Over the past decade, nanomedicine has gained considerable attraction through its relevance, for example, in "smart" delivery, thus creating platforms for novel treatments. Here, we report a natural polymer-DNA conjugate that undergoes self-assembly in a K-dependent fashion to form a G-quadruplex (GQ) and generate superpolymeric structures. We derivatized a thiolated conjugate of the naturally occurring glycosaminoglycan polymer hyaluronic acid (HASH) with short G-rich DNA (HASH-DNA) that can form an intermolecular noncanonical GQ structure. Gel mobility shift assay and circular dichroism measurements confirmed HASH conjugation to DNA and K-dependent GQ formation, respectively. Transmission electron microscopy and scanning electron microscopy results indicated that the addition of K to the HASH-DNA conjugate led to the formation of micron-range structures, whereas control samples remained unordered and as a nebulous globular form. Confocal microscopy of a fluorescently labeled form of the superpolymer verified increased cellular uptake. The HASH-DNA conjugates showed toxicity in HeLa cells, whereas a scrambled DNA (Mut) conjugate HASH-Mut showed no cytotoxicity, presumably because of nonformation of the superpolymeric structure. To understand the mechanism of cell death and if the superpolymeric structure is responsible for it, we monitored the cell size and observed an average of 23% increase in size compared to 4.5% in control cells at 4.5 h. We believe that cellular stress is generated presumably by the intracellular assembly of this large superpolymeric nanostructure causing cell blebbing with no exit option. This approach provides a new strategy of cellular delivery of a targeted naturally occurring polymer and a novel way to induce superpolymeric structure formation that acts as a therapeutic.

Polyimide-based azobenzene polymer networks have demonstrated superior photomechanical performance over more conventional azobenzene-doped pendent and cross-linked polyacrylate networks. These materials exhibit larger yield stress and glass transition temperatures and thus provide robustness for active control of adaptive structures directly with polarized, visible light. Whereas photochemical reactions clearly lead to deformation, as indicated by a rotation of a linear polarized light source, temperature and viscoelasticity can also influence deformation and complicate interpretation of the photostrictive and shape memory constitutive behavior. To better understand this behavior we develop a rate-dependent constitutive model and experimentally quantify the material behavior in these materials. The rate dependent deformation induced in these materials is quantified experimentally through photomechanical stress measurements and infrared camera measurements. Bayesian uncertainty analysis is used to assess the role of internal polymer network evolution and azobenzene excitation on both thermomechanical and photomechanical deformation in the presence polarized light of different orientations. A modified Arrhenius relation is proposed and validated using Bayesian statistics which provide connections between free volume, shape memory, and polarized light.

Azobenzene polymer networks have drawn interests in the area of adaptive materials and structures due to their novel photo-responsive material coupling. These materials undergo a complex light driven molecular conformation change of the azobenzene chromophore when the material is exposed to ultraviolet (UV) or blue-green light. This photoisomerization process is characterized by a molecular conformation change from a rod shaped molecule to a strongly kinked molecule, also known as trans-cis photoisomerization under UV light exposure. Exposure to blue-green light can lead to a trans-cis-trans photoisomerization or a relaxation from the kinked cis state back to the trans rod state. The latter process is of strong interests for adaptive structure applications because the relaxation back to the trans state can be controlled by the orientation of polarized light. When these azobenzene molecules undergo this process in a polymer network, bending and twisting deformation can be controlled by the polarization orientation of the blue-green light. To better understand the distribution of the molecular conformation changes that influences macroscopic polymer deformation, we have conducted solid state Nuclear Magnetic Resonance (ss-NMR) tests on fluorine doped azobenzene polymer networks. Here, we illustrate measurable chemical shifts due to blue light exposure near the 450 nm wavelength using a static ss-NMR probe. The results are compared to ss-NMR at different temperatures using Magic Angle Spinning (MAS) NMR to understand any potential influences of heat relative to photoisomerization.

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