BIO INT Scientists are scientists and researchers working for BIO INT.
They appeared in Xionic Madness 1.5 where they were encountered by Xero while he was looking for a place to recharge Kary. Xero instructed the scientists to lay down their weapons, but the scientists instead attempted to shoot him. Xero unsurprisingly responded by cutting them down with the Ripper.
Several more scientists soon teleported in via teleport belts, but Xero was able to kill them as well.