Well I used those tubes in the past and there is no special care you should take, Those tubes are pre-treated in a way such that proteins in general and therefore, your protein of interest will not bind to the plastic. Their efficiency was very good in our case, avoiding a-specific binding and increasing the yield recovery. What you can do to check is to put your protein inside and then as a function of time check the amount of protein that you have in the sample, if it decreases then means that you are having problem but I doubt it might happen. You should have a constant concentration unless other problem of precipitation etc....

Thank you!