Biomedical Engineering Reference
In-Depth Information
7.1 Introduction
Hydrogels are three-dimensional, hydrophilic, polymeric networks
capable of imbibing large amounts of water or biological fluids.
1
Among several hydrogels, the
in situ
-forming hydrogels are based
ontheideathatifahydrogelundergoesasimpleliquid-to-gelphase
transition under physiological conditions, this biomaterial could be
prepared as a liquidandthen form the
in situ
macroscopic gelspon-
taneously at the site of injection (Fig. 7.1).
2
During the last decade, research interest has shifted from
ex vivo
-fabricated hydrogel scaffolds to
in situ
-forming hydro-
gel scaffolds, largely due to minimal invasiveness. Specifically, a
hydrogel solution at room temperature can easily incorporate
various cells and/or growth factors by simple mixing and offer
the advantage of avoiding surgical procedures to fill the tissue
void, thus facilitating patient compliance and quality of life via
comfort.
3
The method of preparing
in situ
-forming hydrogels can fall into
two main categories, self-assembly by reversible either electrosta-
tic or hydrophobic interactions and nonreversible chemical reac-
tions after introducing nonreversible covalent bonds. Among these
in situ
-forminghydrogels,wearefocusingonself-assemblinghydro-
gels, which can be formed by physical interactions in response to
biologicalconditions.
Figure 7.1.
Images of hydrogel in (a) the liquid state at 25
◦
Cand(b)the
gel state at 37
◦
C. See also Color Insert.
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