Quantum Dot Probes: Structural Features, Imaging Advantages, and Applications in Tumor Angiogenesis

Quantum dots are semiconductor nanocrystals that exhibit quantum confinement effects. Their fluorescence wavelength can be adjusted by controlling their composition, particle size, and surface structure. Their relatively narrow emission spectra, strong resistance to photobleaching, and ease of conjugation with antibodies, peptides, or nucleic acid ligands make them suitable for imaging tumor vascular morphology, tracing blood flow, detecting angiogenic targets, and multiplex molecular labeling.

Keywords: quantum dots; fluorescent probes; core–shell structure; NIR-II; tumor angiogenesis; VEGFR2; integrin αvβ3

1 What Are Quantum Dots?

1.1 Basic Definition

Quantum dots (QDs) are generally semiconductor nanocrystals with diameters of approximately 2–10 nm. When their dimensions approach or fall below the exciton Bohr radius of the material, the movement of electrons and holes becomes confined in three dimensions, converting continuous energy bands into size-dependent discrete energy levels. This phenomenon is known as the quantum confinement effect.

1.2 How Quantum Dots Produce Fluorescence

When a quantum dot absorbs a photon with energy greater than its bandgap, an electron is excited from the valence band to the conduction band, leaving a hole in the valence band. The electron and hole form an exciton, which subsequently releases a photon through radiative recombination. A portion of the excitation energy may also be lost through surface defects, lattice vibrations, or nonradiative recombination.

The excitation process can be represented as follows:

Photon absorption → electron–hole pair formation → exciton relaxation → radiative recombination → fluorescence emission

1.3 Why Particle Size Can Regulate Emission Wavelength

Within the same semiconductor material, reducing particle size strengthens the quantum confinement effect and increases the effective bandgap, shifting fluorescence emission toward shorter wavelengths. Increasing particle size decreases the effective bandgap and shifts emission toward longer wavelengths. The emission wavelength of a quantum dot is also influenced by elemental composition, doping, crystal defects, and shell structure and cannot be determined solely from particle size.

1.4 Major Material Types

Material Type	Representative Materials	Major Characteristics	Application Boundaries
II–VI quantum dots	CdS, CdSe, CdSe/ZnS	Relatively high luminescence efficiency and readily tunable emission wavelengths	Cadmium-containing materials require careful evaluation of ion leakage and long-term toxicity
I–III–VI quantum dots	CuInS₂, CuInS₂/ZnS	Broad emission range and reduced use of cadmium	Emission peaks are generally broader, and batch-to-batch consistency must be controlled
Silver chalcogenide quantum dots	Ag₂S, Ag₂Se, AgAuSe	Can cover near-infrared and NIR-II wavelengths	Silver-ion release, surface stability, and in vivo clearance must be evaluated
Lead chalcogenide quantum dots	PbS	Emission can extend into the NIR-II region	Lead-containing materials are more suitable for optical and materials research; biological applications require rigorous assessment
Carbon-based quantum dots	Carbon quantum dots and graphene quantum dots	Generally favorable water dispersibility and surface modifiability	Their luminescence mechanisms are not completely identical to those of conventional semiconductor quantum dots

2 Structural Composition of Quantum Dot Probes

Structural Level	Major Components	Structural Function	Design Considerations
Luminescent core	CdSe, CdS, CuInS₂, Ag₂S, Ag₂Se, or PbS	Determines the fundamental bandgap and emission range	Control elemental composition, particle size, and crystal defects
Inorganic shell	Wide-bandgap materials such as ZnS	Passivates surface defects and isolates the luminescent core	Control shell thickness, lattice matching, and structural integrity
Surface ligands	Thiol-, phosphine-, amine-, or carboxylic acid-based ligands	Stabilize the nanocrystal and provide reactive sites	Prevent ligand detachment, aggregation, and fluorescence quenching
Hydrophilic protective layer	PEG, amphiphilic polymers, or proteins	Improves water dispersibility and reduces nonspecific adsorption	Control hydrodynamic size, surface charge, and protein corona formation
Targeting module	Antibodies, peptides, aptamers, or small-molecule ligands	Recognizes vascular endothelial targets	Control conjugation orientation, ligand density, and binding activity
Functional module	Drugs, photosensitizers, magnetic components, or radioactive groups	Expands therapeutic or multimodal imaging functions	Avoid excessive increases in particle size or interference with quantum dot luminescence

2.1 Luminescent Core

The luminescent core determines the fundamental spectral range of the quantum dot. CdS, CdSe, or CuInS₂ systems are commonly used for visible-light imaging, whereas narrow-bandgap materials such as Ag₂S, Ag₂Se, AgAuSe, and PbS can be selected for NIR-II imaging.

