A Proximity-Based Programmable DNA Nanoscale Assembly Line

Nanopore actuation of a DNA-tracked nanovehicle

As a kind of nanomachine that has great potential for applications in nanoscale sensing and manipulation, nanovehicles with unique shapes and functions have received extensive attention in recent years. Different from the existing common method of using synthetic chemistry to design and manufacture a nanovehicle, here we theoretically report a molecularly assembled DNA-tracked nanovehicle that can move on a solid-state surface using molecular dynamics simulations. A graphene membrane with four nanopores acts as the chassis of the nanoscale vehicle, and two circular ssDNAs across the nanopores serve as the wheels. The electroosmotic flows induced by independently charged nanopores with different surface charge densities under external electric fields were found to be the main power to actuate the controlled rotary motion of circular ssDNAs across every two nanopores. By tuning the rotary speed of each circular ssDNA, the linear and turning movements of the designed nanovehicle were realized. The designed nanovehicle makes it possible to have access to almost everywhere in the human body, which would lead to significant breakthroughs in the fields of nanoscale surgery, drug delivery and so on. The research not only enriches the family of nanorobots, but also opens another way for designing nanovehicles.

Quantitative Analysis of Mitochondrial RNA in Living Cells with a Dual-Color Imaging System

Accurate quantification and dynamic expression profiling of mitochondrial RNA (mtRNA for short) are critical for illustrating their cellular functions. However, there lack methods for precise detection of mtRNA in situ due to the delivery restrictions and complicated cellular interferences. Herein, a dual-color imaging system featured with signal amplification and normalization capability for quantitative analysis of specific mtRNA is established. As a proof-of-concept example, an enzyme-free hairpin DNA cascade amplifier fine-tailored to specifically recognize mtRNA encoding NADH dehydrogenase subunit 6 (ND6) is employed as the signal output module and integrated into the biodegradable mitochondria-targeting black phosphorus nanosheet (BP-PEI-TPP) to monitor spatial-temporal dynamics of ND6 mtRNA. An internal reference module targeting β-actin mRNA is sent to the cytoplasm via BP-PEI for signal normalization, facilitating mtRNA quantification inside living cells with a degree of specificity and sensitivity as high as reverse transcription-quantitative polymerase chain reaction (RT-qPCR). With negligible cytotoxicity, this noninvasive "RT-qPCR mimic" can accurately indicate target mtRNA levels across different cells, providing a new strategy for precise analysis of subcellular RNAs in living systems.

Dynamic DNA nanostructures in biomedicine: Beauty, utility and limits

DNA composite materials are at the forefront, especially for biomedical science, as they can increase the efficacy and safety of current therapies and drug delivery systems. The specificity and predictability of the Watson-Crick base pairing make DNA an excellent building material for the production of programmable and multifunctional objects. In addition, the principle of nucleic acid hybridization can be applied to realize mobile nanostructures, such as those reflected in DNA walkers that sort and collect cargo on DNA tracks, DNA robots performing tasks within living cells and/or DNA tweezers as ultra-sensitive biosensors. In this review, we present the diversity of dynamic DNA nanostructures functionalized with different biomolecules/functional units, imaging smart biomaterials capable of sensing, interacting, delivery and performing complex tasks within living cells/organisms.