Carrier And Biological Level Evaluation Method of Oral Nano-Drug Delivery System
The oral nano-drug system is evaluated at the body level mainly through intact animals, which have complete blood supply and innervation to ensure that the intestinal nerves are intact and directly reflect drug absorption. This evaluation method can be used to study drug penetration and absorption kinetics. The related detection methods mainly include: in vivo intestinal perfusion method, intestinal loop method, intestinal vascular intubation method and nitrogen measurement method.
- Intestinal Perfusion
In vivo intestinal perfusion is to insert a double-lumen tube into the intestine through the mouth (in experimental animals, the perfusion tube and the drainage tube are inserted into the proximal and distal ends of the intestine respectively through open surgery), and a peristaltic pump is used to transfer the drug solution to enter the intestinal cavity at a certain amount speed, collect the effluent, measure the concentration of the drug and the tracer respectively, and calculate the drug absorption rate. In vivo perfusion methods can be divided into one-way perfusion, circulation perfusion and vibration perfusion. The method is limited to solution administration, where the pH, drug concentration, absorption site and other factors may affect the accuracy of the determination.
- Intestinal Loop
Intestinal loop method is to anesthetize the rat, open abdominal and ligate intestinal cavity (the intestinal cavity can be ligated segmentally when doing domain research). After inject artificial intestinal fluid into the intestinal loop for a certain period of time, remove the intestinal loop, collect the intestinal loop for flushing Liquid, determine the remaining amount of drug. The method is simple to operate, but the intestinal cavity has a large amount of contents and sample processing is complicated. The rat intestinal loop model is used to study the absorption of lactic acid glycolic acid copolymer particles. Small particles pass through the intestinal tissue 15 to 250 times more efficiently than large particles. Histology found that 100nm particles are distributed in the submucosa, while large nanoparticles are mainly distributed in the epithelial tissue.
- Vascular Cannulation
Vascular cannulation method is to intubate the intestinal vessels on the basis of intestinal perfusion. It can be intubated in the mesenteric vessel that supplies blood to a section of intestine, or in the superior mesenteric artery that supplies blood to the entire small intestine. And hepatic portal vein, the portal vein or systemic venous blood is drawn at different times to study the absorption of medicated blood from the intestinal cavity. The drug absorption in this method is calculated based on the amount of drug absorbed into the blood, and is not limited by animal size and blood volume. It can truly reflect the intestinal absorption of the drug, but the result is affected by the catabolism of the drug in the body.
- Measuring nitrogen
Measuring nitrogen is to measure the difference between the amount of nitrogen in animal excrement and food to calculate the absorption of the drug. The method does not require animal surgery, has no physiological impact on animals, and is simple. However, this method is relatively rough. When studying organic substances such as amino acids, it is susceptible to the influence of bacteria and endogenous substances in the animal’s intestines.
- Live animals
Live animal evaluation is also called in vivo method, which can reflect the overall absorption of drugs in the body and is suitable for the pharmacokinetic study of a variety of drugs. After oral administration, blood, urine, etc. were collected at different time points, the drug concentration was measured, the drug-time curve in the body was drawn, and pharmacokinetic parameters such as Cmax and Tmx were calculated to evaluate the rate and extent of drug absorption. In vivo bioimaging technology uses in-vivo tracing and imaging methods to intuitively express the transport and distribution of drugs in the body. The radiolabeled tracing method uses radioisotopes 99Tc, 111In, 152Sm and 172E as labels, and incorporates nanoparticles.These marks can track the transport behavior of drugs in the body. Other imaging technologies include bio-luminescence and fluorescence imaging, which are highly sensitive, safe, easy to operate, intuitive results, true and reliable data, and low cost. Bioluminescence is the integration of luciferase gene into cell chromosomal DNA to express luciferase. In the presence of adenosine triphosphate (ATP) and oxygen, luciferin is given to the substrate, and the luciferase catalyzes the oxidation reaction of the substrate to produce emission light. CCD photosensitive device, record and display its luminescence. Fluorescence imaging technology uses excitation light to make the fluorophore reach a higher energy level, and then detects the longer wavelength light emitted. Commonly used fluorescent groups are green fluorescent protein (GFP) and red fluorescent protein.