Shield Body: Something similar to the Water Shield bubble design, but coloured green (think Jazz green), slightly less transparent, a few small bubbles rising up inside (like in a fizzy drink) and an overall "slimy" appearance.

Projectiles: I imagine the projectiles to be small, green, gelatinous orbs (similar in size and shape to the Water Shield bullets).

Particles: Smaller bubble-like particles could potentially "drip" from the shield body and/or the the projectiles, but this isn't really necessary (and could get excessive).

Shield Monitor: Biohazard/radioactive warning sign?

Projectiles: The Biohazard projectiles stick to any masked surfaces that they come into contact with. After a few seconds, these bullets explode. However, they are still hostile to enemies and other players when stuck to a surface. Due to this property, this weapon is extremely effective for defensive purposes such as area denial. It is poor in general combat though, as the bullets are slow, move upwards in a parabolic trajectory and do not travel very far. This is the kind of trajectory the bullet would take if it was fired standing still:

If the bullet hasn't hit a masked tile yet, it has a counterEnd of the same value as a Blaster bullet. If it hits a masked tile, the counterEnd value resets and lasts about three seconds before the bullet explodes. Unlike the other shields, the Biohazard projectiles cannot be autofired (like Seeker/RF/TNT). They deal two damage to both enemies and players. However, they are unable to deal any damage to destruct scenery, and just stick to them like they would to any other masked surface.

Looped Sound: Something akin to the bubbling sound in this track, perhaps?

Projectiles: Not sure really. I guess they could sound like the Biorifle from UT (the weapon of which this shield was partially inspired by), or use a sound effect similar to the Water Shield bullets.