Mitigating the foreign body response (FBR) — an immune reaction to any foreign object implanted in the body — is a major challenge when developing materials and technologies for biomedical devices. In particular, the FBR increases the impedance of bioelectronic devices, making signal transduction less efficient. Although strategies to alleviate the FBR have been developed mainly for non-electrical materials, there have been few reports on FBR-suppressing designs for electronic materials, particularly semiconductors. Now, writing in Nature Materials, Sihong Wang and colleagues present a molecular design strategy that reduces the FBR by modifying both the backbone and the side chains of semiconducting polymers, without compromising their electrical performance.

To test the effectiveness of these molecular design strategies, thin polymer films were created from the control polymer and from polymers with backbone or side-group modifications (or both) and subsequently implanted into the dorsal region of mice. All of the modified polymers demonstrated considerably reduced collagen deposition — a major marker of the FBR — and immune cell recruitment. Analysis of inflammatory markers also showed a decrease in pro-inflammatory molecules and an increase in anti-inflammatory molecules, indicating a shift towards a state that promotes healing and reduces inflammation.