People are looking into it, but I don't think there's all that much promise. Fine structure of shielding doesn't really matter to an energetic particle that's blowing through meters of it.

Gamma rays are stopped by electron density. Electron density requires high mass density heavy (high Z) nuclides.

Neutrons are stopped by light nuclei via conservation of momentum, and by neutron absorbing nuclei like boron.

If metamaterials can be made with higher density electrons in a way that's cheaper than lead and high hydrogen density that's cheaper than concrete, paraffin wax, or water, then I guess it could be interesting.