RNA has important and diverse roles in biology, but molecular tools to manipulate and measure it are limited. For example, RNA interference can efficiently knockdown RNAs, but it is prone to off-target effects, and visualizing RNAs typically relies on the introduction of exogenous tags. Here we demonstrate that the class 2 type VI RNA-guided RNA-targeting CRISPR–Cas effector Cas13a (previously known as C2c2) can be engineered for mammalian cell RNA knockdown and binding.
After initial screening of 15 orthologues, we identified Cas13a from Leptotrichia wadei (LwaCas13a) as the most effective in an interference assay in Escherichia coli. LwaCas13a can be heterologously expressed in mammalian and plant cells for targeted knockdown of either reporter or endogenous transcripts with comparable levels of knockdown as RNA interference and improved specificity. Catalytically inactive LwaCas13a maintains targeted RNA binding activity, which we leveraged for programmable tracking of transcripts in live cells.
Our results establish CRISPR–Cas13a as a flexible platform for studying RNA in mammalian cells and therapeutic development.
Chronic wounds do not heal in an orderly fashion in part due to the lack of timely release of biological factors essential for healing. Topical administration of various therapeutic factors at different stages is shown to enhance the healing rate of chronic wounds. Developing a wound dressing that can deliver biomolecules with a predetermined spatial and temporal pattern would be beneficial for effective treatment of chronic wounds. Here, an actively controlled wound dressing is fabricated using composite fibers with a core electrical heater covered by a layer of hydrogel containing thermoresponsive drug carriers. The fibers are loaded with different drugs and biological factors and are then assembled using textile processes to create a flexible and wearable wound dressing. These fibers can be individually addressed to enable on-demand release of different drugs with a controlled temporal profile. Here, the effectiveness of the engineered dressing for on-demand release of antibiotics and vascular endothelial growth factor (VEGF) is demonstrated for eliminating bacterial infection and inducing angiogenesis in vitro. The effectiveness of the VEGF release on improving healing rate is also demonstrated in a murine model of diabetic wounds.
Instead of plain sterile cotton or other fibers, this dressing is made of “composite fibers with a core electrical heater covered by a layer of hydrogel containing thermoresponsive drug carriers,” which really says it all.
It acts as a regular bandage, protecting the injury from exposure and so on, but attached to it is a stamp-sized microcontroller. When prompted by an app (or an onboard timer, or conceivably sensors woven into the bandage), the microcontroller sends a voltage through certain of the fibers, warming them and activating the medications lying dormant in the hydrogel.
Those medications could be anything from topical anesthetics to antibiotics to more sophisticated things like growth hormones that accelerate healing. More voltage, more medication — and each fiber can carry a different one.
These little robots are powered by an electromagnetic field, similar to how you would wirelessly charge a cell phone. By changing the frequency of the magnetic field, the researchers are able to precisely control the exact movement of their prototype.
For instance, one triangular robot that’s no bigger than a quarter is composed of three triangular pieces of thin plastic, attached with hinges to a middle triangle that has a circuit. The hinges are controlled by coils of a metal called “shape-memory alloy,” which changes its form when it’s exposed to heat. When an electric current starts running through the central circuit, these coils heat up and contract, causing the three triangles to fold up toward the center of the robot. When the current stops, the hinges return to their flat state.