Quantum dots (QDs), also known as semiconductor nanocrystals, are colloidal particles with a size ranging from 2 to 10 nm in diameter and a size-dependent and various optical and electronic properties. Due to their superior optical properties including brightness, lifetime, and tunable emission wavelength, quantum dots have shown significant promise in a wide variety of medical applications in cancer research and therapy. As a novel fluorescent probe, quantum dots exhibit many unique advantages over traditional fluorescent labels in bioimaging, drug delivery, and photodynamic therapy (PDT).
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Basic Properties and Advantages of Quantum Dots
1. Optical properties
The size and composition of quantum dots are the main factors affecting their optical properties. By controlling the size of quantum dots, the emission wavelength can be finely tuned, which endows quantum dots with good flexibility in biomedical applications. For example, the excitation wavelength of quantum dots is broad and continuously distributed, while the emission wavelength band is narrow and symmetrical, which enables multiple biomolecules to be detected simultaneously in the same spectral range without spectral overlap. Moreover, high quantum yield (QY) and long fluorescence lifetime are also the basis of quantum dots to perform well in bioimaging and biosensing.
2. Electronic properties
The electronic properties of quantum dots are also worth exploring. Quantum dots have semiconductor properties and can be controlled by external stimuli (electric field or photon). This enables quantum dots' performance to be more precisely controlled. Such control capabilities also endow quantum dots with broad application prospects in the field of electronic and optoelectronic devices and sensors.
3. Advantages compared to traditional fluorescent markers
Compared to traditional fluorescent molecules, quantum dots possess far superior optical stability. For example, quantum dots are 100 times more resistant to photobleaching than traditional organic dyes, which endow them with higher stability for long-term biological imaging. In addition, the narrow emission band and wide absorption spectrum also provide quantum dots with unique advantages in multicolor imaging and high-sensitivity detection.
Application of Quantum Dots in Cancer Diagnosis and Treatment
Quantum dots (QDs) are often used as an auxiliary tool for clinical cancer diagnosis due to their excellent optical properties, high fluorescence efficiency, long fluorescence lifetime and adjustable emission wavelength. QDs have been applied in the visualization of cancer cells, multi-channel immunofluorescence detection, in vivo imaging, tumor localization, lymph node tracing, and other aspects, showing a broad application prospect in the field of cancer diagnosis.
1. Used as fluorescent probes for visualization of cancer cells
QDs can be used as fluorescent probes to mark specific molecules or organelles on the surface of cancer cells. By combining QDs with antibodies, peptides, small molecules and other specific binders, the high sensitivity and high specificity of cancer cells can be detected. For example, researchers successfully labeled Her2 protein on the surface of breast cancer cells using quantum dots coupled to IgG and avidin, thereby realizing the detection of breast cancer cells. In addition, the high fluorescence efficiency and long-term stability of quantum dots can be used as ideal tools for cancer cell imaging, which can help doctors accurately locate tumor tissues during surgery.
2. Used for multi-channel immunofluorescence detection to improve diagnostic accuracy
The multicolor fluorescence properties of quantum dots can be used to detect multiple biomolecules simultaneously, thus improving the accuracy of diagnosis. For example, researchers used four different colors of quantum dots to couple with antibodies against cholera toxin, ricin toxin, Shigella toxin 1 and Staphylococcus enterotoxin B, respectively, and detected four toxins on the same microplate at the same time. This multi-channel detection method not only improves detection efficiency, but also reduces experimental costs and time.
3. Used for in vivo imaging to achieve real-time monitoring of tumors
The near-infrared emission properties of quantum dots can be used to penetrate tissues and achieve in vivo imaging. For example, researchers encapsulated quantum dots in phospholipid microspheres, and used them to conduct in vivo imaging experiments in Xenopus embryos, the results showed that quantum dots had good stability and low toxicity during embryonic development. In addition, near-infrared quantum dots also have the prospect of sensitive detection and in vivo imaging of cancerous tumors in animal experiments. By monitoring the growth and metastasis of tumors in real time, doctors can detect tumors earlier and develop more effective treatment plans.
