Scientists at Uppsala University report the development of a new technique to study proteins, which does not require advanced equipment, specialized labs, or expensive reagents. The technique, which was developed with colleagues in Scotland and Austria, could be further developed to be used in point- of-care devices, for instance for diagnostic purposes.
The possibility to identify and localize proteins in tissues is essential for understanding disease mechanisms and for diagnostics. However, today advanced instruments are often needed to study proteins and how they interact with each other. An example is the microscopy technique that was awarded for last year's Nobel Prize in chemistry; super resolution fluorescence microscopy.
Such equipment is expensive to purchase and often requires special training to handle. To use protein detection for diagnostic purposes, e.g. in a clinic, new, less complicated methods to study proteins are needed. Such methods should be temperature insensitive and not require expensive instruments, costly reagents, or specially trained staff.
In Nature Communications the researchers present a technique (“Proximity-dependent initiation of hybridization chain reaction”) that could be used by, for instance hospital staff, to detect relevant proteins. The technique is based on the binding of antibodies, either to two sites on the same protein or to two proteins that are localized very close to each other. The antibodies have been linked to DNA strands that will attach to each other if they are close enough. When this happens a chain reaction will start in which increasing numbers of DNA strands are attached. To each DNA strand a fluorescent substance has been linked, which will emit light when it is irradiated with light of a certain wavelength.
“When the chain reaction has run for a while enough fluorescent molecules have been incorporated to allow us to observe them as very bright dots in a microscope, reflecting the presence of a protein of interest. The more dots there more protein”, says Ola Söderberg, Ph.D., who has developed the technique together with Masood Kamali-Mogaddam, Ph.D., and their research teams.
The chain reaction does not include any enzymes, which means that it can take place at room temperature. “As no enzymes are needed, proxHCR [proximal binding with hybridization chain reaction] may be an inexpensive and robust alternative to proximity ligation assays,” wrote the investigators.
The microscopes needed to study the bright dots are relatively simple and commonly available in hospital and research labs. Since two antibodies are bound in the first step “false” signals can be avoided, making the reaction very specific for the studied protein.
“All this implies that our technique can be used as a robust and inexpensive method to localize proteins in tissues. We hope that it soon can be used both for clinical applications and for research purposes,” says Dr. Söderberg.