University of Michigan Engineers Develop "Trojan Horse" Starch Nanoparticles to Deliver Antibacterial Copper Directly to Drug-Resistant Biofilms

University of Michigan researchers create copper-loaded starch nanoparticles that use bacterial enzymes to release targeted treatment for drug-resistant biofilms.

By: AXL Media

Published: Mar 31, 2026, 5:54 AM EDT

Source: Information for this report was sourced from Michigan Medicine - University of Michigan

Addressing the Crisis of Antibiotic Resistance in Hospitals

Antibiotic-resistant bacteria represent one of the most significant threats to modern medicine, contributing to over 23,000 deaths annually in the United States alone. Traditional antibiotics often struggle to penetrate biofilms—slimy, protective microbial communities that account for up to 70% of healthcare-associated infections. To address this, a team at the University of Michigan has turned to nanotechnology. While previous attempts to use metal-based nanoparticles failed due to poor solubility and instability in clinical environments, the Michigan researchers have successfully used starch as a biological carrier to stabilize and transport antibacterial copper molecules directly to the site of infection.

The Trojan Horse Mechanism of Starch Nanoparticles

The innovative delivery system functions through a "Trojan Horse" strategy. The copper is encased within starch nanoparticles, which are positively charged. Because the surfaces of most bacteria are negatively charged, the nanoparticles are naturally drawn to and adhere to the pathogens. Once attached, specific bacteria that produce the enzyme amylase begin to break down the starch for energy. This metabolic process inadvertently triggers the release of the encapsulated copper, which then enters and destroys the bacterial cells. This localized release ensures that high concentrations of copper are delivered exactly where needed, minimizing the risk of systemic toxicity to the patient.

Targeting Staphylococcus Aureus and Multi Species Communities

During the study, the team tested the nanoparticles against Staphylococcus aureus, a primary cause of hospital-acquired infections, and Bacillus subtilis. Interestingly, while S. aureus cannot break down starch on its own, it often lives within diverse microbial communities alongside species like B. subtilis that do produce amylase. The researchers found that the presence of amylase-producing bacteria in a wound or biofilm can trigger the release of copper that kills the surrounding S. aureus. This suggests that the nanoparticles are particularly effective for treating complex, multi-species wound infections where bacterial growth conditions favor starch degradation.