Study On Optimizationand Application Of Dynamic In Vitro Biomimetic Rat Stomach Digestive Systems

In vitro biomimetic digestive tract is a device used to simulate human or animal gastrointestinal tract.Compared with in vivo tests,the in vitro digestion models can be used as 'pre-screening' tools to predict digestive behaviors occurred in vivo and to optimize in vivo conditions,thus replacing or partially replacing the in vivo trials with the advantages of time and labor-saving,lower cost and better repeatability as well as no ethical constraints.As a result,they are widely developed and used in the areas of food,pharmacy and microbiology etc.However,most of them developed both at home and abroad ignored effects of gastrointestinal morphology and inner structure on the digestive and gastric emptying behaviors.In the past over ten years,our group has designed and created the first and second generation of the dynamic in vitro rat stomach system according to the relevant physiological parameters obtained from the in vivo test on living rats based on the principle of morphological bionics.The rat stomach systems were validated by showing consistent similar digestive behaviors for the model foods with different components and structures(including casein powder suspension,raw rice particles,cooked rice and pig feeds)to those found in vivo.The thesis is aimed to improve and optimize the second generation of dynamic in vitro rat stomach system(DIVRS-?)by eliminating its drawbacks.The specific research contents mainly include:1)the 3D printing technology was applied to fabricate the silicone rat stomach model instead of the previously handcraft method;2)some new rat stomach models with varying gastric juice secretion tubes and inserting locations on the model surface were made to explore the effect of gastric juice secretion pattern on the mixing and digestive efficiency of the casein suspensions in the DIVRS-?;3)the effect of the rolling-extrusion frequency on the digestive efficiency was also investigated and the result under the optimized conditions was then compared with that in vivo;4)the DIVRS-? plus was created by placing all the syringe pumps and the stomach and duodenum device in the temperature-controlled box to make it more integrated and automatic,and the digestive behaviors of soybean milk and tofu were studied using the DIVRS-II plus.The results indicated that the 3D-printed silicone rat stomach models have better repeatability in terms of stomach morphology,dimension and wall thickness,and better compressive property and simpler fabrication process while lower cost compared to the handcraft stomach models.There was no obvious difference in the digestibility of the casein suspensions between the stomach models with single and four gastric juice secretion tubes;the rat stomach model with the single gastric tube inserting at the glandular portion(the rolling-extrusion area)could produce the highest digestibility than the other 5 rat stomach models with the single gastric tube inserting at the other locations.This indicates that the gastric juice secretion pattern had significant effect on the casein digestibility.Moreover,the digestibility was improved with the increase of the rolling-extrusion frequency and it reached the highest when the frequency was 12 cpm which was very close to that in vivo.The above results indicate that it is feasible to make the DIVRS-? as a 'near real' in vitro biometric rat stomach system by the optimization of relevant parameters.In addition,the particle size of the tofu was significantly reduced after being digested in the more integrated and automatic DIVRS-? plus;the digestion rate of the tofu was lower than that of the soybean mill whereas the final concentration of soluble peptides was almost the same.