It was the aim of this study to prepare trypsin decorated mucus permeating self-emulsifying drug delivery systems (SEDDS). Lipophilicity of enzyme was increased by hydrophobic ion pairing (HIP) with the anionic surfactants sodium dodecyl sulfate (SDS), sodium taurocholate (ST) and sodium deoxycholate (SDO) to facilitate its incorporation in SEDDS. Blank SEDDS and trypsin decorated SEDDS were characterized regarding droplet size, polydispersity index (PI), zeta potential and proteolytic activity using N alpha-benzoyl-Larginine ethyl ester (BAEE) assay. Log D-SEDDS/release medium of each complex was determined to assess its affinity towards SEDDS oily droplet upon emulsification. Ability of trypsin decorated SEDDS to enhance mucus permeation was studied on mucus gel from porcine small intestine for the period of 4 h at 37 C. Degree of enzyme precipitation via HIP was 94.5%, 85.7% and 48.2% for SDS, ST and SDO complex, respectively. SEDDS composed of 50% (w/w) cremophor EL, 20% (w/w) captex 300, and 30% (w/w) propylene glycol with a complex payload of 1% (w/w) exhibited a droplet size in the range of 29.92 +/- 0.09 nm to 39.15 +/- 0.37 nm, a polydispersity index of 0.116-0.265 and zeta potential in the range of -2.36 my to -4.25 my. The enzymatic activity of trypsin complexed with SDO, SDS and ST in SEDDS was 51.9%, 44.8%, and 40.7% respectively, of the corresponding activity of free trypsin. Log D values of trypsin, SDS, ST and SDO complex were -2.73,1.97,1.89 and 1.68, respectively, suggesting higher lipophilicity of trypsin complexes as compare to free trypsin and ability to reside on SEDDS droplets. Enzyme decorated SEDDS improved mucus permeation 1.6- to 2.6-fold in comparison to blank SEDDS. Results demonstrated that decorating SEDDS with trypsin can be a promising technique to improve their mucus permeating properties. (C) 2018 Elsevier Inc. All rights reserved.