Photochemical tussue penetration via photosensitizer for the efficient penetration of drug into tumor tissue

摘要

Introduction: A non-vascular drug eluting stent (DES) is a biomedical device that is implanted in the gastrointestinal (GI) tract for stabilizing the flow of body fluids when obstructive symptoms are shown due to tumor growth. Recently, gemcitabine (GEM) eluting membrane covered stents have been developed and highlighted because of the strong therapeutic effect of GEM in Gl tumor therapy. However, GEM has a low tissue penetration efficiency (PE%) in the Gl tract because of its hydrophilicity and the epithelial barrier function. For this reason, some cells of a GEM treated tumor can continue to proliferate and allow tumor growth. We believe that an alteration of the epithelial layer is required for improving drug penetration. Materials and Methods: To prepare the membranes, 200 mL of the above mixed solution(Gemcitabine(GEM), Photosensitizer(PS), Polyurethane(PU)) was poured into the polytetrafluorethylene (Teflon) mold and dried. The surface morphologies of each membrane were observed with Field emission-scanning electron microscopy (FE-SEM). To confirm the drug release behaviors, GEM-PU (PS absent membrane) and PS-GEM-PU were placed into conical tubes, and phosphate buffer saline was added. To confirm the generation of singlet oxygen, PS-GEM-PU was incubated in PBS for 0,1 or 2 weeks. To confirm the PE% enhancing mechanism, CT-26 cells were cultured in a 6-well plate and Chang cells were cultured . To visualize the tissue penetration of the hydrophilic molecule, fluorescein was loaded instead of GEM in the drug eluting membrane. To evaluate in vivo tumor growth inhibition activity, CT-26 bearing Balb/c nude mice were used. Results: PS was uniformly spread in the membrane. GEM was located in the nearby abluninal side of the membrane. The releasing of GEM was not influenced by the addition of PS. Also, under the light exposure, the singlet oxygen was generated by PS at the membrane surface for 2 weeks. The PE% of GEM from PS-GEM with light was 30% higher than the others of in vitro penetration test. To visualize the tissue penetration test of the hydrophilic molecule, the intensity of the penetrated FITC in the PS-fluorescein with light group increased by approximately 200% compared to the others. To evaluate the tumor growth inhibition efficiency, the tumor with GEM-PU with or without light and PS-GEM-PU without light grew exponentially; almost 3 times larger tumor volumes were measured than in the PS-GEM-PU group. In TUNEL assay, apoptotic cells were detected at the nearby tumor-membrane interface in the case of GEM-PU with or without light and PS-GEM-PU without light. Discussion: To improve the tissue penetration efficiency of hydrophilic-drugs in non-vascular drug eluting stents(DES), we designed photochemical tissue penetration invested DES. Consequentially, tumor growth, when implanted with PS-GEM-PU, was effectively inhibited without significant side effects. Based on these results, we believe that the photochemical tissue penetration-DES system has great potential for improving the therapeutic effect of conventional DES. Conclusion: PS-GEM-PU was designed and prepared to increase both the tissue penetration and the therapeutic efficacy of a GEM loaded DES. In this study, we overcame this barrier using a PS-DES membrane. Thus, the membrane has a higher therapeutic effect than a conventional GEM eluting membrane. To improve the therapeutic potency of PS-DES system, further experiments were required to optimize drug content in DES membrane.