Cell-laden cardiac patches have recently been emerging to renew cellular sources for myocardial infarction(MI,commonly know as a heart attack)repair.However,the fabrication of cell-laden patches with porous structure remains challenging due to the limitations of currently available hydrogels and existing processing techniques.The present study utilized a bioprinting technique to fabricate hydrogel patches and characterize them in terms of printability,mechanical and biological properties.Cell-laden hydrogel(or bio-ink)was formulated from alginate dialdehyde(ADA)and gelatin(GEL)to improve the print-ability,degradability as well as bioactivity.Five groups of hydrogel compositions were designed to investigate the influence of the oxidation degree of ADA and hydrogels concentration on the properties of printed scaffolds.ADA–GEL hydrogels have generally shown favorable for living cells(EA.hy926 cells and hybrid human umbilical vein endothelial cell line).The hydrogel with an oxidation degree of 10％and a concentration ratio of 70/30(or 10％ADA70–GEL30)demonstrated the best printability among the groups examined.Formulated hydrogels were also bioprinted with the living cells(EA.hy926),and the scaffolds printed were then subject to the cell culture for 7 days.Our results illustrate that the scaffolds bioprinted from 10％ADA70–GEL30 hydrogels had the best homogenous cell distribution and also the highest cell viability.Taken together,in the present study we synthesized a newly formulated bio-ink from ADA and GEL and for the fist time,used them to bioprint cardiac patches,which have the potential to be used in MI repair.