50um Streptavidin Microspheres SAPS50UM-10 1%

50µm Streptavidin Microspheres for Biological Research

SHBC SAPS50UM-10 Streptavidin Microspheres are 50µm surface-functionalized microspheres developed for the immobilization and capture of biotinylated antibodies, antigens, proteins, peptides, enzymes, receptors, oligonucleotides, DNA, RNA, aptamers, lectins, and other biotin-labeled molecules.

The product is supplied as a 1% solids suspension and is designed for biological assay development, biomolecule immobilization, affinity interaction research, microscopy, cell–particle interaction studies, nucleic acid capture, microfluidics, particle agglutination research, imaging-based detection, and research reagent manufacturing.

The 50µm particle diameter provides a large surface on each individual microsphere and makes the particles easy to identify under suitable optical or fluorescence microscopy. The large particle size is especially relevant for projects requiring individual-particle analysis, visible particle manipulation, size-coded assays, cell-size-range particle models, microfluidic transport, or imaging-based biological detection.

Shanghai SanYu Biotechnology Co., Ltd. supports laboratory sample evaluation, pilot-scale development, repeated manufacturing, OEM cooperation, private-label projects, and enterprise bulk supply.

Quick Product Answer

SAPS50UM-10 is a 50µm streptavidin-coated microsphere suspension supplied at 1% solids. Its streptavidin-functional surface binds biotinylated biomolecules for antibody and protein immobilization, nucleic acid capture, biological assays, microscopy, microfluidic research, cell–particle interaction studies, particle agglutination, and imaging-based detection.

Product Highlights

• Product name: 50µm Streptavidin Microspheres

• Catalog number: SAPS50UM-10

• Brand: SHBC

• Manufacturer: Shanghai SanYu Biotechnology Co., Ltd.

• Nominal particle diameter: 50µm

• Surface modification: Streptavidin

• Solids content: 1%

• Binding principle: Streptavidin–biotin affinity

• Physical form: Aqueous microsphere suspension

• Primary application: Biological research and particle-based assays

• Supply capability: Samples, pilot batches, and bulk production

• Customization: Available according to technical feasibility

• Intended use: Research use only

What Are SAPS50UM-10 Streptavidin Microspheres?

SAPS50UM-10 consists of 50µm microspheres with streptavidin immobilized on the particle surface.

The streptavidin coating provides binding sites for biotinylated molecules. Researchers can attach a selected biotinylated antibody, antigen, protein, peptide, nucleic acid probe, receptor, ligand, lectin, aptamer, or other biomolecule without directly activating the microsphere surface with EDC/NHS chemistry.

After a capture molecule has been immobilized, the functionalized particles can be used as a solid phase for:

• Target capture

• Antibody immobilization

• Protein interaction analysis

• Nucleic acid hybridization

• Cell-surface binding studies

• Microscopy-based assays

• Imaging-based biosensors

• Particle agglutination

• Microfluidic research

• Affinity capture experiments

• Individual-particle analysis

• Size-coded multiplex research

Potential biotinylated capture molecules include:

• Monoclonal antibodies

• Polyclonal antibodies

• Recombinant antibodies

• Antibody fragments

• Antigens

• Recombinant proteins

• Peptides

• Enzymes

• Receptors

• Lectins

• Cytokines

• Growth factors

• Oligonucleotide probes

• DNA probes

• RNA probes

• PCR products

• Aptamers

• Biotinylated small molecules

The 50µm particles provide significantly more surface area per individual microsphere than smaller particles. At the same mass concentration, however, they provide fewer individual particles and less collective surface area than much smaller microspheres made from the same material.

SAPS50UM-10 is therefore particularly suitable when the project prioritizes:

• Large surface area per individual particle

• Direct microscopic observation

• Individual-particle signal measurement

• Manual or automated particle manipulation

• Cell-size-range particle modeling

• Size-based particle differentiation

• Imaging-based biological assays

• Microfluidic transport and trapping

• Particle agglutination

• Visual confirmation of particle recovery

SAPS50UM-10 is supplied as a research raw material. It should not automatically be represented as a finished diagnostic reagent, certified particle-size standard, absolute counting bead, magnetic bead, or internally fluorescent microsphere unless these properties are specifically included in the final product specification.

SAPS50UM-10 Technical Specifications

The following parameters should be confirmed using the final technical specification or lot-specific Certificate of Analysis:

• Particle material

• Mean particle diameter

• Particle-size range

• Particle-size distribution

• Particle-size coefficient of variation

• Particle morphology

• Particle density

• Streptavidin coating level

• Biotin-binding capacity

• Particle number concentration

• Number of particles per milligram

• Suspension buffer

• Buffer pH

• Stabilizer or surfactant

• Preservative

• Recommended washing method

• Recommended recovery conditions

• Package size

• Shelf life

• Storage conditions

Biotin-binding capacity should be reported together with:

• Type of biotinylated test molecule

• Molecular weight of the test molecule

• Number of biotin groups per molecule

• Binding-buffer composition

• Incubation time

• Incubation temperature

• Washing procedure

• Detection method

• Calculation basis

• Lot-specific test result

Binding capacity should not be estimated from the 1% solids content or nominal particle diameter alone.

