Switchable DNA-origami nanostructures that respond to their environment and their applications

Structural DNA nanotechnology, in which Watson-Crick base pairing drives the formation of self-assembling nanostructures, has rapidly expanded in complexity and functionality since its inception in 1981. DNA nanostructures can now be made in arbitrary three-dimensional shapes and used to scaffold many other functional molecules such as proteins, metallic nanoparticles, polymers, fluorescent dyes and small molecules. In parallel, the field of dynamic DNA nanotechnology has built DNA circuits, motors and switches. More recently, these two areas have begun to merge—to produce switchable DNA nanostructures, which change state in response to their environment. In this review, we summarise switchable DNA nanostructures into two major classes based on response type: molecular actuation triggered by local chemical changes such as pH or concentration and external actuation driven by light, electric or magnetic fields. While molecular actuation has been well explored, external actuation of DNA nanostructures is a relatively new area that allows for the remote control of nanoscale devices. We discuss recent applications for DNA nanostructures where switching is used to perform specific functions—such as opening a capsule to deliver a molecular payload to a target cell. We then discuss challenges and future directions towards achieving synthetic nanomachines with complexity on the level of the protein machinery in living cells.This work was supported by Australian Research Council Discovery Early Career Research Fellowship DE180101635 (SW), University of Sydney Nano Institute Scholarship (JKDS, MTL)

DNA barrel nanostructure - a programmable building block for hierarchical self-assembly

DNA nanostructures with complex structures and functions are emerging as promising tools for realising new applications, such as nanorobotics and advanced materials. To date, the complexity achieved is still limited, due to shortcomings associated with current self-assembly methods. This thesis presents a new assembly scheme to build more complex nanostructures. DNA barrel nanostructures were used as 3D voxels to build up superstructures. A literature nanostructure design was adopted and improved for use in the proposed hierarchical assembly strategy. Modified barrel nanostructures (referred to as DNA origami brick or DOB) have two-barrel subunits connected laterally. An additional lateral connection motif was developed to assemble DOBs in 2D x-y dimensions. An assembly line (AL) was developed to build arbitrary superstructures using DOB building blocks. The designed lateral motif was used for all x-y connections, while assembly in the z-direction was accomplished utilising a literature connection motif. The proposed AL comprised three integrated modules: 1/shape design, 2/sequence design, and 3/assembly protocol design. Arbitrary 2D and 3D assemblies were successfully built using the proposed AL. Additional analysis (such as particle averaging) was carried out to validate structural features of built superstructures against AL predictions. Structural switching was integrated into DOB units for potentially achieving even more complex superstructures. A motif was designed to reversibly transform DOB units between coaxial and lateral stage upon triggering using strand displacement reactions. The transformation was successfully facilitated by DNA dissociation and hybridisation, to disrupt and form different connections, respectively. An additional stimulation was proposed based on nanoparticle heating effects when iron oxide or gold nanoparticles were exposed to radio-frequency (RF) fields or waves. Preliminary results showed RF energy from an alternating magnetic field is a potential trigger stimulus

Breast Cancer Services in Vietnam: A Scoping Review

Background: Breast cancer incidence has been increasing consistently in Vietnam. Thus far, there have been no analytical reviews of research produced within this area. Objectives: We sought to analyse the nature andextent of empirical studies about breast cancer in Vietnam, identifying areas for future research and systemsstrengthening. Methods: We undertook a scoping study using a five-stage framework to review published and grey literature in English and Vietnamese on breast cancer detection, diagnosis and treatment. We focused specifically on research discussing the health system and service provision. Results: Our results show that breast cancer screening is limited, with no permanent or integrated national screening activities. There is a lack of information on screening processes and on the integration of screening services with other areas of the health system. Treatment is largely centralised, and across all services there is a lack of evaluation and data collection that would be informative for recommendations seeking to improve accessibility and quality of breast cancer services. Conclusions: This paper is the first scoping review of breast cancer services in Vietnam. It outlines areas for future focus for policy makers and researchers with the objective of strengthening service provision to women with breast cancer across the country while also providing a methodological example for how to conduct a collaborative scoping review

