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A method to assemble light-responsive or pH-responsive microcapsules loaded with different loads (tetramethylrhodamine-modified dextran, TMR-D; microperoxidase-11, MP-11; CdSe/ZnS quantum dots; or doxorubicin-modified dextran, DOX-D) is described. The method is based on the layer-by-layer deposition of sequence-specific nucleic acids on poly(allylamine hydrochloride)-functionalized CaCO3 core microparticles, loaded with the different loads, that after the dissolution of the core particles with EDTA yields the stimuli-responsive microcapsules that include the respective loads. The light-responsive microcapsules are composed of photocleavable o-nitrobenzyl-phosphate-modified DNA shells, and the pH-responsive microcapsules are made of a cytosine-rich layer cross-linked by nucleic acid bridges. Irradiating the o-nitrobenzyl phosphate-functionalized microcapsules, λ = 365 nm, or subjecting the pH-responsive microcapsules to pH = 5.0, results in the cleavage of the microcapsule shells and the release of the loads. Preliminary studies address the cytotoxicity of the DOX-D-loaded microcapsules toward MDA-MB-231 breast cancer cells and normal MCF-10A breast epithelial cells. Selective cytotoxicity of the DOX-D-loaded microcapsules toward cancer cells is demonstrated.

We present the assembly of asymmetric two-layer hybrid DNA-based hydrogels revealing stimuli-triggered reversibly modulated shape transitions. Asymmetric, linear hydrogels that include layer-selective switchable stimuli-responsive elements that control the hydrogel stiffness are designed. Trigger-induced stress in one of the layers results in the bending of the linear hybrid structure, thereby minimizing the elastic free energy of the systems. The removal of the stress by a counter-trigger restores the original linear bilayer hydrogel. The stiffness of the DNA hydrogel layers is controlled by thermal, pH (i-motif), K ion/crown ether (G-quadruplexes), chemical (pH-doped polyaniline), or biocatalytic (glucose oxidase/urease) triggers. A theoretical model relating the experimental bending radius of curvatures of the hydrogels with the Young's moduli and geometrical parameters of the hydrogels is provided. Promising applications of shape-regulated stimuli-responsive asymmetric hydrogels include their use as valves, actuators, sensors, and drug delivery devices.

We have used molecular-beam epitaxy to grow high-quality pseudomorphic Ni and Co1Ni9 films on Cu(001). From temperature-dependent surface magneto-optic Kerr effect measurements of these films, we have determined the finite-size scaling behavior of the Curie temperature of ultrathin films for a thickness range of n=2.5–16 monolayers (ML). The film thickness dependent Curie temperature for each of these ferromagnetic thin-film systems, TC(n), is described by a finite-size scaling formula: [TC(∞) − TC(n)]/TC(n) = [(n − n′)/n0]−1/ν, where TC(∞) is the bulk Curie temperature, n0=2.5±0.5 ML for Co films and 3.5±0.4 ML for Ni and Co1Ni9 films is the microscopic length scale, and ν=0.76±0.08 is the bulk correlation length exponent. An interesting result is that TC(n) extrapolates to zero in the single mononolayer limit, n′=1.

Strand displacement cascades are commonly used to make dynamically assembled structures. Particularly, the concept of “toehold-mediated DNA branch migration reactions” has attracted considerable attention in relation to dynamic DNA nanostructures. However, it is a challenge to obtain and control the formation of pure 1:1 ratio DNA duplexes with toehold structures. Here, for the first time, we report a photocontrolled toehold formation method, which is based on the photocleavage of 2-nitrobenzyl linker-embedded DNA hairpin precursor structures. UV light irradiation (λ≈365 nm) of solutions containing these DNA hairpin structures causes the complete cleavage of the nitrobenzyl linker, and pure 1:1 DNA duplexes with toehold structures are easily formed. Our experimental results indicate that the amount of toehold can be controlled by simply changing the dose of UV irradiation and that the resulting toehold structures can be used for subsequent toehold-mediated DNA branch migration reactions, e.g., DNA hybridization chain reactions. This newly established method will find broad application in the construction of light-powered, controllable and dynamic DNA nanostructures or large-scale DNA circuits.

Controlled drug delivery and real-time tracking of drug release in cancer cells are essential for cancer therapy. Herein, we report a protease-responsive prodrug (DOX-FCPPs-PyTPE, DFP) with aggregation-induced emission (AIE) characteristics for controlled drug delivery and precise tracking of drug release in living cells. DFP consists of three components: AIE-active tetraphenylethene (TPE) derivative PyTPE, functionalized cell penetrating peptides (FCPPs) containing a cell penetrating peptide (CPP) and a short protease-responsive peptide (LGLAG) that can be selectively cleaved by a cancer-related enzyme matrix metalloproteinase-2 (MMP-2), and a therapeutic unit (doxorubicin, DOX). Without MMP-2, this prodrug cannot go inside the cells easily. In the presence of MMP-2, DFP can be cleaved into two parts. One is cell penetrating peptides (CPPs) linked DOX, which can easily interact with cell membrane and then go inside the cell with the help of CPPs. Another is the PyTPE modified peptide which will self-aggregate because of the hydrophobic interaction and turn on the yellow fluorescence of PyTPE. The appearance of the yellow fluorescence indicates the release of the therapeutic unit to the cells. The selective delivery of the drug to the MMP-2 positive cells was also confirmed by using the intrinsic red fluorescence of DOX. Our result suggests a new and promising method for controlled drug delivery and real-time tracking of drug release in MMP-2 overexpression cells.

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A therapeutic aptamer-lipid-poly(lactide-co-glycolic acid) hybrid nanoparticle-based drug delivery system was prepared and characterized. The hybrid can co-deliver two different drugs with distinct solubility characteristics and different anticancer mechanisms to target cancer cells with high specificity and efficiency.