How Streptavidin–Biotin Binding Works

Streptavidin is a biotin-binding protein that enables the attachment of biotinylated molecules to the microsphere surface.

When a biotinylated capture ligand is mixed with SAPS50UM-10, the biotin group binds to available streptavidin sites on the particle.

The general structure can be represented as:

Microsphere Surface – Streptavidin – Biotin – Capture Molecule

For an antibody-based sandwich assay, the structure may be:

Microsphere – Streptavidin – Biotinylated Capture Antibody – Target Antigen – Detection Antibody

The detection antibody may carry a fluorescent, enzymatic, colorimetric, chemiluminescent, or other measurable label.

Advantages of Streptavidin–Biotin Immobilization

• Direct EDC/NHS activation is normally unnecessary when loading a biotinylated ligand.

• One microsphere platform can be used with many different biotinylated molecules.

• Antibodies, proteins, peptides, DNA, RNA, oligonucleotides, and aptamers can be immobilized.

• Ligand loading can be conducted under relatively mild aqueous conditions.

• The capture molecule can be changed without redesigning the base particle.

• Ligand loading can be optimized separately from target detection.

• Different reporter systems can be used with the same microsphere platform.

• The platform can support single-target and multiplex research.

• The particles can be adapted to imaging, microscopy, microfluidic, and plate-based assays.

Factors Affecting Binding Performance

Final ligand loading and assay performance may be influenced by:

• Streptavidin coating density

• Streptavidin activity

• Number of biotin groups per ligand

• Location of the biotin groups

• Biotin accessibility

• Spacer length

• Ligand molecular size

• Ligand purity

• Ligand aggregation

• Surface crowding

• Buffer composition

• Salt concentration

• Incubation time

• Incubation temperature

• Mixing method

• Particle settling

• Washing efficiency

Free biotin or unreacted biotinylated reagents can occupy available streptavidin sites. Biotinylated biomolecules should therefore be adequately purified when residual free biotin may interfere with immobilization.

Why Choose 50µm Streptavidin Microspheres?

Large Surface Area per Individual Particle

A 50µm microsphere provides substantially more physical surface on each particle than a 30µm, 20µm, 10µm, or 5µm microsphere.

This can be useful when:

• A large amount of capture ligand is required on each particle

• Strong signal generation per individual particle is desired

• Surface fluorescence will be measured by microscopy

• Individual-particle analysis is required

• Particle surface patterning is being studied

• Localized biomolecule binding will be observed

• A large synthetic particle model is needed

A larger individual particle does not necessarily provide greater total surface area per milligram. Smaller particles normally provide many more particles at the same mass concentration.

Excellent Microscopic Visibility

The 50µm diameter makes individual particles easy to identify using suitable optical imaging systems.

Potential imaging methods include:

• Bright-field microscopy

• Phase-contrast microscopy

• Fluorescence microscopy

• Confocal microscopy

• Automated high-content imaging

• Imaging flow cytometry

• Digital particle analysis

Microscopy can be used to evaluate:

• Particle morphology

• Surface-associated fluorescence

• Ligand distribution

• Particle aggregation

• Cell–particle interaction

• Particle recovery

• Size-based differentiation

• Microfluidic movement

• Particle agglutination

Suitable for Individual-Particle Analysis

The large size allows each particle to be treated as a separate reaction surface or analytical unit.

Potential research directions include:

• Single-particle fluorescence measurement

• Particle-to-particle variation analysis

• Surface-binding uniformity

• Individual-particle imaging

• Automated particle classification

• Digital particle counting

• Image-based positive/negative classification

Relevant to Large Cell-Size Models

The 50µm diameter falls within the size range of certain large cells, cell aggregates, embryos, spheroids, biological structures, and synthetic cell models.

SAPS50UM-10 may be evaluated for:

• Large cell-sized particle transport

• Cell–particle contact studies

• Microfluidic cell-model testing

• Particle capture in cell-processing devices

• Imaging-system development

• Synthetic biological particle models

• Mechanical handling research

Synthetic microspheres do not reproduce all optical, mechanical, chemical, or biological properties of living cells. Application-specific validation is required.

Clear Size-Based Identification

The large particle size enables SAPS50UM-10 to be differentiated from many smaller microsphere populations, cells, debris, and background particles.

