The invention relates to a security device for preventing unexpected folding and a child stroller therewith. The present invention further relates to a method for executing the steps on this system. According to the invention, the structure comprises a frame or casing, and the tilting latch and the sliding shoe are guided between the lateral walls of said frame. We found that we could easily control the extent of virion conjugation and demonstrated stoichiometric biotinylation of the introduced lysine.