150nm Quantum Dot Microspheres HQD610-150 1%

150 nm Quantum Dot Microspheres HQD610-150

SHBC HQD610-150 Quantum Dot Microspheres are high-brightness fluorescent microspheres developed for immunoassay research, fluorescence lateral flow assay development, biomarker detection and bulk diagnostic reagent manufacturing.

HQD610-150 has a nominal particle size of 150 nm, a solids content of 1% and a fluorescence emission peak centered at approximately 610 nm. Multiple quantum dots are incorporated into each polymer microsphere to provide a strong and stable orange-red fluorescent signal.

The microsphere surface is functionalized with carboxyl groups for covalent coupling with antibodies, antigens, proteins, peptides and other amine-containing biomolecules.

Compared with individual quantum dots, quantum dot-loaded microspheres provide a larger functional surface, more convenient separation and washing, improved particle handling and greater fluorescence output per labeling particle.

HQD610-150 is suitable for research institutions, IVD developers and immunoassay reagent manufacturers requiring consistent materials from early assay screening through pilot production and commercial-scale manufacturing.

Product Overview

HQD610-150 combines the optical performance of quantum dots with the surface chemistry and handling properties of functional polymer microspheres.

The incorporated quantum dots provide bright fluorescence, a relatively broad excitation range, a narrow emission profile and good resistance to photobleaching. Loading multiple quantum dots into one microsphere can increase the fluorescence generated by each labeling particle and provide a stable platform for biomolecule immobilization.

The nominal 150 nm particle size provides a balance among fluorescence intensity, biomolecule-loading capacity, colloidal stability and membrane migration.

Compared with smaller microspheres, a 150 nm particle can provide more internal volume for fluorescent material and a larger external surface for antibody conjugation. However, particle dosage, membrane flow rate, surfactant concentration and sample viscosity must be optimized to achieve rapid and uniform migration.

HQD610-150 can be evaluated for quantitative lateral flow immunoassays, fluorescence-linked immunoassays, microfluidic detection systems, biosensors and multiplex biomarker detection.

Key Features and Benefits

Strong 610 nm Fluorescence

HQD610-150 produces an orange-red fluorescence signal with an emission maximum centered at approximately 610 nm.

The 610 nm emission channel is compatible with many fluorescence immunoassay readers. Its relatively narrow emission profile can help improve optical channel separation and reduce interference from adjacent fluorescent signals in a properly designed detection system.

The fluorescence intensity of the finished assay will also depend on the excitation light source, optical filters, reader sensitivity, particle dosage and amount of microspheres captured at the detection zone.

Multiple Quantum Dots per Microsphere

Multiple quantum dots are incorporated into each microsphere instead of being used only as individual fluorescent nanocrystals.

This structure can provide:

• Strong fluorescence output per labeling particle

• Better handling during conjugation and washing

• Reduced loss of fluorescent material

• Improved compatibility with routine immunoassay production

• A larger surface for biomolecule immobilization

• More consistent particle-based fluorescence detection

• Better suitability for quantitative assay development

Quantum dot nanobeads have been used as signal-amplification labels in quantitative and multiplex lateral flow immunoassays.

Uniform 150 nm Particle Size

Controlled particle size is important for producing consistent conjugation, fluorescence intensity and capillary migration.

The nominal 150 nm size offers:

• A relatively large surface for antibody loading

• High fluorescence capacity per microsphere

• Lower sedimentation than conventional micron-sized fluorescent beads

• Compatibility with suitable nitrocellulose membranes

• Potential for strong test-line accumulation

• Good suitability for quantitative fluorescence readers

The optimum membrane and running buffer must be selected through experimental screening because particle migration depends on the complete assay formulation.

Carboxyl-Functionalized Surface

HQD610-150 is supplied with carboxyl groups on the microsphere surface.

The carboxyl groups can be activated using EDC and NHS and subsequently coupled with primary amine groups on antibodies, proteins, peptides and other biomolecules. The reaction forms stable covalent amide bonds between the microsphere and the selected ligand.