2.2 Inorganic Shell

The surfaces of quantum dot cores contain undercoordinated atoms and defect energy levels that can capture electrons or holes and enhance nonradiative recombination. Coating the core with a wide-bandgap shell such as ZnS reduces surface defects and improves quantum yield, photostability, and the chemical stability of the core material.

2.3 Hydrophilic Coating and Surface Functional Groups

Quantum dots synthesized in an organic phase are generally stabilized by hydrophobic ligands and cannot be used directly in cellular or animal experiments. Ligand exchange, amphiphilic polymer coating, and PEGylation can transfer them into an aqueous phase while introducing reactive groups such as —COOH, —NH₂, —SH, azide, or alkyne groups onto the surface.

2.4 Target-Recognition Modules

Conjugating anti-VEGFR2 antibodies, RGD peptides, or other vascular-targeting ligands to the quantum dot surface can convert a blood-pool tracer into a molecular probe. An insufficient number of ligands reduces binding capacity, whereas excessive ligand density may increase hydrodynamic size, mask recognition sites, or enhance uptake by the reticuloendothelial system.

3 Imaging Advantages of Quantum Dot Probes

3.1 Spectral Properties and Multiplex Imaging

(1) Broad Absorption and Narrow Emission

Quantum dots can absorb photons over a broad energy range above their bandgap, whereas their fluorescence mainly arises from radiative recombination of band-edge electrons and holes. They therefore generally exhibit broad excitation ranges and relatively narrow emission peaks. Quantum dots with different emission wavelengths can be excited simultaneously under the same or similar conditions and subsequently distinguished according to their respective emission peaks.

(2) Regulation of Emission Wavelength by Size and Composition

The emission wavelength of a quantum dot is jointly determined by its core material, particle size, alloy composition, and core–shell structure. Within the same material system, decreasing particle size generally strengthens quantum confinement and produces a blue shift in emission, whereas altering the semiconductor composition can further expand the tunable wavelength range. Combining quantum dots with different emission wavelengths enables simultaneous labeling of vascular endothelial cells, tumor cells, and other microenvironmental components within the same tissue region.

(3) Practical Advantages of Multicolor Imaging

The advantage of quantum dots in multiplex imaging is not simply the availability of multiple colors. Multiple probes can share the same excitation source while retaining relatively distinct emission channels, reducing conflicts in excitation configurations among different fluorescent probes. Their actual resolving capacity is still affected by emission-peak full width at half maximum, particle-size distribution, detector response range, and spectral crosstalk.

3.2 Fluorescence Brightness and Photostability

(1) Core–Shell Structures Improve Radiative Recombination Efficiency

Undercoordinated atoms on the surfaces of uncoated quantum dots can generate trap states through which electrons or holes are lost by nonradiative processes. Coating the core with a wide-bandgap material such as ZnS can passivate surface defects and restrict carrier migration toward the surface, increasing the proportion of radiative recombination. The actual brightness of a quantum dot depends on its absorption cross-section, quantum yield, crystal quality, and shell integrity rather than solely on its material type.

(2) Resistance to Photobleaching Supports Dynamic Observation

The inorganic crystal and core–shell structures generally provide optimized quantum dots with favorable photostability. Under continuous excitation, they are less susceptible than some organic fluorophores to rapid and irreversible photobleaching. This property makes them suitable for prolonged monitoring of vascular perfusion, blood-flow changes, endothelial-cell migration, and the accumulation of targeted probes along vessel walls.

(3) Stability Does Not Mean Constant Signal Intensity

Quantum dots may still undergo photooxidation, fluorescence blinking, aggregation, and surface-ligand dissociation. Bioconjugation may also alter their surface electronic states and cause fluorescence quenching. Dynamic imaging should therefore monitor fluorescence-intensity changes over time and compare emission peaks, quantum yields, and photostability before and after functionalization.

