(Nanowerk Spotlight) In healthcare settings, textiles like bed sheets, scrubs and curtains can harbor dangerous pathogens, facilitating the spread of infections among patients and staff. Despite advances in antimicrobial fabrics, controlling the transmission of bacteria, viruses and other microorganisms via hospital textiles remains an ongoing challenge. Previous approaches have focused on either repelling pathogens or killing them on contact, but integrating both capabilities along with a detection mechanism has proven elusive.
The field of smart textiles has seen significant progress in recent years, with the development of fabrics that can sense environmental conditions, regulate temperature, or even harvest energy. However, creating textiles that can simultaneously repel, eliminate, and detect microbial contamination has remained a complex undertaking. This is partly due to the difficulty of maintaining fabric functionality and durability while incorporating multiple advanced features.
Additionally, the rise of antibiotic-resistant bacteria has intensified the need for novel approaches to infection control that do not rely solely on antimicrobial agents. The World Health Organization has projected that drug-resistant pathogens could cause 10 million deaths annually by 2050 if more effective preventive measures are not developed.
Against this backdrop, researchers have been exploring ways to engineer fabric surfaces at the micro and nanoscale to prevent bacterial adhesion and biofilm formation. Advances in nanotechnology and materials science have opened up new possibilities for creating hierarchical surface structures and incorporating functional nanoparticles into textiles. These developments, combined with progress in colorimetric sensing techniques, have set the stage for a potential breakthrough in smart fabrics for healthcare applications.
Now, a team of scientists from McMaster University has created a novel smart fabric that integrates multiple functions to combat pathogen transmission. The material can repel liquids and microbes, kill adhered bacteria, and change color to signal contamination. This multifunctional approach represents a significant advance over existing antimicrobial textiles.
Smart Fabric Fabrication and Characterization. a) Schematic outlining the synthesis process and the function of the SF coating. b, i–iv) SEM images depicting the key fabrication stages of the microparticles, including (i) smooth particle, (ii) wrinkled particle, (iii) detailed view of the wrinkle structure, and the (iv) hierarchical nanoparticle coating. (Image: Adapted from DOI:10.1002/adfm.202403157, CC BY)
The researchers developed a spray coating containing several key components to achieve these capabilities. At its core are tiny wrinkled particles made of polydimethylsiloxane (PDMS), a silicone-based polymer. These microparticles, ranging from 1 to 100 micrometers in size, have a hierarchical structure with nanoscale surface features. This structure creates a superhydrophobic surface that repels water and other liquids.
The PDMS particles are then coated with silver nanoparticles that have been modified with a branched polymer called polyethyleneimine. This modification enhances the nanoparticles’ ability to kill bacteria by increasing their affinity for negatively charged bacterial cell walls. The silver nanoparticles provide a potent antimicrobial effect without relying on antibiotics, which could contribute to drug resistance.
Finally, the researchers incorporated a pH-sensitive dye called bromothymol blue into the coating. This dye changes color from blue to yellow as the surrounding environment becomes more acidic – a common occurrence when bacteria form biofilms and produce acidic metabolites. This color change provides a visual indicator of microbial contamination.
The team applied this multifunctional coating to cotton and polyester fabrics using a simple spray coating method. They then conducted a series of experiments to evaluate the material’s performance against various pathogens, including antibiotic-resistant bacteria, fungi, and viruses.
In tests simulating droplet and aerosol transmission, the smart fabric demonstrated remarkable efficacy in repelling pathogens. Compared to uncoated fabrics, it reduced bacterial adhesion by 99.90% for methicillin-resistant Staphylococcus aureus (MRSA), 99.96% for Pseudomonas aeruginosa, 99.92% for the fungus Candida albicans, and 99.91% for the Phi6 virus immediately after exposure. After 4 hours, these reduction rates improved further to 99.97%, 99.98%, 99.99%, and 99.99% respectively, demonstrating the coating’s sustained effectiveness over time.
