RETRACTABLE SYRINGE

You implant a retractable syringe in your hand which can access an internal reservoir of toxin in your arm. You can extend this syringe as a swift action but only while you aren’t holding anything in that hand. Attacks with your syringe deals 1d6 piercing damage and automatically injects a toxin into your target. An affected creature can attempt a Fortitude saving throw against the type of toxin used. The reservoir holds up to 3 doses of any injectable toxin; injury-based poisons, drugs, viruses, nanite colonies are just a few of the possibilities.  See the "Afflictions" section in Chapter 11 of the Starfinder Core Rulebook. You are not required to inject toxin while using the syringe as a weapon.

There is no chance of you exposing yourself to the toxin stored in your reservoir unless the augmentation is destroyed.  If the augmentation is destroyed you suffer all normal effects of the toxin, but are entitled to saving throws.