics and yield guidelines for fabricating devices for the detection and separation of target molecules from complex fluids.Publication Inverting the Swelling Trends in Modular Self-Oscillating Gels Crosslinked by Redox-Active Metal Bipyridine Complexes(Wiley, 2017) Aizenberg, Michael; Okeyoshi, Kosuke; Aizenberg, JoannaThe developing field of active, stimuli-responsive materials is in need for new dynamic architectures that may offer unprecedented chemomechanical switching mechanisms. Towards this goal, syntheses of polymerizable bipyridine ligands, Bis(4-vinylbenzyl)[2,2'-bipyridine]-4,4'- dicarboxylate and N4,N4'-bis(4-vinylphenyl)-2,2'-bipyridine-4,4'-dicarboxamide, and a number of redox-active Ruthenium(II) and Iron(II) complexes with them are reported. Detailed characterizations by NMR, FTIR, HRMS, X-ray and cyclic voltammetry show that the topology of these molecules allows them to serve as both co-monomers and crosslinkers in polymerization reactions. Electronic properties of the ligands are tunable by choosing carboxylate- or carboxamido linkages between the core and the vinylaryl moieties, leading to a library of Ru and Fe complexes with the M(III)/M(II) standard redox potentials suitable for catalyzing self-oscillating Belousov- Zhabotinskii (BZ) reaction. New poly(N-isopropylacrylamide)-based redox-responsive functional gels containing hydrophilic comonomers, which have been prepared using representative Ru bpy complexes as both a crosslinker and redox-active catalyst, exhibit a unique feature: their swelling/contraction mode switches its dependence on the oxidation state of the Ru center, upon changing the ratio of comonomers in the hybrid gel network. The BZ self-oscillations of such crosslinked hydrogels have been observed and quantified for both supported film and free-standing gel samples, demonstrating their potential as chemomechanically active modules for new functional materials.Publication An immobilized liquid interface prevents device associated bacterial infection in vivo(Elsevier BV, 2017) Chen, Jiaxuan; Howell, Caitlin; Haller, Carolyn; Patel, Madhukar; Ayala, Perla; Moravec, Katherine A.; Dai, Erbin; Liu, Liying; Sotiri, Irini; Aizenberg, Michael; Aizenberg, Joanna; Chaikof, ElliotVirtually all biomaterials are susceptible to biofilm formation and, as a consequence, device-associated infection. The concept of an immobilized liquid surface, termed slippery liquid-infused porous surfaces (SLIPS), represents a new framework for creating a stable, dynamic, omniphobic surface that displays ultralow adhesion and limits bacterial biofilm formation. A widely used biomaterial in clinical care, expanded polytetrafluoroethylene (ePTFE), infused with various perfluorocarbon liquids generated SLIPS surfaces that exhibited a 99% reduction in S. aureus adhesion with preservation of macrophage viability, phagocytosis, and bactericidal function. Notably, SLIPS modification of ePTFE prevents device infection after S. aureus challenge in vivo, while eliciting a significantly attenuated innate immune response. SLIPS-modified implants also decrease macrophage inflammatory cytokine expression in vitro, which likely contributed to the presence of a thinner fibrous capsule in the absence of bacterial challenge. SLIPS is an easily implementable technology that provides a promising approach to substantially reduce the risk of device infection and associated patient morbidity, as well as health care costs.Publication New Architectures for Designed Catalysts: Selective Oxidation using AgAu Nanoparticles on Colloid-Templated Silica(Wiley, 2017) Shirman, Tanya; Lattimer, Judith; Luneau, Mathilde; Shirman, Elijah; Reece, Christian; Aizenberg, Michael; Madix, Robert; Aizenberg, Joanna; Friend, CynthiaA highly modular synthesis of designed catalysts with controlled bimetallic nanoparticle size and composition and a well-defined structural hierarchy is demonstrated. Exemplary catalysts—bimetallic dilute Ag-in-Au nanoparticles partially embedded in a porous SiO2 matrix (SiO2-AgxAuy)—were synthesized by the decoration of polymeric colloids with the bimetallic nanoparticles followed by assembly into a colloidal crystal backfilled with the matrix precursor and subsequent removal of the polymeric template. We show that these new catalysts architectures are significantly better than nanoporous dilute AgAu alloy catalysts (nanoporous Ag0.03Au0.97) while retaining a clear predictive relationship between their surface reactivity with that of single crystal Au surfaces. This paves the way for broadening the range of new catalyst architectures required for translating the designed principles developed under controlled conditions to designed catalysts under operating conditions for highly selective coupling of alcohols to form esters. Excellent catalytic performance of the porous SiO2-AgxAuy