This is useful for:

• Size-coded multiplex assays

• Imaging-based assays

• Particle tracking

• Microfluidic sorting

• Agglutination analysis

• Internal process controls

• Multi-population research

Practical Manual Manipulation

Individual 50µm particles may be manipulated using suitable laboratory tools, such as:

• Wide-bore pipette tips

• Micropipettes

• Microcapillaries

• Micromanipulators

• Particle-picking systems

• Meshes or cell strainers

• Microfluidic trapping structures

Key Features and Benefits

50µm Nominal Particle Diameter

The large particle size supports microscopy, individual-particle analysis, size-based identification, microfluidic manipulation, and large-particle biological research.

Streptavidin-Functional Surface

The surface captures biotinylated antibodies, proteins, peptides, enzymes, receptors, oligonucleotides, DNA, RNA, aptamers, lectins, and other biotin-containing molecules.

1% Solids Suspension

SAPS50UM-10 is supplied at 1% solids and can be diluted according to the required number of particles, reaction volume, binding capacity, and detection method.

Simple Ligand Immobilization

Biotinylated capture molecules can be attached without direct carbodiimide activation of the microsphere surface by the end user.

Large Surface per Particle

Each microsphere provides a comparatively large physical surface for capture-ligand immobilization and signal generation.

Strong Imaging Compatibility

The particle size is suitable for optical, fluorescence, confocal, and automated imaging research.

Modular Biological Assay Platform

The same base particle can be combined with different biotinylated capture molecules for different research targets.

Sample-to-Bulk Supply

SHBC supports laboratory evaluation, pilot production, repeated manufacturing, OEM cooperation, and enterprise bulk purchasing.

Custom Development Options

Particle size, streptavidin loading, binding capacity, solids content, buffer, preservative, fluorescence coding, visible color, packaging, and release specifications may be discussed for qualified projects.

Biological Research Applications

Bead-Based Immunoassay Development

SAPS50UM-10 may be used as the solid phase in sandwich, indirect, competitive, or particle-agglutination research assays.

A typical sandwich assay may include:

1. Immobilization of a biotinylated capture antibody.

2. Blocking of the remaining particle surface.

3. Incubation with the test sample.

4. Capture of the target analyte.

5. Addition of a labeled detection antibody.

6. Removal of unbound reagents.

7. Measurement of the particle-associated signal.

Potential research targets include:

• Antibodies

• Antigens

• Cytokines

• Hormones

• Growth factors

• Enzymes

• Biomarkers

• Pathogen-associated proteins

• Food-safety analytes

• Environmental targets

• Veterinary research targets

• Research compounds

Competitive Binding Assays

Competitive formats may be evaluated for:

• Small molecules

• Haptens

• Peptides

• Drugs

• Toxins

• Hormones

• Metabolites

• Targets with limited accessible binding sites

The relationship between analyte concentration and measured signal depends on the final assay design.

Antibody Immobilization and Screening

Biotinylated antibodies may be immobilized for:

• Antigen detection

• Antibody screening

• Hybridoma screening

• Antibody-specificity studies

• Cross-reactivity evaluation

• Affinity comparison

• Capture-antibody selection

• Assay feasibility testing

• Biomarker research

Protein and Peptide Interaction Research

Biotinylated proteins or peptides may be attached to study:

• Antibody–antigen interactions

• Protein–protein interactions

• Receptor–ligand binding

• Epitope recognition

• Enzyme–substrate binding

• Inhibitor screening

• Drug-candidate binding

• Protein-affinity comparison

Nucleic Acid Capture and Hybridization

Biotinylated oligonucleotides, DNA, RNA, PCR products, and aptamers may be attached to SAPS50UM-10.

Potential applications include:

• Sequence-specific capture

• Hybridization assay development

• PCR-product capture

• Genotyping research

• Mutation-detection research

• Aptamer-based detection

• DNA–protein interaction analysis

• RNA-binding research

• Molecular assay development

Cell–Particle Interaction Research

When coated with an appropriate biotinylated antibody, receptor, ligand, lectin, or peptide, SAPS50UM-10 may be evaluated for interaction with cells.

Potential research directions include:

• Cell-surface receptor recognition

• Cell adhesion

• Ligand-mediated cell binding

• Immune-cell interaction

• Large-particle cellular contact

• Cell aggregation research

• Particle-mediated cell positioning

• Synthetic antigen-presenting particle research

• Imaging of cell–particle interfaces

Important variables include:

• Capture-ligand density

• Particle-to-cell ratio

• Cell concentration

• Incubation time

• Incubation temperature

• Mixing method

• Washing conditions

• Cell viability

• Particle aggregation

• Non-specific attachment

Microscopy and High-Content Imaging

The 50µm microspheres may support:

• Bright-field imaging

• Phase-contrast imaging

• Fluorescence imaging

• Confocal microscopy

• High-content screening

• Automated particle counting

• Surface-binding analysis

• Particle classification

• Cell–particle interaction imaging

• Digital positive/negative particle analysis

Microfluidic Research

SAPS50UM-10 may be evaluated in:

• Particle transport studies

• Microchannel flow research

• Size-based separation

• Particle trapping

• Hydrodynamic focusing

• Particle positioning

• Imaging in microfluidic devices

• Large cell-model manipulation

• Device-performance testing

The narrowest channel, connector, valve, filter, and flow path must be compatible with 50µm particles.

