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Synthesis and Characterization of Gelatin-Based Magnetic Hydrogels.

Helminger M, Wu B, Kollmann T, Benke D, Schwahn D, Pipich V, Faivre D, Zahn D, Cölfen H - Adv Funct Mater (2014)

Bottom Line: The magnetite structure characterization is supplemented by small-angle X-ray scattering and microscopy only visualizing magnetite.SANS shows an unchanged gelatin structure of average mesh size larger than the nanoparticles with respect to gel concentration while the magnetite nanoparticles size of around 10 nm seems to be limited by the gel mesh size.Overall, the simple and variable synthesis protocol, the cheap and easy accessibility of the components as well as the biocompatibility of the gelatin-based materials suggest them for a number of applications including actuators.

View Article: PubMed Central - PubMed

Affiliation: Physical Chemistry, University of Konstanz Universitätsstrasse 10, D-78457, Konstanz, Germany.

ABSTRACT

A simple preparation of thermoreversible gelatin-based ferrogels in water provides a constant structure defined by the crosslinking degree for gelatin contents between 6 and 18 wt%. The possibility of varying magnetite nanoparticle concentration between 20 and 70 wt% is also reported. Simulation studies hint at the suitability of collagen to bind iron and hydroxide ions, suggesting that collagen acts as a nucleation seed to iron hydroxide aggregation, and thus the intergrowth of collagen and magnetite nanoparticles already at the precursor stage. The detailed structure of the individual ferrogel components is characterized by small-angle neutron scattering (SANS) using contrast matching. The magnetite structure characterization is supplemented by small-angle X-ray scattering and microscopy only visualizing magnetite. SANS shows an unchanged gelatin structure of average mesh size larger than the nanoparticles with respect to gel concentration while the magnetite nanoparticles size of around 10 nm seems to be limited by the gel mesh size. Swelling measurements underline that magnetite acts as additional crosslinker and therefore varying the magnetic and mechanical properties of the ferrogels. Overall, the simple and variable synthesis protocol, the cheap and easy accessibility of the components as well as the biocompatibility of the gelatin-based materials suggest them for a number of applications including actuators.

No MeSH data available.


Related in: MedlinePlus

Degree of hydrogel swelling plotted as a function of the swelling time at 25 °C for different samples with a gelatin concentration of 10 wt%. The equilibrium swelling degrees Sd (%) for the plotted samples are 779.2 ± 9.6 (gelatin), 1531.4 ± 62.0 (RC 1), 684.65 ± 80.84 (RC 3) and 195.64 ± 0.26 (RC 6).
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fig-8: Degree of hydrogel swelling plotted as a function of the swelling time at 25 °C for different samples with a gelatin concentration of 10 wt%. The equilibrium swelling degrees Sd (%) for the plotted samples are 779.2 ± 9.6 (gelatin), 1531.4 ± 62.0 (RC 1), 684.65 ± 80.84 (RC 3) and 195.64 ± 0.26 (RC 6).

Mentions: Swelling studies were conducted in order to probe structural changes in the gelatin network upon incorporation of the magnetite nanoparticles. To that end, the water uptake of dried gel pieces and ferrogels was measured gravimetrically, until swelling equilibrium was reached. The swelling degree (Sd) of the investigated gels is given by the following equation:4wherein Ws represents the weight of the swollen hydrogel after swelling equilibrium was reached and Wd is the dry weight of the as-prepared xerogels. The swelling experiments were performed with samples containing 6 to 18 wt% gelatin and after 1, 3, and 6 mineralization reaction cycles (RC). Figure 8 shows the swelling behavior of representative ferrogel samples with different mineral content compared to plain gelatin reference samples. It is evident that the ferrogel after 1 RC already shows a more pronounced increase in the degree of swelling compared to the neat gelatin reference. This unexpected effect might be due to the incorporation of the positively charged iron oxide nanoparticles into the polymer matrix, which can increase the osmotic pressure and therefore increase the swelling propensity of the ferrogel. On the other hand, we observe that as the amount of magnetic nanoparticles in the matrix is further increased (i.e. after 3 and 6 reaction cycles), the ferrogels show a systematically decreasing swelling tendency. This result can be attributed to an attractive interaction between the iron oxide nanoparticles and the gelatin polymer matrix, potentially involving the carboxylate groups of gelatin, which can act as iron binding sites. Hence the small crystallites can act as points of crosslinking and therefore strengthen the gelatin hydrogel structure, leading to an effective decrease of the swelling degree and thus in the gravimetric water uptake. These observations are in line with the results obtained from SANS and SAXS studies. In summary, these experiments have shown that the introduction of nanoparticles into the gelatin matrix has a pronounced effect on its swelling behavior. Therefore we conclude that the structure of the gelatin hydrogel changes with varying content of magnetic nanoparticles inside the matrix.


