Super-Resolution Imaging and NMR Reveal Drug Effects at Cellular and Atomic Levels

Researchers used super-resolution microscopy to track the cancer drug sunitinib inside living cells and found that it triggers coordinated disruption of mitochondria, lysosomes, and the endoplasmic reticulum, according to a study published in Biophotonics Discovery. Separately, solid-state nuclear magnetic resonance (NMR) spectroscopy is being used to determine atomic-level structures of formulated drug products, addressing a persistent challenge in pharmaceutical formulation design.

Sunitinib is used to treat several cancers, including kidney cancer. Its therapeutic activity has traditionally been linked to its ability to inhibit enzymes that drive tumor growth. Researchers at the University of Cincinnati combined cell viability testing with structured illumination microscopy (SIM), a super-resolution imaging technique that can reveal structures too small to be clearly seen with conventional light microscopes. Because sunitinib is naturally fluorescent, the team could follow its movement inside living cells without chemically modifying it. Rather than focusing only on whether cells survived treatment, the researchers examined how the drug affected three interconnected cellular systems: lysosomes, which recycle cellular materials; mitochondria, which generate energy; and the endoplasmic reticulum (ER), which helps produce proteins and regulate cellular signaling.

The team first confirmed that sunitinib reduced cell viability in a dose-dependent manner, with higher concentrations causing progressively greater cell death. SIM imaging showed that the drug concentrated primarily inside lysosomes, and quantitative analysis confirmed a much stronger association with lysosomes than with mitochondria. After treatment, healthy mitochondrial networks became increasingly fragmented, with elongated structures breaking into shorter, isolated segments. The number of lysosomes decreased while the remaining structures became larger and more irregular in shape, pointing to increasing stress within the lysosomal system as drug concentrations rose. The ER network, which in untreated cells formed a continuous network extending throughout the cell, progressively broke apart into disconnected fragments. Topological analyses of ER connectivity showed a clear, concentration-dependent loss of ER organization.

The findings suggest that sunitinib's effects extend beyond enzyme inhibition. The drug appears to trigger coordinated disruption of multiple cellular systems, ultimately contributing to the loss of cell function and survival. Instead of relying solely on biochemical measurements, the researchers directly visualized how a therapeutic molecule moved through a living cell and how cellular structures responded over time. The approach combines optical engineering, image analysis, and cell biology to produce quantitative measurements of organelle architecture and connectivity, and demonstrates how modern super-resolution imaging can transform the study of drug behavior by revealing interactions that are invisible to conventional microscopy. The work provides a detailed view of drug behavior at the microscopic level and highlights the growing role of optical imaging in drug development and cellular engineering.

In a separate line of research, solid-state NMR spectroscopy methods developed at Iowa State University and the U.S. Department of Energy's Ames National Laboratory are helping resolve 'a persistent challenge in the pharmaceutical industry': the successful design of formulations for the administration of active pharmaceutical ingredients. In one experiment, a tiny solid sample of a drug, complete with active and inactive ingredients, was spun at 50,000 revolutions per second while tilted at the 'magic angle' of nearly 55 degrees relative to a high magnetic field at the National Magnetic Resonance Facility at the University of Wisconsin-Madison. The position of peaks in the resulting spectra offered clues about the structure of the solid drug, helping to locate the position of hydrogen, oxygen, and nitrogen atoms. Solid-state NMR spectroscopy can be applied to determine the atomic-level structure of materials such as heterogeneous catalysts, next-generation semiconductors, and formulated solid pharmaceuticals.

NMR instruments use superconducting magnets cooled by liquid nitrogen and liquid helium to subject samples to strong magnetic fields. The magnet in the Iowa State lab is rated at 9.4 Tesla, while the National High Magnetic Field Laboratory in Tallahassee, Florida, has an $18.7 million instrument rated at 35 Tesla. The NMR instrument's magnetic field aligns the nuclei; radio pulses then knock the nuclei out of alignment, and the instrument records those differences. NMR tools are 'a cornerstone of modern research in drug design, sustainable energy materials, and quantum systems,' according to a summary of a panel discussion at the annual meeting of the American Association for the Advancement of Science.

A new three-year, $492,000 study of the structures of active pharmaceutical ingredients and commercial drug products, supported by the U.S. National Science Foundation, is developing new methods to improve the sensitivity and resolution of NMR data. Graduate students and undergraduates will be part of the project, learning to prepare drug samples, perform NMR experiments, and computationally model atomic structures. A 2024 report by the National Academies of Sciences, Engineering, and Medicine concluded that the United States needs to reestablish a level of support for state-of-the-art NMR research that will allow laboratories in the United States to regain a position of leadership in NMR-based research areas, which means more instruments producing ultra-high magnetic fields that sharpen resolution and improve the data collected.