In recent years, the penetration and impact of nanotechnology on medicine, bioengineering and pharmacy has been evident. Nanotechnology has an irreplaceable advantage in pharmacy, especially in the fields of targeted and localized drug delivery, mucosal drug delivery, gene therapy and controlled release of protein and polypeptide

Drugs in conventional dosage forms are distributed throughout the body after intravenous, oral or local injection, and the amount of drugs that actually reach the treatment target area is only a small part of the dose, and the distribution of most drugs in non-target areas not only has no therapeutic effect, it will also bring toxic side effects. Therefore, the development of new drug dosage forms has become a direction of the development of modern pharmacy, and the research on targeted drug delivery system (TDDS) has become a hot spot in pharmacy research

Compared with simple drugs, nano drug carriers can realize targeted drug therapy. Targeted drug delivery refers to a drug delivery system that helps carriers, ligands or antibodies to selectively localize drugs to target tissues, target organs, target cells or intracellular structures through local administration or systemic blood circulation. Under the action of a specific guidance mechanism, the nano drug carrier delivers the drug to a specific target and exerts a therapeutic effect. It can achieve an effective drug with less dosage, low side effects, sustained drug effect, high bioavailability, and long-term retention of the concentration effect on the targets.

Targeted preparations are mainly carrier preparations, which mostly use ultrafine particles, which can selectively gather these particle dispersions in the liver, spleen, lymph and other parts due to physical and physiological effects in the body. TDDS refers to a new type of drug delivery system that can concentrate and localize drugs in diseased tissues, organs, cells or intra cells through local or systemic blood circulation.

Nano medicine preparations are targeted. They can concentrate drugs in the target area with little impact on non-target organs. They can improve drug efficacy and reduce systemic side effects. They are considered to be the most suitable dosage forms for carrying anticancer drugs. At present, some targeted nano-preparation products are on the market, and a large number of targeted nano-preparations are in the research stage, which have broad application prospects in tumor treatment.

Features of nano-targeted preparations:

⊙ Targeting: the drug is concentrated in the target area;

⊙ Reduce the dosage of medication;

⊙ Improve curative effect;

⊙ Reduce the side effects of drugs. 

The targeting effect of targeted nano-preparations has a great correlation with the particle size of the preparation. Particles with the size less than 100nm can accumulate in the bone marrow; particles of 100-200nm can be enriched in solid tumor sites; while 0.2-3um uptake by macrophages in the spleen; particles >7 μm are usually trapped by the pulmonary capillary bed and enter lung tissue or alveoli. Therefore, different nano preparations show different targeting effects due to the differences in the state of drug existence, such as particle size and surface charge. 

The commonly used carriers for constructing integrated nano-platforms for targeted diagnosis and treatment mainly include:

(1) Lipid carriers, such as liposome nanoparticles;

(2) Polymer carriers, such as polymer dendrimers, micelles, polymer vesicles, block copolymers, protein nano particles;

(3) Inorganic carriers, such as nano silicon-based particles, carbon-based nanoparticles, magnetic nanoparticles, metal nanoparticles, and up-conversion nanomaterials, etc..

The following principles are generally followed in the selection of nano carriers:

(1) Higher drug loading rate and controlled release characteristics;

(2) Low biological toxicity and no basal immune response;

(3) It has good colloidal stability and physiological stability;

(4) Simple preparation, easy large-scale production, and low cost 

Nano Gold Targeted Therapy

Gold(Au) nanoparticles have excellent radiation sensitization and optical properties, which can be well applied in targeted radiotherapy. Through fine design, nano gold particles can accumulate positively into tumor tissue. Au nanoparticles can enhance the radiation efficiency in this area, and can also convert the absorbed incident light energy into heat to kill cancer cells in the area. At the same time, the drugs on the surface of nano Au particles can also be released in the area, further enhancing the therapeutic effect. 

Nanoparticles can also be targeted physically. Nanopowders are prepared by wrapping drugs and ferromagnetic substances, and using the magnetic field effect in vitro to guide the directional movement and localization of drugs in the body. Commonly used magnetic substances, such as Fe₂O₃, have been studied by conjugating mitoxantrone with dextran and then wrapping them with Fe₂O₃ to prepare nanoparticles. Pharmacokinetic experiments were carried out in mice. The results showed that magnetically targeted nanoparticles can quickly arrive and stay in the tumor site, the concentration of magnetically targeted drugs in the tumor site is higher than that in normal tissues and blood.

Fe₃O₄ has been proven to be non-toxic and biocompatible. Based on unique physical, chemical, thermal and magnetic properties, superparamagnetic iron oxide nanoparticles have great potential to be used in a variety of biomedical fields, such as cell labeling, target and as a tool for cell ecology research, cell therapy such as cell separation and purification; tissue repair; drug delivery; nuclear magnetic resonance imaging; hyperthermia treatment of cancer cells, etc.

Carbon nanotubes(CNTs) have a unique hollow structure and internal and external diameters, which can form excellent cell penetration capabilities and can be used as drug nanocarriers. In addition, carbon nanotubes also have the function of diagnosing tumors and play a good role in marking. For example, carbon nanotubes play a role in protecting the parathyroid glands during thyroid surgery. It can also be used as a marker of lymph nodes during surgery, and has the function of slow-release chemotherapy drugs, which provides broad prospects for the prevention and treatment of colorectal cancer metastasis.

To sum up, the application of nanotechnology in the fields of medicine and pharmacy has a bright prospect, and it will surely cause a new technological revolution in the field of medicine and pharmacy, so as to make new contributions in improving human health and quality of life.