Synthesis and Characterization of Gelatin-Based Magnetic Hydrogels.

Helminger M, Wu B, Kollmann T, Benke D, Schwahn D, Pipich V, Faivre D, Zahn D, Cölfen H - Adv Funct Mater (2014)

Degree of hydrogel swelling plotted as a function of the swelling time at 25 °C for different samples with a gelatin concentration of 10 wt%. The equilibrium swelling degrees Sd (%) for the plotted samples are 779.2 ± 9.6 (gelatin), 1531.4 ± 62.0 (RC 1), 684.65 ± 80.84 (RC 3) and 195.64 ± 0.26 (RC 6).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4379906&req=5

fig-8: Degree of hydrogel swelling plotted as a function of the swelling time at 25 °C for different samples with a gelatin concentration of 10 wt%. The equilibrium swelling degrees Sd (%) for the plotted samples are 779.2 ± 9.6 (gelatin), 1531.4 ± 62.0 (RC 1), 684.65 ± 80.84 (RC 3) and 195.64 ± 0.26 (RC 6).
Mentions: Swelling studies were conducted in order to probe structural changes in the gelatin network upon incorporation of the magnetite nanoparticles. To that end, the water uptake of dried gel pieces and ferrogels was measured gravimetrically, until swelling equilibrium was reached. The swelling degree (Sd) of the investigated gels is given by the following equation:4wherein Ws represents the weight of the swollen hydrogel after swelling equilibrium was reached and Wd is the dry weight of the as-prepared xerogels. The swelling experiments were performed with samples containing 6 to 18 wt% gelatin and after 1, 3, and 6 mineralization reaction cycles (RC). Figure 8 shows the swelling behavior of representative ferrogel samples with different mineral content compared to plain gelatin reference samples. It is evident that the ferrogel after 1 RC already shows a more pronounced increase in the degree of swelling compared to the neat gelatin reference. This unexpected effect might be due to the incorporation of the positively charged iron oxide nanoparticles into the polymer matrix, which can increase the osmotic pressure and therefore increase the swelling propensity of the ferrogel. On the other hand, we observe that as the amount of magnetic nanoparticles in the matrix is further increased (i.e. after 3 and 6 reaction cycles), the ferrogels show a systematically decreasing swelling tendency. This result can be attributed to an attractive interaction between the iron oxide nanoparticles and the gelatin polymer matrix, potentially involving the carboxylate groups of gelatin, which can act as iron binding sites. Hence the small crystallites can act as points of crosslinking and therefore strengthen the gelatin hydrogel structure, leading to an effective decrease of the swelling degree and thus in the gravimetric water uptake. These observations are in line with the results obtained from SANS and SAXS studies. In summary, these experiments have shown that the introduction of nanoparticles into the gelatin matrix has a pronounced effect on its swelling behavior. Therefore we conclude that the structure of the gelatin hydrogel changes with varying content of magnetic nanoparticles inside the matrix.

Bottom Line: The magnetite structure characterization is supplemented by small-angle X-ray scattering and microscopy only visualizing magnetite.SANS shows an unchanged gelatin structure of average mesh size larger than the nanoparticles with respect to gel concentration while the magnetite nanoparticles size of around 10 nm seems to be limited by the gel mesh size.Overall, the simple and variable synthesis protocol, the cheap and easy accessibility of the components as well as the biocompatibility of the gelatin-based materials suggest them for a number of applications including actuators.

View Article: PubMed Central - PubMed

Affiliation: Physical Chemistry, University of Konstanz Universitätsstrasse 10, D-78457, Konstanz, Germany.

ABSTRACT

A simple preparation of thermoreversible gelatin-based ferrogels in water provides a constant structure defined by the crosslinking degree for gelatin contents between 6 and 18 wt%. The possibility of varying magnetite nanoparticle concentration between 20 and 70 wt% is also reported. Simulation studies hint at the suitability of collagen to bind iron and hydroxide ions, suggesting that collagen acts as a nucleation seed to iron hydroxide aggregation, and thus the intergrowth of collagen and magnetite nanoparticles already at the precursor stage. The detailed structure of the individual ferrogel components is characterized by small-angle neutron scattering (SANS) using contrast matching. The magnetite structure characterization is supplemented by small-angle X-ray scattering and microscopy only visualizing magnetite. SANS shows an unchanged gelatin structure of average mesh size larger than the nanoparticles with respect to gel concentration while the magnetite nanoparticles size of around 10 nm seems to be limited by the gel mesh size. Swelling measurements underline that magnetite acts as additional crosslinker and therefore varying the magnetic and mechanical properties of the ferrogels. Overall, the simple and variable synthesis protocol, the cheap and easy accessibility of the components as well as the biocompatibility of the gelatin-based materials suggest them for a number of applications including actuators.

No MeSH data available.


Related in: MedlinePlus