A device is provided for introducing into a patient a combination of adipose tissue and an additive, for example, a hydrogel additive. The device includes a fat cartridge, an additive cartridge containing an additive, and a housing configured to receive, in a side-by-side manner, the fat cartridge and additive cartridge. A mixing tip may be included for causing mixing of the cartridge components prior to extrusion from a needle or cannula.
