Researchers from University of Jyväskylä and Aalto University in Finland have developed a customized DNA nanostructure that can perform a predefined task in human body-like conditions (ACS Nano, “Reconfigurable DNA Origami Nanocapsule for pH-Controlled Encapsulation and Display of Cargo”). To do so, the team built a capsule-like carrier that opens and closes according to the pH level of the surrounding solution. The nanocapsule can be loaded—or packed—with a variety of cargo, closed for delivery and opened again through a subtle pH increase.
The function of the DNA nanocapsule is based on pH-responsive DNA residues.
To make this happen, the team designed a capsule-like DNA origami structure functionalized with pH-responsive DNA strands. Such dynamic DNA nanodesigns are often controlled by the simple hydrogen-bonding of two complementary DNA sequences. Here, one half of the capsule was equipped with specific double-stranded DNA domains that could further form a DNA triple helix — in other words a helical structure comprised of three, not just two DNA molecules — by attaching to a suitable single-stranded DNA in the other half.

‘The triplex formation can happen only when the surrounding pH of the solution is right. We call these pH-responsive strands “pH latches”, because when the strands interact, they function similarly to their macroscopic counterparts and lock the capsule in a closed state. We included multiple motifs into our capsule design to facilitate the capsule opening/closing based on cooperative behaviour of the latches. The opening of the capsule is actually very rapid and requires only a slight pH increase in the solution”, explains first author of the study, doctoral student Heini Ijäs from Nanoscience Center at University of Jyvaskyla..


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