Mucosal Injection of the Silicon Phthalocyanine Pc 4 in a Rabbit Model-A Pilot Study.

Area of Science:

• Biomedical Engineering
• Photodynamic Therapy
• Otolaryngology

Background:

• Silicon phthalocyanine Pc 4 is a photosensitizing agent effective in photodynamic therapy (PDT) for cutaneous neoplasms.
• Preclinical studies suggest Pc 4-PDT may be a targeted treatment for human recurrent respiratory papillomatosis and laryngeal leukoplakia via direct mucosal injection.

Purpose of the Study:

• To assess the safety and tolerance of direct mucosal injection of Pc 4 into buccal and vocal fold mucosae in a rabbit model.
• To evaluate the histopathological effects of Pc 4 injection in mucosal tissues.

Main Methods:

• A proof-of-concept pilot study involving direct submucosal injection of Pc 4 and control solutions into buccal mucosa of five New Zealand white rabbits.
• Monitoring of rabbits for post-injection tolerance, including behavioral and functional assessments.
• Histopathological analysis of punch biopsies from injected buccal and laryngeal mucosa after vocal fold injection in three rabbits.

Main Results:

• Rabbits tolerated Pc 4 and control solution injections into buccal mucosa without gross inflammatory changes, behavioral alterations, or functional impairment.
• Histopathological examination revealed only mild focal inflammatory changes in Pc 4-injected buccal mucosa, with no signs of diffuse inflammation.
• Laryngeal tissue injections showed similar mild histopathological findings, including mild eosinophilia in one sample.

Conclusions:

• Direct mucosal injection of Pc 4 into rabbit buccal and vocal fold mucosae is well-tolerated.
• The procedure resulted in no gross inflammatory changes and only mild, localized histopathological inflammatory responses.
• These findings support further investigation of Pc 4-PDT as a targeted therapy for mucosal laryngeal conditions.