Agglutination Research

Large streptavidin microspheres may be used in research methods where binding of a target or bridging molecule produces measurable particle clustering.

Agglutination may be analyzed by:

• Optical microscopy

• Automated imaging

• Light-scattering methods

• Sedimentation patterns

• Particle-count changes

• Image-analysis algorithms

The relationship between aggregation and analyte concentration must be optimized experimentally.

Particle-Based Biosensors

SAPS50UM-10 may serve as a visible solid-phase carrier in:

• Optical biosensors

• Imaging-based biosensors

• Fluorescent particle assays

• Enzyme-linked particle assays

• Microfluidic biosensors

• Surface-binding studies

• Digital particle assays

Size-Coded Multiplex Research

The 50µm particle population may be combined with smaller microspheres to create size-distinguishable assay populations.

Each particle population can potentially carry a different biotinylated capture ligand.

The final multiplex design should consider:

• Particle-size separation

• Ligand specificity

• Signal channel

• Particle recovery

• Aggregation

• Imaging resolution

• Instrument compatibility

Compatible Biotinylated Biomolecules

Biotinylated Antibodies

Potential antibody formats include:

• Full-length IgG

• IgM

• Fab fragments

• F(ab′)₂ fragments

• Recombinant antibodies

• Single-chain variable fragments

• Single-domain antibodies

• Engineered antibody formats

Antibody activity after immobilization depends on:

• Biotinylation chemistry

• Number of biotin groups

• Location of biotin groups

• Spacer length

• Protein purity

• Antibody aggregation

• Surface loading

• Storage conditions

Biotinylated Proteins

Potential examples include:

• Recombinant antigens

• Enzymes

• Cytokines

• Growth factors

• Receptors

• Lectins

• Binding proteins

• Fusion proteins

• Protein standards

Biotinylated Peptides

Potential applications include:

• Epitope mapping

• Antibody screening

• Receptor-binding studies

• Enzyme research

• Protein-interaction studies

• Drug-screening assays

A suitable spacer between biotin and the peptide may improve molecular accessibility.

Biotinylated Nucleic Acids

Compatible formats may include:

• Single-stranded DNA

• Double-stranded DNA

• RNA

• Oligonucleotide probes

• PCR amplicons

• Aptamers

• Modified nucleic acid probes

• Capture sequences

Biotinylated Small Molecules

Small biotinylated compounds may be immobilized when their biotin groups remain accessible to the streptavidin surface.

Spacer design and molecular orientation should be considered during method development.

Recommended Biotinylated Ligand Loading Protocol

The following procedure is a general development starting point. Final conditions should be optimized for the actual biomolecule, particle material, and application.

1. Resuspend SAPS50UM-10

Allow the suspension to reach the recommended handling temperature.

Mix by gentle inversion, slow rotation, rocking, or controlled vortexing until the suspension is homogeneous.

Because 50µm particles can settle rapidly, mix the stock immediately before every sampling step.

During repeated dispensing, maintain gentle mixing or remix the suspension before each aliquot.

2. Calculate the Required Particle Amount

Determine the required quantity according to:

• Number of tests

• Number of particles required per test

• Surface required per reaction

• Reaction volume

• Expected target concentration

• Lot-specific binding capacity

• Number of washing steps

• Expected processing loss

Do not calculate ligand-loading capacity from solids content alone.

3. Transfer the Microspheres

Transfer the required volume to a clean, low-binding tube or processing vessel.

Use a wide-bore pipette tip or another transfer device with an opening suitable for 50µm particles.

Avoid narrow tips that may:

• Retain particles

• Restrict particle movement

• Produce inconsistent particle numbers

• Promote aggregation

• Reduce transfer accuracy

4. Wash the Microspheres

Wash the particles with a buffer compatible with streptavidin and the selected biotinylated ligand.

Avoid free biotin during ligand immobilization.

Potential recovery methods include:

• Centrifugation

• Membrane filtration

• Mesh or cell-strainer recovery

• Controlled sedimentation

• Manual particle collection

• Other validated solid–liquid separation methods

The method should be established using the actual particle material, density, buffer, processing volume, and required recovery.

5. Prepare the Biotinylated Ligand

Dilute the selected biomolecule in a compatible binding buffer.

Review:

• Ligand concentration

• Biotinylation level

• Molecular purity

• Aggregate level

• Free biotin content

• Residual biotinylation reagent

• Buffer additives

• Protein stability

• Nucleic acid stability

6. Add the Ligand

Combine the washed particles with the biotinylated ligand.

Use gentle rotation, rocking, or controlled mixing to keep the particles exposed uniformly to the ligand.