Suitable biomolecules may include:

• Monoclonal antibodies

• Polyclonal antibodies

• Recombinant proteins

• Antigens

• Enzymes

• Peptides

• Aptamers

• Oligonucleotides

• Other amine-containing ligands

The optimum antibody-loading density should be determined experimentally. Excessive protein loading may increase steric hindrance, aggregation or nonspecific binding.

Stable Aqueous Suspension

HQD610-150 is supplied as a 1% solids aqueous microsphere suspension.

The formulation is designed to support particle redispersion and routine laboratory handling. Before sampling, gently mix the bottle until the suspension becomes uniform.

Avoid prolonged high-power sonication because excessive energy may affect the polymer structure, surface functional groups or fluorescence properties.

Suitable for Quantitative Immunoassays

The 610 nm fluorescent signal can be measured by a compatible fluorescence reader and converted into quantitative results using a calibration curve.

HQD610-150 may be used in:

• Qualitative assays

• Semi-quantitative assays

• Quantitative assays

• Single-analyte detection

• Multiplex biomarker detection

• Laboratory fluorescence platforms

• Point-of-care fluorescence readers

Lot-Controlled Bulk Supply

HQD610-150 is developed for customers requiring more than small research quantities.

SHBC supports:

• Material screening samples

• Assay-development quantities

• Pilot-production batches

• Bulk manufacturing

• Lot reservation

• Customer-specific quality specifications

• Packaging customization

• OEM and ODM projects

Consistent particle size, solids content, fluorescence performance and surface functionality help reduce the risks associated with transferring an assay from laboratory development to batch production.

Technical Specifications

Particle-size tolerance, excitation range, fluorescence intensity, quantum yield, zeta potential, buffer composition, preservative and shelf life should be confirmed using the lot-specific specification or certificate of analysis.

Why Choose 150 nm Quantum Dot Microspheres

Particle size affects fluorescence capacity, antibody loading, colloidal stability and membrane migration.

HQD610-150 is particularly suitable for assay developers who require a stronger per-particle signal than smaller fluorescent nanoparticles while maintaining a nanoscale particle size for rapid immunoassay platforms.

Potential Advantages of the 150 nm Size

The 150 nm particle size may provide:

• Greater internal capacity for quantum dot loading

• Strong fluorescence output per particle

• Increased available surface for antibody conjugation

• Strong accumulation at the test line

• Good compatibility with quantitative fluorescence detection

• Lower sedimentation tendency than large micron-sized beads

• A useful balance between signal intensity and flow performance

150 nm vs. 100 nm Quantum Dot Microspheres

Compared with 100 nm quantum dot microspheres, 150 nm microspheres generally provide more particle volume and surface area.

HQD610-150 may be preferred when the assay requires:

• Higher fluorescence output per labeling particle

• Higher potential biomolecule-loading capacity

• Stronger signal accumulation at the test line

• Improved detection by a portable fluorescence reader

A 100 nm product may be preferred when faster membrane migration, lower steric hindrance or better performance in small-pore membranes is the main requirement.

The final selection should be based on side-by-side assay testing rather than particle size alone.

When to Evaluate HQD610-150

HQD610-150 should be considered when:

• A colloidal gold assay does not provide sufficient quantitative sensitivity

• Free quantum dots are difficult to wash or conjugate

• Conventional fluorescent microspheres do not provide sufficient signal

• A stable 610 nm detection channel is required

• The assay is intended for instrument-based quantitative detection

• Large-scale material consistency is required

• A multiplex fluorescence panel is being developed

How HQD610-150 Works in Immunoassays

HQD610-150 microspheres are first conjugated with a recognition molecule such as an antibody, antigen or aptamer.

When the conjugated microspheres contact the sample, the recognition molecule binds to the target analyte. The resulting complex then migrates to a capture zone, where it is retained by an immobilized capture reagent.