3.3 Near-Infrared Imaging and Deep-Tissue Vascular Observation

(1) NIR-II Reduces Tissue-Scattering Background

Narrow-bandgap quantum dots such as Ag₂S, Ag₂Se, AgAuSe, and PbS can extend fluorescence emission into the NIR-II region at approximately 1,000–1,700 nm. Within this wavelength range, tissue autofluorescence is relatively low, and light scattering is generally weaker than in the visible and shorter-wavelength near-infrared regions, helping preserve vascular boundaries in deep tissues.

(2) Significance for Tumor Vascular Imaging

The value of NIR-II should not be summarized simply as “deeper penetration.” For vascular imaging, its more important advantage is the reduction of contour broadening caused by tissue scattering, which improves discrimination among adjacent vessels, small branches, and blood-flow boundaries. It can be used to observe tumor vascular networks, microcirculation, and dynamic perfusion.

(3) Emission Wavelength Is Not the Only Determinant

Actual imaging quality is also influenced by quantum yield, excitation wavelength, tissue absorption, detector quantum efficiency, and the optical filter system. Even among NIR-II quantum dots, imaging performance may differ substantially according to material composition and emission wavelength.

3.4 Surface Functionalization and Targeted Imaging

(1) Surface Functional Groups Provide a Basis for Conjugation

Following hydrophilization, carboxyl, amino, thiol, azide, or other reactive groups can be introduced onto quantum dot surfaces. These groups can subsequently be conjugated with recognition molecules such as antibodies, peptides, or aptamers, converting simple fluorescent tracers into targeted molecular probes.

(2) Multivalent Effects Enhance Overall Particle Binding

Multiple targeting ligands can be conjugated to the surface of a single quantum dot. When several ligands simultaneously interact with receptors on the cell membrane, multivalent binding can increase the overall binding strength and local retention of the particle on the target-cell surface. This provides an important structural basis for using quantum dots to image vascular targets such as VEGFR2 and integrins.

(3) Targeted Signals Are Also Influenced by Particle Behavior

Surface modification of quantum dots simultaneously changes their hydrodynamic size, surface charge, protein corona formation, and blood-circulation behavior. In vivo targeted signals depend not only on receptor expression and ligand affinity but also on blood-flow perfusion, vascular permeability, nonspecific uptake, and hepatic and splenic clearance. Local fluorescence intensity cannot therefore be directly equated with target-expression levels.

4 Construction of Targeted Quantum Dot Probes

4.1 Material and Wavelength Selection

Visible-light quantum dots can be selected for confocal cellular imaging and tissue sections. Probes emitting at 650–950 nm can be used for superficial vascular imaging in small animals, whereas NIR-II quantum dots are more suitable for deep-tissue imaging, whole-body blood-flow tracing, and dynamic observation of tumor vasculature. In multicolor experiments, the emission peaks of different quantum dots must be effectively distinguishable by the selected filters and detectors.

4.2 Aqueous-Phase Transfer and PEGylation

Quantum dots synthesized in an organic phase require ligand exchange or amphiphilic polymer coating to obtain water dispersibility. A PEG layer can reduce nonspecific protein adsorption and extend circulation time, but excessively long PEG chains or overly dense PEG coverage may reduce the accessibility of targeting ligands to their receptors.

4.3 Ligand Conjugation

Carboxyl-functionalized quantum dots can be activated using EDC/NHS or EDC/Sulfo-NHS and subsequently coupled to primary amines on antibodies, peptides, or proteins through amide-bond formation. Amino-functionalized quantum dots can react with NHS ester-modified ligands. Maleimide groups can conjugate with thiolated ligands, whereas copper-free click reactions between DBCO and azide groups are suitable for bioconjugation systems that are sensitive to metal catalysts.

4.4 Purification and Quality Control

After conjugation, free ligands should be removed by ultrafiltration, size-exclusion chromatography, or centrifugation. Hydrodynamic size, dispersity, Zeta potential, fluorescence spectra, and ligand loading should then be measured. Cadmium- or lead-containing quantum dots also require evaluation of shell integrity, metal-ion release, and cytotoxicity.

