The colon is located between the cecum and rectum and is divided into four parts: the ascending colon, the transverse colon, the descending colon, and the sigmoid colon. Its main function is to absorb water and electrolytes and solidify the contents into feces. The colon cannot actively absorb substances such as sugar, amino acids, and small molecule peptides. Its absorption function is mainly achieved by the content of the colon staying for a long time. Some drugs can be absorbed by passive diffusion. The physiological environment of the colon has the following characteristics: ① The pH is generally 6.5 to 7.5, which varies depending on the diet structure and physiological…

The eye is divided into anterior and posterior segments. The anterior segment includes the cornea, conjunctiva, iris, aqueous humor, and ciliary body. The posterior segment includes the vitreous, retina, choroid, and sclera. The physiological barriers of the eye include the corneal and conjunctival barriers, the aqueous humoral barrier, and the blood-retinal barrier. The cornea and retina are barriers that are not easily penetrated by drugs. The drug absorption of eye drops usually has a corneal route and a non-corneal route. Fat-soluble drugs enter the aqueous humor from tears mainly through the corneal pathway. In the non-corneal pathway, the drug penetrates into the human eye tissue through the conjunctiva and sclera,…

Common kidney diseases include pathological changes in primary and secondary glomeruli, renal tubules, renal mediators, and renal blood vessels. In the clinical treatment of kidney disease, hormone shock treatment is often used, supplemented by triptolide tablets and other drugs for maintenance treatment. The toxic and side effects of large doses of hormones and maintenance drugs severely limit the continuous treatment of kidney disease. When kidney disease develops to a later stage, chronic renal failure will occur, and patients have to rely on expensive hemodialysis or kidney transplantation to prolong life, which will bring a heavy burden on patients’ families and society. It is of great significance to research and develop…

Brain diseases such as brain tumors, Alzheimer’s disease, Parkinson’s disease, central nervous system infections, chronic pain, drug addiction, periodic migraine, neurodegenerative diseases, epilepsy, and schizophrenia are the threat of human body and mind of improtant diseases of health. However, during the treatment process, the blood-brain barrier (BBB) prevents most drugs from entering the brain, resulting in poor drug effects. Brain targeted delivery of drugs to the brain is to use various techniques to promote the drug to break through the BBB into the brain. The current brain targeted delivery methods mainly include changing the physicochemical properties of the drug, preparing prodrugs, and carriers. Among them, nanocarriers have attracted much attention…

Due to the increasing environmental pollution and the harm of smoking, lung diseases have become an important factor affecting human health. One of the more serious diseases is lung cancer. Lung cancer is a malignant lung tumor that results from the uncontrolled growth of lung tissue cells. If left untreated, the tumor cells will metastasize to nearby tissues or elsewhere in the body. The most common primary malignant tumor of the lung is epithelial cancer, which can be roughly divided into small cell carcinoma (SCLC) and non-small cell carcinoma (NSCLC). The most common symptoms of lung cancer are cough (including hemoptysis), weight loss, shortness of breath, and chest pain. The majority (85%) of patients with lung…

Physiological characteristics of the liver The liver is an important organ involved in the processes of digestion, excretion, detoxification and immunity. Liver diseases are common clinical diseases, such as viral hepatitis, cirrhosis and liver cancer, which are extremely harmful to human health. The liver-targeted drug delivery system is an important way to explore an effective treatment method for liver disease, as it enriches the drug at the site of the liver lesion to exert the curative effect, reducing the amount of drug and the number of drug administration. Liver cells are divided into hepatic parenchymal cells, Kupffer cells and endothelial cells, of which parenchymal cells are the main cells that make up the…

The blood-brain barrier (BBB) is a barrier system that exists between the blood system and the brain tissue, and is mainly composed of polarized intercellular tight junctions of polarized brain capillary endothelial cells (BCECs). It maintains a relatively stable internal environment for brain tissue, guarantees the normal physiological function of the central nervous system (CNS), and transports nutrients to the brain; but at the same time, its existence also hinders the drug of diagnosis and treatment  into the brain.  About 98% of small molecule drugs and almost 100% of macromolecular drugs, including proteins, peptides and gene drugs, cannot be directly delivered into the brain by peripheral administration, which is a…