targeted agents

1. Targeted preparations are also called targeted drug delivery systems (TODDS for short).

It refers to a drug delivery system that selectively concentrates drugs in target tissues, target organs, target cells or intracellular structures through local administration, gastrointestinal tract or systemic blood circulation with the help of carriers, ligands or antibodies.

The biological properties of the human body can be exploited, such as pH gradient (colon targeting of oral formulations), differences in capillary diameter, immune defense system, special enzyme degradation, receptor reactions, special chemical environment of the diseased site (such as pH value) and some Physical means (such as magnetic fields).

2. Characteristics of targeted preparations:

Make the drug have specificity of pharmacological activity, increase the directivity and retention of the drug to the target group, reduce the toxicity of the drug to normal cells, reduce the dosage, and improve the bioavailability of the drug preparation;

A successful targeted formulation should have three factors: localized concentration, controlled drug release, and non-toxic and biodegradable properties.

3. Classification of targeted agents:

(1) According to different carriers, it can be divided into liposomes, nanoparticles, nanospheres, and composite emulsions.

(2) According to different routes of administration, it can be divided into: oral drug delivery system

rectal drug delivery system

colon drug delivery system

Dermal drug delivery system

Ophthalmic drug delivery system

(3) According to different target sites, it can be divided into liver-targeting preparations, lung-targeting preparations, and brain-targeting preparations.

Classification of targeted agents:

According to the target area, it is divided into three levels:

Level one refers to reaching the target tissue or organ; level two refers to reaching cells (such as tumor cells instead of normal cells, liver cells instead of Kupffer cells);

Level three refers to reaching specific parts of the cell.

According to the targeted delivery mechanism, they are divided into three categories: passive targeting agents, active targeting agents, and physical and chemical targeting agents.

(1) Passive targeting preparations: drugs are wrapped or embedded in various types of particles, and the drugs are delivered to the target site by utilizing the carrier or phagocytosis of particles of different sizes by different organs, tissues or reticuloendothelial systems in the body;

(2) Active targeting preparations: Drug particle delivery systems with modified surfaces that are not recognized by the mononuclear phagocytic system. Special ligands and monoclonal antibodies are connected to them to enable them to bind to the receptors of target cells;

(3) Physicochemical targeted preparations: Certain physical and chemical methods are used to transport drugs to specific sites to achieve targeting purposes. Including magnetic guidance preparations, heat-sensitive preparations, pH-sensitive preparations, and embolization preparations.

4. Carriers for targeted preparations, including macromolecular linkers and microparticle drug delivery systems. Microparticle drug delivery systems include liposomes, polymer nanoparticles, polymer micelles, and dendrimers.