Document Type

Dissertation - Open Access

Award Date

2017

Degree Name

Doctor of Philosophy (PhD)

Department / School

Pharmaceutical Sciences

First Advisor

Omathanu Perumal

Keywords

Core-shell nanocarriers, Fenretinide, food proteins, Lopinavir, milk proteins, oral delivery

Abstract

Oral delivery is the most preferred route for drug administration. Oral drug delivery is limited by poor physicochemical properties of drugs and physiological barriers in the gastrointestinal tract. To this end, there is a need for developing new carrier systems to enhance the oral bioavailability of poorly absorbed molecules. Food-grade biopolymers are attractive materials for developing drug delivery carriers’ due to their unique properties and proven safety. Six different core-shell nanocarriers were prepared using food-grade biopolymers including zein-casein (ZC) nanoparticles, zein-lactoferrin (ZLF) nanoparticles, zein-β-lactoglobulin (ZLG) nanoparticles, zein-whey protein isolate (ZWP) nanoparticles, zein-pluronic-lecithin (ZPL) nanoparticles and zein-PEG (ZPEG) micelles. The study was aimed at systematically investigating the influence of shell composition on the functional performance of core-shell nanocarriers for oral drug delivery applications. The first goal was to develop and study the structure-function relationship of coreshell nanocarriers for oral drug delivery applications. Nile red (NR) and Cy 5.5 were used as model dyes for this study. The particle size of the nanocarriers ranged from 100 to 250 nm, and the nanocarrier had a uniform size distribution as evidenced from the low PDI (0.08 to 0.3). The zeta potential values varied from -10 to 30 mV depending on the shell composition. The core-shell structure of the nanocarrier was confirmed by Transmission Electron Microscopy (TEM). The nanocarriers sustained the release of NR in simulated gastric and intestinal fluids. NR release from the nanocarriers predominantly followed Peppas model which indicates the diffusion of NR from nanocarriers by polymer erosion by hydrolytic or enzymatic cleavage. NR release from ZPEG micelles followed first order release kinetics. The nanocarriers were taken up by endocytosis in Caco-2 cells, which is an established model for intestinal permeability studies. ZLG nanocarriers showed the highest permeability across Caco-2 cell monolayers, while ZC nanoparticles showed the lowest permeability among the six formulations. ZPEG micelles also showed P-gp inhibitory activity. All the nanocarriers were found to have bioadhesive properties. Among the six different nanocarriers, ZLG and ZWP nanocarriers showed significantly higher bioadhesive property. In-vivo biodistribution of the nanocarriers was studied using Cy 5.5, a near-IR dye and all the formulations showed longer retention in the rat gastrointestinal tract compared to the free dye. Among the formulations, ZLG and ZWP nanoparticles were retained longest in the rat gastrointestinal tract (≥24 hours). All the nanocarriers were found to be non-immunogenic on oral administration to mice. The second goal was to investigate the use of core-shell nanocarriers for oral delivery of a model antiretroviral drug, lopinavir (LPV). LPV is a first-line protease inhibitor used for the treatment of HIV infections, especially in children. The drug has poor oral bioavailability due to its poor water solubility, poor membrane permeability and firstpass metabolism in the intestine. LPV is a substrate for the CYP3A4 enzyme and hence is used in combination with ritonavir (a CYP3A4 inhibitor) to boost the oral bioavailability of LPV. The current pediatric oral liquid formulation contains LPV and ritonavir (RTV) in a mixture of high proportion of propylene glycol and alcohol. The main goal was to test the feasibility of developing a water dispersible RTV free pediatric formulation of LPV using zein-based core-shell nanocarriers. The impact of shell composition on the functional properties of LPV loaded nanocarriers was evaluated in vitro and in vivo. The encapsulation efficiency for LPV was above 70% in all the nanocarriers, and ZPL nanoparticles showed the highest encapsulation efficiency (87.92±7.19%). The loading efficiency ranged from 2 to 5% based on the shell composition. The release of LPV was sustained both in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) for 