Table 1.
Summary of Influencing Factors for SAP Gelation
| Influencing Factors | Mechanisms | References |
|---|---|---|
| Peptide-related factors | ||
| Peptide Hydrophobicity | Peptide with high hydrophobicity is difficult to dissolve, but easier to gelate. | (Banwell et al, 2009)32 |
| Composition of Amino Acids | Peptides with high ratio of hydrophobic residues form hydrogels with better mechanical properties. | (Lutolf et al, 2003)33 |
| Peptide Concentration | Higher concentration benefits gelling. | (Hauser and Zhang, 201021; Du et al, 201512) |
| Peptide Length | Longer peptide benefits gelling. | (Fletcher et)35 |
| Amino Acid Chirality | D-peptide-based hydrogel is more stable than natural L-amino acid-based peptide. | (Schutz et al, 2015)12 |
| Peptides with Capped N- and C-Terminals | Peptides with capped N- and C-Terminals benefit gelling. | (Solaro, 2010)36 |
| Environment-related factors | ||
| Salt | Salt changes the ionic strength, thus inducing noncovalent interactions among peptides. | (Ozbas et al, 200438; Feng et al, 201237) |
| Temperature | Heating and cooling achieve highly ordered hydrogel, especially entropy-driven assembled hydrogel. | Du et al, 201512 |
| Sonication | Ultrasound breaks self-locked intramolecular hydrogen bonds or π stacking, and interlocked structures between peptide and water molecule are formed. | (Yokoi et al, 200541; Pappas et al, 201540) |
| pH | pH can affect protonation/deprotonation of basic or acidic groups in peptide. | (Hutchinson etal, 201942; Lopez-Silva etal, 2019)30 |
| Photochemical | Photo affects the gelling ability inhibited by photo-reactive groups. | (Collier et al, 2001)43 |
| Enzyme | Enzyme cleaves the enzyme-sensitive peptide to remove peptide-inhibited gelation and accelerates the degradation of SAP hydrogel. | (Lian et al, 2016)44 |