Novel Microgels Release Micro-Doses of Antibiotics to Reduce Infection Rates

Joint replacements are one of the most standard optional surgeries—however, nearly 1 in 100 patients is badly affected by postsurgical infections, converting a normal procedure into a costly and hazardous trial.

Currently, scientists from Stevens Institute of Technology have created a “self-defensive surface” for these implants that can discharge selected micro-doses of antibiotics when bacteria come into contact, thereby markedly reducing the infection rates.

The study by the scientists, under the guidance of Matthew Libera, Professor of Materials Science at Stevens, explains a way for coating the implant surfaces with a lattice of microgels: flecks, each one is 100x smaller compared to the diameter of a strand of human hair and has the potential to absorb particular antibiotics. The function of the microgels is controlled by electric charges, and the electrical energy of advancing microorganisms induces them to release antibiotics, thereby inhibiting the development of infections.

Microgels can possibly be used in various medical devices such as tissue scaffolds, heart valves, and surgical sutures—and as it is predicted that by 2024 the demand for hip implants alone would reach $9.1 billion, the technology will have a promising future in the market. The U.S. Army, which financially supported this research, is also interested in using the technology in hospitals, where infections, at present, develop in one-quarter of combat wounds.

The potential impact for patients, and for the healthcare system, is tremendous,” stated Libera, who chairs the Stevens Conference on Bacteria-Material Interactions. Jing Liang (Stevens doctorate candidate) and Hongjun Wang (biomedical engineering professor) worked together on the study, which has been published in Biomaterials.

It is difficult to overcome postsurgical infections because once the microorganisms settle on the surfaces, they develop antibiotic-resistant layers known as biofilms. Libera and his research team disturbed this cycle by killing the microorganisms before they could progress.

It only takes one bacterium to cause an infection. But if we can prevent infection until healing is complete, then the body can take over.

Matthew Libera, Professor of Materials Science, Stevens Institute of Technology

Different from the usual treatments that fill the whole body with antibiotics, the method developed by the Stevens research team is highly focused, discharging antibiotics in small amounts to destroy individual bacteria. This markedly minimizes the targeted pressures that generate antibiotic-resistant “superbugs”—a significant breakthrough in systemic treatments and local methods like releasing orders of magnitude less antibiotic into the patient’s system and blending antibiotics into bone cement.

Other self-defensive surfaces that are currently in progress depend on the metabolic by-products of microorganisms to activate the release of antibiotics—a less certain approach compared to Libera’s approach, which is capable of destroying even inert bacteria. The researchers’ microgels are also exceptionally flexible, simultaneously surviving ethanol sterilization and remaining stable for weeks. Also, microgels respond suitably to human tissue, retaining their antibiotic load until it is needed and promoting healthy bone growth around treated surfaces.

For microgels to be used in a medical device like a knee joint, surgeons have to dip the device in a specifically designed bath for a few seconds; a short dip in a second bath would then fill the microgels with antibiotics. Theoretically, surgeons could prepare devices based on the requirement, immediately before inserting them, using antibiotics meant for specific risk factors of a patient.

To date, the approach has been experimented in vitro, and currently, the team has been working to modify the microgels and allow them to release a broad range of antibiotics. Due to the highly innovative nature of the technology, it is difficult to obtain consent from the U.S. Food and Drug Administration. However, Libera’s research team, in collaboration with industry partners, has aimed to focus on more demonstrations.

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