3D Printing of Gelatin/Alginate Based Hydrocolloids as Delivery Systems for Food and Pharmaceutical Applications

3D printing technology has been applied in bioprinting to fabricate three-dimensional matrices to upload living cells, biomaterials, and active ingredients, thus protecting the encapsulated active compounds. Food-grade, protein-based hydrocolloids such as gelatin, collagen, and carrageenan have been used as bioprinting materials and thickening/gelling agents commonly used in the food industry; however, the research of this area is still in its infancy. The objective of this series of studies was to investigate the feasibility of developing a 3D printed, hydrocolloid-based delivery system for active ingredients in the areas of food and pharmaceutical applications. Hydrogels were prepared using alginate and gelatin (A/G) with total solids (w/w%) of 3%, 5%, and 7% at A/G ratios of 1/2, 1/1, and 2/1. The 3D printability was assessed by flow ramp test and frequency sweep. After 3D printing, freeze-drying was conducted to solidify and dehydrate the hydrogels. Hydrogels with formulations of 3% A/G 1/2, 5% A/G 1/1, and 7% A/G 2/1 demonstrated shear-thinning flow behavior, and viscoelasticity of storage modulus (Gʹ) higher than loss modulus (Gʺ), with a loss factor (tan= Gʺ/Gʹ) in the range of 0.50-0.60 at the frequency sweep of 15-40 rad/s. The freeze-dried matrices demonstrated significantly increased hardness and crunchiness, which indicated that the novel matrix had distinguished texture properties. In one study, Bifidobacterium lactis at 10^11 CFU/g was encapsulated within alginate/gelatin hydrogels, 3D printed into tear-drop shapes, and followed by freeze-drying. The results demonstrated that the probiotics encapsulated in the novel matrix have the potential to maintain > 10^6 CFU/g during an 8-week shelf-life test conducted at ambient temperature. This study validated that this 3D-printed, hydrogel-based matrix has the potential to be used as a convenient, shelf-stable delivery system for active ingredients.