The U.S. Defense Threat Reduction Agency aims to create a broad-spectrum detoxification robotic platform.
MRSA bacterium captured by a hybrid cell membrane-coated nanorobot (colored scanning electron microscope image and black and white image below) (credit: Esteban-Fernández de Ávila/Science Robotics)
Engineers at the University of California San Diego have developed tiny ultrasound-powered nanorobots that can swim through blood, removing harmful bacteria and the toxins they produce.
These proof-of-concept nanorobots could one day offer a safe and efficient way to detoxify and decontaminate biological threat agents — providing an fast alternative to the multiple, broad-spectrum antibiotics currently used to treat life-threatening pathogens like MRSA bacteria (an antibiotic-resistant staph strain). MRSA is considered a serious worldwide threat to public health.
The MRSA superbug (in yellow) is resistant to antibiotics and can lead to death (credit: National Institute of Allergy and Infectious Diseases)
Antimicrobial resistance (AMR) threatens the effective prevention and treatment of an ever-increasing range of infections caused by bacteria, parasites, viruses and fungi, according to the World Health Organization — an increasingly serious threat to global public health.
The researchers coated gold nanowires with a hybrid of red blood cell membranes and platelets (tiny blood cells that help your body form clots to stop bleeding).*
The platelets cloak the nanowires and attract bacterial pathogens, which become bound to the nanorobots.
The red blood cells then absorb and neutralize the toxins produced by these bacteria.
Gold nanorobots coated in hybrid platelet/red blood cell membranes (colored scanning electron microscope image). (credit: Esteban-Fernández de Ávila/Science Robotics)
The interior gold nanowire body of the nanorobots responds to ultrasound, causing the nanorobots to swim around rapidly (no chemical fuel required) — mimicking the movement of natural motile cells (such as red blood cells). This mobility helps the nanorobots efficiently mix with their targets (bacteria and toxins) in blood and speed up detoxification.
The coating also protects the nanorobots from a process known as biofouling — when proteins collect onto the surface of foreign objects and prevent them from operating normally.
The nanorobots are just over one micrometer** (1,000 nanometers) long (for comparison, red blood cells have a diameter of 6 to 8 micrometers). The nanorobots can travel up to 35 micrometers per second in blood when powered by ultrasound.
In tests, the researchers used the nanorobots to treat blood samples contaminated with MRSA and their toxins. After five minutes, these blood samples had three times less bacteria and toxins than untreated samples.
Future work includes tests in mice, making nanorobots out of biodegradable materials instead of gold, and tests of also using the nanorobots for drug delivery.
The ultimate research goal is not to use the nanorobots specifically for treating MRSA infections, but more generally for detoxifying biological fluids — “an important step toward the creation of a broad-spectrum detoxification robotic platform,” as the researchers note in a paper.
* The researchers created the nanorobots in three steps:
1. They created the hybrid coating by first separating entire membranes from platelets and red blood cells.
2. They applied ultrasound (high-frequency sound waves) to fuse the membranes together. (Since the membranes were taken from actual cells, they contain all their original-cell surface protein functions, including the ability of platelets to attract bacteria.)
3. They coated these hybrid membranes onto gold nanowires.
** A micrometer is one millionth of a meter, or one thousandth of a millimeter.
This work was supported by the Defense Threat Reduction Agency Joint Science and Technology Office for Chemical and Biological Defense.