If there are any serious health concerns, like if your office is adjacent to a lab that works with biological materials (and therefore probably warrants a more thorough cleaning process), it would be worthwhile finding the facilities manager or administrator of the building and asking them to remind the cleaners to take more care.
If it's something a little less dangerous, it might be worth waiting to see if they miss it again, to see if they are deliberately doing so. Instead of saying "this is something you should be doing", ask them if it is something they CAN do, so as to not come across as accusing. If the answer is no, have a word with the people above.
It will vary between university or what country you're in; when I was at university, we had cleaners that would clean the curtains, floor etc. but were not permitted to touch the electronics in any way. For some Health & Safety rule, specific cleaners were needed for those. Ask around and find out if any such rules apply for you.