New Polymer Electrode Extends Runtime of Needle-Free Drug Delivery Patches

Wearable, electrically assisted transdermal patches can enable needle-free delivery but often fail when electrodes degrade during prolonged, moist skin contact. This instability undermines dose consistency, limits session length, and hampers reuse in patient care. Hospitals need soft electrodes that remain adherent and electrically stable during operation. Researchers have now developed a dopamine-enhanced polymer electrode designed to extend operating time and reliability for skin‑interfaced iontophoresis patches.

The Chinese University of Hong Kong team integrated dopamine into PEDOT:PSS, a soft conductive polymer commonly used in bioelectronic interfaces. The approach targets three failure modes that limit wearable patches: electrical degradation during operation, loss of mechanical integrity in wet conditions, and detachment from the supporting substrate. By modifying the polymer itself, the design aims to maintain function without relying on conventional silver/silver chloride electrodes.

Dopamine organizes the polymer into a denser, more orderly structure and strengthens its attachment to the device substrate. During operation, it acts as a sacrificial reactant that delays degradation of the main conductive network. Its adhesive chemical groups help resist water-induced swelling and peeling, improving stability under repeated use on hydrated skin. Together, these effects support more consistent iontophoresis across the stratum corneum.

In laboratory testing on excised pig skin, the dopamine‑enhanced electrode operated for extended periods and outperformed an unmodified polymer electrode. At low current density, it functioned for approximately 15 hours, and during repeated trials on new skin samples exchanged every 30 minutes, it remained effective for up to 120 minutes. During first use, its fluorescence signal was about twice that of unmodified PEDOT:PSS and four times that of a commercial silver/silver chloride electrode, indicating stronger electrically assisted transport of model compounds.

Additional diffusion‑cell experiments detected the transdermal movement of both charged and neutral model compounds. Cell assays showed no detectable cytotoxicity under the reported conditions, and a short forearm contact assessment revealed no obvious visible irritation. The researchers cautioned that findings are based on electrochemical testing and ex vivo porcine‑skin studies, with limited, preliminary human skin contact. They noted the need for long‑term safety evaluation, dose‑control studies, testing on diseased or damaged skin, and well‑designed clinical investigations.

“Dopamine improves the electrode at several levels rather than only changing one property. It helps organize the conductive polymer, protects it during electrical operation and strengthens the connection between the electrode and its supporting surface,” said Ni Zhao, corresponding author.

“Additional diffusion-cell experiments detected the transport of both charged and neutral model compounds. Cell tests showed no detectable cytotoxicity under the reported conditions, while a short forearm contact test showed no obvious visible irritation,” said Yixin Qi, first author.

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Chinese University of Hong Kong