I. Achieving Drug Encapsulation and Activity Protection as Drug Carriers
1.1 Ultra - high Drug - loading Capacity
The high specific surface area and rich internal pore structure of mesoporous materials provide ample storage space for drug molecules. Taking mesoporous silica (MSNs) as an example, numerous studies have shown that its drug - loading capacity can reach 30% - 70% of its own mass. A research team synthesized a type of MSNs with a highly ordered pore structure through the improved sol - gel method, and its drug - loading capacity for the poorly soluble anti - cancer drug paclitaxel was as high as 65%. Compared with traditional liposomes and polymer microspheres, the drug - loading capacity increased by 2 - 3 times. This not only improves the drug - loading amount per unit carrier, reduces the use of carriers, but also reduces the immunogenicity and other potential risks that the carriers may cause.
1.2 Drug Activity Protection
In the complex physiological environment of the body, drugs are extremely vulnerable to inactivation due to factors such as changes in pH, enzymatic hydrolysis, and oxidative stress. The nanoscale pores of mesoporous materials can act as micro - protection chambers, encapsulating drug molecules and effectively isolating them from adverse external factors. The stability change of the easily oxidizable coenzyme Q10 after being encapsulated in MSNs was studied by simulating the gastric juice and intestinal juice environment. The results showed that the retention rate of the active ingredient of unencapsulated coenzyme Q10 was only 25% after 30 minutes in simulated gastric juice, while that of coenzyme Q10 encapsulated in MSNs reached more than 95% under the same conditions.
II. Achieving Precise Drug Controlled Release
2.1 Intelligent Responsive Release
By modifying special responsive groups on the surface of mesoporous materials, intelligent drug release can be achieved. Common responsive stimuli include pH, temperature, specific enzyme concentration, and redox potential. A temperature - responsive mesoporous material modified with poly N - isopropylacrylamide (PNIPAM) was prepared. When the environmental temperature reaches the high - temperature characteristic of the tumor site (about 40 °C), PNIPAM undergoes a phase transition, opening the pores of the mesoporous material to release the drug; while at normal body temperature (37 °C), PNIPAM remains in a contracted state, and the drug is released slowly. In animal experiments, when this temperature - responsive mesoporous material was used to load the anti - cancer drug doxorubicin, compared with traditional drug preparations, the drug concentration at the tumor site increased by 3 times, and the toxic and side effects on normal tissues were significantly reduced.
Rapid transport and transformation of biomacromolecules are achieved through the thermal - stimulated active "inhalation - exhalation" cycle of the hierarchical intelligent pNIPAM - DNA hydrogel.
2.2 Sustained and Stable Release
The pore size and surface chemical properties of mesoporous materials can precisely regulate the drug release rate, achieving long - term stable drug release. Using the ordered pore structure of mesoporous carbon material (CMK - 3), the sustained and stable release of the antibiotic vancomycin for up to 20 days was achieved by adjusting the interaction between the drug and the pore wall. It was found that by changing the functional groups on the surface of CMK - 3, such as introducing carboxyl groups, amino groups, etc., the electrostatic interaction and hydrogen - bonding interaction between vancomycin and the pore wall can be effectively adjusted, thereby precisely controlling the drug release rate. This achievement provides a new drug - delivery strategy for the treatment of chronic infectious diseases, reduces the inconvenience of patients taking medicine frequently, and improves the treatment compliance.
Molecular modeling and adsorption properties of CMK mesoporous carbon with ordered silica template
III. Mesoporous Materials Facilitate Drug Targeted Delivery
3.1 Active Targeting Mechanism
Connecting molecules with targeted recognition functions, such as antibodies, aptamers, and polypeptides, to the surface of mesoporous materials can achieve active targeted drug delivery. These targeting molecules can specifically bind to receptors on the surface of diseased cells, guiding the drug - loaded mesoporous materials to accurately reach the diseased site. A monoclonal antibody against HER2 - positive breast cancer cells was modified on the surface of MSNs to prepare an actively targeted drug - loading system. In in vitro cell experiments, the uptake rate of the modified mesoporous materials by HER2 - positive breast cancer cells was more than 6 times that of unmodified mesoporous materials; in animal experiments, the drug concentration at the tumor site increased by more than 4 times, significantly enhancing the treatment effect. This research result shows that modifying targeting molecules on the surface of mesoporous materials is an effective strategy for achieving precise drug delivery.
