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Updated: Aug 14, 2025
Characterization of Intra-Cartilage Transport Properties of Cationic Peptide Carriers
Published on: August 10, 2020
Modeling Electrostatic Charge Shielding Induced by Cationic Drug Carriers in Articular Cartilage Using Donnan Osmotic
Matthew R Warren1, Ambika G Bajpayee1,2
1Department of Bioengineering and Northeastern University, Boston, Massachusetts, USA.
Background:
Positively charged drug carriers are rapidly emerging as a viable solution for long-standing challenges in delivery to dense, avascular, negatively charged tissues. These cationic carriers have demonstrated especially strong promise in targeting drugs to articular cartilage for osteoarthritis (OA) treatment. It is critical to evaluate the dose-dependent effects of their high intratissue uptake levels on charge-shielding of anionic matrix constituents, and the resulting changes in tissue osmotic swelling and mechanical integrity.
Materials And Methods:
We use the ideal Donnan osmotic theory to derive a model for predicting intracartilage swelling pressures as a function of net charge (z) and equilibrium uptake of short-length, arginine-rich, multivalent, cationic peptide carriers (cationic peptide carriers [CPCs], z varied from +8 to +20) in cartilage samples with varying arthritic severities and fixed charge density (FCD). We use this model to determine the dose-dependent influence of CPCs on both physiological osmotic swelling pressures and compressive electrostatic moduli of cartilage in healthy and arthritic states.
Results:
Under physiological conditions, the Donnan model predicted carrier-induced reductions in free swelling pressure between 8 and 29 kPa, and diminished compressive modulus by 20-68 kPa, both dependent on the net charge and uptake of CPCs. The magnitudes of deswelling and stiffness reduction increased monotonically with carrier uptake and net charge. Furthermore, predicted levels of deswelling by CPC charge shielding were amplified in tissues with reduced FCD (which model OA). Finally, the Donnan model predicted markedly higher reductions in tissue compressive modulus in hypotonic bathing salinity compared with physiological and hypertonic conditions.
Conclusion:
This analysis demonstrates the importance of considering charge shielding as a likely adverse effect associated with uptake of cationic drug carriers into negatively charged tissues, especially in the case of damaged tissue. The simple modeling approach and principles described herein can inform the design of cationic drug delivery carriers and their clinical treatment regimens.
Insights
Positively charged drug carriers show promise for osteoarthritis treatment but can negatively impact cartilage. This study models how these carriers affect cartilage swelling and mechanical properties, highlighting potential adverse effects in damaged tissues.
Area of Science:
- Biomaterials Science
- Drug Delivery
- Tissue Engineering
Background:
- Positively charged (cationic) drug carriers are promising for delivering drugs to negatively charged tissues like articular cartilage.
- Challenges remain in understanding the dose-dependent effects of these carriers on tissue integrity, particularly in osteoarthritis (OA).
- Evaluating the impact on charge shielding, osmotic swelling, and mechanical properties is critical for safe and effective OA treatment.
Purpose of the Study:
- To model the effects of cationic peptide carriers (CPCs) on cartilage swelling pressure and mechanical integrity.
- To determine the dose-dependent influence of CPCs on cartilage in healthy and arthritic states.
- To investigate how carrier charge and uptake affect tissue properties under varying conditions.
Main Methods:
- Utilized ideal Donnan osmotic theory to develop a predictive model for intracartilage swelling.
- Investigated swelling pressures and compressive moduli as a function of CPC net charge and equilibrium uptake.
- Modeled effects in cartilage with varying degrees of arthritis and fixed charge density (FCD).
Main Results:
- Donnan model predicted significant reductions in swelling pressure (8–29 kPa) and compressive modulus (20–68 kPa) under physiological conditions.
- These reductions increased monotonically with CPC uptake and net charge.
- Charge shielding effects were amplified in tissues with reduced FCD (modeling OA) and were more pronounced in hypotonic conditions.
Conclusions:
- Charge shielding by cationic drug carriers is a significant adverse effect in negatively charged tissues, especially damaged ones.
- The modeling approach provides insights into designing safer cationic carriers for drug delivery.
- Findings can inform clinical treatment regimens for osteoarthritis using targeted drug delivery systems.