4. Application of quantum dots in tumor localization and lymph node tracing
QDs can be used for tumor localization and lymph node tracing to help doctors more accurately remove tumors during surgery and reduce the risk of postoperative recurrence. For example, researchers used (CdSe)ZnS quantum dots coupled with peptides to detect hemangiomas and lymphomas in mice. In addition, QDs can also achieve specific biomarker targeting through surface modification, thereby improving the specificity and sensitivity of imaging.
Application of Quantum Dots in Drug Delivery
QDs can be used not only as fluorescent probes for cancer diagnosis, but also as drug carriers for cancer treatment. The diversity and adjustability of quantum dots also give them broad application prospects in the field of drug delivery systems.
1. Mechanism of quantum dots as drug carriers
QDs can achieve targeted delivery through surface modification, thereby improving the targeting and therapeutic effects of drugs. For example, researchers synthesized a hyaluronic acid (HA)-based nanocomposite that could target the CD44 receptor widely expressed in cancer cells, thereby enhancing the effect of anticancer drugs. In addition, QDs can also achieve slow release of drugs through sustained release and controlled release mechanisms, thereby reducing drug side effects and improving therapeutic effects.
2. Drug loading capacity of quantum dots in cancer treatment
QDs can be used as drug carriers to deliver therapeutic drugs to target tissues. For example, researchers have developed a method of using luminescent quantum dots as imaging tags to evaluate the performance of different polymer drug delivery formulations, which can also simulate the effectiveness of other important drug delivery schemes. In addition, QDs can also enter cells through endocytosis to achieve intracellular delivery of drugs. For example, PLGA nanoparticles loaded with doxorubicin and containing quantum dot biotags can be engulfed by cells and internalized into the cytoplasm, thereby achieving targeted drug delivery.
3. Application of quantum dots in pH-responsive drug delivery systems
QDs can be used in pH-responsive drug delivery systems to improve therapeutic effects by adjusting the release rate of drugs. For example, ZnO nanocarriers can achieve controlled release of drugs through pH-responsive mechanisms, thereby improving the targeting and therapeutic effects of drugs. In addition, quantum dots can also be combined with other materials to achieve multifunctional drug delivery systems. For example, ZIF-8@Ce6-HA nanocomposites can not only improve the targeting of drugs, but also improve blood circulation time, thereby improving the therapeutic effect of drugs.
4. Research progress of quantum dots in tumor targeted delivery
QDs can achieve targeting of specific biomarkers through surface modification, thereby improving the targeting and therapeutic effect of drugs. For example, the CD44 receptor is a receptor whose natural ligand is HA, which has high affinity and can bind specifically to it. Through HA-modified nanocarriers, targeted delivery of malignant tumors with overexpression of CD44 can be achieved. In addition, quantum dots can also achieve targeting of specific cells through peptide modification, thereby improving the targeting and therapeutic effect of drugs. For example, through surface modification, quantum dots can bind to specific peptides to achieve targeting of specific cells.
Application of Quantum Dots in Cancer Treatment
1. The role of quantum dots in photodynamic therapy (PDT)
Photodynamic therapy (PDT) is a method of killing tumor cells by producing reactive oxygen species (ROS) induced by light-activated photosensitizers. Quantum dots have been widely studied in PDT because of their unique optical properties. Quantum dots have tunable photoluminescence (PL) properties, high photostability, and long fluorescence lifetime. For example, quantum dots can be used as substitutes or enhancers for photosensitizers, thereby improving the efficiency of PDT. Studies have found that quantum dots can generate ROS under light excitation, thereby inducing tumor cell apoptosis. In addition, quantum dots can also be combined with photosensitizers to form a composite photosensitive system to further improve the therapeutic effect. For example, researchers combined quantum dots with anticancer drugs such as doxorubicin, and used tumor-targeting ligands modified on the surface of quantum dots to enable drugs to be specifically enriched in tumor cells, achieving efficient killing of tumor cells.
