Hi I am working on non-viral gene delivery. I need to have a protocol on how to shield my PEI/DNA nanoparticles with a bifunctional PEG. One head of the PEG is NHS desired to attach to the PEI and the other head is maleimide, desired to attach to my targeting antibody. I do not know how to manage this work, this will be needing the temporary blocking of the maleimide end when I want to attach it to the PEI and then removing the blockade to attach it to the targeting antibody. Any help will be appreciated.