Studies On Chitooligosaccharide/pectin Electrostatic Self-assembly And Complex BSA Loading

In acidic solution,positively charged chitooligosaccharide and negatively charged pectin can form chitooligosaccharide/pectin polyelectrolyte complexes?PEC?by the way of electrostatic self-assembly.In this paper,the turbidity,?-potential,heat flow and microscopic state of complexes during the self-assembly process were measured,and the FTIR spectra,TGA and SEM of the complexes were analyzed to infer the electrostatic self-assembly process between chitooligosaccharide and pectins.Furthermore,the effect of ion species and intensity,pH on the self-assembly process between chitooligosaccharide and pectin were discussed,and it is expected to provide technical guidance for the study of the self-assembly of anions and cations..In addition,the loading and release of bovine serum albumin?BSA?by chitooligosaccharide/pectin PEC were preliminarily studied,To lay the foundation for expanding the application of chitooligosaccharides and pectin in the field of material loading.The results were listed as follows:1.The weight ratio of chooligosaccharide to pectin?r value?in solution increased with chooligosaccharide adding into the pectin solution.There are four phases during electrostatic self-assembly between chitosan oligosaccharides and pectin:1)r<0.275,small amount of chitooligosaccharide bound to the pectin chain,and PEC had hydrophilic surface and electrostatic repulsion on the PEC surface was large,which is made PEC became a soluble colloidal substance.2)0.275?r<0.6,bind more chitooligosaccharide bound to pectin molecules,which made pectin culrly and distortion and form granular particles.The electrostatic repulsion between the particles decreased,and the distance between molecules decreased and particles aggregates and showed a structure with different shapes but interconnected,which resulted in lower stability of PEC particles.2)0.6?r<1,more chitooligosaccharide bound to the pectin chain,and PEC became denser particles and participated from solution due to the neutralization of surface charge on PEC.4)1?r?2,excessive chitooligosaccharide bound to the surface of PEC particles,and formed a core-shell structure.The surface of the particles was positively charged and showed electrostatic repulsion resulting that PEC agglomerates separated and dispersed particles were formed gradually.2.With the increase of r value,the chitooligosaccharide/pectin PEC was bonded with each other to form a stacked layered structure.The surface structure of PEC changed from rough to smooth,and the surface became smooth.Dispersed flake-shaped small particles were formed at last.The infrared spectroscopy showed that PEC was mainly formed by electrostatical interaction between amino group in chitooligosaccharide and carboxyl group in pectin accompanied by hydrogen bond and other forces?hydrophobic interaction,etc.?.And with r value increasing,the degree of electrostatical bonding increased,and the combination became tighter.PEC obtained exhibited higher thermal stability than that of chitooligosaccharide and pectin homopolymer.The thermal decomposition temperature of PEC was higher than 210?.3.At pH 3.5,the electrostatic shielding effect of ions added increased with their concentrations,which weakened the self-assembly between chitooligosaccharide and pectin and the pectin molecules became easy to bend and fold to form much smaller particles.For example,PEC particles with size of 200 nm could be seen in 30 mM NaCl.The order of inhibition of various anions for the self-assembly between chitooligosaccharide and pectin was as follow:strong acid ion>monobasic acid ion>weak acid ion.PEC mainly possessed slender network in soluting containing strong acid radical,while the PEC was more likely to aggregate in the presence of weak acid in solution.The effect of three kinds of monovalent cation on self-assembly between chitooligosaccharide and pectin was similar.The OH/NH absorption band changed significantly in infrared spectrum of PEC due to the addition of ions,but remaining positions in infrared spectrum of PEC did not change,indicating that no new interaction between chitooligosaccharide and pectin was found.4.With NaCl concentration rising,turbidity of composite solution decreased and?-potential decreased first and then increased with a minimium at NaCl concentration of 40mM.PEC bound with each other and became larger particles with smooth surface at C_NaCl?10 mM.At C_NaCl?20 mM,PEC gradually showed a surface with shrinkage and convex marks,and particle size decreased respondingly.At NaCl concentration of 70 mM,the electrostatic self-assembly between chitooligosaccharide and pectin was seriously hindered,and less and smaller PEC was formed.5.The self-assembly process between chitooligosaccharide and pectin was highly dependent on solution pH.When pH was in the range from 3 to 6,those two polyion polymers can self-assembled to form insoluble PEC substances in composite solutions at different r-value.Chitooligosaccharide did not interact with pectin at pH<3 or pH>6.6.In the solution containing ions,solution pH affected the self-assembly between chitooligosaccharide and pectin by changing the dissociation degree of various acid radicals.Dissociation degree of acid radicals increased because of higher solution pH value?4.5?,and their effects on the self-assembly between chitooligosaccharide and pectin was similar to strong acid radical ions.the lower the pH?3.5?,the lower dissociation degree of acid radical ions.On the other side,greater acid radical ions enhanced the cross-linking between chitooligosaccharide and pectin,which increased the self-assembly between chitooligosaccharide and pectin.7.BSA loading could be enhanced by chitooligosaccharide.NaCl concentration increasing had a negative effect on BSA loading.Better loading efficiency of BSA by PEC could be achieved at NaCl concentration of 30 mM or solution pH below 4.While at pH above 4.5,BSA loading rate and embedding rate decreased sharply.When r value increased,high-density,densely packed drug-loaded particles could be formed,but the drug loading rate and embedding rate decreased.The effect of various load methods on BSA loading was:pec+BSA>pec+BSA+cos>cos+BSA+pec>cos/pec PEC adsorbing BSA after freeze-drying.8.Results obtained from study on release of BSA showed that BSA almost did not release from drug-loaded particles at pH4.Furthermore,the research of in vitro release of BSA implicated that a sustained release of BSA could be achieved when pH of simulated gastric fluid was 4.PEC made by self-assembly between chito-oligosaccharide and pectin has potential to be used for sustained release and colon-targeted oral delivery of protein or peptides functional foods and medicines.