Preparation and Characterization of Whey Protein Isolate-DIM Nanoparticles.

Abbas Khan,Adam Killpartrick,Cuina Wang,Mingruo Guo,Xiaomeng Sun

doi:10.3390/ijms20163917

Abstract

3,3’-Diindolylmethane (DIM) is a bioactive compound found in Cruciferous vegetables that possesses health benefits such as antioxidant, anticancer, and anti-inflammatory effects. However, hydrophobicity and photolabile limit its pharmaceutical applications. This study aims to prepare and characterize DIM-encapsulated whey protein isolate (WPI) nanoparticles mixed at different ratios of WPI and DIM using the combined heating–ultrasound method. Results showed that all the samples showed adequate physicochemical characteristics: The mean particle size of the nanoparticles could be controlled down to 96–157 nm depending on the DIM to WPI ratio used in the preparation with a low polydispersity index (<0.5), higher negative values of zeta potential (>−40 mV) as well as with greater encapsulation efficiency (>82%). Flow behavior indices showed the shear-thinning Non-Newtonian or pseudoplastic (n < 1) behavior of the nanoparticles. The thermal properties were characterized by differential scanning calorimetry (DSC), which showed that DIM was successfully entrapped in WPI nanoparticles. The secondary structure of WPI was changed after DIM incorporation; electrostatic interaction and hydrogen bonding were major facilitating forces for nanoparticles formation, confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Transmission electron microscopy (TEM) micrographs showed that all the samples had a smooth surface and spherical structure. The wall material (WPI) and encapsulation method provide effective protection to DIM against UV light and a broad range of physiologically relevant pH’s (2.5, 3.5, 4.5, 5.5, and 7). In conclusion, whey protein isolate (WPI)-based nanoparticles are a promising approach to encapsulate DIM and overcome its physicochemical limitations with improved stability.

Highlights

3,3’-Diindolylmethane (DIM) is a hydrophobic phytochemical, mainly found in cruciferous vegetables [1,2]
Whey protein isolate nanoparticles have been developed in our laboratory to protect and improve physicochemical, microstructural, and rheological properties of many hydrophobic compounds, e.g., astaxanthin and totarol [24,28]
The interaction of DIM and whey protein isolate (WPI) was evidenced by differential scanning calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FT-IR) data

Summary

Introduction

3,3’-Diindolylmethane (DIM) is a hydrophobic phytochemical, mainly found in cruciferous vegetables (such as cauliflower, Brussels sprouts, broccoli, kale, and collard greens) [1,2]. The use of DIM in liquid food is difficult, because of their hydrophobic nature and sensitivity to high temperature, UV light, and pH [14,16] These properties largely limited their applications in the pharmaceutical and food industries. In this context, nanoparticles-based microencapsulation is a promising approach to protect the hydrophobic bioactive compounds against harmful conditions. Due to the good emulsification, solubility, and film forming properties, milk proteins are drawing increasing attention as a wall material to encapsulate many bioactive compounds [20,21,22]. Different DIM ratios were used with whey protein isolate (WPI) nanoparticles to prepare a stable formulation, and were assessed regarding physicochemical, thermal, rheological, and micro-structural properties. The nanoparticles were examined for pH stability and photostability

Objectives

Results

Conclusion