A DNA-gelatin mixture may be used for printing onto a slide. Gelatin powder is first dissolved in sterile Milli-Q water to form a 0.2% gelatin solution. Purified DNA plasmid is then mixed with the gelatin solution, and the final gelatin concentration is kept greater than 0.17%. Besides gelatin, atelocollagen and fibronectin are also successful transfection vectors for introducing foreign DNA into the cell nucleus.