When I bioprint, I make sure to keep my printer under a biosafety cabinet to maintain sterilization. To sterilize the bioprinter, I spray it with ethanol or use the UV light in the biosafety cabinet. The UV sterilization initially sterilizes the printer, but you will need a way to maintain that sterilization throughout the entire printing process.
You can check out the printer I use here: http://www.biobots.com. Let me know if you have any questions!