Fill the gaps in wooden stairs with acrylic?

Good day,

Our staircase was delivered and installed. Treads and risers were screwed onto a steel staircase. Now there are small gaps on the left and right sides. Is it recommended to seal these with acrylic? (For cleaning + appearance) Or is it not recommended because the wood might still expand and contract?

Best regards

Better with silicone, it is flexible. However, make sure that it is compatible with wood. As far as I know, it must not be "vinegar-crosslinking" (but should be neutral crosslinking)...