2.1.8.2. Absorbency Under Load (AUL) - BADA

It would be perfect if the crosslinking agents have high selectivity and specificity for a certain
functional groups. The absence of specificity could be important in the modification of polymers
which have more than one kind of functional group, as it exists in protein molecules. Bifunctional
crosslinking reagents are categorize into three groups [22] : ……………………………….
………………………………….. …………………..………….
1- Homobifunctional crosslinking reagents include two similar functional groups which can react
with functional groups of macromolecule. …………………………………………….
2- Hetrobifunctional agents have two similar functional groups of different sensitivity and
specificity because of their neighbor structure is different and so reacts with different functional
groups of the polymer.. …………………………………………………………………………
3- Zero-length crosslinking reagents connect polymers without the addition of additional
compounds like polycondensation reaction. This type of crosslinking agents condense carboxyl
groups with primary amino, carboxylic, hydroxyl and thio groups to forms of amide, ester and
thio-ester components (Fig.9). Hence, zero-length crosslinking reagents are employed in protein
structure with various functional groups.
The use of chemical crosslinking reagents is important not only for joining two macromolecules to
form of hydrogels but also for immobilizing bioactive components, such enzymes and drugs, to
water-soluble polymers or hydrogel matrixes [16] .
OXIDATION
Figure 9. Hydrogel formation of polysaccharides through cysteine-derivatization [16]
22