Combined Mulberry Leaf Polysaccharide-Caged Liposomes for Effective Oral Drug Delivery in Rat Model

Mulberry leaf polysaccharide (MLP) has gained attention as a potential anti-diabetic agent for lowering blood glucose and improving insulin sensitivity. However, the low gastrointestinal stability and oral bioavailability limit its clinical application. To address this issue, a novel drug-caged liposomes (MLP-CL) was developed to enhance oral delivery efficiency of MLP compared to conventional drug-encapsulated liposomes (MLP-L).

MLP-L and MLP-CL were prepared by the thin-film hydration method. Subsequently, the structural integrity of these liposomes was assessed via in vitro release test and confocal laser microscopy (CLSM) analysis. Madin-Darby canine kidney (MDCK) cells were employed to investigate the cellular uptake mechanisms and transcellular transport efficiency. Finally, the biodistribution profiles and transport mechanisms of liposomes were evaluated through in vivo fluorescence imaging and pharmacokinetic studies in Sprague Dawley rats.

Compared to MLP-L, which released 80% of MLP within 4 hours, MLP-CL showed sustained release with only 40% released in the same period. MLP-CL also enabled more effective co-delivery of MLP and liposomes to MDCK cells, indicating improved structural integrity and cellular uptake. Transcellular transport assay confirmed that MLP-CL was transported across cells more efficiently. In vivo, MLP-CL increased intestinal accumulation and raised plasma MLP concentration by 50%. Additionally, by comparing the discrepancy between the lymphatic-suppression model and the normal model, it was found that 63.56% of MLP-CL was absorbed through the lymphatic pathway compared to 18.05% for MLP-L.

Compared to conventional MLP-L, conjugation of polysaccharide improves the structural integrity of MLP-CL in the gastrointestinal tract, which in turn improves lymphatic uptake and bioavailability. This provides an effective strategy for the design of polysaccharide delivery systems.