The researchers also examined the fabric’s performance when exposed to bodily fluids like urine and feces, which can harbor high concentrations of pathogens in hospital settings. In these challenging conditions, the smart fabric still achieved significant reductions in bacterial adhesion. For urine samples contaminated with Escherichia coli, the fabric showed a 99.88% reduction in bacterial adhesion compared to uncoated fabrics after 24 hours. When tested with fecal matter from specific pathogen-free mice, the smart fabric demonstrated a 99.79% reduction in bacterial adhesion after 24 hours, with this effectiveness increasing to 99.99% after 120 hours.
Beyond its repellent properties, the coating demonstrated potent antimicrobial activity against adhered pathogens. In growth assays conducted over 24 hours, the smart fabric reduced MRSA populations by 99.90% and P. aeruginosa populations by 99.88% compared to uncoated controls. This killing effect was attributed to the silver nanoparticles incorporated in the coating.
Perhaps most notably, the fabric’s color-changing capability allowed for real-time detection of contamination. As bacteria formed biofilms on the surface, the bromothymol blue dye shifted from blue to yellow, providing a clear visual indicator of microbial growth. This feature could enable healthcare workers to quickly identify contaminated textiles that require cleaning or replacement.
To enhance the accuracy of contamination detection and eliminate potential user error in interpreting color changes, the researchers developed a machine learning algorithm to analyze images of the fabric. This system achieved 96.67% accuracy for the smart fabric and 96.30% accuracy for control samples in distinguishing between contaminated and uncontaminated samples, demonstrating the potential for automated monitoring of surface hygiene in healthcare settings.
The researchers conducted extensive durability tests to assess the fabric’s performance under various environmental conditions. In humidity tests, the smart fabric was exposed to 90% relative humidity at 25 °C for 24 hours. UV exposure tests involved irradiating the fabric with a UV lamp at 340 nm for 3 hours. High-temperature tests subjected the fabric to 90 °C for 24 hours. After each of these tests, the fabric maintained its repellent properties, with water contact angles remaining above 130°.
The smart fabric also demonstrated good mechanical durability. In abrasion resistance tests, the fabric underwent 5 cycles of wear against a rubber abradant under a 250g load. Flexibility tests involved bending the fabric to a 180° angle for 50 cycles. In both cases, the fabric retained its functional properties, including its water repellency.
To assess the impact of the coating on breathability, the researchers conducted air permeability tests. The uncoated fabric showed an air permeability of 346.25 mm-1 s, while the smart fabric demonstrated a value of 274 mm-1 s. This represents a reduction of about 21% in air permeability, which the researchers noted was within an acceptable range for coated fabrics based on literature values.
The multifunctionality of this smart fabric could significantly reduce the incidence of hospital-acquired infections (HAIs) through several mechanisms. First, its ability to repel pathogens would decrease the initial contamination of hospital textiles, reducing the risk of pathogen transfer to patients and healthcare workers. Second, the antimicrobial properties would help eliminate any microbes that do manage to adhere to the fabric, preventing them from proliferating and forming biofilms. Finally, the color-changing feature would allow for rapid identification of contaminated surfaces, enabling prompt intervention and potentially preventing the spread of pathogens before they can cause infections.
This integrated approach addresses multiple points in the infection transmission chain, potentially offering a more comprehensive solution than current methods. By reducing the microbial load on hospital textiles and providing early warning of contamination, the smart fabric could help break the cycle of pathogen transmission that often leads to HAIs. This could be particularly impactful in high-risk areas such as intensive care units or during outbreaks of highly infectious diseases.
This research represents a significant step forward in the development of advanced materials for infection control. By combining repellent, antimicrobial, and sensing capabilities in a single fabric coating, the technology offers a comprehensive approach to reducing pathogen transmission via textiles in healthcare settings.
The potential applications extend beyond hospital linens to other high-touch surfaces in medical facilities, as well as personal protective equipment for healthcare workers. The colorimetric sensing feature, in particular, could provide a valuable early warning system for detecting contamination before it leads to infection.
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