Under suitable excitation, the accumulated microspheres emit fluorescence at approximately 610 nm. A fluorescence reader measures the test-line and control-line signals.

A typical sandwich immunoassay includes:

1. HQD610-150 conjugated with a detection antibody

2. The target analyte in the sample

3. A capture antibody immobilized at the test line

4. A control reagent immobilized at the control line

5. A running buffer that supports particle migration

6. A fluorescence reader configured for the correct optical channel

7. A calibration curve for quantitative analysis

For small-molecule targets, a competitive immunoassay format may be more appropriate than a sandwich format.

Recommended Applications

Fluorescence Lateral Flow Immunoassay

HQD610-150 can be used as a fluorescent reporter in lateral flow immunoassays.

Potential fields include:

• Infectious disease testing

• Inflammation marker detection

• Cardiac biomarker detection

• Hormone testing

• Tumor-marker research

• Veterinary diagnostics

• Food safety testing

• Mycotoxin detection

• Pesticide and drug-residue testing

• Environmental monitoring

• Agricultural testing

Quantum dot nanobead-based lateral flow assays have been reported for viral targets, bacterial pathogens, toxins, drug residues and clinical biomarkers.

Quantitative Fluorescence Immunoassay

HQD610-150 can be used in fluorescence-linked immunoassays requiring instrument-based quantitative analysis.

Suitable formats may include:

• Sandwich fluorescence immunoassays

• Competitive fluorescence immunoassays

• Fluorescence-linked immunosorbent assays

• Cartridge-based immunoassays

• Automated fluorescence analyzers

• Portable point-of-care readers

A standard curve should be established for each target analyte and sample matrix.

Multiplex Biomarker Detection

Quantum dots with different emission wavelengths may be excited by a common or overlapping light source.

This makes quantum dot microspheres useful for multiplex assay development. HQD610-150 can be used as the 610 nm channel in a multicolor detection panel.

Multiplex development requires optimization of:

• Emission wavelength separation

• Optical filters

• Reader gain

• Particle concentrations

• Antibody combinations

• Capture-line positions

• Cross-reactivity

• Signal compensation

• Sample volume

• Running time

Studies have demonstrated multiplex lateral flow detection using quantum dot microspheres with different colors or particle characteristics.

Biochips and Microfluidic Systems

HQD610-150 may be evaluated in:

• Microfluidic immunoassay cartridges

• Fluorescence biochips

• Lab-on-a-chip systems

• Optical biosensors

• Microarray platforms

• Automated diagnostic cartridges

• Portable fluorescence analyzers

Compatibility with microchannels, membranes, pumps and optical modules should be verified during device development.

Biomolecule Labeling

The carboxyl surface allows HQD610-150 to be conjugated with proteins, antibodies and other ligands for fluorescence labeling and tracing research.

For cell-related applications, cytotoxicity, nonspecific uptake and biological compatibility should be evaluated using the intended cell model.

Antibody and Protein Conjugation

EDC/NHS Coupling Principle

The carboxyl groups on HQD610-150 can be activated using EDC and NHS.

EDC activates the surface carboxyl groups, while NHS helps form a more stable intermediate. Primary amine groups on the antibody or protein then react with the activated surface to form covalent amide bonds.

General Coupling Workflow

A general development workflow includes:

1. Mix the HQD610-150 suspension thoroughly.

2. Transfer the required quantity into a low-binding reaction tube.

3. Wash or exchange the microspheres into a suitable activation buffer.

4. Prepare fresh EDC and NHS solutions.

5. Add EDC and NHS to activate the carboxyl groups.

6. Incubate under controlled mixing conditions.

7. Remove excess activation reagents.

8. Add the antibody or protein.

9. Incubate under the selected coupling conditions.

10. Add a blocking reagent to quench remaining active sites.

11. Wash the conjugated microspheres.

12. Resuspend the conjugate in an optimized storage buffer.

13. Measure particle recovery and fluorescence intensity.

14. Evaluate binding activity in the intended assay.

This workflow is a starting framework rather than a fixed production formula.

