Research Progress of Self-Assembled Drug Delivery Systems 2
Regarding the research progress of self-assembled drug delivery systems, we have introduced the clinical research on acyclovir and didanosine self-assembled systems in previously article. This article will continue to introduce the research results of other drug self-assembly systems, such as zidovudine, isoniazid and gemcitabine self-assembly drug delivery systems.
Zidovudine
Zidovudine (AZT) is the first anti-HIV drug to be marketed and is still the first-line drug. Nano-preparations of zidovudine include liposomes and nanoparticles. As they may obtain the property of sustained release, lymphatic targeting, and macrophage system targeting,these nano preparations can reduce or eliminate the bone marrow toxicity caused by the distribution of zidovudine in the bone marrow tissue. Since zidovudine, as nucleoside analogs, must be converted into triphosphates in the body before it can be incorporated into nucleic acid synthesis, some studies have phosphorylated zidovudine before preparing it into nano-formulations. In terms of zidovudine prodrugs, it is generally prepared into lipid derivatives, and then further prepared into nano-formulations, also to reduce adverse reactions and increase curative effects, such as zidovudine palmitate and zidovudine phospholipid derivative.
Macrophages are the host of HIV and can survive for a long time after being infected with HIV. Therefore, macrophages carry HIV around and become a new source of infection and spreader of HIV. The currently marketed anti-HIV drugs have limited distribution in macrophages, which has become one of the reasons why AIDS is difficult to cure. Therefore, nano drug delivery systems targeting macrophages are particularly important for the treatment of AIDS. The self-assembly of Zidovudine lipid prodrug designed by the researchers can target macrophages in vivo, and has a strong anti-HIV effect, can resist the drug resistance of HIV, and can be used as a new type of AIDS treatment drug.
Isoniazid
Isoniazid (INH) is the most commonly used anti-tuberculosis drug, and its structure is similar to the pyrimidine ring in nucleoside organisms. Isoniazid is mainly converted into inactive metabolites through acetylation in the liver, or is metabolized by partial hydrolysis. Due to genetic differences, the population can be divided into fast acetylation and slow acetylation. Their half-life is significantly different, the average t1/2 of fast acetylation is 1.1 hours; slow acetylation is 3 hours. Among them, the adverse reactions of chronic acetylation are diseases of the blood system, endocrine system and neuropsychiatric system. Fast acetylation is more likely to cause liver toxicity. Isoniazid is difficult to enter the macrophages that swallow tuberculosis bacteria, and increasing the dose will increase the adverse reactions. The nano drug delivery system for preparing isoniazid can reduce side effects and enhance curative effect, such as nanoparticles, liposomes, microemulsions, and a variety of isoniazid prodrugs are synthesized.
The researchers designed three structural types of isoniazid prodrugs. Among them, compound 1 is a fatty acid and isoniazid connected directly through an acyl group, compounds 2 to 4 are fatty alcohols connected to isoniazid through succinyl, and compound 5 is The fatty amine is linked to isoniazid through the thiadiazine thione ring. The Langmuir monolayer behaviors of the five isoniazid lipid derivatives at the air/water interface are quite different. This is directly related to their molecular structure. It can be found through simulation that the short fatty chain isoniazid lipid derivative (compound 2) is highly hydrophilic and is easily squeezed into subphase water, in the Langmuir monolayer surface pressure-molecular area (π-A) curve The display can only withstand low surface pressure (about 20mN/m). The isoniazid lipid derivative with a long fatty chain (compound 4) has strong hydrophobic interaction and can withstand a large surface pressure, and the collapse pressure can reach more than 60 mN/m. At this time, the compound molecules are very tightly compressed. The structure of compound 5 is quite special. Due to the existence of the thiadiazine thione ring, the polar head becomes bulky and flat. The molecules are prone to dislocation and superposition during the compression process, which is typical plateau period in the π-A curve. By analyzing the behavioral characteristics of the Langmuir monolayer of amphiphilic prodrugs, it is possible to understand the three-dimensional structure characteristics of the molecules at the water interface and the interactions between molecules, and to infer whether molecular self-assembly occurs and its driving force.
Gemcitabine
Gemcitabine (GEM) is an anti-tumor drug and is the first-line drug for stage III and IV non-small cell lung cancer. The amino group in gemcitabine molecule is easily deaminated and inactivated, so oral administration is ineffective, and it is quickly inactivated in the blood. The traditional gemcitabine preparation is gemcitabine hydrochloride for injection. The main adverse reaction of gemcitabine is bone marrow suppression. The preparation of gemcitabine into nanoparticles may protect the drug from degradation and increase oral bioavailability. The intravenous injection of gemcitabine triphosphate in nanoparticles may improve the efficiency of treatment of non-small cell lung cancer and pancreatic cancer. Among them, gemcitabine liposomes have been studied more, and higher encapsulation efficiency can be obtained by pH gradient method. After gemcitabine is lipid derivatized, it can be further prepared into liposomes], nanoparticles, polymer gelatin. Gemcitabine prodrugs are generally modified on the amino group in the design, which can prevent deamination in the body and enhance the activity of the drug.
The researchers prepared amino-substituted N-stearyl gemcitabine (NOG) and N-lauroyl gemcitabine (NDG). Their behavior at the air/water interface is quite different due to the difference in fatty chains. Due to the long fatty chain of NOG, it can form a strong monolayer, the collapse pressure can reach more than 50mN/m, and can continue to form a complete film after collapse. However, due to the short fatty chain of NDG, the molecules tend to ” lodging ” on the interface, the collapse pressure is lower, and the film formed is softer.
As an anti-tumor drug, gemcitabine’s nano drug delivery system has the best “long-circulation” effect, and it can achieve tumor targeting as much as possible through the tumor EPR effect. Researchers tried to incorporate long-cycle material cholesteryl succinyl polyethylene glycol into NOG, and investigated the effect of different ratios of CHS-PEG on the behavior of NOG monolayers, and found that CHS-PEG1500 increased the flexibility of the membrane to a certain extent. The energy calculation after mixing shows that when the ratio of CHSPEG/NOG is about 4:6, the energy of the mixed membrane is the smallest and the two molecules are most easily mixed. With reference to the long-circulation nano system in the past, 20% CHS-PEG was added to the NOG self-assembly, and the self-assembly was prepared by the ethanol injection method. It was found that the self-assembly of different forms was obtained with the difference of solvent and concentration.