Shenzhen Institute of Advanced Technology has made progress in the research of artificial targets and immune - recognition dual - guided tumor treatment.
3.2 Passive Targeting Principle
Based on the physiological differences between diseased tissues and normal tissues, such as the high permeability and retention effect (EPR effect) of tumor tissues, mesoporous materials can accumulate at the diseased site through passive targeting. Research shows that mesoporous materials with a particle size of 20 - 150 nm can effectively utilize the EPR effect and accumulate in tumor tissues. By studying the distribution of mesoporous materials with different particle sizes in tumor tissues, it was found that mesoporous materials with a particle size of 60 - 100 nm had the highest accumulation in tumor tissues, which was 5 - 7 times that of normal tissues.
Using PEGylated magnetic nanoparticles to describe the enhanced permeability and retention (EPR) effect of tumors for predicting the efficacy of micellar drugs
4.1 Co - delivery of Multiple Drugs
The multiple pores or adjustable spatial structure of mesoporous materials allows for the simultaneous encapsulation of multiple different types of drugs, enabling combination therapy. For example, co - loading chemotherapeutic drugs and immunotherapeutic drugs in mesoporous materials, the two drugs can work synergistically to improve the treatment effect of diseases such as cancer. Chemotherapeutic drugs can directly kill cancer cells, while immunotherapeutic drugs activate the body's immune system, enhancing the immune surveillance and killing ability against cancer cells.
4.2 Combination of Drugs with Other Treatment Methods
Mesoporous materials can not only load drugs but also be combined with other treatment methods, such as photothermal therapy, photodynamic therapy, magnetothermal therapy, etc. For example, doping nanoparticles with photothermal conversion properties (such as gold nanorods) into mesoporous materials while loading chemotherapeutic drugs. Under near - infrared light irradiation, the gold nanorods generate heat to kill cancer cells (photothermal therapy), and at the same time, the mesoporous materials accelerate drug release due to the increase in temperature, achieving the combination of chemotherapy and photothermal therapy and significantly improving the treatment effect.
V. Improving the Solubility and Stability of Drugs
5.1 Improving Drug Solubility
The low solubility of many poorly soluble drugs in the body limits the exertion of their efficacy. Mesoporous materials can encapsulate poorly soluble drugs in the pores through physical embedding or chemical interaction, increasing the dispersibility of the drug in the solution, thereby improving the drug solubility. For example, some fat - soluble drugs, after being encapsulated in hydrophilic mesoporous silica, can be better dispersed in an aqueous medium, which is beneficial to the absorption and utilization of the drug.
5.2 Enhancing Drug Stability
Mesoporous materials can provide a relatively stable micro - environment for drugs, protecting them from the influence of external environmental factors (such as moisture, oxygen, enzymes, etc.) and preventing drug degradation. Especially for some drugs that are easily oxidized, hydrolyzed, or decomposed by enzymes, the protective effect of mesoporous materials is particularly important, which can extend the shelf - life of the drug and ensure the quality stability of the drug during storage and transportation.
VI. Frontier Exploration of New Mesoporous Materials
6.1 Mesoporous Organosilica Materials (PMOs)
PMOs combine the advantages of organic and inorganic materials, with adjustable pore size, good biocompatibility, and chemical stability. An amino - containing PMOs was synthesized, and its drug - loading capacity for the small - molecule anti - cancer drug doxorubicin reached 45%, and it could achieve pH - responsive release under simulated physiological conditions. In tumor cell experiments, this PMOs drug - loading system showed good cytotoxicity and targeting, providing a new option for cancer treatment.
6.2 Mesoporous Metal - Organic Framework Materials (MOFs)
MOFs have an ultra - high specific surface area and adjustable pore structure, capable of loading a large number of drug molecules. A MOFs based on ZIF - 8 was prepared, and its drug - loading capacity for the hydrophobic drug curcumin was as high as 70%. At the same time, through surface modification with folic acid molecules, active targeting of tumor cells was achieved. In animal experiments, this MOFs drug - loading system significantly inhibited tumor growth, showing good application prospects.
Common characterization methods of metal - organic frameworks (MOFs)
With their unique structures and properties, mesoporous materials have made significant progress in the field of high - efficiency drug delivery. From traditional mesoporous silica to new mesoporous organosilica materials and mesoporous metal - organic framework materials, the boundaries of drug delivery are constantly expanding. They show great application potential in drug carriers, controlled release, and targeted delivery, providing new ideas and methods to solve the problems of traditional drug delivery systems.
