Hydrogels Flashcards
What is a Hydrogel?
Hydrogels are three-dimensional insoluble macromolecular networks of polymer chains that swell in water
What are Hydrogels in Biosensing?
1) bioreceptor immobilization -> high loading due to 3D properties
2) visual indication of target detection
3) provide solution-like environment
4) responsive material
What are the classification of hydrogels? based on sources and crosslinks
1) Based on source: Synthetic or Natural
2) based on crosslinks: Physical or chemical
What are the advantages of natural hydrogels?
1) Recognition and degradation by body
2) Binding of biomolecules like growth factors
and proteins
3) Chemically-modified versions introduce tailorability
What are the disadvantages of natural hydrogels?
1) immunogenicity
2) Synthetic challenges
3) Batch-to-batch variation
What are the advantages of synthetic hydrogels?
1) tailorable for preferred properties – easier to specialize
2) Reproducibility (through synthesis and purification)
3) Easier to incorporate intelligence – smart polymers (pH or temp sensitive)
What are the disadvantages of synthetic hydrogels?
1) Toxicity and chronic inflammation
2) Poor clearance of degradation products (Accumulate in lymph nodes)
What are Physically-Crosslinked hydrogels?
Reversible crosslinks formed by molecular entanglements or intermolecular forces (Van der
Waals, ionic crosslinks, H-bonding, hydrophobic
interactions)
Gelation can be reversed by changing physical
conditions: pH, temperature, mechanical stress,
solute concentration, adding EDTA
Like agarose
What are Chemically-Crosslinked hydrogels?
Irreversible crosslinks formed by covalent bonds
between polymer chains.
Crosslinks formed by adding crosslinkers,
irradiation, reaction with functional groups, free radical polymerzation, etc
How to manipulate agarose?
Agarose is thermo reversible. Therefore, it is physically crosslinked. It can be manipulated by varying the agarose concetration which changes the mesh structure.
Why is chemically cross-linked hydrogels are better?
Because it offers higher homogeneity as, greater thermodynamic and, mechanical stability
What are the types of chemical crosslinking for hydrogels?
1) crosslinking molecules
2) polymer - polymer / hybrid polymer
3) photosensitive agents or changes in the initiation conditions
4) Enzymatic crosslinks
What are some of the strategies used for chemical cross linking of hydrogels?
1) copolymerisation of a monomer
2) crosslinking of hydrophilic polymers via radiation or chemical crosslinkers
3) Crosslinking hydrophilic polymers through reaction between functional groups
What is Stop -flow lithography (SFL)?
A setup which uses compressed air driven flows to synthesize hydrogel particles in microfluidic
channels.
