The first part is rather logical, even given the difficulty in defining "intelligent": Can a device, assembled out of matter, be intelligent in the same sense that a human being is intelligent?

See exhibit A, a typical human being. (s)he is made completely out of matter, and is by definition "intelligent in the same sense that a human being is intelligent". Therefor it is possible, at least in principle.

If you claim that "awareness" not intelligence is key, this changes nothing - just replace "intelligent" with "aware" throughout.

For the second part: Could intelligence be implemented using other materials? Or to put it differently, is there anything innately special about the materials and structures used to build human beings? Can it be done in silico?

I'm inclined to believe that no, there isn't, our design just happens to be the adequate solution to the problem of conciousness that nature hit upon, and that there are many other designs as good or better.

And if there is something special about our design, sooner or later we will work out what that special thing is, and replicate it.

But would a concousness implemented in different materials be indistinguishable from ours? I would think that this is a difficult, maybe even impossible, and in any case a useless goal. Why reimplement all the quirks and failings of old hardware on a new platform?