(141b) Magnetic Drug Screening Nanoplatform Using Immobilized Ion Channels As Targets

Many studies have shown that voltage-gated sodium ion channel (VGSCs, Nav1.1-1.9) play an important role in cancer metastasis with certain subtypes associated with specific cancer types. For example, substantial evidences have shown Nav1.5 overexpression in metastatic breast cancer cells (e.g., highly metastatic MDA-MB-231 cells). The Nav1.5 overexpression was also associated with metastasis and tumor progression in vivo and in clinical patient samples. Therefore, targeting ion channels is evolving as a direction for metastatic cancer therapy. Magnetic bead separation have been explored for direct compound fishing through the immobilized protein targets on the bead surfaces from a mixture. Unfortunately, magnetic bead separation suffers from significant non-specific binding of compounds to the bead surfaces, which makes them not suitable for screening complex matrices. In addition, the immobilized proteins are limited to cytosolic proteins (e.g. enzymes and antibodies). Transmembrane proteins are not suitable because they require boundary lipids for function. This is a great limitation, because over 60% of all modern pharmaceuticals target membrane proteins. We recently developed a novel drug screening platform based cell-membrane coated magnetic nanoclusters (CMMNs),where the functional transmembrane receptors on the coating membrane serve as “smart baits” for direct identification of binding compounds and the encapsulated magnetic nanoparticles enable quick isolation of identified compounds.

In this presentation, using Nav1.5 as a model system, we evaluated the potential of this drug-screening platform in identifying binders from artificial mixtures and a synthetic library containing about 100 ion channel blockers. The CMMNs were prepared using MDA-MB-231, a highly metastatic breast cancer cell line with known Nav1.5 overexpression. The formation of CMMNs was confirmed with transmission electron microscopy. The presence of Nav1.5 receptors on CMMN surfaces was studied using confocal microscopy with antibody labeling. The fishing experiments were performed by incubating CMMNs with an artificial mixture containing a known ion channel blocker and several non-binders and by incubating CMMNs with a synthetic library at 37 °C for 20 minutes. The identified Nav1.5-bound compounds were analyzed using a Water Xevo G2xs QTof-MS with iclass UPLC system. Our fishing experiments suggested that the immobilized Nav1.5 receptors on CMMN surfaces were able to selectively retain the known blocker and could identify compounds from the synthetic library.