AsianScientist (Jun. 24, 2020) – Unlike the usual drug delivery microrobots that require a continuous magnetic field to target them to tumors, this corkscrew-shaped microrobotic needle can effectively target and remain attached to cancerous tissue. These results, published in Advanced Healthcare Materials, allow for more precise drug delivery.
“Chemotherapeutic drugs cause a wide range of side effects due to their impacts on healthy and cancerous tissues,” explained study leader Professor Choi Hongsoo of Daegu-Gyeongbuk Institute of Science & Technology (DGIST), South Korea. “To avoid these unwanted effects, scientists have been experimenting with microrobots of different shapes that deliver drugs to specific tissues.”
Drug-toting microrobots usually require a magnetic field to direct them to targeted tissues and then hold them in place, otherwise they are easily flushed away by body fluids such as blood flow. To design a functional microrobot that avoids impractical and prolonged use of an energy-consuming magnetic field, Choi and colleagues designed a microrobot shaped like a corkscrew with a needle at its end.
Choi worked with DGIST’s Professor Lee Seungmin to fabricate the corkscrew-shaped microneedle using laser lithography. The microrobot is layered with nickel and titanium oxide to ensure it can be magnetically manipulated and be biocompatible with the human body. Drugs can be loaded onto the porous, corkscrew-shaped scaffold and inside the needle.
The team tested the microrobots in tiny chambers filled with fluid where they successfully used a magnetic field to direct the microrobots to spear and attach to tissue. Once fixed, it took a fluid flow speed of 480 millimetres per second to flush the needle out of the tissue. For comparison, the flow rate in small arterioles is around 100 millimetres per second.
The team then used a computational approach for more precise automatic, rather than manual, targeting of tissue using a magnetic field. Automatic targeting and fixation took only seven seconds, whereas manual control of the magnetic field took 55 seconds.
Finally, they loaded the microneedles with the anticancer drug paclitaxel and tested them in a microchamber containing human colorectal cancer cells, showing that the microrobots effectively targeted and killed cancerous cells.
Next, the team plans to improve the microrobot for more efficient drug loading and to optimize the magnetic field system for more precise control. Further tests in animals and human trials will be needed before the microrobots can be used as a treatment strategy, the authors cautioned.
The article can be found at: Lee et al. (2020) A Needle‐Type Microrobot for Targeted Drug Delivery by Affixing to a Microtissue.
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Source: Daegu Gyeongbuk Institute of Science and Technology; Photo: Shutterstock.
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