Research progress of delivery strategies related mucus barrier in mucosal drug delivery

The mucous barrier is a major physiological obstacle that the mucosal drug delivery system needs to deal with. In response to this physiological barrier, many achievements have been made in research of mucosal adhesion and mucus penetration. This review puts emphasis on the progress of the research on new mucosal adhesion strategies such as cationization, sulfhydrylization, maleimide functionalization, lectinization and catechol conjugation; polyethylene glycol (PEG), polyvinyl alcohol (PVA), poly (2-alkyl-2-oxazoline) (POZ), zwitterionic polymers and other mucus-inert materials, strategies to enhance mucus penetration ability such as enzyme functionalization, reducing agent pretreatment and so on. The problems of each strategy are also analyzed and discussed, which can provide some references for clinical transformation.