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Updated: Jul 15, 2026
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Injectable Supramolecular Polymer-Nanoparticle Hydrogels for Cell and Drug Delivery Applications
Published on: February 7, 2021
Evaluation of novel injectable hydrogels for nucleus pulposus replacement
J Vernengo1, G W Fussell, N G Smith
1Department of Chemical and Biological Engineering, Biomaterials and Drug Delivery Laboratory, Drexel University. Philadelphia, Pennsylvania 19104, USA.
Summary
Branched copolymers of poly(N-isopropylacrylamide) (PNIPAAm) and poly(ethylene glycol) (PEG) show promise for nucleus pulposus replacement. Higher PEG content enhanced elasticity and water content, identifying PNIPAAm-PEG (4600 g/mol) as a leading candidate.
Area of Science:
- Biomaterials Science
- Polymer Chemistry
- Orthopedic Research
Background:
- Intervertebral disc degeneration necessitates novel tissue engineering solutions.
- Current treatments for nucleus pulposus (NP) defect lack ideal in situ formation and mechanical properties.
- Branched copolymers offer tunable properties for potential NP replacement.
Purpose of the Study:
- To synthesize and characterize branched PNIPAAm-PEG copolymers for NP replacement.
- To investigate the influence of PEG molecular weight and content on copolymer properties.
- To evaluate copolymer suitability for in situ formation and mechanical performance.
Main Methods:
- Synthesis of PNIPAAm-PEG branched copolymers with varying PEG molecular weights and ratios.
- In vitro characterization of gel swelling, dissolution, and mechanical properties (compressive, stress relaxation) over 30-90 days.
- Evaluation of elasticity and water content in relation to copolymer composition.
Main Results:
- NIPAAm to PEG molar ratio did not significantly impact equilibrium swelling or compressive mechanics.
- Increased PEG molecular weight and content led to higher equilibrium water content and decreased compressive modulus.
- All branched copolymers exhibited enhanced stress relaxation compared to homopolymers.
- PNIPAAm-PEG copolymers with higher PEG content (4600 and 8000 g/mol) demonstrated maximum elasticity.
Conclusions:
- PNIPAAm-PEG branched copolymers are viable candidates for nucleus pulposus replacement.
- PEG molecular weight and content are critical for tuning gel elasticity and water retention.
- PNIPAAm-PEG (4600 g/mol) shows optimal characteristics (high water content, stiffness, elasticity) for further evaluation.
