Bromelain-Decorated Chitosan-Coated Nanoscale Liposomes for Enhancement of Mucus Permeation and Oral Drug Delivery

The mucus layer presents a major barrier to drug carrier absorption in oral drug delivery systems. This study aimed to enhance the liposomal mucus permeability through sequential surface modification using chitosan (CS) and bromelain. The CS-coated liposomes (C1-Lip), prepared with a 0.1% CS solution, exhibited high mucoadhesion with uniform CS coverage. To activate mucolytic properties, bromelain, which is a protease complex extracted from pineapple stems, was conjugated onto the surface of C1-Lip, generating bromelain-decorated CS-coated liposomes (Bro-CS-Lip). The conjugation efficiency of Bro-CS-Lip ranged from 54.3% to 72.5%, with particle sizes between 220.1 and 263.8 nm. The enzyme densities in Bro05-C1-Lip and Bro10-C1-Lip were 5.0 and 9.2 nmol/mg of lipid, respectively. Bro10-C1-Lip exhibited significantly enhanced permeability, with a 6.50-fold increase in Caco-2 and 2.53-fold increase in Caco-2/HT29 cell layers compared to C1-Lip. Confocal z-stack imaging further confirmed that Bro10-C1-Lip penetrated deeply into the cell layer, while C1-Lip remained trapped within the mucus matrix. Therefore, Bro10-C1-Lip, integrating both mucoadhesive and mucopenetrating properties in balance, effectively overcomes the mucus barriers and improves cellular uptake. This dual-functional liposome, Bro-CS-Lip, holds great promise for improving drug delivery across the mucus layer, offering a potential breakthrough for oral drug delivery systems.