What is Hydrogel?
Hydrogels are defined as three-dimensional (3D) cross-linked polymeric networks, which have the ability to absorb a large amount of water and exhibit the great potential of shrinking depending upon environmental changes. In 1960, the first literary reference to a hydrogel substance was made. A biocompatible polyhydroxy ethyl methacrylate (PHEMA) hydrogel was reported by Wichterle and Lim which was explored for permanent contact application with human tissues like contact lenses, arteries, etc. Modern hydrogel material has drawn a lot of scientific attention in recent years.
Importance of Hydrogels
Hydrogels are very promising and potential candidates that have been developed over the last decades due to their unique properties such as swelling, shrinking, biocompatible, pH-responsive, etc. Promising properties of the hydrogel explored by the researchers and provide solutions to various problems.
Classification of Hydrogels
The classification of hydrogels usually depends upon their physical properties, swelling mode, manufacturing method, ionic charge, rate of biodegradation and type of crosslinking observed. Prominent hydrogels are classified based on cross-linking behavior such as:
(i) Physically cross-linked hydrogels:
The physical cross-linking method to prepare hydrogel is an attractive manufacturing method as it is a very easy and simple route that does not require any foreign reagent (cross-linking agent). The absence of cross-linkers eliminates the accumulation of unwanted materials within the hydrogel matrix and the need to remove them before use. So by adjusting the tuning of the hydrocolloid, concentration, and pH environment, hydrogel with different properties can be obtained. Because of the simplicity and practicality of physically cross-linked hydrogel networks, they are getting a lot of attention.
However, it is also important to note that hydrogels prepared by physically cross-linked hydrogel are fragile and weak as the polymeric chains are associated with weak interactions such as H-bonding, hydrophobic, and ionic interaction within the hydrogel network. The physical cross-linking method includes various methods such as heating and cooling of polymer solution, H-bonding, freezing-thawing cycles, etc.
(ii) Chemically cross-linked hydrogels :
Another widely used method to fabricate hydrogels is the chemical cross-linking method. This method occurs in the presence of a cross-linking agent which involves covalent bonding between polymer chains during polymerization. In both natural and manufactured polymers, chemical cross-linking is accomplished by the reaction of various functional groups, such as carboxyl, hydroxyl, and amine groups with cross-linkers. Various reactions are involved in the chemical cross-linking method such as click chemistry, thiol-Michael addition reaction, diels-alder cycloaddition reaction, condensation reaction, and Schiff’s base reaction, etc. Applications of Hydrogels
- Controlled Drug Delivery
- Agriculture
- Self-Healing
- Cell Delivery
- Biomedical Influence
Conclusion
Hydrogels are an essential candidate in biomedical engineering. The application has been tested in most organ systems with promising results which have already been achieved. Promising biomaterial hydrogels have been researched for possible application in drug delivery, biosensors, etc. Dr. D. Y. Patil School of Science and Technology, Tathewade campus, Pune offers B.Tech. in Computer Science and Artificial Intelligence and Data Science as having chemistry subjects with the goal of teaching students with all the recent advanced research in the field of chemistry.