Implantable ‘living materials’ that deliver drugs on demand could help fight infections

A new study published in *Science* on Thursday introduces implantable ‘living materials’ designed to treat infections on demand, eliminating the need for diagnostics, pills, or injections. Researchers at Harvard University engineered bacteria to detect pathogens and release drugs when activated, encasing them in a hydrogel—a jellylike, permeable material—to prevent bacterial escape. The hydrogel, tested for durability under stress and nutrient exposure, successfully contained bacteria for six months without leakage. The study involved implanting hydrogel-coated prosthetic pins in mice, some treated with bacteria programmed to target *Pseudomonas aeruginosa*. When the pathogen was introduced at the surgery site, mice with the ‘living’ hydrogel showed significantly reduced infection rates compared to untreated controls. Lead author Tetsuhiro Harimoto, a postdoctoral fellow at Harvard, emphasized the breakthrough in containing engineered bacteria at the implantation site without systemic risks. Quanyin Hu, an associate professor at the University of Wisconsin-Madison, highlighted the study’s potential as a first-of-its-kind long-term therapeutic. The hydrogel’s ability to retain bacteria for months suggests future applications in preventing surgical infections or chronic conditions. Researchers stress the need for further validation in humans before clinical use. The technology builds on existing ‘living medicine’ approaches, such as CAR-T cells, but addresses concerns about bacterial dissemination by using a durable, mesh-like hydrogel container. Stress tests, including stretching the material 10,000 times and prolonged nutrient exposure, confirmed its stability. The study marks a step toward on-demand, localized infection treatment without traditional diagnostic or drug-delivery methods.