Alpha-MSH Targeted Liposomal Nanoparticle for Imaging in Inflammatory Bowel Disease (IBD).

Background: The purpose of our study was to find a novel targeted imaging and drug delivery vehicle for inflammatory bowel disease (IBD). IBD is a common and troublesome disease that still lacks effective therapy and imaging options. As an attempt to improve the disease treatment, we tested αMSH for the targeting of nanoliposomes to IBD sites. αMSH, an endogenous tridecapeptide, binds to the melanocortin-1 receptor (MC1-R) and has anti-inflammatory and immunomodulating effects. MC1-R is found on macrophages, neutrophils and the renal tubule system. We formulated and tested a liposomal nanoparticle involving αMSH in order to achieve a specific targeting to the inflamed intestines.

Methods: NDP-αMSH peptide conjugated to Alexa Fluor™ 680 was linked to the liposomal membrane via NSuccinyl PE and additionally loaded into the lumen of the liposomes. Liposomes without the αMSH-conjugate and free NDP-αMSH were used as a control. The liposomes were also loaded with ICG to track them. The liposomes were tested in DSS treated mice, which had received DSS via drinking water order to develop a model IBD. Inflammation severity was assessed by the Disease Activity Index (DAI) score and ex vivo histological CD68 staining of samples taken from different parts of the intestine. The liposome targeting was analyzed by analyzing the ICG and ALEXA 680 fluorescence in the intestine compared to the biodistribution.

Results: NPD-αMSH was successfully labeled with Alexa and retained its biological activity. Liposomes were identified in expected regions in the inflamed bowel regions and in the kidneys, where MC1-R is abundant. In vivo liposome targeting correlated with the macrophage concentration at the site of the inflammation supporting the active targeting of the liposomes through αMSH. The liposomal αMSH was well tolerated by animals.

Conclusion: This study opens up the possibility to further develop an αMSH targeted theranostic delivery to different clinically relevant applications in IBD inflammation but also opens possibilities for use in other inflammations like lung inflammation in Covid 19.