Using microparticles crafted from remarkably thin petals, medications can be delivered accurately through the bloodstream to specific targets such as tumors or blood clots. Techniques like ultrasound and other acoustic methods help in navigating these particles within the body and pinpointing their locations. This method is advantageous as ultrasound is widely utilized in medical practices.
These tiny particles resemble delicate paper flowers or desert roses. Doctors can use them to direct medications precisely where they are needed within the body. Moreover, the particles can be easily monitored using ultrasound due to their ability to scatter sound waves.
How is it possible to direct medicines exactly where they are needed in the body? Researchers have been exploring this question for years. For instance, directly delivering cancer drugs to a tumor ensures that they work specifically at that site, minimizing side effects elsewhere in the body. Ongoing studies focus on identifying carrier particles to which therapeutic agents can attach. These particles must satisfy several criteria, including: the ability to absorb as many active substance molecules as possible; the capability to navigate through the bloodstream using simple techniques like ultrasound; and the capacity for tracking their journey with non-invasive imaging methods. Successfully confirming the delivery of medications relies on this last criterion.
Finding a universal solution that meets all these standards has proven difficult. A team from ETH Zurich has now introduced a specialized type of particle that satisfies all these requirements. Beyond their effectiveness, these particles are visually intriguing under a microscope, resembling miniature paper flowers or desert roses. Comprised of extremely thin petals, these particles are structured into flower shapes. Measuring between one and five micrometers in diameter, they are slightly smaller than a red blood cell.
This unique shape offers two key benefits. Firstly, the flower particles have a vast surface area relative to their size. The spaces between the tightly packed flower petals are only a few nanometers wide, functioning like pores. This design allows them to absorb substantial amounts of therapeutic agents. Secondly, these petals scatter sound waves or can be coated with light-absorbing molecules, making them easily visible with ultrasound or optoacoustic imaging techniques.
These groundbreaking findings have been shared by the research teams led by Daniel Razansky and Metin Sitti in a study published in Advanced Materials. Razansky holds the position of Professor of Biomedical Imaging with joint appointments at ETH Zurich and the University of Zurich, while Sitti is an expert in microrobotics and recently transitioned from ETH Zurich and the Max Planck Institute for Intelligent Systems in Stuttgart to Koç University in Istanbul.
More effective than gas bubbles
“Traditionally, researchers have mainly explored tiny gas bubbles as a method of transport through the bloodstream utilizing ultrasound or similar techniques,” explained Paul Wrede, co-author and doctoral student in Razansky’s group. “We have now shown that solid microparticles can also be steered acoustically.” The advantage of these flower particles over gas bubbles lies in their ability to carry larger amounts of active ingredient molecules.
The research team has demonstrated that the flower particles can be loaded with a cancer medication in experiments conducted in Petri dishes. They also injected these particles into the circulatory systems of mice. Using focused ultrasound, they successfully maintained the particles at a specific location within the blood circulation, even amidst rapid blood flow. Focused ultrasound involves concentrating sound waves at a precise spot. “In essence, we don’t just inject the particles and hope for the best. We actively control their positioning,” Wrede stated. The researchers aspire to apply this technology in the future for delivering medications to tumors or clots obstructing blood vessels.
These particles can be created from various materials and can have different coatings, depending on their intended use and the researchers’ chosen imaging technique for tracking the particles’ positions. “The fundamental concept is driven by their shape, rather than the materials from which they are constructed,” said Wrede. In their research, they examined flower particles made from zinc oxide in detail, along with particles made from polyimide and a composite of nickel and organic compounds.
The researchers now aim to enhance their concept further. They plan to conduct additional animal trials before this technology can beneficially impact patients afflicted with cardiovascular diseases or cancer.