Variables Requiring Optimization

Important coupling variables include:

• EDC concentration

• NHS concentration

• Activation-buffer pH

• Coupling-buffer pH

• Antibody-to-particle ratio

• Particle concentration

• Reaction time

• Reaction temperature

• Mixing speed

• Blocking reagent

• Washing method

• Final storage buffer

• Surfactant concentration

• Preservative system

Recommended Coupling Evaluation

After conjugation, evaluate:

• Particle recovery

• Fluorescence retention

• Hydrodynamic particle size

• Visible aggregation

• Redispersion performance

• Antibody-binding activity

• Nonspecific binding

• Test-line signal

• Background signal

• Control-line performance

• Conjugate storage stability

Do not select the final formula based only on antibody consumption or fluorescence intensity. The conjugate must also provide suitable migration, specificity and stability in the finished assay.

Recommended Assay Development Workflow

Step 1: Confirm Material Characteristics

Confirm:

• Particle size

• Solids content

• Emission peak

• Excitation range

• Surface functional group

• Dispersion buffer

• Initial fluorescence intensity

Step 2: Screen Antibody-Loading Levels

Evaluate several antibody-to-microsphere ratios.

Too little antibody may produce weak target binding. Excessive antibody may increase steric hindrance, aggregation, background or raw-material cost.

Step 3: Optimize Activation Conditions

Screen different EDC/NHS concentrations, activation times and pH conditions.

The strongest chemical activation does not always produce the best functional conjugate.

Step 4: Optimize Blocking and Storage Buffers

Potential components include:

• Bovine serum albumin

• Casein

• Inert proteins

• Amino-containing blocking molecules

• Sugars

• Polyols

• Surfactants

• Salts

• Preservatives

The selected formulation should maintain fluorescence, particle dispersion and antibody activity.

Step 5: Screen Conjugate Pads

Evaluate:

• Glass-fiber pads

• Polyester pads

• Pad pretreatment

• Conjugate concentration

• Drying temperature

• Drying time

• Sugar stabilizers

• Surfactants

Step 6: Screen Nitrocellulose Membranes

Compare membranes with different:

• Capillary-flow rates

• Protein-binding capacities

• Pore structures

• Thicknesses

• Surface treatments

A membrane providing a high signal but poor flow consistency may not be suitable for production.

Step 7: Optimize Running Buffer

Evaluate:

• pH

• Ionic strength

• Protein blockers

• Surfactants

• Chelating agents

• Viscosity modifiers

• Heterophilic-antibody blockers

Step 8: Configure the Reader

Confirm:

• Excitation wavelength

• Emission filter

• Exposure time

• Detector gain

• Reading position

• Test-to-control signal algorithm

• Calibration model

Step 9: Validate the Sample Matrix

Test:

• Negative samples

• Positive samples

• Low-positive samples

• High-concentration samples

• Hemolytic samples

• Lipemic samples

• Icteric samples

• Samples containing potential cross-reactants

Step 10: Perform Stability Testing

Recommended evaluations include:

• Conjugate stability

• Accelerated strip stability

• Real-time strip stability

• Open-bottle stability

• Temperature-transport simulation

• Lot-to-lot reproducibility

Quantum Dot Microspheres vs. Other Signal Labels

Quantum dot microspheres are particularly useful when the assay requires strong quantitative fluorescence, a narrow emission channel or multiplex detection.

The optimum label should be selected according to the target detection limit, sample matrix, assay format, reader platform, production cost and required shelf life.

Factors Affecting Immunoassay Performance

HQD610-150 provides a fluorescent signal platform, but it does not independently determine the detection limit.

