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Updated: Feb 14, 2026

Injectable Supramolecular Polymer-Nanoparticle Hydrogels for Cell and Drug Delivery Applications
Published on: February 7, 2021
Self-healing hydrogels formed by complexation between calcium ions and bisphosphonate-functionalized star-shaped
Paula M Lopez-Perez1,2, Ricardo M P da Silva3, Iossif Strehin1
1Biomedical Engineering Department, Materials Science and Engineering Department, Chemical and Biological Engineering Department, Chemistry of Life Processes Institute, Institute for Bionanotechnology in Medicine, Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Evanston, IL, USA.
Abstract:
Star-shaped poly(ethylene glycol) (PEG) chain termini were functionalized with alendronate to create transient networks with reversible crosslinks upon addition of calcium ions. The gelation ability of alendronate-functionalized PEG was greatly dependent on the number of arms and arm molecular weight. After mixing polymer and calcium solutions, the formed hydrogels could be cut and then brought back together without any visible interface. After 2 minutes of contact, their connection was strong enough to allow for stretching without tearing through the previous fracture surface. Oscillatory rheology showed that the hydrogels recovered between 70 and 100% of the original storage and loss modulus after rupture. Frequency sweep measurements revealed a liquid-like behavior at lower frequencies and solid-like at high frequencies. Shifting frequency curves obtained at different calcium and polymer concentrations, all data collapsed in a single common master curve. This time-concentration superposition reveals a common relaxation mechanism intrinsically connected to the calcium-bisphosphonate complexation equilibrium.
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