cytocompatibility, enzymatic degradability by elastase, and entrapping and slow
release of a water-soluble biopolymer (Texas Red-labeled dextran with
M w ¼ 70,000). In summary, we present an easy entry to functional biohybrid
microgels, where the responsiveness to temperature and pH can be exploited further
for application of the microgel as a drug carrier.
Keywords Inverse miniemulsion Á Microgels Á Native elastin Á pH responsive Á
Thermoresponsive
Contents
1 Introduction . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . 416
2 Experimental Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418
2.1
Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418
2.2
Elastin-PEG DGE and Elastin-BS3 Microgels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418
2.3
XTT Cytotoxicity Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419
2.4
Sedimentation Analysis . . . . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . 419
2.5
Field Emission Scanning Electron Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420
2.6
UV–Visible Spectrophotometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420
2.7
Zeta Potential Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . 420
2.8
Dynamic Light Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420
2.9
Circular Dichroism Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421
2.10 Enzymatic Degradation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421
2.11 Model Drug Release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429
1 Introduction
Covalently crosslinked hydrogel particles of size in the nanometer to micrometer
range (i.e., microgels), have found increasing interest for controlled and targeted
drug delivery [1–3]. These particles are soft colloids that are swollen by the aqueous
medium in which they are dispersed. Typically, they have a gradient in the
distribution of their crosslinks, such that the corona contains more dangling ends
and the crosslinks are more densely distributed in the core. This gradient not only
results in a gradient of the swelling but also in a gradient of the solubility/solubilization, mostly due to endgroup effects [4]. Thus, if the solvent quality is
decreased, the hydrogel particles tend to collapse first in the core and maintain a
solubilizing corona. In this aspect they can be regarded as a primitive analogue to
proteins that can adopt a globular structure with the hydrophilic segments directed
towards the outside.
In the medical application of micro- and nanoparticles for the therapeutic
delivery of an active ingredient important aspects are:
416
S. Singh et al.
release of a water-soluble biopolymer (Texas Red-labeled dextran with
M w ¼ 70,000). In summary, we present an easy entry to functional biohybrid
microgels, where the responsiveness to temperature and pH can be exploited further
for application of the microgel as a drug carrier.
Keywords Inverse miniemulsion Á Microgels Á Native elastin Á pH responsive Á
Thermoresponsive
Contents
1 Introduction . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . 416
2 Experimental Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418
2.1
Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418
2.2
Elastin-PEG DGE and Elastin-BS3 Microgels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 418
2.3
XTT Cytotoxicity Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419
2.4
Sedimentation Analysis . . . . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . 419
2.5
Field Emission Scanning Electron Microscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420
2.6
UV–Visible Spectrophotometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420
2.7
Zeta Potential Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . 420
2.8
Dynamic Light Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 420
2.9
Circular Dichroism Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421
2.10 Enzymatic Degradation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421
2.11 Model Drug Release . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429
1 Introduction
Covalently crosslinked hydrogel particles of size in the nanometer to micrometer
range (i.e., microgels), have found increasing interest for controlled and targeted
drug delivery [1–3]. These particles are soft colloids that are swollen by the aqueous
medium in which they are dispersed. Typically, they have a gradient in the
distribution of their crosslinks, such that the corona contains more dangling ends
and the crosslinks are more densely distributed in the core. This gradient not only
results in a gradient of the swelling but also in a gradient of the solubility/solubilization, mostly due to endgroup effects [4]. Thus, if the solvent quality is
decreased, the hydrogel particles tend to collapse first in the core and maintain a
solubilizing corona. In this aspect they can be regarded as a primitive analogue to
proteins that can adopt a globular structure with the hydrophilic segments directed
towards the outside.
In the medical application of micro- and nanoparticles for the therapeutic
delivery of an active ingredient important aspects are:
416
S. Singh et al.