Supramolecular capture of highly polar amidosquaraine dye in water with nanomolar affinity and large turn-on fluorescence

A supramolecular dye-capture system comprising anionic amidosquaraine guest and macrocyclic tetralactam host exhibits nanomolar affinity and "turn on" visible fluorescence. Utility is demonstrated with a new fluorescent assay for liposome leakage induced by the biomedically important enzyme phospholipase A₂.

Rapidly Reversible Organic Crystalline Switch for Conversion of Heat into Mechanical Energy

Solid-state thermoelastic behavior-a sudden exertion of an expansive or contractive physical force following a temperature change and phase transition in a solid-state compound-is rare in organic crystals, few are reversible systems, and most of these are limited to a dozen or so cycles before the crystal degrades or they reverse slowly over the course of many minutes or even hours. Comparable to thermosalience, wherein crystal phase changes induce energetic jumping, thermomorphism produces physical work via consistent and near-instantaneous predictable directional force. In this work, we show a fully reversible thermomorphic actuator that is stable at room temperature for multiple years and is capable of actuation for more than 200 cycles at near-ambient temperature. Specifically, the crystals shrink to 90% of their original length instantaneously upon heating beyond 45 °C and expand back to their original length upon cooling below 35 °C. Furthermore, the phase transition occurs instantaneously, with little obvious hysteresis, allowing us to create real-time actuating thermal fuses that cycle between on and off rapidly.

Supramolecular optimization of the visual contrast for colorimetric indicator assays that release resorufin dye

A tetralactam macrocycle acts as a novel supramolecular adjuvant to capture a released resorufin dye and create a higher contrasting yellow/blue color change for enhanced naked eye interpretation of a colorimetric indicator assay.

Enhanced Stability and Controlled Delivery of MOF-Encapsulated Vaccines and Their Immunogenic Response In Vivo

Vaccines have an innate tendency to lose their structural conformation upon environmental and chemical stressors. A loss in conformation reduces the therapeutic ability to prevent the spread of a pathogen. Herein, we report an in-depth study of zeolitic imidazolate framework-8 and its ability to provide protection for a model viral vector against denaturing conditions. The immunoassay and spectroscopy analysis together demonstrate enhanced thermal and chemical stability to the conformational structure of the encapsulated viral nanoparticle. The long-term biological activity of this virus-ZIF composite was investigated in animal models to further elucidate the integrity of the encapsulated virus, the biosafety, and immunogenicity of the overall composite. Additionally, histological analysis found no observable tissue damage in the skin or vital organs in mice, following multiple subcutaneous administrations. This study shows that ZIF-based protein composites are strong candidates for improved preservation of proteinaceous drugs, are biocompatible, and are capable of controlling the release and adsorption of drugs in vivo.

Nitroxyl Modified Tobacco Mosaic Virus as a Metal-Free High-Relaxivity MRI and EPR Active Superoxide Sensor

Superoxide overproduction is known to occur in multiple disease states requiring critical care; yet, noninvasive detection of superoxide in deep tissue remains a challenge. Herein, we report a metal-free magnetic resonance imaging (MRI) and electron paramagnetic resonance (EPR) active contrast agent prepared by "click conjugating" paramagnetic organic radical contrast agents (ORCAs) to the surface of tobacco mosaic virus (TMV). While ORCAs are known to be reduced in vivo to an MRI/EPR silent state, their oxidation is facilitated specifically by reactive oxygen species-in particular, superoxide-and are largely unaffected by peroxides and molecular oxygen. Unfortunately, single molecule ORCAs typically offer weak MRI contrast. In contrast, our data confirm that the macromolecular ORCA-TMV conjugates show marked enhancement for T1 contrast at low field (<3.0 T) and T2 contrast at high field (9.4 T). Additionally, we demonstrated that the unique topology of TMV allows for a "quenchless fluorescent" bimodal probe for concurrent fluorescence and MRI/EPR imaging, which was made possible by exploiting the unique inner and outer surface of the TMV nanoparticle. Finally, we show TMV-ORCAs do not respond to normal cellular respiration, minimizing the likelihood for background, yet still respond to enzymatically produced superoxide in complicated biological fluids like serum.

Regulating the Uptake of Viral Nanoparticles in Macrophage and Cancer Cells via a pH Switch

Controlling the uptake of nanomaterials into phagocytes is a challenging problem. We describe an approach to inhibit the cellular uptake by macrophages and HeLa cells of nanoparticles derived from bacteriophage Qβ by conjugating negatively charged terminal hexanoic acid moieties onto its surface. Additionally, we show hydrazone linkers can be installed between the surface of Qβ and the terminal hexanoic acid moieties, resulting in a pH-responsive conjugate that, in acidic conditions, can release the terminal hexanoic acid moiety and allow for the uptake of the Qβ nanoparticle. The installation of the "pH switch" did not change the structure-function properties of the hexanoic acid moiety and the uptake of the Qβ conjugates by macrophages.

Investigation of Controlled Growth of Metal-Organic Frameworks on Anisotropic Virus Particles

Biomimetic mineralization with metal-organic frameworks (MOF), typically zeolitic imidazolate framework-8 (ZIF-8), is an emerging strategy to protect sensitive biological substances against denaturing environmental stressors such as heat and proteolytic agents. Additionally, this same biomimetic mineralization process has the potential of being used to create distinct core-shell architectures using genetically or chemically modified viral nanoparticles. Despite the proliferation of examples for ZIF-8 growth on biological or proteinaceous substrates, systematic studies of these processes are few and far between. Herein, we employed the tobacco mosaic virus (TMV) as a model biological template to investigate the biomimetic mineralization of ZIF-8, which has been proven to be a robust MOF for encasing and protecting inlaid biological substances. Our study shows a systematic dependence upon ZIF-8 crystallization parameters, e.g., ligand to metal molar ratio and metal concentration, which can yield several distinct morphologies of TMV@ZIF-8 composites and phases of ZIF-8. Further investigation using charged synthetic conjugates, time dependent growth analysis, and calorimetric analysis has shown that the TMV-Zn interaction plays a pivotal role in the final morphology of the TMV@ZIF-8, which can take the form of either core-shell bionanoparticles or large crystals of ZIF-8 with entrapped TMV located exclusively on the outer facets. The design rules outlined here, it is hoped, will provide guidance in biomimetic mineralization of MOFs on proteinaceous materials using ZIF-8.

The thermo-responsive behavior in molecular crystals of naphthalene diimides and their 3D printed thermochromic composites

Alteration of the number of carbon atoms on the alkoxyphenyl substituent in naphthalene diimides results in tunable thermo-salient behavior.

Thermo-mechanically responsive crystalline organic cantilever

Dynamic molecular crystals lift weights up to ∼100× heavier than themselves powered by a thermally induced single-crystal to single-crystal phase transition.

Template-Directed Synthesis of Porous and Protective Core-Shell Bionanoparticles

Metal-organic frameworks (MOFs) are promising high surface area coordination polymers with tunable pore structures and functionality; however, a lack of good size and morphological control over the as-prepared MOFs has persisted as an issue in their application. Herein, we show how a robust protein template, tobacco mosaic virus (TMV), can be used to regulate the size and shape of as-fabricated MOF materials. We were able to obtain discrete rod-shaped TMV@MOF core-shell hybrids with good uniformity, and their diameters could be tuned by adjusting the synthetic conditions, which can also significantly impact the stability of the core-shell composite. More interestingly, the virus particle underneath the MOF shell can be chemically modified using a standard bioconjugation reaction, showing mass transportation within the MOF shell.