5 Biological Basis of Tumor Angiogenesis

5.1 Tumor Blood Vessel Formation

Continued tumor growth can create hypoxic regions, leading to HIF-1α stabilization and increased expression of pro-angiogenic factors such as VEGF-A. After VEGF-A binds to VEGFR2 on endothelial cells, it activates endothelial-cell proliferation, migration, and vascular sprouting. Basement-membrane degradation, tip-cell selection, stalk-cell expansion, and lumen formation collectively establish the new vascular network.

5.2 Structural Characteristics of Tumor Blood Vessels

Tumor blood vessels are often tortuous, abnormally branched, heterogeneous in diameter, loosely connected at endothelial junctions, and insufficiently covered by pericytes. Blood-flow velocity, perfusion uniformity, and permeability can vary across tumor regions and developmental stages. Fluorescence intensity measured at a single time point cannot fully represent vascular function.

5.3 Major Imaging Targets

Target or Marker	Biological Localization	Applicable Probes	Major Interpretive Information
VEGFR2	One of the principal receptors for pro-angiogenic signaling, with relatively high expression in activated endothelial cells	Anti-VEGFR2 antibody-conjugated quantum dots or VEGF ligand-conjugated quantum dots	Vascular endothelial activation and changes related to VEGF signaling
Integrin αvβ3	Participates in endothelial-cell adhesion, migration, and extracellular matrix recognition	RGD peptide-modified quantum dots	Localization of newly formed vessels and migratory endothelial cells
CD105	An auxiliary component of the TGF-β receptor complex that can be upregulated in proliferating endothelial cells	Anti-CD105 antibody-conjugated quantum dots	Detection of proliferative tumor vasculature
CD31	Endothelial cell-junction-associated molecule	Anti-CD31 antibody-conjugated quantum dots or tissue costaining	Vascular identity, distribution, and microvessel density
MMP-2/MMP-9	Participate in basement-membrane and extracellular matrix remodeling	Enzyme-responsive quantum dot probes	Vascular invasion regions and protease activity
HIF-1α/hypoxic regions	Located upstream of the angiogenic response	Combination of hypoxia-responsive probes and quantum dots	Spatial relationship between hypoxic regions and vascular distribution

6 Applications of Quantum Dots in Tumor Angiogenesis Research

6.1 Vascular Morphology and Blood-Flow Imaging

After entering the circulation, PEGylated near-infrared quantum dots can function as blood-pool fluorescent tracers for observing tumor vessel boundaries, branching patterns, vessel diameters, and perfusion. Ag₂S quantum dots have been used for real-time blood-flow imaging and imaging of small tumor-associated vessels within the NIR-II window.

6.2 VEGFR2-Targeted Imaging

After conjugation with quantum dots, anti-VEGFR2 antibodies can recognize VEGFR2-expressing endothelial cells. Cellular experiments can detect probe binding to endothelial cells, whereas animal experiments can reveal fluorescence accumulation in tumor vascular regions. Free-antibody competition and nontargeted quantum dot controls are required to exclude passive accumulation.

6.3 Integrin αvβ3-Targeted Imaging

The RGD sequence recognizes integrin αvβ3 and can be used to label regions of active angiogenesis. RGD-modified quantum dots can also be combined with magnetic components to construct fluorescence–magnetic resonance multimodal probes that provide both cellular-scale localization and whole-body anatomical information.

6.4 Multiplex Imaging of the Vascular Microenvironment

Quantum dots with different emission wavelengths can separately label vascular endothelial cells, pericytes, hypoxic regions, and tumor cells under the same excitation light. Spectral unmixing can then be used to analyze the spatial relationships among vascular density, pericyte coverage, and hypoxic distribution while reducing the localization bias caused by serial tissue sectioning.

6.5 Evaluation of Anti-Angiogenic Therapy

Changes in targeted quantum dot signals, vascular branching, perfusion, and permeability can be compared before and after treatment. A decrease in targeted signal may result from reduced target expression, fewer blood vessels, insufficient blood-flow perfusion, or restricted probe delivery and should be interpreted together with immunostaining and functional indicators.

