This invention provides a device for delivering substances such as medical implants and tissues. The device comprises a mandrel and a mandrel guide whereby substances are delivered by retracting the mandrel guide relative to the mandrel. Included among the various embodiments are devices specialized for delivering retinal pigment epithelial (RPE) cells or nanoplates containing RPE cells to the retina, devices with precise control of delivery, devices with specialized mandrels and/or nozzles, and multifunctional devices adapted to provide additional functions such as infusion and/or suction, illumination, and diathermy.