| Summary: | Thermoresponsive
hydrogels are three-dimensional polymer networks which undergo conformational
changes in aqueous media depending on the external temperature. As the lower
critical temperature (LCST) is close to the body temperature,
poly(N-isopropylacrylamide) (PNIPAM) is the main thermoresponsive hydrogel used
for biomedical applications. Below LCST, PNIPAM hydrogels swell in aqueous
media, above LCST they become insoluble and shrink. This behavior makes it
possible to design drug release systems controlled by external temperature.
Swelling/shrinking response of PNIPAM hydrogel depends on several factors such
as crosslinker type, crosslinking density, hydrophobic/hydrophilic balance and
initiator type. In this study, the effects of the initiation system and the
crosslinker type on different thermoresponsive hydrogels were compared. For
this purpose, thermoresponsive hydrogels were synthesized by using ethylene
glycol dimethylacrylate (EGDMA) and N,N′-ethylene bisacrylamide (EBAM) as
crosslinkers via photo and thermal initiation systems. The hydrogels were
characterized by scanning electron microscope (SEM) and FTIR spectroscopy. Effects
of the initiation system and the crosslinker type on the release, swelling
behavior, morphology and the biocompatibility behavior of the hydrogels were
investigated. The hydrogels synthesized with EBAM demonstrated more promising
results compared to the one synthesized EGDMA. It was concluded that poly(EBAM-co-NIPAM)-P
has the highest swelling ratio and poly(EBAM-co-NIPAM)-T is the most
biocompatible hydrogel. In terms of release characteristics, there was not a
significant difference between the hydrogels, even though their swelling
characteristics differ.
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