Peptides actively transported across the tympanic membrane: Functional and structural properties.

Area of Science:

• Biotechnology
• Microbiology
• Otolaryngology

Background:

• Otitis media (OM) is a common pediatric infection requiring frequent antibiotic prescriptions and surgical interventions.
• Current treatments for OM often involve invasive procedures or systemic drug administration.
• Developing noninvasive methods for delivering therapeutics to the middle ear is a significant clinical need.

Purpose of the Study:

• To identify and characterize peptides capable of transporting bacteriophage particles across the tympanic membrane (TM) into the middle ear (ME).
• To assess the physiochemical properties of these peptides that facilitate trans-TM transport.
• To evaluate the safety and efficacy of these peptide-bearing phages for potential therapeutic applications in the ME and inner ear (IE).

Main Methods:

• Screening of a genetically engineered bacteriophage library expressing random surface peptides.
• Incubation of peptide-bearing phages on the intact TM to assess transport efficiency.
• Characterization of optimal peptide features, including amino acid composition and isoelectric point.
• Application of the optimal peptide independently of phage to the TM.
• Direct application of trans-TM phages into the ME to evaluate morphological and functional effects on ME and IE structures.
• Analysis of perilymph titers to determine phage transmigration into the IE.

Main Results:

• One specific peptide demonstrated superior and time-dependent transport of phage particles across the TM into the ME.
• The optimal peptide possesses a central lysine residue, an isoelectric point of 0.0 at physiological pH, and a hydrophobic C-terminus.
• Transport across the TM was observed even when the peptide was applied independently of the phage.
• No significant morphological or functional damage to the ME or IE was detected after direct ME application of trans-TM phages.
• Mild, reversible hearing loss was observed, attributed to ME fluid, comparable to controls.
• Minimal transmigration of peptide-bearing phages from the ME into the IE was confirmed by perilymph titers.

Conclusions:

• Specific peptides can actively facilitate the transport of bacteriophage particles across the intact tympanic membrane into the middle ear.
• These trans-TM peptides exhibit favorable physiochemical properties for targeted delivery.
• The tested peptide-bearing phages appear safe for use in the middle ear, with no significant adverse effects on ME or IE morphology or function.
• These findings suggest that trans-TM peptides hold promise as noninvasive agents for delivering drugs, particles, and gene therapy vectors to the middle ear.