Carvacrol Loaded Solid Lipid Nanoparticles of Propylene Glycol Monopalmitate and Glyceryl Monostearate: Preparation, Characterization, and Synergistic Antimicrobial Activity.

Junbo He,Qixin Zhong,Shuangshuang Huang,Lijuan Han,Chao Chang,Weinong Zhang,Xiaotao Sun

doi:10.3390/nano9081162

Abstract

To develop solid lipid nanoparticles (SLNs) with stable lipid matrix structures for the delivery of bioactive compounds, a new class of SLNs was studied using propylene glycol monopalmitate (PGMP) and glyceryl monostearate (GMS) mixtures and carvacrol as a model lipophilic antimicrobial. Stable SLNs were fabricated at PGMP:GMS mass ratios of 2:1 and 1:1, and the carvacrol loading was up to 30% of lipids with >98% encapsulation efficiency and absence of visual instability. Fluorescence spectra and release profiles indicated the carvacrol was successfully encapsulated and homogeneously distributed within the SLNs. SLNs fabricated with equal masses of PGMP and GMS had better stability of carvacrol during storage and higher sphericity than those with a ratio of 2:1 and were much more effective than free carvacrol against Escherichia coli O157:H7 and Staphylococcus aureus. These findings demonstrated the potential applications of the studied SLNs in delivering lipophilic bioactive compounds in food and other products.

Highlights

Solid lipid nanoparticles (SLNs) are a class of colloidal particles composed of solid lipids at the application temperature and have become a group of fascinating delivery vehicles in food, cosmetic, and medical sciences owing to the good biocompatibility [1,2,3]
The high purity of propylene glycol monopalmitate (PGMP) can be attributed to the steric effect that the formation of PGMP hinders the further esterification with another palmitoyl chloride molecule
The 2:1 and 1:1 mass ratio of PGMP:glyceryl monostearate (GMS) were feasible to prepare stable SLNs at the studied conditions and were capable of loading carvacrol at up to 30% mass of the lipids with an EE of higher than 98%

Summary

Introduction

Solid lipid nanoparticles (SLNs) are a class of colloidal particles composed of solid lipids at the application temperature and have become a group of fascinating delivery vehicles in food, cosmetic, and medical sciences owing to the good biocompatibility [1,2,3]. Low loading capacity and polymorphic transformation during storage are two major drawbacks of SLNs greatly limiting their application [5]. The polymorphism transformation of lipid matrixes in SLNs results from rearrangement of crystalline lattices to form thermodynamically more stable polymorph, e.g., from α- to β-form crystals, and the resultant increase in lipid molecular ordering causes the expulsion of initially incorporated bioactive compounds [6,7]. We recently reported that the SLNs prepared with a diacylglycerol, 1-laurin-3-palmitin, had a higher loaded capacity and better stability than those of glyceryl monostearate (GMS) and glyceryl tripalmitate due to the stable, mostly β-form, crystalline polymorph of 1-laurin-3-palmitin [8]. Identifying solid food lipids forming stable crystalline structures is a new direction to study SLNs for food application

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