Therapeutic effect of local photothermal heating of gold nanoparticle-coated self-expandable metallic stents for suppressing granulation tissue formation in the mouse colon

Abstract

Purpose To investigate the therapeutic effect of local photothermal (PT) heating on suppression of stent-induced granulation tissue formation in mouse colon. Materials and methods A gold nanoparticle (GNP)-coated self-expandable metallic stent (SEMS) was prepared using a two-step synthesis process for local PT heating under near-infrared laser irradiation. Twenty-four mice were randomly divided into two groups of 12 and subjected to SEMS placement in the colon. Group A received a GNP-coated SEMS without local heating and Group B received a GNP-coated SEMS and underwent local heating at 55◦C after SEMS placement. The therapeutic effect of local heating was assessed by comparing the histopathological, immunohistochemical, and endoscopic results. Results Four mice were excluded because of stent migration (n = 3, group B) or death (n = 1, group A). Stent-induced granulation tissue-related variables were significantly lower in group B than in group A (p < 0.001). In vivo endoscopic images, 4 weeks after stent placement, showed granulation tissue formation over the wire mesh in group A and relatively good patency of the stented colon with no definite irregularities in group B. There was more vascular endothelial growth factor (VEGF) positivity in group A than in group B. Conclusion Local PT heating suppresses granulation tissue formation after stent placement in mouse colon.