Study On The Construction Of Electrospun Salmon Calcitonin Colon-targeted Drug Delivery System And Its Property

Salmon calcitonin(SCT)is an active peptide composed of thirty-two amino acids,which plays an important role in maintaining calcium balance and inhibiting osteoclast activity.Currently,the main routes of administration for calcitonin in clinic are injections and sprays.However,the compliance of injections is poor,while spray is easy to be accepted by patients,but its bioavailability is low,so the clinical application is limited.In recent years,colon-targeted drug delivery system has become an important target for protein or peptide absorption with the discovery of intestinal microflora and its important functions.Therefore,the application of oral colon-targeted drug delivery system to transport peptide and improve its stability and bioavailability has received extensive attention.At present,several efforts have been made by some researchers to improve the stability and bioavailability of SCT through utilizing liposome as the carrier.However,liposome has poor stability and it can't achieve the colon-targeted release of SCT to effectively improve the oral bioavailability of SCT.Recently,electrospinning is a simple and mild technique for the direct and continuous preparation of nanofibers.The obtained fibers,which exhibit small diameter,high specific surface area as well as high porosity,are supposed as an suitable alternative for the sustained and colon-targeted release of drugs.Therefore,the fiber mat containing pectin coated liposomes was developed by electrospinning to improve the stability of liposome and achieve the colon targeted release of SCT in this study,thus providing theoretical and practical basis for the studies concerning the administration of SCT.The main research results of this paper are as follows:(1)Preparation of SCT liposome and its characterization.Firstly,uncoated SCT liposomes and pectin coated SCT liposomes were prepared by thin film dispersion method.In our study,The optimal conditions were determined as lecithin concentration 30 mg/mL,cholesterol concentration 5 mg/m L,ultrasonic power 200 W and ultrasonic time 3 min.The average particle size,Zeta potential,encapsulation efficiency of the uncoated liposomes were 75.0 nm,-35.8 mV and 83.2%,respectively.The pectin coated liposomes were prepared under above conditions.For pectin coated liposomes,the suitablepectin concentration was 2 mg/mL.The average particle size,zeta potential,encapsulation efficiency were 120.6 nm,-39.1 m V and 84.6%,respectively.Then TEM images indicated that both liposomes were spherical in shape.Finally,results of FTIR analysis showed that the hydrogen bond was formed between the pectin and the liposomes and SCT was successfully encapsulated in the liposomes.(2)Preparation of electrospun single fiber mat containing pectin coated liposomes and its properties.Firstly,the influence of the solution composition and electrospinning parameters on the electrospinnability was investigated,and the optimal electrospinning conditions were determined as the mixed solution of PVA(polyvinyl alcohol,100 g/L): SA(sodium alginate,20 g/L)=8:2(w:w)concentration,distance 15 cm,voltage 16 kV,and flow rate 0.3 mL/h.Under the optimal conditions,the obtained fiber mat had good morphology with average diameter being 350 nm.Subsequently,FTIR,XRD and TGA were applied to investigate the structure of the fiber mat.The results of TGA analysis showed that the thermal properties of fiber mat were improved compared with the PVA/SA fiber mat.FTIR and XRD analysis indicated that the molecular interaction was occurred among pectin,liposome,PVA and SA in fiber mat.Additionally,the release kinetics analysis demonstrated that the release of SCT in SGF and SIF followed the Fickian diffusion mechanism.However,the release of SCT in SCF followed the case II transport.The results of in vitro simulated continuous release showed that the release of SCT in SCF from the fiber mat containing pectin coated SCT liposomes was16% higher than that of the fiber mat containing uncoated SCT liposomes,which indicated that the fiber mat containing pectin coated SCT liposomes had better colon targeting property.Finally,the SCT ELISA kit and HPLC were used to study the biological activity of SCT,respectively.The results indicated that the bioactivity of the released SCT was not destroyed by the preparation processes of liposome and fiber mat(P>0.05).(3)Preparation of electrospun coaxial fiber mat containing pectin coated liposomes and its properties.In order to further improve the colon targeting property of SCT fiber mat,coaxial fiber mat containing pectin-coated SCT liposomes was prepared by coaxial electrospinningTechnology.Firstly,the influence of the solution composition and electrospinning parameters was investigated,and the optimal electrospinning conditions were determined as mass of PEO concentration 80 g/L(in shell solution),PVA concentration 100 g/L(in core solution),distance 14 cm,voltage 16 kV,core solution flow rate 0.2 mL/h and shell solution flow rate0.2 mL/h.Under the optimal conditions,the obtained fiber mat had good morphology and distinct core-shell structure with average diameter being 390 nm.Then the structure of the fiber mat was characterized.TGA analysis showed that the thermal properties of fiber mat were improved compared with PVA,SA,and PEO.The results of FTIR and XRD analysis indicated that the molecular interaction was occurred between PEO and SA,and between PVA and pectin in fiber mat.Then the release kinetics analysis demonstrated that the release of SCT in SGF and SIF followed the Fickian diffusion mechanism.However,the release of SCT in SCF followed the case II transport.The results of in vitro simulated continuous release showed that the release of SCT in SCF from the coaxial fiber mat containing pectin coated SCT liposomes was 12.9% higher than that of the single fiber mat containing uncoated SCT liposomes,which indicates that the coaxial fiber mat containing pectin coated SCT liposomes exhibited better colon targeting property.Finally,the SCT ELISA kit,HPLC and circular dichroism spectrum measurements were used to study the biological activity of SCT.The results showed that there was no obvious change in the secondary structure of SCT,and the preparation process of core-shell fiber mat had no significant effect on the bioactivity of the released SCT(P>0.05).