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This new study could pave the way for pain relief therapies, which can assist patients with intractable pain and even cancer-related pain.
The gold nanorods measure between 1 and 100 nanometers in width and length. The nanorods were coated by the researchers with a unique type of protein, which enables fat within the body called lipoprotein to be transported.
This action allows the nanorods to effectively attach to nerve cell membranes, where pain receptors called transient receptor potential vanilloid type 1 (TRPV1) are located.
The nanorod-coated pain receptors are then exposed to near-infrared light. As the nanorods heat up, the pain receptors are activated, thus allowing an influx of calcium ions through the membrane.
When TRPV1 is activated for an extended period, desensitization occurs, which provides relief from pain. The key safety factor is that the heating of the gold nanorods only caused the activation of the TRPV1 pain receptors without interfering with the surrounding membrane.
In previous studies, magnetic nanoparticles were used to trigger TRPV1 receptors by using a magnetic field. However, for this method to be successful, the target cells need to be genetically modified.
In the iCeMS research, no genetic modification of the target cells was required. In addition, it was observed that the lipoprotein-coated gold nanorods showed an efficiency of 1000 times greater than magnetic nanoparticles, in terms of both heat generation and in triggering TRPV1 receptors.
The gold nanorods can be retained in the body for a prolonged period. Local injection of our gold nanorods might enable repetitive and on-demand treatment for people experiencing intractable pain because prior genetic engineering of the target cells is unnecessary.
Tatsuya Murakami, Associate Professor at Kyoto University
The research findings were published in Angewandte Chemie International Edition on August 6th, 2015.