Yes, the blades can be sharpened. Clean the blades first as food debris can often build up on them. Then soak the blades in warm, soapy water for a while and use a small brush to scrub it. Once clean, tear off a sizable aluminum foil and fold it in half to double the breadth.
Run this foil steadily over the blade to sharpen it. Twist the blade along the length of the aluminum foil to make sure you’ve covered the entire blade, and do this multiple times. If the blades won’t cut after this, you may need to purchase a replacement from a repair store or get a brand-new gadget.