(T1030-07-41) A Targeted Drug Delivery System for the Treatment of Colorectal Cancer

Purpose: Colorectal cancer (CRC) is one of the deadliest of cancers, ranking second to lung cancer in males and 3^rd in females.CRC mortality is 36% higher among African Americans than other ethnic groups. Most CRC cases are diagnosed at advanced stages, with chemotherapy as the main treatment option. Resistance to these chemotherapeutic agents is increasing, and severe adverse effects are being reported. This study aims to develop targeted pegylated niosomes of two cytotoxic agents (5-fluorouracil and irinotecan) for oral delivery. The optimized niosomes will then be functionalized with a transferrin receptor targeting ligand and encapsulated for delivery to the colorectal region.

Methods: Pegylated blank niosomes were prepared by a modified thin film hydration technique and characterized for their physical properties, followed by drug loading. Vesicular size and polydispersity index (PDI) were analyzed with a 90-plus particle size analyzer (Brookhaven Instruments Corp, NY, USA). Morphological imaging of the niosomes was done with Scanning electron microscopy (SEM), and assay of drug loading was done using a validated HPLC method. Drug release studies was carried out using the dialysis bag method. In addition, the T7-Cys (C-HAIYPRH), cell-targeting peptide with specificity and high binding affinity for transferrin receptor that is overexpressed on CRC cells, was synthesized using the solid phase peptide synthesis (SPPS) technique. T7-Cys was then conjugated to DSPE-PEG-MAL via thiol-maleimide click chemistry to form DSPE-PEG-T7. The ligand was analyzed and confirmed with NMR spectroscopy. Cell uptake studies was carried out using fluorescence microscopy, and in vitro cytotoxicity studies on HT29 cells was carried out using the MTT assay.

Results: The average size of Pegylated blank niosome was 215±/ 2.65nm, while the drug-loaded niosome had a size of 251 ±2.20nm and PDI of 0.293 ±0.01. Vesicle size and PDI were significantly influenced by % proportion of surfactant (SP60) to cholesterol. Irinotecan (MW 586.678; logP 3.94, aq sol 0.107 mg/mL & BCS class I) loaded more poorly and released faster than 5-fluorouracil (MW 130.0772; logP -0.89, aq sol 5.86 mg/mL & BCS class III). Peaks from NMR spectroscopy confirmed the synthesis of DSPE-PEG-T7. Cell uptake studies show time-dependent cellular uptake, and cytotoxicity studies show potency of formulation with IC₅₀ values of 2µM.

Conclusion: The nature of lipid material, which is known to influence the critical packing concentration of the niosomes-forming materials, had a significant impact on niosomes’ size and encapsulation efficiency. Also, the molecular size and chemical nature of the drug significantly influenced drug loading and encapsulation behavior of the formulations. Generally, vesicular size decreases with the proportion of surfactant and increases with that of the membrane stabilizer, cholesterol.  Ligand targeting of anticancer drugs loaded into niosomes appears to hold significant promise in the delivery of chemotherapeutic agents to CRC cells.