Final assay performance depends on:

• Antibody affinity

• Antibody specificity

• Epitope accessibility

• Antibody orientation

• Antibody-loading density

• Particle aggregation

• Microsphere dosage

• Membrane selection

• Capture-reagent concentration

• Running-buffer composition

• Sample viscosity

• Sample autofluorescence

• Nonspecific adsorption

• Optical-reader sensitivity

• Excitation and emission matching

• Strip assembly

• Reaction time

• Environmental temperature

Weak Test-Line Signal

Possible causes include:

• Insufficient antibody loading

• Low antibody affinity

• Incorrect reader channel

• Inadequate particle dosage

• Poor capture-antibody activity

• Excessive membrane flow rate

• Fluorescence quenching

• Incomplete conjugate release

High Background

Possible causes include:

• Excessive particle dosage

• Excessive antibody loading

• Inadequate blocking

• Poor membrane compatibility

• High nonspecific adsorption

• Inappropriate surfactant level

• Aggregated conjugate

• Incorrect reader gain

Slow Migration

Possible causes include:

• Particle aggregation

• High conjugate concentration

• Small membrane pores

• High sample viscosity

• Inadequate surfactant

• Poor conjugate-pad release

• Excessive protein concentration

Poor Lot-to-Lot Reproducibility

Possible causes include:

• Inconsistent particle dispersion

• Variation in activation reagents

• Differences in antibody activity

• Uncontrolled reaction temperature

• Inconsistent mixing

• Variation in washing recovery

• Changes in membrane or pad batches

• Inconsistent reader calibration

Quality Control for Batch Production

For commercial immunoassay development, lot consistency is as important as initial fluorescence intensity.

Recommended quality-control parameters include:

• Mean particle size

• Particle-size distribution

• Polydispersity

• Solids content

• Fluorescence emission peak

• Relative fluorescence intensity

• Fluorescence spectrum width

• Surface functional-group consistency

• Zeta potential

• Appearance

• Dispersion stability

• Redispersion performance

• Protein-coupling performance

• Functional immunoassay performance

• Storage stability

• Microbial control when required

Customers developing commercial reagents should establish a retained reference lot and compare new production lots using the same conjugation and assay procedures.

SHBC can discuss customer-specific testing methods and acceptance criteria for pilot and bulk orders.

Customization and Bulk Manufacturing

SHBC supports customized quantum dot microspheres for different immunoassay platforms.

Available customization options may include:

• Different particle sizes

• Alternative emission wavelengths

• Carboxyl-functionalized surfaces

• Amine-functionalized surfaces

• Streptavidin-functionalized surfaces

• Customized solids content

• Customized dispersion buffer

• Customized preservative

• Low-nonspecific-binding surface treatment

• Customized packaging

• Pilot-batch production

• Bulk manufacturing

• Lot reservation

• OEM and ODM services

Information Required for Product Selection

To recommend a suitable product, please provide:

• Target analyte

• Intended assay format

• Sandwich or competitive format

• Sample matrix

• Required detection limit

• Quantitative range

• Fluorescence-reader model

• Excitation wavelength

• Emission channel

• Preferred surface group

• Required sample quantity

• Expected annual demand

• Packaging requirements

Support from Research to Production

SHBC can support different project stages:

Material screening

Small quantities for comparing particle sizes, fluorescence channels and surface chemistries.

Assay development

Materials for conjugation optimization, membrane screening and reader configuration.

Pilot production

Larger quantities for process transfer, stability testing and validation.

Bulk manufacturing

Lot-controlled production for routine reagent manufacturing.

Storage and Handling

Recommended storage and handling practices include:

• Store at 2–8°C unless otherwise stated on the label or COA.

• Protect the product from direct light.

• Do not freeze.

• Avoid repeated freeze-thaw cycles.

• Mix thoroughly before sampling.

• Use clean, low-binding laboratory containers.

• Avoid contaminating the original suspension.

• Avoid strong acids, strong alkalis and incompatible solvents.

• Avoid prolonged high-power sonication.

• Close the container immediately after use.

• Follow the lot-specific expiration date.

