With the help of camera-guided endoscopes, clinicians can look inside the body’s cavities to diagnose and treat many different conditions, but the endoscope instruments can prove very challenging to use due to the tendency for blood and other bodily fluids to obscure the camera lens in the midst of critical procedures.

The problem inspired a team led by Joanna Aizenberg, core faculty member at the Wyss Institute at Harvard University, to engineer a transparent surface coating for an endoscope lens that could keep blood and other fluids at bay.

Steffi Sunny, graduate researcher at the Wyss Institute, holds an endoscope. Image credit: Wyss Institute at Harvard University.Steffi Sunny, graduate researcher at the Wyss Institute, holds an endoscope. Image credit: Wyss Institute at Harvard University.Aizenberg’s previously developed slippery liquid-infused porous surfaces (SLIPS) technology creates non-wetting and robust self-cleaning surfaces that can resist almost any fouling a surface may come into contact with. But to develop the technology for endoscopic use, the team needed to adapt SLIPS specifically to endure the harsh environment of a living body’s cavities.

"In addition to being entirely transparent and able to coat the curvature of the glass camera lens on the endoscope, the coating also needs to withstand constant contact and abrasion with soft tissues and corrosive bodily fluids," says Steffi Sunny, graduate researcher at the Wyss Institute.

To achieve this, the team deposited silica nanoparticles layer by layer onto an endoscope’s glass camera lens. These silica layers create a porous surface that, at the nanoscale, would be considered "rough" and filled with caverns. They then functionalized this "rough" surface and infused it with a medical-grade silicone oil, filling in the porous cavities and creating a self-replenishing liquid layer. The end result, an entirely biocompatible coating, can endure many procedural uses and standard sterilization protocols—and even be reapplied with silicone oil intermittently to maintain its extreme repellency.

Working with George Cheng, an interventional pulmonary fellow at Harvard at the time of the study, the team tested their antifouling endoscope by performing a bronchoscopy on an anesthetized pig.

"The proof-of-concept experiment in the pig lung worked beautifully," says Cheng. "It very easily repelled blood and mucus and dramatically reduced the complexity of the procedure."

Conventional scopes generally cause the procedure time to be longer than necessary, due to the need to repeatedly clean and wipe away fluids that obscure the optical field. An antifouling endoscope could not only improve ease and precision of endoscopies, but could also result in more positive patient outcomes due to a shortened procedural time, reduced side-effects associated with mid-procedure lens cleaning, less sedation and decreased recovery time.

SLIPS-coated endoscopes could eventually be used in new areas of the body that have not yet been accessible with a camera. Today’s endoscopes, which contain irrigation and suction channels to flush away buildup from the lens, are limited in how small they can be made. But the super-repellent coating on the lens could potentially eliminate the need for a wash port, leading to more miniaturized endoscopes and allowing physicians to reach, observe and treat areas of the body that are off-limits to endoscopes of current sizes.

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