I agree with all the comments made here, and would like to add mah52’s plastic syringe example that as plastic is chemically inert, use of a different grade plastic material would not require a PMA. Also the syringe wouldn’t be coming in contact with the body, so there is no chance of occurrence of infection. Even if it did come in contact with the the body, plastic is biocompatible, so that wouldn’t be a cause of concern either.