According to Max himself, it injects "mega-doses" of insect DNA to reconstruct a person's body chemistry, and with prolonged injections the person would turn into a humanoid insect. Max implies that after building it, he repeatedly used it on himself to become the villain that the girls encounter.
The insect DNA appears as a green mist, and while Alex is inside the machine the DNA weakens her and cause her some pain.
Max used it on Alexandra in order to transform her into his insect queen. He only managed to give her antennae, cockroach wings, and hairlike protrusions (creating an incomplete transformation) before taking off with her. Unfortunately for Max, the DNA wore off before any more could be injected.