Avoid excessive vortexing, foaming, and mechanical conditions that may damage the biomolecule.

7. Optimize the Incubation

Evaluate:

• Particle concentration

• Ligand concentration

• Ligand-to-particle ratio

• Incubation time

• Incubation temperature

• Buffer pH

• Salt concentration

• Mixing speed

• Reaction volume

Continuous gentle mixing is particularly important for 50µm particles because sedimentation can cause uneven ligand loading.

8. Remove Unbound Ligand

Separate and wash the particles to remove unbound biotinylated molecules.

Insufficient washing may increase background, while excessive washing may reduce particle recovery.

9. Block the Particle Surface

Incubate the ligand-loaded microspheres with an application-compatible blocking reagent.

Potential blockers include:

• Bovine serum albumin

• Casein

• Fish gelatin

• Non-immune immunoglobulin

• Synthetic blocking polymers

• Commercial particle-blocking buffers

The blocker should reduce negative-sample signal without substantially reducing target-specific binding.

10. Resuspend the Prepared Microspheres

Resuspend the coated and blocked particles in a suitable assay or storage buffer.

Evaluate:

• Particle dispersion

• Ligand retention

• Binding activity

• Non-specific binding

• Particle recovery

• Settling behavior

• Redispersion performance

• Short-term stability

• Long-term stability

• Microbial stability

Recommended Biological Assay Workflow

1. Prepare the Capture Microspheres

Load SAPS50UM-10 with the selected biotinylated capture molecule.

Wash and block the particles before sample testing.

2. Prepare Experimental Controls

Recommended controls may include:

• Assay-buffer blank

• Streptavidin microspheres without capture ligand

• Capture-ligand-loaded particles without target

• Negative sample

• Positive sample

• Reporter-only control

• Isotype control

• Non-relevant biotinylated ligand control

• Unlabeled target control

• Single-color controls when fluorescence is used

3. Add the Test Sample

Combine the prepared microspheres with the sample.

Optimize:

• Sample volume

• Sample dilution

• Particle concentration

• Particles per reaction

• Target concentration range

• Incubation time

• Incubation temperature

• Mixing method

• Sample matrix

Maintain gentle mixing throughout incubation.

4. Wash the Particles

Remove unbound sample components while maintaining acceptable recovery.

Record:

• Number of washes

• Wash-buffer composition

• Wash volume

• Separation method

• Residual supernatant volume

• Mixing procedure

• Particle recovery

5. Add the Detection Reagent

Add a fluorescent, enzymatic, colorimetric, chemiluminescent, or other compatible reporter.

The selected detection system must match the intended analytical platform.

6. Incubate and Wash

Optimize reporter concentration and incubation time.

Remove unbound detection reagent to reduce background.

7. Resuspend for Detection

Resuspend the particles in a clean detection buffer.

Mix immediately before transferring the sample to the microscope slide, imaging chamber, microplate, microfluidic device, or other instrument.

8. Measure the Signal

Potential analytical outputs include:

• Mean particle fluorescence

• Median particle fluorescence

• Percentage of positive particles

• Surface fluorescence distribution

• Signal-to-background ratio

• Particle-associated enzyme activity

• Color intensity

• Agglutination level

• Particle-count changes

• Dose-response curve

• Assay precision

• Recovery

• Specificity

• Cross-reactivity

9. Analyze the Results

Establish positive and negative thresholds using appropriate controls.

Do not define a positive result using the test sample alone.

Handling, Mixing and Sampling of 50µm Microspheres

Rapid Particle Settling

The 50µm microspheres may settle rapidly when mixing stops.

Settling can cause:

• Unequal particle concentration

• Variation between aliquots

• Inconsistent ligand loading

• Different particle numbers between reactions

• Uneven exposure to samples or reporters

• Variable assay signals

• Reduced batch reproducibility

Maintaining a Uniform Suspension

Suitable mixing methods may include:

• Gentle inversion

• End-over-end rotation

• Slow orbital mixing

• Gentle rocking

• Controlled vortexing before sampling

• Slow mechanical stirring

• Intermittent wide-bore pipette mixing

Avoid vigorous mixing that produces foam, damages proteins, or causes particle collisions and aggregation.

Consistent Sampling

For repeated dispensing:

1. Mix the stock thoroughly.

2. Aspirate the required volume promptly.

3. Dispense the complete volume.

4. Remix before the next aliquot.

5. Use the same transfer method for all samples.

6. Minimize delays between mixing and sampling.

For pilot or bulk filling, continuous slow mixing should be validated to maintain uniform particle distribution.

Wide-Bore Pipette Tips

Wide-bore or cut tips may improve the transfer of large particles.

The opening should be sufficiently larger than the particle diameter to reduce:

• Particle retention

• Shear

• Inconsistent particle delivery

• Tip blockage

• Sampling variation

Particle Counting

When particle number per test is important, use an appropriate counting method rather than relying only on the suspension volume.