7 Experimental Evaluation and Interpretation of Quantum Dot Probes

Evaluation Stage	Key Indicators	Essential Controls	Result Interpretation
Optical performance	Emission peak, full width at half maximum, quantum yield, fluorescence lifetime, and resistance to photobleaching	Quantum dots before functionalization	Determines whether shell coating, hydrophilization, and conjugation affect luminescence
Colloidal stability	Hydrodynamic size, dispersity, Zeta potential, and fluorescence retention	PBS, culture medium, and serum-containing systems	Determines whether aggregation, sedimentation, or fluorescence attenuation occurs
Cellular targeting	Uptake, membrane localization, intracellular distribution, and colocalization with markers	Nontargeted probe, ligand-competition group, and receptor-blocking or knockdown group	Distinguishes specific binding from nonspecific adsorption
In vivo imaging performance	Signal-to-background ratio, target-to-background ratio, imaging window, and tissue penetration	Nontargeted probe and equal-dose control	Evaluates vascular recognition capacity and the optimal imaging time
Tissue distribution	Fluorescence or elemental content in the tumor, liver, spleen, kidneys, and lungs	Pre-administration control and nontargeted probe	Determines tumor accumulation, organ uptake, and in vivo clearance
Angiogenic phenotype	Microvessel density, branch number, vessel diameter, perfusion, and permeability	Untreated group and anti-angiogenic intervention group	Distinguishes changes in vascular abundance, structure, and function
Vascular markers	CD31, CD105, VEGFR2, and integrin αvβ3	Isotype control, target blocking, or genetic intervention	Validates the correspondence between quantum dot signals and target expression

8 Products

8.1 Visible and Near-Infrared Core–Shell Quantum Dots

Catalog #	Product Name	Grade & Purity/Specifications	Functional Characteristics and Research Positioning
C475605	CdS/ZnS core-shell type quantum dots	PEG functionalized, fluorescence λₑₘ 450 nm, 4 μM in H₂O	Blue emission suitable for the short-wavelength channel in multiplex imaging
C475606	CdSe/ZnS core-shell type quantum dots	PEG functionalized, fluorescence λₑₘ 520 nm, 4 μM in H₂O	Green emission suitable for fluorescent labeling of cells and tissues
C475607	CdSe/ZnS core-shell type quantum dots	PEG functionalized, fluorescence λₑₘ 580 nm, 4 μM in H₂O	Orange emission that can be combined with green- and red-emitting quantum dots
C475608	CdSe/ZnS core-shell type quantum dots	PEG functionalized, fluorescence λₑₘ 620 nm, 4 μM in H₂O	Red emission that helps reduce short-wavelength background interference
C475339	CdSeS/ZnS alloyed quantum dots	COOH functionalized, fluorescence λₑₘ 630 nm, diameter 6 nm, 1 mg/mL in H₂O	Carboxyl-functionalized surface suitable for EDC/NHS-mediated conjugation with primary amine-containing ligands
C475340	CdSeS/ZnS alloyed quantum dots	COOH functionalized, fluorescence λₑₘ 665 nm, diameter 6 nm, 1 mg/mL in H₂O	Red emission suitable for constructing antibody- or peptide-conjugated probes
Q638974	Qdot 565 Amino (PEG) Quantum Dots	Ex:300 nm, Em:565 nm, Concentration: 3 mg/mL	Amino- and PEG-functionalized quantum dots suitable for conjugation with carboxylated ligands
Q638977	Qdot 605 Amino (PEG) Quantum Dots	Em:603 nm, Ex:300 nm, Concentration: 3 mg/mL	Red-orange fluorescent probe substrate suitable for multiplex immunolabeling
Q638984	Qdot 705 Amino (PEG) Quantum Dots	Ex:450 nm, Em:702 nm, Concentration: 3 mg/mL	Emission near the near-infrared region suitable for tissue imaging and deep-signal detection
C282543	Copper Indium Disulfide/Zinc Sulfide Quantum Dots	Peak Emission 550 nm ± 10 nm, QY > 75%	Visible-emitting material system that reduces reliance on cadmium
C282544	Copper Indium Disulfide/Zinc Sulfide Quantum Dots	Peak Emission 590 nm ± 10 nm, QY > 75%	Orange emission suitable for multicolor cellular labeling
C282545	Copper Indium Disulfide/Zinc Sulfide Quantum Dots	Peak Emission 630 nm ± 10 nm, QY > 75%	Red emission suitable for tissue-section and vascular labeling
C282547	Copper Indium Disulfide/Zinc Sulfide Quantum Dots	Peak Emission 800 nm ± 10 nm, QY > 75%	NIR-I emission suitable for superficial vascular imaging in small animals
C282548	Copper Indium Disulfide/Zinc Sulfide Quantum Dots	Peak Emission 950 nm ± 10 nm, QY > 75%	Emission near the NIR-II boundary suitable for evaluating near-infrared imaging systems

