The images of the internal walls of cells

Researchers continue to uncover new ways to improve the effectiveness of nanoparticles as biomedical tools. Nanoparticles are particles smaller than 100 nanometers in size. They are usually obtained from metals and thanks to their tiny size they have unique properties that make them useful in biomedical applications

Researchers continue to uncover new ways to improve the effectiveness of nanoparticles as biomedical tools. Nanoparticles are particles smaller than 100 nanometers in size. They are usually obtained from metals and thanks to their tiny size they have unique properties that make them useful in biomedical applications.

Researchers at the University of Tokyo continue to uncover new ways to improve the effectiveness of nanoparticles as biomedical tools. They are usually obtained from metals and thanks to their tiny size they have unique properties that make them useful in biomedical applications. However, without a special treatment that makes their surface biologically inert, their effectiveness is quite limited. Researchers from the University of Tokyo became the pioneers in the use of MPC (2-methacryloyloxyethyl phosphorylcholine) polymers to modify the surface of nanoparticles. In an article recently published in the scientific journal Science and Technology of Advanced Materials, the researchers described the ways in which polymeric nanoparticles can be used to deliver tiny quantum dot-type nanoparticles into the cells themselves.

MPC polymers are large molecules made of chains of the substance whose chemical name is 2-methacryloyloxyethyl phosphorylcholine. Biologically active nanoparticles whose outer surface has been bound to these polymers can be used as anti-cancer compounds, gene carriers, contrast agents that enhance the images obtained from an MRI machine, and protein detectors. MPC polymers mimic cell membranes and enable the transfer of biologically active molecules that are normally not particularly soluble in water and which may even cause unwanted side effects. When scientists attach these polymers to the surface of inorganic nanoparticles, they can facilitate the entry of substances into the blood or various tissues within the body.

The team of researchers from Tokyo recently began using this process for quantum dots with the goal of producing nanoparticles that can compete in terms of their performance with conventional fluorescent dyes in the field of biomedical imaging. Using a simple solvent evaporation method, the researchers were able to produce polymeric nanoparticles containing a core of quantum dots trapped inside a PLA polymer wrapped in turn by a derivative of the MPC polymer known as PMBN. This combination produces particles that maintain the same level of fluorescence in solution even after a period of six months at a temperature of 4 degrees Celsius. While regular organic dyes lose their fluorescence after a certain period of time, the quantum dot nanoparticles do not lose their function.

In order to be useful, the nanoparticles need to enter the cells. To achieve this, the researchers tested the performance of several molecules by immobilizing them on the surface of PMBN/PLA/quantum dot particles. The experiments showed that when a peptide that penetrates into the cell called R8 - an octa-peptide made of eight amino acids of arginine - was added to the nanoparticles, they were able to penetrate into the cells within five hours without any toxic or inflammatory effect on the cells even after three days. Additional experiments showed that the cells containing the quantum dots divided normally, and that the nanoparticles were distributed equally among the daughter cells after the cell division phase. Unlike organic dyes, this condition did not weaken the fluorescence signal even after thirty hours of cell division. "Our study is the first report ever showing the long-term preservation of the activity of the nanoparticles inside the cells. The preparation of biologically active nanoparticles attached to MPC polymers can be used for the production of nanodevices that are inside the cells while fully controlling these devices," explains the lead researcher.

Article Summary

Cells can take up polymeric nanoparticles containing quantum dots coated with phospholipid polymer and cell-penetrating peptides. [Courtesy Kazuhiko Ishihara, Weixin Chen, Yihua Liu, Yuriko Tsukamoto and Yuuki Inoue]