Minimizing Cholesterol-Induced Aggregation of Membrane-Interacting DNA Origami Nanostructures

DNA nanotechnology provides methods for building custom membrane-interacting nanostructures with diverse functions, such as shaping membranes, tethering defined numbers of membrane proteins, and transmembrane nanopores. The modification of DNA nanostructures with hydrophobic groups, such as cholesterol, is required to facilitate membrane interactions. However, cholesterol-induced aggregation of DNA origami nanostructures remains a challenge. Aggregation can result in reduced assembly yield, defective structures, and the inhibition of membrane interaction. Here, we quantify the assembly yield of two cholesterol-modified DNA origami nanostructures: a 2D DNA origami tile (DOT) and a 3D DNA origami barrel (DOB), by gel electrophoresis. We found that the DOT assembly yield (relative to the no cholesterol control) could be maximised by reducing the number of cholesterols from 6 to 1 (2 ± 0.2% to 100 ± 2%), optimising the separation between adjacent cholesterols (64 ± 26% to 78 ± 30%), decreasing spacer length (38 ± 20% to 95 ± 5%), and using protective ssDNA 10T overhangs (38 ± 20% to 87 ± 6%). Two-step folding protocols for the DOB, where cholesterol strands are added in a second step, did not improve the yield. Detergent improved the yield of distal cholesterol configurations (26 ± 22% to 92 ± 12%), but samples re-aggregated after detergent removal (74 ± 3%). Finally, we confirmed functional membrane binding of the cholesterol-modified nanostructures. These findings provide fundamental guidelines to reducing the cholesterol-induced aggregation of membrane-interacting 2D and 3D DNA origami nanostructures, improving the yield of well-formed structures to facilitate future applications in nanomedicine and biophysics

Valorization of the treatment of antibiotic and organic contents generated from an in-situ-RAS-like shrimp farming pond by using graphene-quantum-dots deposited graphitic carbon nitride photocatalysts

In this study, we investigated the possibility of a photocatalytic system that uses graphene-quantum-dot (GQD)-deposited graphitic carbon nitride (g-C3N4) to treat tetracycline (TC) and other organic compounds generated from an in-situ-recirculatory-aquaculture-system (RAS)-like shrimp farming pond. GQDs were successfully deposited on the exfoliated g-C3N4 base through a hydrothermal treatment. The results showed that the incorporation of GQDs into the g-C3N4 enhanced its porosity without aggregating its mesoporous structure. The GQDs-deposited g-C3N4 photocatalysts revealed sheet-like structures with nanopores on their surface that facilitate photocatalysis. More than 90% of the TC was removed by the photocatalysts under UV-LED irradiation. Low loadings of GQDs over g-C3N4 resulted in a faster and more effective photocatalysis of TC, mainly driven by.O2- radicals. The photocatalysts were also applicable in the degradation of organic compounds with 27% of the total organic compounds (TOC) being removed from the wastewater of a RAS-like shrimp farming pond

New cerebroside and chondrocyte proliferation activity of <i>Caryota mitis</i> L.

<p><i>Caryota mitis</i> L., a flowering plant, belongs to the family Arecaceae. In Vietnam, its fruits were used to treat joint pain. The present study was designed to investigate the phytochemicals and chondrocyte proliferation activity of <i>C. mitis</i> L. fruits on young human chondrocyte. The results showed that all of extracts (crude extract as well as n-hexane, chloroform, ethyl acetate and methanol fractions) were stimulated the growth of chondrocyte at 0.1 μg/mL; 0.01 μg/mL concentrations, of which the n-hexane and methanol fractions significantly increased the proliferation of chondrocyte by 30.75 and 24.42% at concentrations of 0.01 μg/mL, respectively. Repeated chromatography of the methanol fraction on silica gel, Sephadex LH-20 and ODS columns afforded a new cerebroside and eight known ones. Their structures were elucidated by analysis of spectral data and in comparison with the published reports.</p