Possible approaches include:

• Microscopic counting

• Automated imaging

• Particle counters

• Gravimetric calculation supported by measured particle size and density

• Lot-specific particle-number data

Particle Recovery and Washing Methods

Centrifugation

Centrifugation may be used when the particle composition and density permit efficient recovery.

The minimum effective centrifugal force and time should be determined experimentally.

The selected conditions should provide:

• Acceptable recovery

• A manageable particle pellet

• Easy redispersion

• Minimal aggregation

• Limited damage to immobilized biomolecules

Filtration

A membrane, mesh, or cell strainer with a suitable pore size may be used for recovery or washing.

Confirm:

• Particle retention

• Low biomolecule adsorption

• Acceptable recovery

• Easy particle release

• Compatibility with the processing volume

• Minimal particle deformation

Controlled Sedimentation

Natural or accelerated sedimentation may be considered in selected workflows.

Sedimentation may reduce mechanical stress but can require longer processing times and careful removal of the supernatant.

Manual Particle Manipulation

For microscopy and single-particle projects, individual microspheres may be collected using:

• Wide-bore micropipettes

• Microcapillaries

• Micromanipulation systems

• Particle-picking tools

• Mesh-based devices

Magnetic Separation

SAPS50UM-10 should not be assumed to be magnetic.

Magnetic separation is appropriate only when the product specification explicitly confirms that the microspheres contain a magnetic component.

Microscopy, Imaging and Microfluidic Detection

Optical Microscopy

The 50µm particles can generally be observed using standard optical microscopy.

Potential uses include:

• Particle morphology assessment

• Aggregate inspection

• Particle counting

• Surface-binding visualization

• Cell–particle interaction imaging

• Particle-recovery confirmation

• Size-distribution observation

Fluorescence Microscopy

When the particles carry a fluorescent reporter, internal dye, or fluorescently labeled target, fluorescence microscopy may be used to evaluate:

• Surface signal

• Binding uniformity

• Positive and negative particles

• Reporter localization

• Cell–particle interactions

• Multiplex particle populations

Confocal Microscopy

Confocal imaging can support three-dimensional analysis of surface-associated fluorescence and help distinguish microsphere-bound signal from surrounding fluorescence.

Automated Imaging

Because the particles are relatively large, automated image-analysis software may be used to quantify:

• Particle number

• Particle diameter

• Fluorescence intensity

• Positive-particle percentage

• Aggregate level

• Surface-signal distribution

• Cell-contact events

Microfluidic Detection

Before using SAPS50UM-10 in a microfluidic device, confirm that:

• Channels are sufficiently wide

• Constrictions can pass the particles

• Valves and connectors are compatible

• Filters will not retain the particles unintentionally

• The flow rate will not promote blockage

• Particle concentration is appropriate

• Aggregation is adequately controlled

Flow Cytometry Compatibility

SAPS50UM-10 may be evaluated by flow cytometry only when the instrument fluidics are designed to handle particles of this size.

Before testing, confirm:

• Sample tubing diameter

• Flow-cell dimensions

• Nozzle or orifice size

• Narrowest fluidic pathway

• Sample probe dimensions

• Particle concentration

• Aggregate level

• Sample flow rate

• Scatter-detector range

Some conventional flow cytometers may not be suitable for 50µm particles.

The particles should remain substantially smaller than the narrowest internal flow path.

Imaging flow cytometry, large-particle cytometry, automated microscopy, or image-based particle analysis may be more appropriate for certain applications.

Blocking and Non-Specific Binding Control

Non-specific adsorption may increase background and reduce assay sensitivity.

Potential causes include:

• Inadequate blocking

• Incompatible blocking reagent

• Excess capture ligand

• Excess detection reagent

• Insufficient washing

• Aggregated antibodies

• Hydrophobic sample components

• High sample protein concentration

• Particle aggregation

• Sample-matrix interference

Screen Multiple Blocking Reagents

Compare several blocking formulations.

The preferred blocker should reduce negative-sample signal while maintaining target-specific binding.

Optimize Capture-Ligand Loading

Maximum ligand loading does not always provide maximum assay performance.

Excessive loading may:

• Cause steric crowding

• Reduce target accessibility

• Increase reagent consumption

• Increase non-specific interactions

• Increase assay variation

Titrate the Detection Reagent

Excess detection reagent may increase background.

Evaluate several reporter concentrations using positive and negative controls.

Optimize Washing

Evaluate:

• Number of washes

• Wash-buffer composition

• Wash volume

• Separation method

• Mixing method

• Residual supernatant

• Particle recovery

Evaluate Detergents Carefully

A small amount of compatible detergent may improve particle dispersion and reduce non-specific adsorption.

Excessive detergent may interfere with biomolecule interactions or reporter binding.

