fishing net at sunset

Polymer ‘nanonet’ captures therapeutics, accelerating vaccine development

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Northwestern University researchers have developed a new method for fabricating nanoparticles, using a polymer net which captures drug molecules. The researchers hope that this could help the rapid creation and testing of vaccine formulations.

The novel method presents a world of possibilities for applications in water purification, diagnostics and vaccine formulation generation, which requires many different types of molecules to be captured or delivered at the same time.

While molecules found in nature, such as DNA, can rapidly self-assemble into diverse and complex structures, engineering this process with synthetic polymer systems is a challenge. Previous attempts have been time-consuming, tedious, difficult to scale up, as well as very inefficient. This results in a very small fraction of the drug ending up inside the delivery system.

Professor Evan Scott, who led the Nature Communications study, explained: “Clinical application of self-assembled nanoparticles has been limited by difficulties with scalability and with loading large or multiple therapeutics, especially proteins. We present a highly scalable mechanism that can stably load nearly any therapeutic molecule with high efficiency.”

This new method involves using a polymer net which spreads out due to electrostatic repulsion and then collapses into a hydrogel, capturing over 95 per cent of proteins, DNA or other small molecule drugs (either alone or in combinations). In comparison, other nanoparticle delivery systems have a loading efficiency of around five per cent to 20 per cent.

“We use a polymer that forms a wide net throughout an aqueous solution,” said Scott. “Then we induce the net to collapse. It collects anything within the solution, trapping therapeutics inside of nanogel delivery vehicles with very high efficiency.”

Postdoctoral researcher Fanfan Du described the nanonet as “like a fishing net, which first spreads out due to electrostatic repulsion and then shrinks upon hydration to trap 'fish' [theraupetics].”

Scott and his team found success by using a polypropylene sulphone (PPSU) homopolymer, which is soluble in a particular solution, but forms electrostatic and hydrophilic aggregates in water. These aggregates are amphiphilic (with both hydrophilic and hydrophobic elements), allowing them to self-assemble into networks and collapse into gels.

“Adding more water induces the network to collapse, leading to the formation of nanogels,” said Du. “The manner in which water is added affects the PPSU chain formation, which changes the nanogels’ size and structure.”

In addition to its applications in drug delivery, the researchers believe that the method could have applications in water purification; the nanonet could collapse to collect contaminants in water, leaving purified water behind.

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