Krydsbinding

Krydsbinding, or crosslinking, is the process by which two or more polymer chains or molecules are linked together by chemical bonds or non-covalent interactions to form a network. This linking changes physical properties such as solubility, swelling, mechanical strength, thermal stability, and permeability. Krydsbinding is common in synthetic polymers, natural polymers, and biological systems.

Crosslinking occurs in several forms. Chemical crosslinking creates covalent bonds between chains using bifunctional or multifunctional reagents (for example glutaraldehyde, genipin, carbodiimides such as EDC/NHS, or silane reagents). Physical crosslinking relies on non-covalent interactions, such as ionic interactions (for example alginate with calcium ions), hydrogen bonding, crystallization, or metal coordination. Photocrosslinking uses light to activate a crosslinker to form bonds in situ.

Mechanism and properties: The extent of crosslinking determines network density and properties like modulus, strength, elasticity, and swelling capacity. Higher crosslink density generally yields stiffer materials with reduced solvent uptake. The choice of crosslinker and conditions also affects biocompatibility and degradation behavior.

Applications: In materials science and bioengineering, krydsbinding is used to make hydrogels for tissue engineering, wound dressings, and drug delivery systems. It also improves properties of coatings, adhesives, elastomers, and contact lens materials. In biology, crosslinking fixes cellular structures or proteins for imaging and analysis, though reagents can be cytotoxic.

Characterization and safety: Crosslink density is assessed by swelling tests, gel fraction, mechanical testing, spectroscopy, and thermal analysis. Residual reagents such as glutaraldehyde require thorough washing due to toxicity.