Microscopic robots made from white blood cells that could treat and prevent life-threatening illnesses have been created by scientists. The tiny machines are made from white blood cells called neutrophils - and are set to revolutionise medicine.
Named 'neutrobots', they can deliver drugs to precise locations in the body after being directed by laser beams. Other devices developed to perform similar tasks contain synthetic materials - raising the risk of serious side effects.
Project leader Dr Xianchuang Zheng, of the Institute of Nanophotonics at Jinan University, said: "The neutrophil microcrafts can be remotely activated by light and then navigated to the target position along a designated route."
In experiments on zebrafish, the Chinese team used scanning optical tweezers (SOTs) to perform three potential applications on their tails. These included cell therapy, targeted nanomedicine and removal of debris, or organic waste, that can trigger disease.
Dr Zheng said: "By integrating the non-invasive manipulation of optical tweezers and innate immunologic function of neutrophils, the proposed microcraft provides new insight for the construction of native medical microdevices for precision medicine."
They could carry payloads directly to a tumour, blood clot or infection. SOTs point a highly focused beam to hold and move microscopic and sub-microscopic particles in a manner similar to tweezers. Dr Zheng said: "The neutrophil microcraft can be activated or recovered in a controlled manner and the migration is fully steerable - just like driving a vehicle."
Ordinary neutrophils can also be triggered as an inflammatory response but they are often slow - and go in the wrong direction Dr Zheng said: "With the development of optically manipulated neutrophil microcraft, the behaviours can now be actively controlled."
This includes remote activation by SOTs at a desired time and location - precisely navigated to achieve a designed route and speed, he explained. The beam enabled multi-functional manipulation of the neutrophils by being irradiated onto the fish using a specialised mirror and microscope.
Dr Zheng said: "The zebrafish was selected as the animal model in this study due to its high genome homology with human and readily observable blood circulation in the tail. The neutrophils were clearly identified through fluorescence labelling."
Medical microrobots currently in development would require injections or the consumption of capsules to get them inside an animal or person. But researchers have found the objects trigger immune reactions in small animals - resulting in their removal before they can perform their jobs.
Neutrophils are a non-invasive alternative as they are already in the body picking up dead nanoparticles. They travel through vessels into adjacent tissues. The study in the journal ACS Central Science is the first time they have been guided with lasers in living animals.
The light-driven microrobot could be moved up to a velocity of 1.3 microns a second - three times faster than a neutrophil naturally moves. In one test, a neutrobot was moved through a blood vessel wall into the surrounding tissue.
Another picked up and transported a plastic nanoparticle, showing its potential for carrying medicine. When one was pushed toward red blood cell debris, it engulfed the pieces.
Surprisingly, at the same time, a different neutrophil which wasn't controlled by a laser, tried to naturally destroy it. Added Dr Zheng: "Unlike traditional medical microdevices, this neutrophil microcraft is free from artificial structures and invasive implantation processes, thus avoiding complicated preparation technology and unavoidable tissue damage.
"Meanwhile, it exhibits high biocompatibility. This concept, coupled with the intelligent control of multiplexed assignment execution, could hold great promise for the active execution of complex medical tasks, with great potential utility in the treatment of inflammatory diseases."
