Study On Colon-targeted Co-delivery Of Hydrophilic And Hydrophobic Active Substances By Shellac Nanoparticle S Enhanced Calcium Alginate Hydrogels

Ulcerative colitis(UC)is a chronic,recurrent inflammatory disease.Long-term use of current drugs or hormones to treat UC can bring hormone dependence,extensive side effects,etc.Nutritional intervention is regarded as a feasible strategy for the remission and treatment of UC,and the delivery of functional factors with anti-inflammatory and antioxidant activities to the colon can improve the symptoms of UC.Resveratrol(RES)has many biological activities,but its practical application is limited due to its low water solubility,wide metabolism and low bioavailability.Oligomeric Proanthocyanidins(OPC)are flavonoids that can reduce gastrointestinal inflammation,but they are easily degraded and unstable.The combination of RES and OPC brings a better intervention effect on UC than the use of RES or OPC alone.However,RES and OPC have opposite polarity,consequently,it is necessary to design a transport system that can deliver both hydrophilic and hydrophobic active substances.Therefore,in this paper,a shellac nanoparticles reinforced calcium alginate hydrogel was constructed to co-deliver hydrophilic and hydrophobic active substances to relieve UC.The main research contents and conclusions are as follows:(1)Preparation and properties of shellac nanoparticles loaded with resveratrolShellac nanoparticles loaded with RES(R-SNPs)were prepared by reverse solvent precipitation method.The morphology and structure of R-SNPs were analyzed by SEM and TEM.The interaction between R-SNPs and R-SNPs was analyzed by FTIR,DSC and TG.The optimal encapsulation rate and load rate of R-SNPs are 99.03% and 10.73% respectively by single factor and response surface test.The optimized R-SNPs particle size is 87 nm and potential is-29 m V.Its microstructure is a smooth sphere with uniform particle size.The apparent bilayer structure of RES was observed by TEM,thus proving that RES was successfully loaded into the nanoparticles.The good intermolecular force between RES and shellac was demonstrated by infrared spectroscopy and thermal stability analysis.In DPPH· and ABTS+· radical scavenging experiments,R-SNPs showed higher antioxidant activity than SNPs.In the photosensitivity test,the encapsulation of RES by shellac can effectively inhibit the isomerization of RES by ultraviolet light.When stored at 4°C and 25°C for 25 days,The particle size and potential of R-SNPs didn’t change much.R-SNPs aggregates and precipitates at p H 1.2,and disperses stably at p H 6.8 and 7.4.(2)Preparation,properties and in vitro digestion of calcium alginate hydrogel reinforced by shellac nanoparticlesShellac nanoparticles reinforced calcium alginate hydrogel(R-SNPs-P-GEL)was successfully prepared by droplet method.The microstructure of the hydrogel was observed by SEM,and its texture properties were evaluated by texture analyzer.The molecular interaction of R-SNPs-P-GEL was analyzed by FTIR,DSC and TG.Finally,the swelling and in vitro digestion properties of R-SNPs-P-GEL were investigated.The viscosity of the sol was measured during the preparation of R-SNPs-P-GEL.It was found that the interaction force between R-SNPs and hydrogel might increase the viscosity.The addition of OPC or RES can increase the strength of hydrogel.The texture analysis of R-SNPs-P-GEL revealed that the hydrogel was elastic,smooth and homogeneous.By SEM observation,it was found that the nanoparticles were successfully encapsulated in the influent gel.According to FTIR and thermal stability analysis,OPC and R-SNPs cross-linked and interacted with wall material sodium alginate successfully through hydrogen bond and van der Waals force.In the swelling test,the hydrogel did not significantly swell in the simulated gastric juice,but significantly swell in the simulated intestinal juice,and dissolved in the simulated colonic juice.In the in vitro release experiments,the cumulative release rates of OPC and RES in simulated gastric juice were low.The cumulative release rates of RES and OPC reached 82.3% and 95.3% in simulated colon fluid,indicating full release of active substances.(3)Effect of calcium alginate hydrogel enhanced with shellac nanoparticles on ulcerative colitis in miceDSS induced UC mouse model was constructed to study the effect of R-SNPs-P-GEL on UC.The changes of body weight and disease activity index during the treatment were investigated,and the changes of colon length,spleen index,colon tissue inflammation,cell apoptosis and related inflammatory factors were assessed after the treatment.The results disclosed that R-SNPs and R-SNPs-P-GEL could control body weight gain and decrease disease activity index,inhibit colonic atrophy and decrease spleen index in mice.The intervention of R-SNPs and R-SNPs-P-GEL resulted in significant improvement in crypt loss,goblet cell loss,and neutrophil infiltration of the colon tissue,and no accumulation of immune cells was observed,showing complete epithelium.The intervention group could inhibit the apoptosis of colon tissue cells,down-regulate the expression of apoptotic cells cleaved caspase-3,Bax,bcl-2,and decrease the levels of inflammatory cytokines TNF-α,IL-6,IL-1β,NF-κB,INF-γ,PEG2 and NO.In addition,Treg/Th17 signal transduction in UC mice could be regulated by R-SNPs and R-SNP-P-GEL,and the Treg/Th17 ratio increased after intervention,so that UC symptoms could be alleviated.Moreover,due to the synergistic effect of OPC and RES,the R-SNPs-P-GEL intervention group had better remission effect.This study proved that OPC and RES could reach the colon after being encapsulated by hydrogels containing nanoparticles,which could play a synergistic role in alleviating UC,and provide certain reference value for future research.