structure for selective oxidation of both methanol and ethanol to produce esters with high conversion efficiency, selectivity, and stability was demonstrated, illustrating the ability to translate design principles developed for support-free materials to the colloid-templated structures. The synthetic methodology reported is customizable for the design of a wide range of robust catalytic systems inspired by design principles derived from model studies. Fine control over the composition, morphology, size, distribution and availability of the supported nanoparticles was demonstrated.Publication Enhancing microvascular formation and vessel maturation through temporal control over multiple pro-angiogenic and pro-maturation factors(Elsevier BV, 2013) Brudno, Yevgeny; Ennett-Shepard, Alessandra B.; Chen, Ruth R.; Aizenberg, Michael; Mooney, DavidPublication An aptamer-functionalized chemomechanically modulated biomolecule catch-and-release system(Nature Publishing Group, 2015) Shastri, Ankita; McGregor, Lynn Marie; Liu, Ya; Harris, Valerie; Nan, Hanqing; Mujica, Maritza; Vasquez, Yolanda; Bhattacharya, Amitabh; Ma, Yongting; Aizenberg, Michael; Kuksenok, Olga; Balazs, Anna C.; Aizenberg, Joanna; He, XiminThe efficient extraction of (bio)molecules from fluid mixtures is vital for applications ranging from target characterization in (bio)chemistry to environmental analysis and biomedical diagnostics. Inspired by biological processes that seamlessly synchronize the capture, transport and release of biomolecules, we designed a robust chemo-mechanical sorting system capable of the concerted “catch and release” of target biomolecules from a solution mixture. The hybrid system is composed of target-specific, reversible binding sites attached to microscopic fins embedded in a responsive hydrogel that moves the cargo between two chemically-distinct environments. To demonstrate the utility of the system, we focus on the effective separation of thrombin by synchronizing the pH-dependent binding strength of a thrombin-specific aptamer with volume changes of the pH-responsive hydrogel in a biphasic microfluidic regime, and show the non-destructive separation with quantitative sorting efficiency, system’s stability and amenability to multiple solution recycling.Publication A bioinspired omniphobic surface coating on medical devices prevents thrombosis and biofouling(Nature Publishing Group, 2014) Leslie, Daniel; Waterhouse, Anna; Berthet, Julia B; Valentin, Thomas M; Watters, Alexander; Jain, Abhishek; Kim, Philseok; Hatton, Benjamin D; Nedder, Arthur; Donovan, Kathryn; Super, Elana H; Howell, Caitlin; Johnson, Christopher P; Vu, Thy L; Bolgen, Dana; Rifai, Sami; Hansen, Anne; Aizenberg, Michael; Super, Michael; Aizenberg, Joanna; Ingber, DonaldThrombosis and biofouling of extracorporeal circuits and indwelling medical devices cause significant morbidity and mortality worldwide. We describe a bioinspired coating that repels blood from virtually any material by covalently tethering a molecular layer of perfluorocarbon, which holds a thin liquid film of medical-grade perfluorocarbon on the substrate surface, mimicking the liquid layer certain plants use to prevent adhesion. This coating prevents fibrin attachment, reduces platelet adhesion and activation, suppresses biofilm formation, and is stable under blood flow in vitro. Surface-coated medical-grade tubing and catheters, assembled into arteriovenous shunts and implanted in living pigs, remain patent for at least 8 hours without anticoagulation. This coating technology offers the potential to significantly reduce anticoagulation in patients while preventing thrombotic occlusion and biofouling of medical devices.Publication In Vivo Targeting through Click Chemistry(Wiley-Blackwell, 2015) Brudno, Yevgeny; Desai, Rajiv M.; Kwee, Brian; Joshi, Neel; Aizenberg, Michael; Mooney, DavidTargeting small molecules to diseased tissues as therapy or diagnosis is a significant challenge in drug delivery. Drug-eluting devices implanted during invasive surgery allow the controlled presentation of drugs at the disease site, but cannot be modified once the surgery is complete. We demonstrate that bioorthogonal click chemistry can be used to target circulating small molecules to hydrogels resident intramuscularly in diseased tissues. We also demonstrate that small molecules can be repeatedly targeted to the diseased area over the course of at least one month. Finally, two bioorthogonal reactions were used to segregate two small molecules injected as a mixture to two separate locations in a mouse disease model. These results demonstrate that click chemistry can be used for pharmacological drug delivery, and this concept is expected to have applications in refilling drug depots in cancer therapy, wound healing, and drug-eluting vascular grafts and stents.