If sedimentation occurs during storage, gently invert, vortex at a low setting or apply brief mild sonication until the particles are uniformly dispersed.

Sedimentation alone does not necessarily indicate product failure. Confirm that the microspheres can be completely redispersed and that particle size and fluorescence remain within specification.

Frequently Asked Questions

What is HQD610-150?

HQD610-150 is a carboxyl-functionalized quantum dot microsphere suspension with a nominal particle size of 150 nm, a solids content of 1% and a fluorescence emission peak centered at approximately 610 nm.

It is developed for immunoassay research, fluorescence lateral flow development and bulk diagnostic reagent production.

What does 610 mean in the catalog number?

The number 610 indicates the approximate fluorescence emission wavelength of the microspheres.

The exact emission maximum and tolerance should be confirmed using the lot-specific fluorescence spectrum.

What does 150 mean in HQD610-150?

The number 150 indicates the nominal particle diameter of 150 nm.

Actual particle-size tolerance should be confirmed in the product specification or certificate of analysis.

Why use 150 nm quantum dot microspheres?

The 150 nm size provides a useful balance among fluorescence output, biomolecule-loading capacity, dispersion stability and membrane migration.

It may provide a stronger per-particle fluorescence signal than smaller microspheres while remaining suitable for nanoscale immunoassay applications.

Can HQD610-150 be used in lateral flow assays?

Yes. HQD610-150 can be evaluated as a fluorescent reporter particle in lateral flow immunoassays.

The membrane, conjugate pad, running buffer, particle dosage and reader settings must be optimized for the intended assay.

Is HQD610-150 suitable for quantitative detection?

Yes. A compatible fluorescence reader can measure the 610 nm signal and convert the fluorescence intensity into quantitative results using a calibration curve.

How are antibodies coupled to HQD610-150?

Antibodies can be covalently coupled to the carboxyl-functionalized surface using EDC/NHS chemistry.

The activation conditions and antibody-to-particle ratio must be optimized for each antibody.

Can HQD610-150 be used for competitive assays?

Yes. HQD610-150 may be used in competitive immunoassays for small molecules such as toxins, antibiotics, pesticides and other chemical residues.

The conjugated biomolecule and competitive assay structure should be selected according to the target.

Can it be used for multiplex detection?

Yes. HQD610-150 can serve as the 610 nm fluorescence channel in a multiplex detection system.

Other microspheres with different emission wavelengths can be combined when the reader and optical filters provide sufficient channel separation.

Does HQD610-150 always provide higher sensitivity than colloidal gold?

No signal label automatically guarantees higher sensitivity.

Quantum dot microspheres provide a strong instrument-readable fluorescence signal, but final sensitivity also depends on antibodies, conjugation, membrane selection, sample matrix and reader performance.

What is the recommended storage temperature?

The product should generally be stored at 2–8°C, protected from light and not frozen.

Follow the lot-specific storage instructions and expiration date.

Can the concentration be customized?

Customized solids content may be available depending on the required quantity and project specifications.

Is bulk supply available?

Yes. SHBC supports research samples, pilot quantities, bulk production, lot reservation and customized packaging.

Is HQD610-150 a finished diagnostic reagent?

No. HQD610-150 is a raw material supplied for research use and diagnostic reagent development. It is not a finished diagnostic product.

Request a Sample or Bulk Quotation

SHBC provides 150 nm Quantum Dot Microspheres HQD610-150 for immunoassay research, fluorescence lateral flow development and batch reagent production.

To request a sample, technical consultation or bulk quotation, please provide:

• Target analyte

• Sample matrix

• Assay format

• Required detection limit

• Fluorescence-reader specifications

• Preferred surface chemistry

• Required quantity

• Expected annual demand

• Packaging requirements

• Special quality-control requirements

Contact SHBC to evaluate HQD610-150 for your quantitative immunoassay, fluorescence lateral flow, biosensor or multiplex diagnostic reagent project.