Bacteria are fast evolving resistance to antibiotics, and it takes time to figure out if a particular infection is drug-resistant or not. Now, researchers from the Chinese Academy of Sciences have developed a smart bandage that changes color to signal the presence of either drug-resistant or drug-sensitive bacteria. It can then be triggered to release antibiotics or other chemicals to kill off the bugs.

The concept goes that the bandage starts off green, when it’s applied to the wound. If it detects bacteria that are still sensitive to antibiotics, it will turn yellow over a period of about four hours. If it detects drug-resistant bacteria, it will turn red.

This color-changing mechanism is made possible by chemicals loaded into the bandage. Pathogenic bacteria often create more acidic environments for themselves, so the bandage contains a simple pH indicator that will change colors if those bugs are around. Meanwhile, the chemical nitrocefin turns red when it senses an enzyme known as beta-lactamase, which are produced in droves by drug-resistant bacteria.

The bandage slowly changes from green to yellow in the presence of drug-sensitive bacteria (top row), and to red in the presence of drug-resistant bacteria (bottom) ACS Central Science

That makes it easy for doctors and patients to see what they’re dealing with and respond as needed. It saves antibiotics being used when they aren’t required – which is a large part of why drug-resistance is so prevalent – but also indicates when to resort to other methods.

Going one step further, the bandage has some of these treatments built in as well. The antibiotic ampicillin is loaded into nanomaterials that dissolve under the acidic conditions of bacterial infection, releasing the drugs and killing the bugs.

Of course, that won’t work for the resistant bacteria, but there’s a secondary attack in store for them. The bandage is also loaded with a material that reacts to bright light by releasing reactive oxygen species (ROS). These molecules are known to deal high damage to microbes, either killing them or at least weakening them enough that the antibiotics can finish them off.

The team tested the concept in mice that had infections of either drug-sensitive or drug-resistant E. coli. They found that the bandages changed color as hoped, and were effective in killing off both strains of bacteria.

While this is just a proof of concept tested in mice at this stage, the researchers say that it should be relatively easy and inexpensive to scale up for clinical use since the bandage itself is mostly made of paper. It also cuts back on the time-consuming processes usually required to diagnose infections and determine if they’re drug-resistant, and slows the spread of that resistance.

This is far from the first smart bandage we’ve seen. Other prototypes change color in response to heat (another sign of infection), kill bacteria, monitor chronic wounds and deliver drugs on a schedule.

The new research was published in the journal ACS Central Science.

Source: American Chemical Society