Comparison of 50µm, 30µm and 20µm Streptavidin Microspheres

Choose SAPS50UM-10 When:

• Maximum surface per individual particle is preferred.

• Direct microscopy is a primary detection method.

• Individual-particle analysis is required.

• Manual or automated particle manipulation is important.

• Clear size-based identification is needed.

• Large-particle microfluidic trapping is being studied.

• Large-particle agglutination research is planned.

• Strong visual confirmation of particle recovery is required.

Choose SAPS30UM-10 When:

• A large microsphere is required with somewhat easier transfer and fluidic compatibility.

• Microscopy and cell-size-range research remain important.

• A greater particle number per unit mass is desired.

• Lower settling than 50µm particles is preferred.

Choose SAPS20UM-10 When:

• A smaller large-particle platform is required.

• More particles per unit mass are needed.

• Flow-based analysis is more important.

• Lower settling is preferred.

• Easier microfluidic compatibility is required.

The final particle size should be selected according to the biological application, detection platform, required particle number, ligand loading, settling behavior, recovery method, and instrument compatibility.

Quality Control and Batch Consistency

Potential quality-control parameters for SAPS50UM-10 include:

• Mean particle diameter

• Particle-size range

• Particle-size distribution

• Particle-size coefficient of variation

• Particle morphology

• Suspension appearance

• Solids content

• Streptavidin coating consistency

• Biotin-binding capacity

• Particle-number concentration

• Particle dispersion

• Aggregate level

• Settling rate

• Redispersion performance

• Particle recovery

• Background signal

• Non-specific binding

• Microbial control

• Packaging integrity

• Storage stability

• Lot-to-lot consistency

Particle-Size Testing

Particle-size characterization may include:

• Mean diameter

• Median diameter

• Minimum and maximum size

• Size distribution

• Coefficient of variation

• Microscopy results

• Instrumental particle-size analysis

The measurement method should be stated when reporting size data.

Biotin-Binding Capacity

Binding capacity should be measured using a defined biotinylated test molecule.

The result may be affected by:

• Probe type

• Molecular size

• Biotinylation level

• Probe purity

• Incubation conditions

• Buffer composition

• Washing procedure

• Detection method

• Calculation basis

Binding-capacity results obtained using different test probes or methods may not be directly comparable.

Functional Quality Control

A functional QC assay may evaluate:

• Binding of a standardized biotinylated probe

• Percentage of positive particles

• Signal distribution

• Background separation

• Particle recovery

• Aggregate percentage

• Repeatability

• Redispersion after storage

Filling and Sampling Consistency

Because 50µm particles can settle rapidly, filling procedures should be validated carefully.

Potential controls include:

• Continuous gentle mixing during filling

• Particle-count testing at the beginning, middle, and end of filling

• Solids-content verification

• Visual homogeneity inspection

• Particle-count comparison between containers

• Repeated redispersion testing

Lot-Specific Documentation

Available documentation may include:

• Certificate of Analysis

• Product specification

• Particle-size results

• Solids-content results

• Binding-capacity results

• Particle-count results

• Safety Data Sheet

• Handling instructions

• Storage recommendations

• Lot number

• Production date

Required release tests and acceptance criteria should be agreed upon before bulk manufacturing.

Bulk Manufacturing and Customization

Shanghai SanYu Biotechnology Co., Ltd. supplies SHBC streptavidin microspheres for laboratory research, pilot development, repeated production, and enterprise bulk purchasing.

Research Sample Evaluation

Samples may be evaluated for:

• Particle morphology

• Particle-size distribution

• Particle dispersion

• Streptavidin activity

• Biotinylated ligand loading

• Non-specific binding

• Particle recovery

• Assay feasibility

• Microscopy compatibility

• Microfluidic compatibility

• Settling and redispersion

• Sampling consistency

Pilot-Scale Development

Pilot batches may support:

• Assay optimization

• Binding-capacity verification

• Stability studies

• Buffer selection

• Preservative evaluation

• Packaging evaluation

• Filling-process development

• Quality-control development

• Customer verification

• Process transfer

Bulk Production

Bulk manufacturing can be arranged after technical requirements and release specifications have been confirmed.

Please provide:

• Required quantity

• Expected annual demand

• Preferred package size

• Intended biological application

• Required particle diameter

• Required solids content

• Required binding capacity

• Required particle-number concentration

• Type of biotinylated ligand

• Buffer requirements

• Preservative restrictions

• Quality-control requirements

• Documentation requirements

• Delivery schedule

• Delivery destination

Custom Particle Diameter

Alternative particle sizes may be discussed according to application and manufacturing feasibility.

Custom Streptavidin Loading

Project-specific streptavidin coating levels or binding-capacity targets may be evaluated.

Custom Fluorescence or Color Coding

For imaging and multiplex research, fluorescently encoded or visibly colored streptavidin microspheres may be discussed.

