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The human amniotic membrane (HAM) is one of the rare allograft tissues that are in use in clinical trials. Biocompatibility, antibacterial effect, low immunogenicity, and scar prevention are properties that have made HAM attractive for tissue engineering (TE) applications, for example, as a cell carrier, injectable hydrogel, and cell culture substrate. In this research, the effect of digestion time on the structure, gelation kinetics, rheological and biological properties of amniotic membrane-derived hydrogels was studied. The results determined that digestion with pepsin should be performed at least for 24 h.  Prolonging the digestion time to 72 h increased the shear modulus, fiber diameter, and gelation rate. Cytocompatibility assays with L929 fibroblast cells showed that the digestion time had no effect on the cell toxicity of the hydrogels. However, cell proliferation was improved due to preserved constitutive bioactive molecules. The results of this research can be used to develop amniotic membrane-derived hydrogels for TE applications.

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The aim of this work was to develop an enriched apple jelly with Spirulina sp. Four formulations were developed: C, J1, J2, J3 with 0, 0.75, 1.5 and 3% Spirulina sp. and their rheological, textural, color and sensorial properties were evaluated. The results showed that all samples presented predominant behavior of the elastic solid. Also, the non-intersection of the loss and storage modulus curves at the applied frequencies showed the behavior of a typical gel. Also, in all samples, the dependence of the storage modulus on the frequency was not observed, but in larger frequencies, especially the storage modulus of sample with higher percentage of spirulina algae, decreased, indicating a more liquid behavior. Indicators n and m also confirmed such behavior, decreasing the strength of gel structure with increasing spirulina concentration. The data obtained from the force-time curve showed that even though the variables of all samples were within the range of a typical jelly, but increasing spirulina algae content decreased the hardness, adhesiveness elasticity, gumminess and increased cohesiveness. These results follow the trend of those obtained by dynamic rheology. Also, the results related to the sample color showed that the addition of spirulina in 1.5 and 3% percentages significantly decrease the variables L*, b* and C* especially in the sample with 3% algae, presenting a darker sample. The overall color difference between the samples also was more than 6 degrees, which detected different color groups. Sensorial scores of samples, mainly color and overall acceptance also reduced with increasing the percentage of microalgae.
In general, it can be concluded that incorporating of Spirulina in the apple jelly regarding to its negative effect on the most evaluated parameters, requires further research and a better understanding of its gel formation mechanism to optimize the formulation and process treatments.