8.2 Surface-Functionalized Quantum Dots

Catalog #	Product Name	Grade & Purity/Specifications	Functional Characteristics and Research Positioning
F122251	Fluorescent quantum dots	Amino functionalized,Emission wavelength：525 nm,0.05 μmol/L	Amino-functionalized surface suitable for conjugation with carboxylated antibodies, peptides, or linkers
F122257	Fluorescent quantum dots	Amino functionalized,Emission wavelength：565 nm,0.05 μmol/L	Yellow-green emission suitable for dual or multiplex labeling
F122263	Fluorescent quantum dots	Amino functionalized,Emission wavelength：585 nm,0.05 μmol/L	Orange emission suitable for labeling cell membranes and proteins
F122269	Fluorescent quantum dots	Amino functionalized,Emission wavelength：605 nm,0.05 μmol/L	Red-orange emission suitable for developing antibody-conjugated probes
F122252	Fluorescent quantum dots	Carboxylic functionalized,Emission wavelength:525 nm,0.05 μmol/L	Can be activated by EDC/NHS and conjugated with primary amine-containing ligands
F122258	Fluorescent quantum dots	Carboxylic functionalized,Emission wavelength:565 nm,0.05 μmol/L	Suitable for conjugation with peptides, antibodies, and proteins
F122264	Fluorescent quantum dots	Carboxylic functionalized,Emission wavelength:585 nm,0.05 μmol/L	Suitable for constructing orange-emitting targeted quantum dot probes
F122270	Fluorescent quantum dots	Carboxylic functionalized,Emission wavelength:605 nm,0.05 μmol/L	Suitable for molecularly targeted imaging in the red fluorescence channel
C139721	CdSe/ZnS Quantum Dots	fluorescence λem 525 nm,8μmol/L in H2O	Aqueous amino-functionalized quantum dots suitable for direct downstream conjugation
C139736	CdSe/ZnS Quantum Dots	fluorescence λem 600 nm,8μmol/L in H2O	Aqueous red-orange probe substrate
C139745	CdSe/ZnS Quantum Dots	fluorescence λem 645 nm,8μmol/L in H2O	Long-wavelength red emission suitable for tissue labeling
C139689	CdSe/ZnS Quantum Dots,COOH functionalized	fluorescence λem 525 nm,8μmol/L in H2O	Aqueous carboxyl-functionalized quantum dots suitable for conjugation with antibodies and peptides
C139705	CdSe/ZnS Quantum Dots,COOH functionalized	fluorescence λem 605 nm,8μmol/L in H2O	Suitable for constructing red-emitting targeted probes
C139709	CdSe/ZnS Quantum Dots,COOH functionalized	fluorescence λem 625 nm,8μmol/L in H2O	Suitable for tissue-section imaging and vascular target labeling
C1521548	Carboxyl fluorescent quantum dot nanospheres	Particle size:300nm, 10mg/ml in H2O	The relatively large particle size and high surface-loading capacity are suitable for in vitro detection and material-conjugation evaluation

