| The weaned piglets are suffered diarrhea,indigestion and slow growth due to the incomplete development of immune organs,digestive system and other tissues in the aquaculture production,it is brings great economic losses to livestock production.Potassium diformate is an organic acid which can effectively enhance the growth function of animals.However,potassium diformate is absorbed too fast in the stomach and it can not effectively alleviate the pH of intestinal,so it is necessary to develop a novel drug release system.Microcapsules can be used to deliver the target drug directly to the lesion.In this paper,NaP zeolite were prepared from epidesmine and it was a carrier to load potassium diformate.Sodium alginate and chitosan were used as shell materials to prepare microcapsules with controlled drug release and reflected antibacterial effect.The structure and performance characteristics of NaP zeolite were analyzed by XRD?FT-IR?SEM?XPS?TG and Zeta.The effects of different factors on the preparation of NaP zeolite and the nucleation and crystal growth were discussed.The process of forming core material of NaP zeolite and potassium diformate,and the reaction mechanism of sodium alginate and chitosan were studied in the preparation process of microcapsules.The effects of different factors on the antibacterial properties and the sustained release effect were investigated.The study obtained the following results?1?Zeolite is treated with hydrochloric acid to obtain an acidified zeolite.The process of acidification destroys the original structure of the zeolite,removes other impurity elements such as aluminum,potassium and calcium in the raw material.The silica was main residue in the product,it provides a source of silicon for subsequent preparation of NaP zeolite.?2?The NaP zeolite is spherical and its particle size is about 1.5 um,its pore size is about 3.2 nm,and the infrared characteristic peak of the NaP zeolite is the 3443cm-1,1644 cm-1,998 cm-1,744 cm-1,674 cm-1,606 cm-1 and 440 cm-1.Si element of NaP zeolite exist in two different forms of[SiO4]4-and Si-OH.NaP zeolite has zero electric point at pH=5.75,when the pH value of the solution is less than 5.75,the surface of NaP zeolite is positively charged and can adsorb anions,when the pH value of the solution is greater than 5.75,the surface of the NaP zeolite is negatively charged and can adsorb cations.It is seen from the TG curve that the combined water was lost in the temperature range of 200 to 400°C,there is almost no mass loss after400°C-600°C,which proves NaP zeolite has good thermal stability.?3?The n?SiO2?/n?Al2O3?,n?Na2O/SiO2?,n?H2O/Na2O?ratio was 3.7,1.1 and 50,the crystallization temperature was 90°C,and the crystallization time was 6.5 h,the higher purity and better crystallization of NaP zeolite were synthesized.when the crystallization time was set from 0 h to 10 h.It was found that the nucleation period occurred before 1 h,secondary nucleation occurs in the product when crystallization time exceeds 1.5 h.The number of crystals increases significantly and the particle size become bigger as time increases.The FT-IR spectrum of NaP zeolite are very similar within 4 h.A certain degree of displacement of peaks occurs and the vibration intensity increases with the extension of reaction time,it is indicated that the crystallites are gradually growing and approaching the standard vibration frequency of the NaP zeolite.?4?NaP zeolite is reacted with potassium diformate and formed the core material of microcapsules at normal temperature.The C=O symmetric stretching vibration in the potassium diformate appeared in the core material near 1398 cm-1,it was indicated that the potassium diformate supported the NaP zeolite.The Al2p binding energy in the core material adds a binding energy peak at 75.3 eV compared with the NaP zeolite,it was indicated that the Al element participates in the reaction.It may be the H of the potassium diformate with O of the NaP zeolite Al-O structure forms a hydrogen bond.The carboxyl group of sodium alginate is electrostatically attracted to the amino group of the chitosan to form a polyelectrolyte membrane,which constitutes the shell material of the microcapsule.The potassium diformate microcapsules was formed by the shell material encapsulates the NaP zeolite and potassium diformate.?5?The antibacterial effect of the prepared microcapsules was discussed on Escherichia coli by setting different the quality of NaP zeolite,the concentrations of potassium diformate and the different mass ratio of sodium alginate to chitosan,the best experimental conditions was determined.The results showed that the quality of NaP zeolite was 0.1 g,the concentration of potassium diformate was 8 mg/ml,and the mass ratio of sodium alginate to chitosan was 2:1,the highest inhibition rate was reached 94%.?6?The acidity test showed that the pH was hardly changed in the gastric juice system when the microcapsules stayed in the stomach for 2 h or even longer in the simulated gastric juice environment,it was indicated that potassium diformate was not released in the gastric juice environment.In the simulated intestinal environment,when the microcapsules were retained for 3 h,the intestinal pH decreased from 7.2 to5.9,it was indicated that the microcapsules released potassium diformate in the intestinal environment and effectively reducing the pH of intestinal.?7?The concentration of potassium ion increased rapidly in the first 0.5 h and it increased slowly from 0.5 h to 3 h in the simulated intestinal environment with pH=7.4,The concentration was reached 27.50 mg/L.The concentration of potassium ion was almost no significant change with 3 h later,it was indicated that the potassium ions were all released in the microcapsules.In this process,the release amount of potassium diformate was 137.50 mg/g and the release rate was 45.66%.The potassium diformate of microcapsules can be released in the intestinal tract,it effectively solved that potassium diformate was excessive absorbed in the stomach and promoting the growth and development of piglets in the livestock industry. |
PDF Full Text Request