Multifunctional Droplets Formed by Interfacially Self-Assembled Fluorinated Magnetic Nanoparticles for Biocompatible Single Cell Culture and Magnet-Driven Manipulation

The ability to encapsulate and manipulate droplets with
a picoliter
volume of samples and reagents shows great potential for practical
applications in chemistry, biology, and materials science. Magnetic
control is a promising approach for droplet manipulation due to its
ability for wireless control and its ease of implementation. However,
it is challenged by the poor biocompatibility of magnetic materials
in aqueous droplets. Moreover, current droplet technology is problematic
because of the molecule leakage between droplets. In the paper, we
propose multifunctional droplets with the surface coated by a layer
of fluorinated magnetic nanoparticles for magnetically actuated droplet
manipulation. Multifunctional droplets show excellent biocompatibility
for cell culture, nonleakage of molecules, and high response to a
magnetic field. We developed a strategy of coating the F-MNP@SiO2 on the outer surface of droplets instead of adding magnetic
material into droplets to enable droplets with a highly magnetic response.
The encapsulated bacteria and cells in droplets did not need to directly
contact with the magnetic materials at the outer surface, showing
high biocompatibility with living cells. These droplets can be precisely
manipulated based on magnet distance, the time duration of the magnetic
field, the droplet size, and the MNP composition, which well match
with theoretical analysis. The precise magnetically actuated droplet
manipulation shows great potential for accurate and sensitive droplet-based
bioassays like single cell analysis.