Cross-linked microcapsules formed from self-deactivating reactive polyelectrolytes.

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Hydrogel Engineering

Background:

• Calcium alginate capsules are widely used but can be susceptible to chemical degradation.
• Surface modification is crucial for enhancing capsule stability and functionality.
• Poly(methyl vinyl ether-alt-maleic anhydride) (PMM) offers reactive anhydride groups for cross-linking.

Purpose of the Study:

• To create robust, shell-cross-linked hydrogel capsules with enhanced chemical resistance.
• To investigate the use of partially hydrolyzed PMM and poly-L-lysine (PLL) for capsule coating.
• To assess the protein-binding resistance and permeability of the modified capsules.

Main Methods:

• Partial hydrolysis of PMM(0) to PMM(50) in a acetonitrile-d(3)/D(2)O mixture.
• Coating of PMM(50) onto poly-L-lysine (PLL)-coated calcium alginate capsules.
• Monitoring hydrolysis kinetics using potentiometry and assessing shell properties via microscopy and chemical challenges.

Main Results:

• The PMM(50)-PLL interaction formed a stable, shell-cross-linked hydrogel capsule resistant to sodium citrate and sodium hydroxide.
• Residual anhydride groups on PMM(50) were rapidly hydrolyzed, preventing undesired protein binding.
• Capsule resilience improved with higher PLL concentration and lower PMM(50) molecular weight.
• Capsule permeability to dextrans was comparable to standard alginate-PLL-alginate (APA) capsules.

Conclusions:

• Partially hydrolyzed PMM, when cross-linked with PLL, forms highly stable hydrogel capsules.
• The developed capsules demonstrate excellent chemical resistance and minimal protein adsorption.
• These modified capsules show promise for applications requiring robust and non-fouling biomaterials.