Del propio artículo enlazado en #1 su fuente en español. Como en esa fuente no he visto enlace al trabajo científico lo he buscado y aquí lo tenéis.
Las conclusiones desde su abstract:
This new SQ-based nanoformulation prevented rapid plasma degradation of LENK and conferred on the released neuropeptide a notable antihyperalgesic effect that lasted longer than after treatment with morphine in a rat model of inflammation (Hargreaves test). The biodistribution study as well as the use of brain-permeant and -impermeant opioid receptor antagonists indicated that LENK-SQ NPs act through peripherally located opioid receptors. This study represents a novel nanomedicine approach, allowing the specific delivery of LENK neuropeptide into inflamed tissues for pain control.
Parece que la cosa promete, pero el trabajo se refiere a experimentos con ratas todavía. Ya sabéis cómo es el amarillismo científico.
#4 del propio artículo científico (en la introducción, podría decirse la motivación):
The misuse of and addiction to opioids, especially morphine, is a serious national crisis in the United States (and probably also in other countries) that affects public health as well as social and economic welfare. This highlights the need to urgently find new painkillers. In this context, endogenous neuropeptides, such as enkephalin, remain an attractive option. Enkephalins activate both μ- and δ-opioid receptors, but with a 10-fold higher affinity toward δ-opioid receptors (4). Compared with μ-opioid receptor agonists, δ-opioid receptor ligands are believed to have a much lower abuse potential (5), as well as reduced respiratory (6), gastrointestinal (7), and cognitive (8) impairments.