Exosomes, which are lipid membrane-bound nanovesicles (50-150 nm in diameter), have great potential for non-invasive molecular diagnostics and represent a novel therapeutic delivery system but are limited by poor targeting ability and a lack of efficient isolation techniques. Here, researchers from the Huazhong University of Science and Technology present a three-dimensional nanostructured microfluidic chip, in which arrays of micropillars were functionalized with crisscrossed multiwall carbon nanotubes by chemical deposition, to capture exosomes with high efficiency through a combination of a specific recognition molecule (CD63) and the unique topography of the nanomaterials. It was demonstrated that this nanostructured interface greatly improved the immuno capturing efficiency of exosomes. A high percentage of intact vesicles < 150 nm were readily purified. As a further application, the researchers added functionality to the exosomes by a chemical editing approach for targeted drug delivery. Donor cells were labeled chemically with dual ligands (biotin and avidin) in the phospholipid membrane and encapsulated drugs in the cytosol. While the engineered donor cells secreted exosomes, the dual ligands, together with the drugs, were inherited by the exosomes, which were then isolated with the microfluidic chip. Then, the isolated exosomes were used as drug delivery vehicles and showed strong targeting abilities to tumor cells and highly efficient receptor-mediated cellular uptake when exposed to recipient cells both in vitro and in vivo. Thus, the anti-cancer effect of chemotherapeutic drugs was improved significantly. It suggested that this platform could provide a useful tool for isolating intact exosomes with high efficiency and exploiting their natural carrier function to deliver chemotherapeutic drugs to tumor cells with increased efficacy and targeting capacity.
Schematic of microfluidic chip isolation of exosomes secreted from engineered
donor cells and application to active targeted drug delivery
In Step 1: the donor cells were labeled with the target ligand (biotin) on the cell membrane, encapsulated with anti-tumor drugs for therapy and further functionalized with another ligand (avidin) to improve the targeting efficiency. When the donor cells secreted the exosomes, the two ligands and drugs would be inherited by exosomes to form chemical edited exosomes. In Step 2: The donor cells culture media was subjected to microfluidic chip with MWCNTs nanostructured interfaces and immunoaffinity immobilization for isolation and collection of the exosomes with high efficiency. In Step 3: The isolated exosomes were used for targeted drug delivery and led to tumor cells apoptosis.