London, Feb 15 (IANS): Researchers have developed a new painkiller using nanoparticles that lasts longer than morphine, paving the way for intense pain treatments without the severe side effects associated with opioids.

Chronic pain is a major global heath challenge and its most common medications are morphine and synthetic opioids, which have severe side effects like addiction.

Researchers, including Jiao Feng from the Universite Paris-Saclay in France, tested the nano-painkiller in rodents as an alternative to morphine.

In the study, published in the journal Science Advances, three versions of their natural nanoparticle showed anti-pain effects when administered to inflamed rat paws.

The team focused on small, naturally occurring peptides in the body like enkephalin, which bind to the body's opioid receptors. These peptides are an appealing option to treat pain because they activate d-opioid receptor ligands, which are thought to have a lower abuse potential than the receptors that morphine activates.

However, enkephalin-based approaches have not been adopted in the clinic because of the inability of these peptides to penetrate the blood-brain barrier.

In search of a better solution to control pain, the team developed a new nano-drug using Leu-enkephalin (LENK) neuropeptides.

By connecting LENK to squalene -- a natural and biocompatible lipid -- the team created nanoparticles that could be precisely delivered to the area of pain through intravenous injection.

These LENK-squalene nanoparticles act through peripherally located opioid receptors, which have a lower abuse potential than what morphine activates.

Four hours after the drug was administered, the researchers saw signs of reduced thermal sensitivity to pain in all treated rats.

Additionally, the drug's pain-alleviating effect lasted longer than that achieved with morphine, the researchers said, adding that it showed no indication of toxicity.