Question re: coating gold w/ DNA

[C Coward]

Possibly a simple question here, but tracking relevant things down in the
literature is proving annoying.

When gold particles are coated with DNA (eg for biolistic transformation)
the DNA is precipitated (eg w/ spermidine) onto the gold. Presumably there
is an interaction between the precipitated DNA and the gold that causes
the DNA to stick. What is this interaction? I'm wondering whether DNA
precipitates can be used to coat other materials you see (as opposed to
metallic microparticles).

Cheers

Chris