Novel approach shows efficacy in fragmenting kidney stones

An innovative approach to fragmenting kidney stones using photonic nanoparticles is effective for several common types of stones. That is the major finding of a proof-of-concept study by Cleveland Clinic researchers published in Nano Letters.

“The lasers here are simply activating the nanoparticles which is different from using lasers to break the stones,” says says Smita De, MD, PhD, a physician and researcher specializing in urology and minimally invasive surgery in Cleveland Clinic’s Department of Urology.

Kidney stones affect nearly 1 in 10 people in the United States and the prevalence is expected to increase to 13% by 2030. They are associated with morbidity and sometimes mortality and can be difficult to treat. The most common treatments are laser lithotripsy by ureteroscopy and extracorporeal shock wave lithotripsy (ESWL); if those treatments aren’t feasible, more invasive procedures (like percutaneous nephrolithotomy) are an option. Recent studies using more sensitive scans report that often only 60% of patients have no stones following treatment; the residual stones can cause complications and require repeat procedures to remove them.

“There’s a lot of room for improvement in treating kidney stones. In complex cases, it can be difficult to access the stones and some patients aren’t good candidates for the more common treatment options,” says Smita De, MD, PhD, a physician and researcher specializing in urology and minimally invasive surgery in Cleveland Clinic’s Department of Urology.

Nanoparticles have been used in various medical applications, including drug delivery in chemotherapy and the COVID-19 vaccine. They are being studied for novel applications at the Cleveland Clinic Lerner Research Institute, Department of Biomedical Engineering.

“One of the unique properties of certain nanoparticles is their ability to produce both mechanical and thermal energy which we thought could be strong enough to break stones. This made them a good candidate for investigation as a kidney stone treatment,” says Dr. De, study investigator along with biomedical engineers from the Lerner Research Institute.

Investigating nanoparticles

Using human kidney stones obtained from the Cleveland Clinic Pathology Laboratory, the research team experimented with different carbon- and gold-based nanomaterials, as well as laser settings, wavelengths and distances. They coated the kidney stones with nanoparticles and activated the nanoparticles with low-intensity near-infrared lasers from a distance. In comparison, current laser lithotripsy uses high-intensity lasers that must touch the stones to be effective.

“The lasers here are simply activating the nanoparticles which is different from using lasers to break the stones,” says Dr. De.

The technique they developed, photonic lithotripsy, was effective across all nanoparticles in breaking down common stone types including calcium oxalate dihydrate, calcium phosphate, uric acid, and the hardiest type, calcium oxalate monohydrate, using lasers ranging from 2-4 W at a distance of 1-2 cm.

“We are very pleased at how well this technique works with different types of stones and nanoparticles. It changes how we think about kidney stone treatment,” says Dr. De.

As a non-contact, low-intensity treatment, photonic lithotripsy has the potential to reduce procedure time and complexity, minimize risk of injury to tissues, improve surgeon ergonomics, increase surgical success rates and decrease the need for radiation.

“It could be an alternative for patients who don’t succeed with current techniques or can’t have them,” says Dr. De.

Future prospects for photonic lithotripsy

The research team is continuing its work on photonic lithotripsy to better understand the mechanism of stone breakdown and refine the process. They are also planning animal studies to evaluate the technique’s safety and efficacy.

“The research is at an early stage but based on our findings so far, the prospects are good that photonic lithotripsy could become a safe and effective kidney stone treatment,” says Dr. De.