Lap shear adhesion measurements

1. Peel off tissues.

2. Cut tissues into similar size according to the size of glass slides used (e.g. 2.5 cm × 2.5 cm).

3. Glue tissues firmly to one end of each glass slide.

4. Dissolve HA-Cat and HA-NCSN in PBS.

5. Mix the precusor with an equal volume of MT (Sigma-Aldrich) (100 units ml^-1 in PBS) and vortex the mixture immediately.

6. Apply the mixture to tissue surface on the glass slides.

7. Place two glass slides together oppositely to achieve overlap of two tissue surfaces in which one of the tissue surface is covered with hydrogel mixture.

8. Fasten the whole installation with two clips clipping two parallel eage of the overlapping area. 

9. Incubate the whole installation at 37C for some time to achieve uniform adhesion.

10. For lap shear strength measurments, pull the samples from two sides of two glass slides in one installation to failure using a tensile testing machine with a speed of 1 mm/min at room temperature.

11. Record the load (force) and displacement.

12. The lap shear strength is the highest intensity of adhesion force sensed by the tensile testing machine, that is the highest of force divided by the remaining overlapping area.
    

    
    

Notes: this protocol is aiming for measuring tissue adhesion. And this protocol is based on the enzymatic gelation of our HA-Cat-NCSN hydrogels. For other hydrogels, please make modifications depends on the situations.