Surface Charge-Reversible Tubular Micromotors for Extraction of Nucleic Acids in Microsystems

Extraction of nucleic acids in microsystems is of significance for biomedical applications, but the current extraction methods generally require sophisticated microchannels and external equipment, hindering their practical applications. In this work, we have demonstrated a simple, versatile and efficient approach to extract nucleic acids in microsystems by developing cationic branched polyethyleneimine (PEI)-functionalized tubular micromotors. The as-developed tubular micromotors are fabricated by a two-step process combining the template-assisted electrodeposition and carbodiimide chemistry, and contain an inner catalytic Pt layer, a middle magnetic Ni layer and an outer cationic PEI layer. They exhibit autonomous bubble-propelled motion in aqueous hydrogen peroxide solutions, which can be guided by an external magnetic field, and the surface charges can be reversibly modulated by changing the pH value of the solution. Consequently, the as-developed tubular micromotors can selectively absorb nucleic acids from acidic solutions and desorb them into alkaline solutions, leading to the extraction of nucleic acids with high efficiency without external stirring. Furthermore, they can be operated in a microchannel chip without the aid of a pumping system. Our results indicate that this PEI-functionalized tubular micromotor platform provides a novel, simple and versatile microsystem nucleic acid extraction technology, holding considerable promise for important practical applications.