8.3 NIR-II Quantum Dots

Catalog #	Product Name	Grade & Purity/Specifications	Functional Characteristics and Research Positioning
A1452427	Ag2S Oil phase (1200 nm)	—	Oil-phase NIR-II quantum dots that require aqueous-phase transfer before biological imaging
A1452775	Ag2S-COOH (1200 nm)	—	Carboxyl-functionalized NIR-II quantum dots suitable for conjugation with antibodies or peptides
A1454549	Ag2S-PEG-NH2 (1200 nm)	—	PEG- and amino-functionalized quantum dots combining water dispersibility with reactive conjugation sites
P1452034	Pb:Ag2Se QDs	—	Lead-doped silver selenide quantum dots suitable for NIR-II materials and spectroscopic research
A1452063	AgAuSe Oil phase (1000 nm)	—	Emission at the beginning of the NIR-II region, suitable for phase-transfer and material-development studies
A1452042	AgAuSe Oil phase (1120 nm)	—	Oil-phase NIR-II quantum dots suitable for constructing deep-tissue imaging probes
A1452639	AgAuSe QDs	—	AgAuSe material system suitable for investigating near-infrared luminescence properties
A1452181	AgAuSe-COOH (1000 nm)	—	Carboxyl-functionalized surface suitable for EDC/NHS-mediated conjugation
A1452027	AgAuSe-COOH (1120 nm)	—	Suitable for constructing long-wavelength near-infrared targeted probes
A1451008	AgAuSe-PEG-NH2 (1000 nm)	—	PEGylated amino-functionalized quantum dots suitable for aqueous-phase bioconjugation
A1451918	AgAuSe-PEG-NH2 (1120 nm)	—	Suitable for developing NIR-II targeted imaging probes
P140913	PbS Quantum Dots	fluorescence λem 1120 nm, stabilized with octadecylamine ligands	Oil-phase NIR-II quantum dots suitable for phase-transfer and spectroscopic research
P140915	PbS Quantum Dots	fluorescence λem 1250 nm, stabilized with octadecylamine ligands	Suitable for evaluating detectors and imaging systems operating at 1,250 nm
P140916	PbS Quantum Dots	fluorescence λem 1330 nm, stabilized with octadecylamine ligands	Emit within a longer-wavelength NIR-II region with relatively reduced tissue scattering
P140917	PbS Quantum Dots	fluorescence λem 1420 nm, stabilized with octadecylamine ligands	Suitable for long-wavelength NIR-II materials and deep-tissue imaging research
P140918	PbS Quantum Dots	fluorescence λem 1520 nm, stabilized with octadecylamine ligands	Suitable for evaluating NIR-IIb spectroscopy and imaging platforms

8.4 Products for Quantum Dot Probe Conjugation

Catalog #	Product Name	Grade & Purity/Specifications	Functional Characteristics and Research Positioning
E106172	N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride	≥98%	Activates carboxyl groups on quantum dot surfaces and promotes amide-bond formation with primary amines
H109330	N-Hydroxysuccinimide (NHS)	≥98%	Forms an NHS active ester in combination with EDC and improves carboxyl-to-amine conjugation efficiency
H109337	N-Hydroxysulfosuccinimide sodium salt	≥98%	A water-soluble activation auxiliary reagent suitable for quantum dot conjugation in buffer
M163910	Maleimide PEG NHS, MAL-PEG-NHS	MW 2000 Da	The NHS terminus reacts with primary amines, whereas the maleimide terminus reacts with thiolated ligands
D404366	DBCO-PEG4-NHS Ester	≥95%	The NHS terminus modifies amino-containing molecules, whereas the DBCO terminus undergoes copper-free click conjugation with azide groups
N103916	D-Biotin N-Succinimidyl Ester	≥98%	Conjugates biotin to primary amine-containing antibodies, proteins, or quantum dot surfaces

Quantum dot probes can image tumor vascular architecture, blood-flow perfusion, and angiogenic molecules through emission-wavelength regulation, core–shell passivation, surface hydrophilization, and targeting-ligand conjugation. Practical applications require simultaneous control of optical stability, targeting specificity, tissue distribution, and material safety, with results interpreted in combination with histological and vascular functional indicators.

References

[1] Tripathi SK, Kaur G, Khurana RK, Kapoor S, Singh B. Quantum Dots and Their Potential Role in Cancer Theranostics. Crit Rev Ther Drug Carrier Syst. 2015;32(6):461-502.

[2] Medintz IL, Uyeda HT, Goldman ER, Mattoussi H. Quantum dot bioconjugates for imaging, labelling and sensing. Nat Mater. 2005;4(6):435-446.

[3] Hong G, Robinson JT, Zhang Y, Diao S, Antaris AL, Wang Q, Dai H. In vivo fluorescence imaging with Ag₂S quantum dots in the second near-infrared region. Angew Chem Int Ed Engl. 2012;51(39):9818-9821.

[4] Song C, Zhang Y, Li C, Chen G, Kang X, Wang Q. Enhanced Nanodrug Delivery to Solid Tumors Based on a Tumor Vasculature-Targeted Strategy. Adv Funct Mater. 2016;26(23):4192-4200.

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