Atypical Renal Clearance of Nanoparticles Larger Than the Kidney Filtration Threshold

In recent years, several publications reported that nanoparticles larger than the kidney filtration threshold were found intact in the urine after being injected into laboratory mice. This theoretically should not be possible, as it is widely known that the kidneys prevent molecules larger than 6-8 nm from escaping into the urine. This is interesting because it implies that some nanoparticles can overcome the size limit for renal clearance. What kinds of nanoparticles can bypass the glomerular filtration barrier and cross into the urine? What physical and chemical characteristics are essential for nanoparticles to have this ability? And what are the biomolecular and cellular mechanisms that are involved? This review attempts to answer those questions and summarize known reports of renal-clearable large nanoparticles.

Automated summary

Recent studies found nanoparticles larger than the kidney filtration threshold remaining intact in the urine of laboratory mice, challenging the known size limit for renal clearance. This raises questions on what types of nanoparticles can bypass the filtration barrier, essential physical and chemical characteristics required, as well as the biomolecular and cellular mechanisms involved.