cells are used. [2] This technique enables cell transplantation into the host body without using immunosuppressant drugs [1] and simultaneously avoiding cells to disperse from the targeted site. [5] Microand macroencapsulation approaches have been explored in cell-based therapy applications to treat many diseases, especially, diabetes. [4] Moreover, cell encapsulation has been used in the field of tissue regeneration. [6] In this case, the matrix acts as a scaffold which allows the encapsulated cells to proliferate and differentiate in the capsules. [2] Biomaterials that have been widely used for cell encapsulation are hydrogels [7,8] because they can provide a highly hydrated environment which is suitable for cell and tissue growth. [9] Alginatebased hydrogels have been widely used in tissue engineering (TE) because of their biocompatible character. [10] However, alginate hydrogels have some limitations including a slow degradability and poor cell adhesion capability. [11] Degradability of alginate can be improved, for example, by the oxidation of alginate leading to alginate dialdehyde (ADA). [10] Moreover, combination of specific proteins with alginate based hydrogels can improve the cell-matrix interaction of the hydrogel. [12] Gelatin (GEL) is the most popular protein which has been incorporated into ADA based hydrogels for TE applications forming ADA-GEL hydrogels. [10] Because gelatin contains a cellular binding motif, namely arginineglycine-aspartic acid sequence, ADA-GEL can improve the adhesion, differentiation, and proliferation of cells. [13] Gelatin can covalently crosslink with ADA through the Schiff base formation between the amino groups of lysine and hydroxylysine of gelatin and the aldehyde groups of ADA. [14,15] The extrusion method is the most common microencapsulation technique which needs only simple equipment for the fabrication process. With this approach, cell-laden microcapsules are produced by extruding the hydrogel precursor containing cells through a small needle to generate droplets of the mixture into an appropriate hardening bath which will harden the hydrogel precursor. Because ADA based hydrogels can be easily crosslinked using CaCl 2 solution, this approach has been used efficiently for the fabrication of ADA-GEL based microcapsules. However, the diameter of the microcapsules fabricated by this method is strongly related to the properties of the hydrogel precursor. [2] The The effect of the incorporation of 45S5 bioactive glass (BG) microparticles (mean particle size ≈ 2 µm) on the fabrication and physicochemical properties of alginate dialdehyde-gelatin hydrogel capsules is investigated. The addition of BG particles decreases the hydrogel gelation time by ≈79% and 91% for the samples containing 0.1% w/v and 0.5% w/v BG, respectively. Moreover, it results in increasing average diameter of hydrogel capsules produced via a pressure-driven extrusion technique from about 1000 µm for the samples without BG to about 1700 and 1900 µm for the samples containing BG at concentrations of 0...