Coatings & surface treatment
a limited effective window, and potential risks associated with antimicrobial resistance and cytotoxicity,” he explains. “Conventional hydrophilic coatings are largely passive anti-adhesive barriers that may lack stimulus-responsive on-demand reinforcement under high bacterial burden or continuous urine flushing, leading to insufficiently stable inhibition of complicated urinary tract infection and biofilm formation.”
His team wanted to overcome these limitations. Their coating has a synergistic function: it prevents bacteria from adhering to the surface (passive protection), as well as killing pathogens (active protection). On the passive protection front, it contains segments of something called MPC (2-methacryloyloxyethyl phosphorylcholine), which work via a zwitterionic mechanism to form a stable hydration layer. In tests, the bacterial adhesion force dropped by nearly 97%, while overall adhesion dropped by around 75%. Meanwhile, the coating reduced friction dramatically, to reach an ultralow coefficient of friction of 0.007–0.009 (around seven times lower than the original surface). “This hydrated interface not only reduced friction but also suppressed the early stages of bacterial attachment through hydration-mediated repulsion,” says Zhang.
On the active protection front, it contains an antibiotic called sulfamethoxazole (SMX) linked via a urease-cleavable bond, becoming active only in the elevated-urease conditions characteristic of infection in the urinary tract. In tests, the coating released negligible amounts of the drug under ordinary conditions, versus near-complete release in the desired environment.
$11bn
The estimated value of the
global hydrophilic coatings segment by 2030–31.
Mordor Intelligence 88
“When uropathogens secrete urease, the responsive linkage was selectively cleaved, triggering SMX release and enabling on-demand killing of both surface-adhered bacteria and planktonic bacteria, thereby effectively preventing the establishment and maturation of biofilms,” says Zhang. Once they moved on to in vivo tests, the team found that bacteria on the coated samples were nearly undetectable. There was also a clear reduction in inflammation, indicating that the stent was well tolerated by the body. “Collectively, these results supported the conclusion that the coating effectively improved the surface’s wear-related tribological performance by maintaining a low-shear hydrated interface,” says Zhang. “Moreover, a seven-day rat bladder implantation study corroborated the coating’s in vivo antibacterial and anti-infection efficacy, underscoring the synergistic benefit of combining passive anti-fouling with urease- triggered active bactericidal function.”
The road ahead
Multi-function coatings of this kind present a clear path forward, as far as the scientific community is
concerned. A January 2026 article in Frontiers in Bioengineering and Biotechnology reported a pH-triggered antibacterial and lubricating dual- function hydrogel coating for infection-resistant urinary catheters, incorporating the antimicrobial peptide LL-37 and magnesium oxide to provide controlled antibacterial activity alongside sustained lubrication. The researchers remarked that the coating shows ‘broad potential for clinical application’. A November 2025 article in Reactive and Functional Polymers reported a sodium alginate- based coating incorporating the broad-spectrum antimicrobial polyhexamethylene biguanide (PHMB) for thermoplastic polyurethane catheters. This coating, like the others, displays combined hydrophilicity and antibacterial properties, and could one day provide an important defence against catheter-associated infections.
Despite the successes we are seeing in the lab, it’s important to note that most of these examples remain at an early stage of development. As Zhang explains, there is still a lot of work to do before his coating reaches the clinic.
“In the next stage, we will conduct durability evaluations under conditions that more closely mimic clinical service,” he says. “These include establishing in vitro urinary tract infection models under dynamic urine-like flow and complex biofouling environments and extending in vivo indwelling durations to assess long-term coating stability and performance on ureteral stents during prolonged use.” Quite possibly, the chemistry will need to be finessed along the way. Designing a dual-function coating is far from straightforward, as the various functions can sometimes work against each other. For instance, introducing antimicrobials can sometimes negatively impact the lubricity and mechanical strength of the coating.
“A central challenge in designing a dual-functional coating is balancing hydration lubrication with the incorporation of hydrophobic drug components,” remarks Zhang. “Introducing antimicrobial drugs or hydrophobic responsive motifs can compromise hydration-layer integrity, thereby weakening lubrication and anti-fouling stability. Conversely, pushing the surface towards extreme hydrophilicity may reduce drug loading capacity or limit release efficiency. This trade-off was reflected in our study.” As a result, researchers need to be precise in their formulations, so that all the desired functions can be realised. Companies that wish to commercialise new coatings will face challenges too: materials are costly, manufacturing processes are laborious and the regulatory landscape is stringent.
That said, the trend is clear: hydrophilic coatings are becoming smarter, more functional and more durable. That in turn bodes well for the future of patient care, with scope to reduce the risk of healthcare-associated infections. ●
www.medicaldevice-developments.com
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