In Vitro Evaluation Method of Oral Nano Drug Delivery System
The in vitro evaluation method of oral nano-drug system is a simple and rapid method to evaluate the transport and absorption of oral nano-drug. This method is simple and easy to implement, has good reproducibility, and the experimental environment and conditions are easy to control, so that the influencing factors are singularized and simplified, but it cannot reflect the actual absorption state of the drug in the body. This method is often used to study the intestinal absorption mechanism of the nano drug delivery system. The method mainly includes inverted intestinal sac method, intestinal piece incubation method, membrane vesicle method, cell culture model method, parallel artificial membrane permeability determination method, computer simulation, drug dissolution/absorption biomimetic system method, etc.
Inverted Gut Sacs Method
Inverted gut sacs method is to take out the small intestine of the anesthetized animal, put the intestinal segment on a glass rod, and place it in the medicine-containing Krebs-Ringer’s solution. Regularly take samples from both the inside and outside of the intestine to determine the change in drug concentration. This method can be used to study the transport mechanism of biofilms. Due to the relatively small volume of the serosal side, the drug accumulates quickly, which is convenient for sample analysis. However, this method can only observe the concentration of the drug passing through the intestinal wall, and cannot calculate more detailed absorption kinetic parameters. Because of its lack of blood and nerve supply, the tissue is easy to die, the experiment time should not be too long, and the morphological damage is likely to be caused when the small intestine is turned over.
Ussing Chamber Method
Ussing chamber method is to fix intestinal pieces or mucosa of suitable size on the holes between the grooves containing mucosal fluid and serous fluid which are not connected to each other. After incubation, the drug content on both sides of the membrane is measured, and the drug is calculated. Absorption rate from mucosa to serosa. Use Ussing trough to obtain the passive drug transport volume by controlling the membrane potential on both sides of the membrane. This method can determine the survival of the small intestine by measuring the resistance of the small intestine membrane. This method can compare the effects of different parts of the small intestine on drug absorption; the number of drugs required is relatively small and the samples are clean and easy to analyze; it is suitable for the study of the human small intestine and is used to compare species differences. However, this method lacks blood and nerve supply, and it is easy to cause morphological damage during the operation and inlay process.
Membrane Vesicle Method
Membrane vesicle method is to suspend the membrane vesicles in a drug-containing buffer to ingest drugs, thereby simulating the process of drug absorption, for studying drug absorption or metabolism, including brush border membrane vesicles and basement membrane Vesicles. The experiment time of this method is relatively short, the required drugs are relatively small, the preparation of membrane vesicles is relatively convenient, the accuracy is high, and the drug properties and nutrient substance transportation can be studied in depth. But the membrane vesicles are not very pure and may contain other fragments. The digestive juice used in the preparation of membrane vesicles may cause damage to the protein, resulting in poor reproducibility of the preparation of membrane vesicles. In addition, this method lacks cell metabolism, so it cannot be used to study ATP-dependent transport and cell bypass transport.
Parallel Artificial Membrane Permeability Assay
Parallel artificial membrane permeability assay (PAMPA) is a method for measuring the passage of negatively charged phospholipid bilayer barriers. It can be used as a permeability screening tool and is mainly used for Passive diffusion of charged compounds can be used to simulate active transport of compounds.
DDASS
Drug dissolution/absorption simulating system (DDASS) is composed of a drug dissolution chamber (simulating stomach), a pH adjustment chamber (simulating intestine), and a diffusion cell. The diffusion cell is composed of a supply chamber, a receiving chamber, and Caco-2 monolayer cells or rat intestinal tubes embedded in the two. During the measurement, the drug to be tested is added to the drug dissolution chamber, and the dissolved drug is transferred to the pH adjustment chamber by the constant flow peristaltic pump, and further transferred to the diffusion cell supply chamber. The sample program-controlled automatic collector can be separately from the supply chamber and the receiving chamber at any time Collect samples. The bionic system takes into account the dynamic process of drug migration from the stomach (pH 1.8) to the intestine (pH 6.0), and monitors drug release and permeation in real time.