Thrombin: A Comprehensive Analysis from Basic Properties to Research Applications

1 Basic Definition and Properties of Thrombin

Thrombin is a proteolytic enzyme converted from prothrombin, with a molecular weight of approximately 33,580 Daltons. It appears as white to off-white non-crystalline solid, commonly supplied in the form of lyophilized lumps or powder. This enzyme directly acts on plasma fibrinogen, cleaving fibrinopeptide A and B to generate insoluble fibrin clots and thus accelerate blood coagulation. Thrombin is soluble in water but insoluble in organic solvents, making it ideal for topical hemostatic application in aqueous solutions.

Biochemically, thrombin activity is susceptible to environmental conditions. Its aqueous solution is unstable and must be freshly prepared right before use to guarantee hemostatic efficacy. In addition, acids, alkalis and heavy metals will inactivate thrombin. Sterile normal saline is recommended for preparation, and the solution temperature should not exceed 37°C. For long-term activity retention, store the product hermetically below 10°C.

Thrombin plays a central role in the blood coagulation system. As a key enzyme in coagulation cascade, it also promotes epithelial cell mitosis and accelerates wound healing. With multiple biological functions, thrombin serves as not only a hemostatic agent but also a multifunctional bioactive protein.

2 Diverse Applications of Thrombin

2.1 Medical Applications

As an efficient topical hemostatic drug, thrombin is widely used in clinical practice. It targets the final step of blood coagulation, converting soluble plasma fibrinogen into insoluble fibrin to achieve rapid hemostasis. Its clinical applications are mainly divided into two categories:

• Surgical Hemostasis: Thrombin is primarily used to control bleeding from small blood vessels, capillaries and parenchymal organs that are difficult to ligate. Common scenarios include trauma, oral cavity, otorhinolaryngology, urology, burn treatment, orthopedics, neurosurgery, ophthalmology and obstetrics & gynecology. Dissolve thrombin with sterile sodium chloride solution to prepare 50–200 U/mL solution for spraying, or apply powder directly onto wound surfaces. Combined with absorbable gelatin sponge, its hemostatic effect can be further enhanced, especially for small vessel bleeding during surgery.
• Gastrointestinal Hemostasis: For upper gastrointestinal bleeding such as gastroduodenal hemorrhage, hematemesis and melena, thrombin can be administered orally or via local perfusion. Prepare 10–100 U/mL solution with normal saline or warm water (≤ 37°C). Since thrombin loses activity in acidic environment, antacids are usually taken orally or administered intravenously beforehand to neutralize gastric acid. Phosphate buffer (pH 7.6) or cold milk can also be used to prepare latex-like thrombin solution for better efficacy and reduced dosage.

2.2 Administration Methods and Dosage

Different administration methods and concentrations are adopted for various applications. The table below summarizes standard protocols:

Thrombin can also be formulated into latex solution with excipients such as acacia, gelatin, fructose gum and honey to improve hemostatic efficiency and reduce dosage. In all applications, ensure full contact between thrombin and wound surface for optimal effect.

3 Research Applications of Thrombin

3.1 Disease Model Establishment

Thrombin is widely used to establish animal disease models, especially for thrombotic diseases and disseminated intravascular coagulation (DIC). By controlling dosage and delivery route, researchers can simulate pathological conditions of human diseases for mechanism study and drug evaluation.

• DIC Model: A rabbit DIC model is commonly induced by combined use of thrombin and aminocaproic acid. Inject 100 U/kg thrombin plus 50 mg/kg aminocaproic acid via femoral vein at a constant rate of 1 mL/min for 60 minutes. This method establishes stable DIC with high success rate. After administration, PT is gradually prolonged, PLT and FIB levels decline, and 3P test turns positive, showing obvious time-dependent pathological changes consistent with clinical DIC manifestations.
• Mesenteric Venous Thrombosis Model: Thrombin is applied to build rabbit mesenteric venous thrombosis models for studying thrombosis mechanisms and antithrombotic drugs. Inject thrombin solution at 80 U/mL or 40 U/mL into branches of anterior mesenteric vein. The average time for extensive thrombosis formation is 15.6±2.0 minutes for 80 U/mL group and 22.3±2.5 minutes for 40 U/mL group, indicating an apparent dose-dependent effect. Thrombosis duration and plasma D-dimer levels can be monitored to evaluate antithrombotic therapies.

3.2 Detection Technology & Biosensing

As a core biomarker in coagulation system, thrombin has become a target for developing high-sensitivity detection assays. Based on specific molecular recognition, a variety of biosensors have been developed for quantitative detection of thrombin in biological samples.

Recently, aptamer-based assays have shown outstanding performance. A colorimetric biosensor was constructed using dual-aptamer sandwich recognition combined with nicking enzyme-assisted loop-mediated isothermal amplification for signal amplification. The system utilizes G-quadruplex-hemin DNAzyme to catalyze ABTS-H₂O₂ reaction and produce characteristic green color. The linear detection range is 0.01–1.0 ag/mL with a limit of detection down to 0.008 ag/mL, featuring ultra-high sensitivity and excellent specificity even in rat serum containing interfering proteins.

These ultrasensitive detection methods are promising for basic research and clinical diagnosis, facilitating early screening and therapeutic monitoring of thrombotic disorders. Integrated technologies achieve ultra-sensitive thrombin detection with simple operation, good stability and low cost.

3.3 Pharmaceutical Research & Therapeutic Evaluation

Thrombin-induced animal models are essential for evaluating the efficacy of anticoagulants and thrombolytic agents, helping researchers assess drug efficacy and action mechanisms accurately.

In the study of Lipo-PGE1 for mesenteric venous thrombosis, rabbit models induced by thrombin were divided into different treatment groups. Plasma D-dimer levels were detected at multiple time points. The results proved that Lipo-PGE1 significantly enhances fibrinolytic activity and elevates D-dimer concentration, demonstrating its therapeutic potential against mesenteric venous thrombosis.

Related studies also confirmed that Lipo-PGE1 can strengthen the in vivo fibrinolytic effect of low-dose urokinase in a synergistic manner. These applications fully reflect the great value of thrombin in new drug development and combined therapy exploration.

4 Important Precautions

Although widely applied in clinic and research, thrombin must be used in compliance with strict regulations to ensure safety and efficacy.

Injection is strictly prohibited. Thrombin is only for topical use, oral administration or local perfusion. Intravenous, intramuscular or subcutaneous injection may cause intravascular thrombosis, local tissue necrosis and even life-threatening risks. Strict safety control is required during production and application.

Allergic reactions occur occasionally. Discontinue use immediately once allergy appears. Mild fever has been reported after surgical application. Patients with thrombin allergy are contraindicated.

Use with caution in special populations. Thrombin is only recommended for pregnant women when clearly necessary. For children and elderly patients, weigh benefits and risks before administration.

Distinguish between research-grade and clinical-grade thrombin. Though purity varies, their basic properties and functions remain consistent. Record product source, concentration, activity unit and batch number for experimental repeatability and data reliability.

5 Conclusion

As a vital bioactive enzyme, thrombin is an inherent component of human coagulation system, an indispensable clinical hemostatic agent and a key reagent for scientific research. Its applications cover surgical hemostasis, gastrointestinal bleeding treatment, disease model construction and high-performance biosensor development. With technological advancement, thrombin will have broader prospects in basic research and clinical diagnosis. In-depth research on its mechanism will also promote the development of novel hemostatic and anticoagulant drugs.

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