M. Khalili1, L. Daniels1, A. Thadi1, B. Polyak1, W. F. Morano1, H. Zhou1, F. Zhiyuan1, H. Cheng1, W. B. Bowne1 1Drexel University College Of Medicine,Philadelphia, Pa, USA
Introduction:
Treatment failures in pseudomyxomaperitonei (PMP) may result from ineffective delivery of therapeutics through dense PMP mucinous tumor barriers. Nanoparticle (NP) diffusion depends on surface interaction with proteins. Thus NPs that interact weakly with mucin matrix will penetrate mucin faster. We have modified the surface of Poly (lactic-co-glycolic acid)-b-polyethylene glycol (PEG-NPs) with a low-density, 2nd PEG layer (TPEG-NPs-20) to reduce it’sbinding affinity to proteins and improve diffusion through mucin.
Methods:
Nanoprecipitation method was used to engineer PEG-NPs. To construct the 2nd PEG layer of TPEG-NPs-20, PEG-Thiol was conjugated to PEG-NPs via maleimide-thiol reaction. DiD-labeled NPs were added to inner wells of two separate transwell diffusion systems to characterize NP diffusion through PMP tissue and cultured LS174T cells. Diffusionrate of DiD-labeled NPs through mucin was characterized by measuring fluorescence signal in the bottom well as a function of time. NP diffusion rates were recorded under shear stress (plate placed on an orbital shaker at 100 rpm) and static conditions at 37 °C. Diffusion properties of TPEG-NPs-20 were further demonstrated in ex-vivo rat small intestine mucin penetrating model. Rat small intestine was collected and submerged and in a solution of either DiD-labeled TPEG-NPs-20 or PEG-NPs for 30 mins. The intestinal loops were then washed, placed in embedding matrix, and frozen for cryosection. The sliced sections were mounted with DAPI-containing mounting media and inspected via confocal microscopy.
Results:
Diffusion profiles of TPEG-NPs-20 and PEG-NPs through PMP and cultured LS174T cells were generated. Under static conditions, there was no significant difference in the overall diffusion rate through PMP between TPEG-NPs-20 and PEG-NPs. Under shear stress, diffusion of PEG-NPs through PMP tissue remained similar to the diffusion rate at static condition. However, TPEG-NPs-20 diffused faster; after 8 hours with ~100% penetration through the PMP tissue layer vs. only ~40% diffusion of PEG-NPs (Figure). Similarly, transwell experiment with LS174T inside the inner wells resulted in superior diffusion rate of TPEG-NPs-20 compared to PEG-NPs under shear stress conditions. Superior diffusion of TPEG-NPs-20 was also observed in ex-vivo rat small intestine mucin penetrating model. TPEG-NPs-20 showed faster diffusion under shear stress with elevated luminal NP fluorescent signals detected 30 minutes after NP addition, whereas PEG-NPs werebarely detectable on the luminal surface of the intestine.
Conclusion:
TPEG-NPs-20 can be an effective anti-cancer drug delivery system to penetrate the dense mucin barrier secreted by gastrointestinal tumors.