2. Application of quantum dots in photothermal therapy (PTT)
Photothermal therapy (PTT) is a method of killing cancer cells by locally heating tumor tissue through photothermal effect. Quantum dots work in PTT mainly by absorbing light of a specific wavelength and converting it into heat energy. For example, graphene quantum dots (GQDs) are widely used in photothermal therapy. This is mainly due to the high loading capacity for the delivery of small molecule drugs and the ability of graphene quantum dots to absorb incident radiation. GQDs can produce enough heat under 808 nm laser irradiation to achieve efficient killing of cancer cells. In addition, MoS2 quantum dots are also used in photothermal therapy, which can produce a significant thermal effect under 808 nm laser irradiation, and have fluorescence imaging and MRI functions, realizing multimodal imaging and treatment.
3. Quantum dots as a combined treatment platform
Quantum dots can be used not only for diagnosis but also for treatment, so they are widely studied as a combined treatment platform. For example, quantum dots can be combined with chemotherapy drugs to form a complex with dual therapeutic and diagnostic values. This complex can not only increase the concentration of drugs in tumor tissues and reduce toxic side effects on normal tissues, but also achieve real-time monitoring of tumors through fluorescence imaging. In addition, quantum dots can also be combined with gene therapy for targeted drug delivery and gene therapy. For example, researchers combine quantum dots with DNA to detect specific DNA sequences, thereby achieving early diagnosis of tumors.
4. Responsiveness of quantum dots in tumor microenvironment
The responsiveness of quantum dots in tumor microenvironment is an important advantage in cancer treatment. The tumor microenvironment has unique physical and chemical properties, such as low pH and high enzyme activity. Quantum dots can be designed to be responsive to these environmental factors by designing their surface modifications. For example, quantum dots can be designed to release drugs at low pH values, thereby improving the targeting of drugs in tumor tissues. In addition, quantum dots can also respond to specific enzymes through enzyme responsiveness design, thereby improving the release efficiency of drugs. These characteristics make the application of quantum dots in tumor microenvironment have broad prospects.
Other Applications of Quantum Dots in Biomedicine
1. Application of quantum dots in biosensing and bioimaging
Quantum dots are widely used in biosensing and bioimaging. Due to their unique optical properties, quantum dots can be used as efficient fluorescent probes for highly sensitive and specific biomarker detection. For example, quantum dots can be used to detect biomolecules such as DNA, proteins, and sugars, thereby achieving early diagnosis of diseases. In addition, quantum dots can also be used for live cell imaging and in vivo imaging to monitor tumor growth and metastasis. For example, researchers combine quantum dots with DNA to detect specific DNA sequences, thereby achieving early diagnosis of tumors.
2. The role of quantum dots in drug development and drug metabolism research
Quantum dots also play an important role in drug development and drug metabolism research. Due to their unique optical and chemical properties, quantum dots can be used in the development of drug delivery systems. For example, quantum dots can be loaded with chemotherapeutic drugs and achieve targeted delivery to tumors through surface modification, thereby improving the therapeutic effect of drugs. In addition, quantum dots can also be used in drug metabolism research, monitoring the distribution and metabolic process of drugs in the body through fluorescence imaging technology. For example, researchers combined quantum dots with anticancer drugs such as doxorubicin, and used tumor-targeting ligands modified on the surface of quantum dots to enable drugs to be specifically enriched in tumor cells, achieving efficient killing of tumor cells.
3. Application of quantum dots in biomarker detection
Quantum dots are also widely used in biomarker detection. Due to their high sensitivity and high specificity, quantum dots can be used to detect a variety of biomarkers, such as bombesin receptors for pancreatic cancer, Alpha-Fetoprotein for liver cancer, and Epidermal Growth Factor Receptor for lung cancer. In addition, quantum dots can also be used for multicolor imaging to diagnose Hodgkin's lymphoma. For example, researchers combined quantum dots with antibodies to detect specific cell surface markers, thereby achieving early diagnosis of tumors.
