Bioactive Nanocoatings Encode Bacterial Settlement Cues for Coral Restoration

Increasing larval settlement can substantially accelerate coral reef restoration by overcoming a key bottleneck in coral population recovery. Successful settlement depends on biological and chemical cues associated with microbial biofilms and crustose coralline algae that are often reduced or absent on degraded reefs. Here, we present two complementary nanocarrier strategies for delivering a single defined bacterial settlement signal, lipopolysaccharides (LPS), from hydrogel coatings applied to coral settlement surfaces. One platform presents LPS at the hydrogel surface using liposome nanoparticles, while the other encapsulates LPS in silica nanoparticles embedded in the hydrogel matrix for gradual release. Both systems increased settlement of Montipora capitata larvae by >5-fold compared to uncoated control surfaces. Because this approach relies on a single cue derived from cultured bacteria, it offers a potentially scalable alternative to live biofilms or complex natural extracts. These results establish a promising biomaterials strategy for enhancing coral recruitment and supporting reef restoration.