Controlled Envelopment of Magnetic Particles within Liposomes using a Custom-Built Multi-Layer Magnetic Microfluidic Device

Abstract

Liposomes can be magnetically triggered to release chemicals by encasing magnetic particles in an organized and predetermined fashion (e.g. linear array). Here we demonstrate a controlled arrangement of magnetic particles within liposomes using a custom-built microfluidic device. The multi-layer magnetic microfluidic device consists of two thin bottom layers containing low-melting point (117° C) 52% In - 48% Sn solder and a third top layer devoted to the input of lipids and magnetic particles. The microchannels containing the solder are electrically isolated and arranged in a lattice pattern; the top layer contains one channel, which is wide enough to span this solder lattice. To facilitate installing the solder into the channels, we reduce the surface free energy by first injecting a solution of 3-mercaptopropyltrimethoxysilane in acetonitrile and allowing it to dry. By controlling the current in the solder lattice we can non-invasively corral magnetic particles contained in the top channel. To control the magnetic multi-layer microfluidic device, we are implementing a digital potentiometer (AD7151) using an Arduino (Mega 2560) microcontroller with analog inputs for connecting the potentiometers. An AD7151 can step through 64 different positions offering fine control of the current within the solder lattice. This digital potentiometer permits us to vary the current by changing the resistance electronically rather than manually as in a conventional analog potentiometer. This device can not only be used to assemble magnetic particles within the liposomes for potential in vivo delivery, but it can also be adapted to sort liposomes based on their magnetic content.