24 hours. To test the feasibility of developing a food sprinkle formulation, the compatibility of the nanoformulations with model food matrices were studied. The nanocarriers were stable when incubated in food matrices (milk and applesauce) andZC>ZLF>ZWP>ZLG>ZPL. In vivo pharmacokinetic study in rats showed that the oral bioavailability of LPV increased by 2-fold compared to marketed LPV/RTV liquid formulation (Kaletra®). The highest oral bioavailability was obtained with LPV loaded ZPEG micelles followed by ZWP and ZLG nanoparticles. Highest plasma concentration (Cmax) of LPV was achieved with ZPEG micelles which was comparable to Kaletra® formulation. The extent of absorption (AUC) of LPV was in the following decreasing order of ZPEG>ZWP>ZLG>Kaletra®>free LPV. Multiple dose PK study further demonstrated that similar or higher steady-state plasma concentration can be obtained using ZPEG micelles compared to Kaletra®. Findings from this chapter concludes that zein-based nanocarriers can be used to develop ritonavir free LPV formulation which will ultimately reduce the total drug load and drug-drug interaction in the treatment of HIV infection. The last objective was to demonstrate the feasibility of using zein-based core-shell nanocarriers for oral delivery of fenretinide, an investigational anti-cancer molecule. Fenretinide has been found to be effective against several cancers including pediatric neuroblastoma, However, the clinical development of fenretinide is limited by its poor physicochemical properties. Fenretinide is a poorly soluble and poor permeable anti-cancer agent. Further, the compound has poor chemical stability. The encapsulation efficiency for fenretinide was above 70% in all the nanocarriers and zein-β-casein (ZC) nanoparticles showed the highest encapsulation efficiency (90±0.091%). The release of fenretinide was sustained both in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) for 24 hours. The nanocarriers were stable when incubated in food matrices (milk and applesauce), and less than 30% of fenretinide was released after incubation for 1 hour in food matrices. About 60% of fenretinide was released over 24 hours when the nanocarriers was transferred from food matrices to SGF and SIF. The nanocarriers enhanced the permeability of fenretinide across the Caco-2 cell monolayers from 1x10-6 to 72.42x10-6 cm/s. The order of permeability of fenretinide loaded nanocarriers was found to be in the following decreasing order ZPL>ZLG>ZC>ZWP>ZLF>ZPEG. Among others tested for single dose PK study of fenretinide, ZLG nanocarriers showed the highest oral bioavailability of fenretinide (6-fold) compared to free fenretinide suspension. Nanocarriers increased the elimination half-life (t1/2) by 2- to 4-fold. ZPL nanocarriers showed the highest Cmax (0.61 μg/mL) of fenretinide, while fenretinide loaded ZC nanocarriers showed the lowest Cmax (0.23 μg/mL). Nanocarriers showed the following decreasing rank order for relative oral bioavailability, ZWP>ZLG>ZPL>ZC, indicating that shell composition has a significant influence on the oral bioavailability. Further, multiple dose pharmacokinetic (PK) studies of fenretinide and fenretinide loaded zeinpluronic- lecithin (ZPL) nanocarriers was performed. The pharmacokinetics of twice a day free fenretinide suspension was compared with once a fenretinide loaded ZPL nanocarriers. The steady state concentration of fenretinide and fenretinide loaded ZPL nanocarriers was achieved at around 50-hours. However, the steady-state plasma concentration of fenretinide from the ZPL nanocarriers was 5-fold higher compared to free fenretinide suspension. Overall, the outcomes from this study demonstrate the structure-function relationship of core-shell protein nanocarriers for oral drug delivery applications. The findings from this study can be used to develop food protein based oral drug delivery systems with specific functional attributes for various oral drug delivery applications.

Library of Congress Subject Headings

Drug delivery systems.
Nanoparticles.
Drug carriers (Pharmacy)

Description

Includes bibliographical references (pages 202-261)

Format

application/pdf

Number of Pages

285

Publisher

South Dakota State University

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Rights Statement

In Copyright