title: Hybrid processes in enzymatically gelled gelatin: impact on , macroscopic properties and cellular response.
abstract: Physical, chemical and hybrid tilapia fish gelatin hydrogels were investigated by small-angle neutron scattering (), molecular dynamic simulations and their biological effect in cell cultures studied; results from the different experimental techniques were then correlated and linked to the rheological properties of the gels (F. Bode et al., Biomacromolecules, 2011, 12, 3741-3752). Hydrogels were obtained by cross-linking with the microbial enzyme transglutaminase (mTGase) under two conditions: above and below gelatin physical temperature (ca. 23 °C). Hydrogels cross-linked at 37 °C, from the sol-state, are referred to as 'chemical' gels (C); hydrogels cross-linked at 21 °C, thus with concurrent physical , are referred to as 'physical-co-chemical' gels (PC). The data were appropriately described by a combination of a Lorentzian and a power law model. For physical gels, the correlation length (ξ) obtained from the fits decreased linearly with gelatin concentration, from 42 to 26 Å for 3.5 to 10% w/w gelatin, respectively. Independently of temperature, all physical gels at a given concentration showed a similar correlation length ξ (26 ± 2 Å), with no significant difference with the sol-state (23 ± 2 Å). In both C and PC gels, ξ increased with mTGase concentration over the range studied: 40 to 167 Å for 10 and 40 U mTGase per g gelatin in C gels (after 120 min cross-linking) and 40 to 82 Å for 10 and 40 U mTGase per g gelatin for PC gels. ξ reached a plateau at the highest mTGase concentration studied for both types of gels. In addition, kinetic studies on C gels revealed that ξ increased linearly with time in the first two hours and grew faster with increasing mTGase concentration. ξ values in the PC gels were smaller than in the corresponding C gels. Cell proliferation studies showed that the gels were compatible with cell growth and indicated no statistically relevant dependence on mTGase concentration for C gels. For PC gels, cell proliferation decreased with increases in mTGase concentration, by approximately 80% from 10 to 40 U mTGase per g gelatin. With the exception of the highest mTGase concentration studied, PC gels overall showed a slightly (but statistically significant) higher cell proliferation than the corresponding chemical gels.
authors.affiliation: Institute of Pharmaceutical Science, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, UK. cecile.dreiss@kcl.ac.uk.
authors.forename: Franziska
authors.initials: F
authors.lastname: Bode
authors.affiliation: Institute of Pharmaceutical Science, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, UK. cecile.dreiss@kcl.ac.uk.
authors.forename: Marcelo Alves
authors.initials: MA
authors.lastname: da Silva
authors.affiliation: Theory & Simulation of Condensed Matter Group, Department of Physics, King's College London, Strand, London WC2R 2LS, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Smith
authors.affiliation: Theory & Simulation of Condensed Matter Group, Department of Physics, King's College London, Strand, London WC2R 2LS, UK.
authors.forename: Christian D
authors.initials: CD
authors.lastname: Lorenz
authors.affiliation: Department of Materials, Department of Bioengineering and Institute for Biomedical Engineering, Imperial College London, Exhibition Road, London SW72AZ, UK.
authors.forename: Seth
authors.initials: S
authors.lastname: McCullen
authors.affiliation: Department of Materials, Department of Bioengineering and Institute for Biomedical Engineering, Imperial College London, Exhibition Road, London SW72AZ, UK.
authors.forename: Molly M
authors.initials: MM
authors.lastname: Stevens
authors.affiliation: Institute of Pharmaceutical Science, King's College London, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, UK. cecile.dreiss@kcl.ac.uk.
authors.forename: Cécile A
authors.initials: CA
authors.lastname: Dreiss