Fabrication,Stability,and Bioavailability Of Cannabidiol Delivery System

Cannabidiol（CBD）is a non-psychoactive cannabinoid with a wide range of therapeutic properties,including anti-convulsive,anti-anxiety,anti-psychotic,anti-nausea,anti-rheumatoid and arthritic properties coupled with a favorable safety and tolerability profile.However,the application of CBD in the food and pharmaceutical industries is limited due to its inherent sensitives towards environmental pressures,which may experience isomerization,polymerization,or degradation when exposed in harsh environments,e.g.,heating,light,and oxygen.Oral administration of CBD is challenging with bioavailability of approximately 6%in humans due to its poor solubility in the gastrointestinal system.Therefore,it is very important to construct a delivery system to encapsulate and protect CBD molecules and improve its bioavailability in human body.Nanoparticles and nano-emulsions are two common delivery systems which can effectively deliver and protect the active substances.In this paper,zein and whey protein（zein-WP）composite nanoparticles were firstly constructed by two anti-solvent precipitation methods according to the self-assembly characteristics of zein.The nanoparticles were characterized to explore the environmental stability,antioxidant activity and gastrointestinal release of nanoparticles.The in vivo oral bioavailability of CBD in zein-WP composite nanoparticles was studied.Subsequently,the ternary complex of WP and maltodextrin（MD）conjugate with rosmarinic acid（RA）was constructed as a novel emulsifier to stabilize the CBD-loaded emulsions.The effect of ternary complex on the physical stability of emulsion and the protective effect on CBD were investigated by environmental stability experiments.The effect of oil phase composition on emulsion properties was also investigated.Different emulsifiers and oil phases with different mixing ratios were used to understand how the properties of components affect the interface behavior and subsequent emulsifying properties.Finally,the effects of medium chain triglyceride（MCT）,long chain triglyceride（LCT）,and medium chain triglyceride/long chain triglyceride（MCT/LCT）mixed oil phase（1:1）as oral emulsion carrier on in vitro gastrointestinal digestion and in vivo bioavailability of CBD were investigated.It provides a new idea for improving the environmental stability and in vivo bioavailability of CBD,and provides a sound information about the application of CBD delivery system.The main findings of this study are as follows:（1）The 3D fluorescence spectra and Docking technology confirmed that CBD and zein can be bound by hydrogen bonding,van der Waals force and hydrophobic force.CBD-loaded zein-WP composite nanoparticles were prepared by ASP method.The particle size of composite nanoparticles was small ranging from 150 to 160 nm and had high negatively zeta potential.The ratio of zein to WP affected the particle size,PDI,zeta potential and encapsulation efficiency of the nanoparticles.Differential scanning calorimetry showed that CBD molecule changed from crystallized state to amorphous state.The main driving forces of the complexation of zein and WP were hydrogen bond and hydrophobicity.Compared with zein nanoparticles,zein-WP nanoparticles provided better protection for CBD against heat treatment and UV irradiation.In addition,composite nanoparticles significantly improved the antioxidant capacity and in vitro gastrointestinal release rate of CBD.（2）Zein nanoparticles were stabilized by WP for the delivery of CBD using a modified ASP.The particle size was smaller and more uniform than that obtained by ASP method.With the addition of whey protein coating,the redispersion of nanoparticles and water solubility of CBD were significantly improved.XRD and FT-IR spectroscopy suggested that crystalline CBD may be successfully encapsulated within the particles.WP absorbed on zein surface via hydrogen bond,hydrophobic forces,and electrostatic attraction.The zein-WP nanoparticles showed excellent storage stability（4^oC,dark）and effectively protected CBD degradation against heat and UV light.In vivo pharmacokinetic study demonstrated that CBD in zein-WP nanoparticles displayed 2-times and 1.75-folds en-hancement in maximum concentration(C_max)and the area under curve（AUC）as compared to those in free form.Data indicated the feasibility of developing zein-WP based nanoparticles for encapsulation,protection,and delivery of CBD.（3）WP-MD glycosylated products were prepared by Maillard reaction,and a novel WP-MD-RA ternary complex was obtained by non-covalent reaction with rosmarinic acid（RA）.WP-MD-RA ternary complex was used as emulsifier to stabilize the emulsion and its stability characteristics were investigated under various environmental conditions.WP-MD conjugates were formed via dry heating.The interaction between WP and MD was assessed by browning intensity,reduced amount of free amino groups,the formation of high molecular weight components in SDS-PAGE,and changes in secondary structure of whey proteins.WP-MD-RA non-covalent complex was prepared and confirmed by fluorescence quenching and FT-IR spectra.Results showed that WP-MD-RA was an effective emulsifier to produce fine droplets for CBD-loaded emulsion and remarkably improved the p H and salt stabilities of emulsions in comparison with WP.Emulsion prepared by WP-MD-RA showed the highest protection of CBD against UV and heat-induced degradation among all emulsions.The ternary complex kept emulsions in small particle size during storage at 4^oC.（4）The properties of the oil phase affect the composition of the interface and then affect the properties of the emulsion.The correlation was explored through different composition of MCT/LCT.The interfacial tension increased with the increase of LCT ratio,indicating that oil viscosity affected interfacial tension.However,the opposite trend between adsorped protein and surface load was observed.According to the particle size,the particle size of emulsion increased significantly with the increase of LCT ratio.CBD partition in the emulsion was mainly located in the oil phase,accounting for more than 90%.The content of CBD in oil phase increased from 90%to96%with the increase of LCT proportion.The increase of LCT ratio is not conducive to the physical stability of emulsion and the oxidation stability of oil.However,the retention rate of CBD increased significantly with the increase of the percentage of LCT.In addition,the type of emulsifiers also affects the characteristics of the emulsion.（5）The oil phase composition has a significant effect on the bioavailability of CBD in the nanoemulsion delivery system.The particle size changes of the three emulsions during gastrointestinal digestion were consistent:stable in oral phase,sharply increased in gastric phase,and finally decreased in small intestine.And the particle size throughout the digestive process of the gastrointestinal tract was in the order of MCT<MCT/LCT<LCT.MCT showed the highest digestibility of about 90%,followed by MCT/LCT（76%）and LCT（45%）.LCT emulsion had the highest bioavailability of CBD after gastrointestinal digestion（43%）,followed by MCT/LCT（39%）and MCT（33%）,which was determined by the transformation stability.After intestinal digestion,most CBD was degraded,and the transformation stability of CBD in oil phase was in the order of LCT>MCT/LCT>MCT.However,the bioaccessibility of oil phase had a different trend.MCT and MCT/LCT had higher bioaccessibility to CBD than LCT.In vivo pharmacokinetic experiments showed that MCT/LCT and LCT were more favorable for CBD in vivo transport and absorption.