Chemical engineers develop ‘smart bandages’

Negar Rahmani, University of Rhode Island

RESEARCHERS at the University of Rhode Island (URI), US have embedded nanosensors into microfibres to create “smart bandages”, which offer the chance to detect and monitor wound infections in a continuous, non-invasive manner.

The novel bandages detect hydrogen peroxide in wounds at concentrations up to 1,000 μM, without needing to embed electronics or power sources within the textile of the bandage. Hydrogen peroxide is a messenger involved in wound healing and is present at low concentrations (100–250 μM) in normal wounds. Higher concentrations indicate the presence of inflammation and chronicity, conditions in which pathogens can grow significantly faster.

The wearable optical textiles developed in this work can wirelessly detect the presence of hydrogen peroxide in real-time. Daniel Roxbury, Assistant Professor of Chemical Engineering at URI, explained that the technology is based on the principle of near-infrared fluorescence.

When excited, the embedded nanosensors become illuminated and can be captured by a near-infrared camera and then the fluorescence spectrum from the carbon nanotubes is resolved by optical grating, a technique which separates light into its components. He added that the system developed at URI has a probe that can direct the light source while simultaneously collecting the emitted light. “This is convenient, as the smart bandages do not need to fit on or inside of an instrument or microscope,” Roxbury concluded.

He explained that the nanosensors are a formulation of single-walled carbon nanotubes (SWCNTs) with engineered surfaces that allow them to respond to hydrogen peroxide. To create the smart bandages, the URI team used an electrospinning process to encapsulate their nanosensors within the core of biocompatible fibres.

Roxbury said that the researchers used polymers approved by the US Food and Drug Administration – polycaprolactone and polyethylene oxide – to form the shell and core of the microfibres, respectively. The microfibres’ core and shell contain nano-sized pores that enable analytes, such as hydrogen peroxide, to diffuse into the fibres and to the nanotubes.

He noted that electrospinning is an established technique involved in a variety of commercial applications and he believes the machinery is already in place to allow scaleup of the technology.

“I am excited to see how far we can progress this work and make at-home monitoring of wounds a reality.”

The devices also operate in a reversible manner and, according to Roxbury, reversible biosensors are generally preferred to single-use sensors. “Biological processes are inherently transient, and the hydrogen peroxide concentration may rise and fall over time,” he added.

These devices would be solely for diagnostic purposes, but they could potentially enable early detection of infection that would mean fewer antibiotics could be used, and drastic measures such as limb amputation could be avoided. Roxbury highlighted that the devices could be particularly useful for those with diabetes, for whom management of chronic wounds is routine.

According to Roxbury, it was previously a challenge to immobilise nanotubes in a biocompatible manner that allowed them to remain sensitive to their surroundings. The microfibres which the team developed overcome this.

Additionally, Roxbury highlighted that the nanotubes do not leach from the material. He said that leaching is an issue with most nanoparticles embedded within some other types of media, as due to their size most are able to diffuse out of porous materials.

In its current form, the detection system uses a benchtop near-infrared probe spectrometer but in future the aim is to miniaturise the external unit to make a portable and wearable version of the detection platform. The signal could then be transmitted to a smartphone-type device that automatically alerts patients or healthcare providers. 

The researchers see the potential to develop wearable technologies that can detect a wide range of other biomolecules including proteins, hormones, and carbohydrates based on their technology. Detection could be in wounds or of other biological fluids, such as sweat.

Researchers at URI have collaborations in place to further their work through in vivo studies in animal models. This could include mice and canines. Research would then advance to clinical trials involving wearable devices on humans.

Advanced Functional Materials: https://doi.org/f3k3