Nanomachines in living systems - on route to microcyborgs
(Nanowerk Spotlight) From interaction with bacteria, propulsion based on cells, in vivo medical applications to even intracellular applications, the rapidly expanding development of micro- and nanomachines with sizes comparable to or even smaller than mammalian cells, has led this field to advance from understanding of basic motion mechanisms to applications in living biosystems.
The field of nanomachines has developed rapidly over the last few years, with several groups exploring new methods of navigation and demonstrating their potential benefits as therapeutic tools. In the future, these nanomachines could be used in a clinical environment, where they are injected close to a specific diseased site and they are navigated to a deep location of a tissue in a completely untethered and safe manner. The nanomachines can then perform tasks like sensing or therapy at the particular site, without affecting the functionality of adjoining cells and tissues.
The authors, professors Hong Wang (China University of Mining and Technology) and Martin Pumera (Nanyang Technological University), review the applications of micro/nanomachines in living biosystems from two aspects: their interaction with other microscopic organisms or biological units, and the efforts toward their application in the human body. They discuss four key application areas of micro- and nanomachines in living biosystems. Regarding the first aspect: interaction with bacteria and propulsion based on cells. Regarding the second aspect: in vivo applications and intracellular applications.
Wang and Pumera discuss examples that demonstrate the feasibility and enormous potential of employing micro/nanomachines in biosystems.
Utilizing different functionalization strategies, micro/nanomachines are capable of detecting, selectively capturing and broad spectrum killing of bacteria. Biological cells could be employed as actuators of micro/nanomachines to form coordinated biohybrid systems whereas the tiny machines could in turn carry sperm cells with motion deficiencies to implement natural function.
To translate micro/nanomachines into clinical applications, substantial efforts have been devoted to pushing them to in vivo studies and a series of novel strategies to address biomedical problems in diagnosis and treatment of diseases have proven to be effective. Nanomachines could also be engineered down to perform tasks at cellular level, thus enabling intracellular sensing, drug delivery, and genetic intervention.
The two scientists caution, though, that despite the tremendous progress obtained in recent years, micro- and nanoscale machines are far from mature in both theory and applications. To push forward in-depth applications of micro/nanomachines in biosystems, they list improvements that still are needed in many aspects:
Most of the current bactericidal operations were conducted in vitro conditions and extension to in vivo studies would pave way for treatment of infection by multidrugresistant bacteria in deep regions inside the body.
Collective behavior of micro/nanomachine in swarms is of great interest, as parallel or distributed operations are usually required in practice. However, the researches on this aspect are still limited.
Biohybrid micro/nanomachines fusing biological cells with the synthetic functional component inherit the natural intelligence of cells and are good candidates to fill this gap.
Clinical translation of micro/nanomachines demands a wider variety of structures beyond the simple tube, sphere geometric structures, and materials with good biocompatibility, immunogenically safety, and low waste profiles, the combination of which relies on the reasonable design and fabrication of micro/nanomachines.
Despite the high-performance control systems of magnetically propelled micro/nanomachines, the control of the micro/nanomachines with other propulsion systems needs to be enhanced to achieve precise guidance and distribution.
For intracellular applications, the movement of micro/nanomachines inside cells should be better regulated to allow targeted delivery to specific cytoplasmic organelles and the operations should be carried forward from in vitro to in vivo conditions."
"Just as today's automatic machines were well beyond the initial expectations of many people at the start of industrial evolution, continuing research on multiple disciplines will doubtless fuel the development of micro/nanomachines and may far surpass what we can forecast today," the authors conclude.