DNA origami mechanisms offer promising tools for precision nanomanipulation of molecules or nanomaterials. Recent advances have extended the function of individual DNA origami devices to material scales via hierarchical assemblies. However, achieving rapid and precise control of large conformational changes in hierarchical assemblies remains a critical challenge. Here, we demonstrate a method for controlling DNA origami-nanoparticle assemblies through a multiscale approach, in which nanoparticles impart control on the conformation of individual DNA origami mechanisms, whereas DNA origami assemblies control the conformation of nanoparticle arrays. Specifically, we show that the angular distributions of DNA origami hinge mechanisms are tunable as a function of nanoparticle size and distance from the hinge vertex. We selectively adjust the affinity of nanoparticle binding sites, resulting in hinge actuation via DNA melting without releasing the nanoparticle, thereby enabling rapid and reversible temperature-based actuation. Finally, we demonstrate this rapid actuation in DNA origaminanoparticle arrays of length scales extending over a micron. These results provide guiding principles toward the design of dynamic, DNA-origami hierarchical materials capable of storing and releasing mechanical energy.
Quantum dot (QD) biological imaging and sensing applications often require surface modification with single-stranded deoxyribonucleic acid (ssDNA) oligonucleotides. Furthermore, ssDNA conjugation can be leveraged for precision QD templating via higher-order DNA nanostructures to exploit emergent behaviors in photonic applications. Use of ssDNA-QDs across these platforms requires compact, controlled conjugation that engenders QD stability over a wide pH range and in solutions of high ionic strength. However, current ssDNA-QD conjugation approaches suffer from limitations, such as the requirement for thick coatings, low control over ssDNA labeling density, requirement of large amounts of ssDNA, or low colloidal or photostability, restraining implementation in many applications. Here, we combine thin, multidentate, phytochelatin-3 (PC3) QD passivation techniques with strain-promoted copper-free alkyne-azide click chemistry to yield functional ssDNA-QDs with high stability. This process was broadly applicable across QD sizes (i.e., λem = 540, 560, 600 nm), ssDNA lengths (i.e., 10–16 base pairs, bps), and sequences (poly thymine, mixed bps). The resulting compact ssDNA-QDs displayed a fluorescence quenching efficiency of up to 89% by hybridization with complementary ssDNA-AuNPs. Furthermore, ssDNA-QDs were successfully incorporated with higher-order DNA origami nanostructure templates. Thus, this approach, combining PC3 passivation with click chemistry, generates ssDNA-PC3-QDs that enable emergent QD properties in DNA-based devices and applications.
Biopolymers are feasible materials for preparing biocompatible drug-delivery systemsbecause of their chemical similarityto natural polymers. Poly(succinimide) is an anhydrous form of poly(aspartic acid), hence it has outstanding degradation property at physiological conditions. By the help of electrospinning technique, prolonged drug release can be obtained due to the nanofibrous mesh structure of the polymer conjugates. These systems have large specific surface and porosity, therefore the dissolution kinetics and drug absorption can be increased.The aim of this work was to prepare biocompatible, biodegradable drug conjugates using poly(aspartamide) based nanofibers and dopamine, to characterize the dissolution kinetics and drug release kinetics of these samples and to investigate the incidental cytotoxicity. The dopamine-polymer fibrous conjugates were characterized by FT-infrared spectrometry, scanning electron microscopy, atomic force microscopy and two-photon microscopy. The kinetics of dissolution and dopamine release were monitored by UV-Vis spectrophotometry. The biocompatibility of the conjugates was examined in the presence of human periodontal ligament stem cells (PDLSCs) and the SH-SY5Y neuroblastoma cell line. The cell viability tests were assessed by WST-1 cell proliferation reagent. The morphology of the cells was observed by phase-contrast, confocal and two-photon microscopic techniques. The presence of dopamine receptors on both cell types were investigated by immunocytochemical analysis.Dopamine containing, nanofibrous polymer-drug conjugates were successfully prepared with prolonged dopamine release. The result of cell viability tests shows the biocompatibility of the poly(aspartamide) based conjugates. Applying these materials, the dopamine can be dosed in higher concentration without side-effect compared to the treatment with free dopamine. Acknowledgements
The optical properties of quantum dots (QD) make them excellent candidates for bioimaging, biosensing, and therapeutic applications. However, conventional QDs are comprised of heavy metals (e.g., cadmium) that pose toxicity challenges in biological systems. Synthesising QDs without heavy metals or introducing thick surface coatings, e.g., by encapsulation in micelles, can reduce toxicity. Here, we examined the toxicity of micelle encapsulated tetrapod-shaped Mn-doped ZnSe QDs, comparing them to 3-mercaptopropionic acid (MPA)-capped Mn-doped ZnSe QDs prepared by ligand exchange and commercial CdSe/ZnS QD systems that were either capped with MPA or encapsulated in micelles. HepG2 cell treatment with MPA-coated CdSe/ZnS QDs resulted in a dose-dependent reduction of viability (MTT assay, treatment at 0–25 μg/mL). Surprisingly, no reactive oxygen species (ROS) or apoptotic signaling was observed, despite evidence of apoptotic behavior in flow cytometry. CdSe/ZnS QD micelles showed minimal toxicity at doses up to 25 μg/mL, suggesting that thicker protective polymer layers reduce cytotoxicity. Despite their shape, neither MPA- nor micelle-coated Mn-doped ZnSe QDs displayed a statistically significant toxicity response over the doses investigated, suggesting these materials as good candidates for bioimaging applications.
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