Switchable Soft Material Could Improve On-Demand Drug Delivery

Controlling when and how therapeutic agents are released remains a challenge in drug delivery and biosensing. Materials that respond predictably to external triggers could improve precision while reducing invasive procedures and dosing variability. Researchers have now developed a switchable soft material that toggles between gel and liquid-like states under user-selected signals. The approach supports on-demand assembly and disassembly, offering a foundation for future targeted delivery, sensing, and catalysis.

Scientists at the University of Birmingham report the first multi‑responsive gel built from foldamers—synthetic molecules that fold into defined shapes and can be assembled, disassembled, and reassembled on demand. The findings were published in the Journal of the American Chemical Society. The team designed the system to enable externally controlled transitions while preserving the ability to rebuild the gel network.

In this material, helical foldamers are linked by palladium ions that act as four‑way molecular connectors, creating an extended network that traps liquid and confers gel‑like behavior. Ultraviolet light changes the shape of light‑sensitive units within the foldamers, and that molecular event propagates through the network until the gel flows like a liquid. Heating restores the gel, while acid disrupts the foldamer–palladium connections through a separate mechanism, providing multiple, orthogonal control inputs.

The researchers also converted the organic solvent‑based gel into a water‑containing hydrogel without disrupting the underlying molecular architecture. Hydrogels are widely used in biotechnology and medicine because they retain large amounts of water while maintaining structural integrity. The team highlights potential applications that include targeted drug delivery, controlled release of therapeutic molecules, biomedical materials, smart sensing systems, and catalysis and chemical manufacturing.

To resolve how the network is built and remodeled, the group used dynamic nuclear polarisation‑enhanced solid‑state nuclear magnetic resonance spectroscopy (DNP NMR) to obtain an atomic‑level view. The sensitivity gain was substantial, reducing an experiment estimated to require around seven years with conventional NMR to just 12 hours. Specialist low‑temperature DNP NMR infrastructure was accessed at the University of Gothenburg to support these measurements.

“Seeing a material change is only half the story. If we want to design better responsive gels, we need to know precisely how their molecular building blocks are connected. DNP NMR gave us that atomic-level picture in a material that is otherwise exceptionally difficult to study – allowing us to solve a major challenge in gel science,” said Dr. Dominik Kubicki, lead for atomic‑level structure characterisation at the University of Birmingham’s School of Chemistry.

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University of Birmingham’s School of Chemistry