The competitive adsorption of gelatin and sodium dodecylbenzenesulfonate (SDBS) at hydrophobic surfaces was investigated with surface and interfacial tension measurements, ellipsometry, surface plasmon resonance spectroscopy (SPR), and total internal reflectance fluorescence spectroscopy (TIRF). From both ellipsometry and SPR, initial additions of SDBS after gelatin preadsorption were found to result in a total adsorbed amount increase, as well as in a swelling of the adsorbed layer. At higher SDBS concentrations, both the total adsorbed amount and the amount of gelatin adsorbed decrease, which was observed from ellipsometry, SPR, and TIRF. From surface and interfacial tension measurements, it was found that the critical aggregation concentration (cac) for the SDBS-gelatin system decreases with decreasing pH. Analogous to this, ellipsometry, SPR, and TIRF indicate that the SDBS concentration required to cause a significant decrease in the gelatin adsorbed amount decreases with decreasing pH. The desorption therefore seems to be correlated to the SDBS binding to the adsorbed gelatin molecules rather than to purely competitive adsorption.

Gelatin nanofibrous structures, characterized by high specific surface area and high porosity, have been widely researched for biomedical and food applications. The present paper researches the potential of electrospinning to produce a nanofibrous cold-gelling (or instant) gelatin product. Our results show that gelatin nanofibers are cold-water-soluble due to their high surface-to-volume ratio, facilitating easy water penetration and dissolution, and this for several gelatin types. Additionally, fast gelation after dissolution in cold water indicates that the electrospinning process does not significantly reduce the gelatin molecular weight, nor compromise triple helix formation. These conclusions were supported by thorough investigation of the internal gelatin structure, using a new approach based on modulated temperature scanning calorimetry. Oscillation rheology revealed that the nanofiber-based gels have moduli comparable to powder-based gels. Gelatin nanofibers can thus be used as instant gelatin product, without the drawbacks of traditional amorphous instant gelatins such as sensitivity to moisture, low wettability and low modulus of the cold gel. Using the approach reported here, every electrospinnable, but non-cold-water-soluble gelatin can be transformed into a cold-water-soluble variant, regardless of the type or modification. Electrospinning can thus offer enormous flexibility in materials selection, enabling the production of cold gels loaded with temperature-sensitive components, UV-cross-linkable cold gels, etc.

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In the medical device sector, bloom index and residual endotoxins should be controlled, as they are crucial regulators of the device’s physicochemical and biological properties. It is also imperative to identify a suitable crosslinking method to increase mechanical integrity, without jeopardising cellular functions of gelatin-based devices. Herein, gelatin preparations with variable bloom index and endotoxin levels were used to fabricate non-crosslinked and polyethylene glycol succinimidyl glutarate crosslinked gelatin scaffolds, the physicochemical and biological properties of which were subsequently assessed. Gelatin preparations with low bloom index resulted in hydrogels with significantly (p < 0.05) lower compression stress, elastic modulus and resistance to enzymatic degradation, and significantly higher (p < 0.05) free amine content than gelatin preparations with high bloom index. Gelatin preparations with high endotoxin levels resulted in films that induced significantly (p < 0.05) higher macrophage clusters than gelatin preparations with low endotoxin level. Our data suggest that the bloom index modulates the physicochemical properties, and the endotoxin content regulates the biological response of gelatin biomaterials. Although polyethylene glycol succinimidyl glutarate crosslinking significantly (p < 0.05) increased compression stress, elastic modulus and resistance to enzymatic degradation, and significantly (p < 0.05) decreased free amine content, at the concentration used, it did not provide sufficient structural integrity to support cell culture. Therefore, the quest for the optimal gelatin crosslinker continues.

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