TY  - JOUR
A1  - Wöhl-Bruhn, Stefanie
A1  - Badar, Muhammad
A1  - Bertz, Andreas
A1  - Tiersch, Brigitte
A1  - Koetz, Joachim
A1  - Menzel, Henning
A1  - Müller, Peter P.
A1  - Bunjes, Heike
T1  - Comparison of in vitro and in vivo protein release from hydrogel systems
JF  - Journal of controlled release
N2  - Hydrogel systems based on hydroxyethyl starch-polyethylene glycol methacrylate (HES-P(EG)(6)MA) or hydroxyethyl starch methacrylate (HES-MA) were used to assess the protein release behavior. Here, we analyzed the in vitro release of FITC-anti-human antibodies incorporated in either HES-P(EG)(6)MA or HES-MA hydrogel delivery systems in PBS or human serum. In addition, hydrogel disks and microparticles prepared from the two polymers were subcutaneously implanted in BALB/c mice. The in vivo release of FITC-IgG was non-invasively monitored by an in vivo imaging system (IVIS 200) over a time period of up to 3 months. The imaging system allowed to asses individual animals over time, therefore only a small number of animals was required to obtain high quality data. The reduction in fluorescence intensity at the site of administration was compared to in vitro release profiles. These investigations demonstrated a sustained release from HES-MA hydrogel disks compared to rapidly degrading HES-P(EG)(6)MA disks and microparticles. The sustained release from HES-MA disks could be further optimized by using increased polymer concentrations. Human serum as in vitro release medium reflected better the in vivo release from HES-P(EG)(6)MA systems than PBS, suggesting that the presence of organic substances like proteins or lipids may play a significant role for the release kinetics.
KW  - In vivo imaging system (IVIS)
KW  - Hydrogel disks
KW  - Hydrogel microparticles
KW  - Release
KW  - In vivo-in vitro correlation
KW  - Hydroxyethyl starch (HES)
Y1  - 2012
U6  - https://doi.org/10.1016/j.jconrel.2012.05.049
SN  - 0168-3659
VL  - 162
IS  - 1
SP  - 127
EP  - 133
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Bertz, Andreas
A1  - Wöhl-Bruhn, Stefanie
A1  - Miethe, Sebastian
A1  - Tiersch, Brigitte
A1  - Koetz, Joachim
A1  - Hust, Michael
A1  - Bunjes, Heike
A1  - Menzel, Henning
T1  - Encapsulation of proteins in hydrogel carrier systems for controlled drug delivery influence of network structure and drug size on release rate
JF  - Journal of biotechnology
N2  - Novel hydrogels based on hydroxyethyl starch modified with polyethylene glycol methacrylate (HES-P(EG)(6)MA) were developed as delivery system for the controlled release of proteins. Since the drug release behavior is supposed to be related to the pore structure of the hydrogel network the pore sizes were determined by cryo-SEM, which is a mild technique for imaging on a nanometer scale. The results showed a decreasing pore size and an increase in pore homogeneity with increasing polymer concentration. Furthermore, the mesh sizes of the hydrogels were calculated based on swelling data. Pore and mesh size were significantly different which indicates that both structures are present in the hydrogel. The resulting structural model was correlated with release data for bulk hydrogel cylinders loaded with FITC-dextran and hydrogel microspheres loaded with FITC-IgG and FITC-dextran of different molecular size. The initial release depended much on the relation between hydrodynamic diameter and pore size while the long term release of the incorporated substances was predominantly controlled by degradation of the network of the much smaller meshes.
KW  - Hydrogel
KW  - Hydrogel microspheres
KW  - Network structure
KW  - Release studies
KW  - Protein delivery
KW  - Mesh size
Y1  - 2013
U6  - https://doi.org/10.1016/j.jbiotec.2012.06.036
SN  - 0168-1656
VL  - 163
IS  - 2
SP  - 243
EP  - 249
PB  - Elsevier
CY  - Amsterdam
ER  -