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We have previously shown that gelatin addition to calcium phosphate bone cement improves its mechanical properties. To clarify the role of gelatin on the setting reaction of the cement, we carried out powder X-ray diffraction, DSC, TG, and SEM investigations on samples frozen after different times of soaking in simulated body fluid (SBF). The results indicate that the onset of the setting reaction is under the control of CaHPO4·2H2O, which is contained in small amounts (5 wt %) in the α-tricalcium phosphate (α-TCP) cement, whereas the accelerating role of gelatin becomes the key factor just in a second step of the setting reaction. Gelatin controls the transformation of α-TCP into calcium deficient apatite (CDHA) and produces a composite biomimetic material with a close relationship between gelatin and CDHA crystals, which resembles that between collagen and apatite crystals in bone. With respect to the control cement, which does not contain gelatin, the gelatin−cement after setting exhibits reduced crystallinity, much smaller CDHA crystals, and a more compact microstructure, which can account for the improved mechanical properties.

In vitrobioactivity of gelatin sponges and hydroxyapatiteenriched gelatin sponges was tested through evaluation of the variations in their composition and morphology after soaking in simulated body fluid 1.5 for periods up to 21 days at 37°C. The presence of hydroxyapatite inside the sponges promotes the deposition of bonelike apatite crystals. The deposits are laid down as spherical aggregates, with mean diameters increasing from about 1–2 μm, after 4 days of soaking in simulated body fluid solution, up to about 3.5 μm in the samples soaked for 21 days. Simultaneously, the relative amount of inorganic phase increases up to about 56 wt, leading to a composite material with a composition quite close to that of bone tissue. The inorganic phase is a poor crystalline carbonated apatite similar to trabecular bone apatite. © 2001 Wiley Periodicals, Inc. J Biomed Mater Res 59: 709–714, 2002

The results of this paper indicate that poly(acrylic acid)s of different molecular weights (PAA2, Mw = 2000; PAA250, Mw = 250 000) inhibit the hydrolysis of octacalcium phosphate (OCP) into hydroxyapatite (HA) to an extent that depends on their concentration in solution, as well as on their molecular weights. This inhibition, which takes place through poly(acrylic acid) adsorption on OCP crystals, is more effective for PAA2 than for PAA250. The significant increase of the roughness of the OCP crystal surface after adsorption of PAA250, put into evidence by AFM images, and the decrease of the coherence lengths of the perfect crystalline domains along the c-axis direction of OCP crystals after adsorption of PAA2 suggest that the shorter length of PAA2 molecules allows a greater and more ordered interaction with the hydrated layers of the (100) face of OCP. The results of TEM investigation suggest that OCP hydrolysis occurs according to a layer-to-layer mechanism that implies splitting into smaller crystals and accounts for the platelet-like morphology of the final apatitic crystals.

Gelatin films were used as biomimetic substrates for the nucleation of hydroxyapatite from simulated body fluid (SBF). Stretching and presence of sodium polyacrylate appear to be essential factors for the specific nucleation and growth of hydroxyapatite crystals inside the films. After soaking in 1.5SBF for periods longer than 4 days, all the films display a completely calcified surface. However, the spherical aggregates on the film surfaces do not give any X-ray diffraction effect and exhibit a low Ca/P molar ratio, typical of amorphous calcium phosphate. The ordered deposition of crystalline hydroxyapatite has been verified to take place only in stretched polyacrylate−gelatin films. The crystals grow as tablets about 2 μm thick among the gelatin layers, with their crystallographic c-axes preferentially oriented parallel to the direction of orientation of the collagen molecules, thus resembling the parallel orientation of apatitic crystals and collagen fibrils in calcified biological tissues.

Biobased polymers represent a sustainable alternative for packaging materials. Gelatin, obtained by chemical-thermal degradation of collagen, is one of the most used biopolymers thanks to its biodegradability, excellent biocompatibility, plasticity, adhesiveness, abundance, and low cost. In particular, gelatin-based films are thin, flexible, and transparent biodegradable materials, useful in engineering food, packaging, drug recover, and other applications. The main drawback of gelatin as a material is its poor mechanical performance, that can be improved through crosslinking or by combining the biopolymer with an inorganic filler. To this aim, the possibility to modulate solubility and mechanical properties of gelatin films through the use of natural, non-toxic, crosslinking agents has been explored. Recent results obtained on gelatin films enriched with different amounts of Na-MMT, and GO allow to establish the role of the nanofillers on the mechanical, structural, morphological and swelling properties, as well as on the water vapor permeability and stability in aqueous environment, of the composite films. Moreover, the effect of sterilization performed by g-irradiation on the mechanical, structural and stability properties of gelatin films has been investigated. The obtained results could be very promising for the development of multifunctional gelatin films as packaging materials. [ABSTRACT FROM AUTHOR]