Stimuli responsive polymer-based membrane for isolation of exosomes

In this study, we developed a stimuli responsive polymer-based membrane to isolate mesenchymal stem cells (MSCs) derived exosomes directly from the culture media in one step without any pre-treatment. The developed membrane was obtained by modifying the surface of sulfonated polysulfone support with subsequent polyelectrolyte layers and temperature/pH responsive cationic pentablock co-polymer (PBC) via electrostatic interactions. The membrane demonstrated ∼80% rejection of the macromolecules/proteins in cell culture media (e.g., high molecular weight proteins, protein complexes, lipoproteins, and other macromolecular aggregates) at 37 °C and pH 7.4 with higher permeability. We obtained total exosome yield of ∼3 x 1011 particles/mL and total exosomal protein concentration of ∼2000 μg/mL with membrane, which was significantly higher than commercially available conventional exosome isolation methods. Moreover, the purity of the exosomes isolated at 37 °C operating temperature for pH 7.4 was around ∼8 x 109 particles/μg protein, which was significantly higher than the conventional isolation methods. The developed membrane maintained its isolation performance after multiple filtration cycles and backwash. The exosomes were characterized in terms of size, shape and exosome marker expression confirming the successful exosome isolation. In addition, the biological activity of the isolated exosomes was tested on 3T3 fibroblast cells to evaluate the effect of exosomes on cell migration as well as on PC12-TrkB cells to evaluate the effect of exosomes on neurite outgrowth. In both cases, exosomes demonstrated significant biological activity indicating that the PBC modified membrane could be used to isolate exosomes with high yield and purity as an alternative to existing methods.