Optimizing Ligand Valency to Maximize Tendon Accumulation of Peptide-Targeted Nanoparticles

Area of Science:

• Biomaterials Science
• Drug Delivery Systems
• Musculoskeletal Tissue Engineering

Background:

• Systemic drug delivery to musculoskeletal tissues like tendons is often inefficient.
• Targeted nanoparticle (NP) systems using tartrate-resistant acid phosphatase (TRAP) binding peptide (TBP) ligands were previously developed for tendon healing.
• TRAP activity fluctuates during tendon healing, suggesting potential for temporal therapeutic optimization.

Purpose of the Study:

• To investigate if varying ligand density on nanoparticles can optimize tendon accumulation based on TRAP levels.
• To determine the effect of ligand density on nanoparticle homing and retention within tendon tissue.
• To explore the potential of ligand density modulation for therapeutic targeting in tendon healing and pathology.

Main Methods:

• Synthesized multivalent nanoparticles with varying TBP ligand densities (9,000-55,000 per NP).
• Loaded nanoparticles with three different fluorophores for in vitro and in vivo tracking.
• Assessed nanoparticle physicochemical properties, TRAP binding affinity, and in vivo tendon homing and retention.

Main Results:

• In vitro studies showed ligand density positively correlated with TRAP binding affinity.
• Nanoparticle physicochemical properties (size, charge, PDI) were unaffected by ligand density or fluorophore.
• In vivo studies demonstrated a positive correlation between ligand density and nanoparticle homing/retention in tendons.

Conclusions:

• Nanoparticle ligand density is a critical factor for optimizing tendon targeting and retention.
• Leveraging ligand density offers a strategy for temporal therapeutic delivery across the tendon healing cascade.
• This approach holds promise for treating tendon pathologies, including tendinopathies and age-related degeneration.