Potential options may include:

• Alternative excitation wavelengths

• Alternative emission wavelengths

• Different fluorescence colors

• Multiple fluorescence-intensity levels

• Visible particle colors

• Customer-specific coding systems

Custom Buffer and Concentration

Alternative solids concentrations, buffer formulations, surfactants, preservative systems, and packaging formats may be evaluated.

OEM and Private-Label Supply

Available cooperation formats may include:

• OEM packaging

• Customer-specific labels

• Private-label supply

• Customer-specific catalog numbers

• Bulk raw material supply

• Customized technical documents

• Customer-specific release specifications

Storage and Stability Recommendations

Follow the final product label, technical data sheet, and lot-specific Certificate of Analysis.

General recommendations include:

• Store under the specified refrigerated conditions.

• Do not freeze unless freeze–thaw stability has been validated.

• Keep the container tightly closed.

• Store the vial upright.

• Maintain the microspheres in liquid.

• Mix thoroughly before sampling.

• Maintain gentle mixing during repeated dispensing.

• Use clean, wide-bore pipette tips and low-binding tubes.

• Avoid contamination of the original suspension.

• Do not allow the particles to dry.

• Avoid repeated unnecessary temperature changes.

• Do not return diluted material to the original container.

• Record the product lot number and opening date.

Established supplier protocols similarly recommend keeping streptavidin particles in liquid, avoiding drying, and avoiding freezing because these conditions can reduce performance or cause irreversible aggregation.

Settling and Resuspension

Because SAPS50UM-10 contains large particles, settling may occur rapidly.

Before use:

1. Allow the vial to reach the recommended handling temperature.

2. Gently invert or rotate the vial.

3. Apply controlled vortexing when necessary.

4. Confirm that the suspension is homogeneous.

5. Mix immediately before sampling.

6. Continue gentle mixing during repeated dispensing.

7. Inspect for irreversible aggregates.

Reversible settling does not necessarily indicate product failure.

Avoid Drying

Do not allow the particle pellet to dry during washing.

Drying may cause:

• Irreversible aggregation

• Reduced streptavidin activity

• Difficult redispersion

• Increased assay background

• Reduced particle recovery

Avoid Freezing

Freezing may cause:

• Particle aggregation

• Changes in suspension stability

• Reduced streptavidin activity

• Reduced particle recovery

• Increased assay variability

Evaluate Prepared Reagent Stability

Biotinylated-ligand-loaded and blocked microspheres may have different stability from the original SAPS50UM-10 suspension.

Evaluate the final prepared reagent under the intended storage, transport, and operating conditions.

Troubleshooting Guide

Weak Biotinylated Ligand Binding

Possible causes:

• Free biotin in the buffer

• Residual biotinylation reagent

• Low ligand biotinylation

• Inaccessible biotin groups

• Insufficient ligand concentration

• Inadequate incubation time

• Inactive streptavidin

• Incompatible buffer

• Particle settling during incubation

Recommended actions:

• Remove free biotin.

• Purify the biotinylated ligand.

• Verify the biotinylation level.

• Evaluate a suitable spacer.

• Maintain continuous gentle mixing.

• Increase ligand concentration gradually.

• Test a positive-control biotinylated ligand.

High Background Signal

Possible causes:

• Insufficient blocking

• Excess detection reagent

• Inadequate washing

• Non-specific reporter adsorption

• Sample-matrix interference

• Aggregated antibodies

• Excess capture-ligand loading

Recommended actions:

• Compare different blockers.

• Titrate the detection reagent.

• Optimize washing.

• Remove protein aggregates when appropriate.

• Dilute the sample.

• Reduce capture-ligand loading.

Unequal Particle Numbers Between Aliquots

Possible causes:

• Rapid particle settling

• Inadequate stock mixing

• Delay between mixing and sampling

• Narrow pipette-tip opening

• Inconsistent transfer technique

• Particle retention in the tip

Recommended actions:

• Mix before every aliquot.

• Use a wide-bore pipette tip.

• Maintain slow mixing during repeated dispensing.

• Standardize the sampling interval.

• Verify particle numbers during filling.

Particle Aggregation

Possible causes:

• Incompatible buffer

• Extreme pH

• High ionic strength

• Freezing

• Drying

• Excessive ligand loading

• Insufficient stabilizer

• Microbial contamination

Recommended actions:

• Evaluate buffer compatibility.

• Avoid freezing and drying.

• Optimize ligand loading.

• Use controlled gentle mixing.

• Review stabilizer and preservative requirements.

Low Particle Recovery

Possible causes:

• Loss during supernatant removal

• Adhesion to tubes

• Incorrect filter or mesh size

• Incomplete sedimentation

• Incomplete transfer

• Excessive washing

• Particle retention inside pipette tips

Recommended actions:

• Use low-binding tubes.

• Optimize separation conditions.

• Validate the filter or mesh.

• Mix before every transfer.

• Reduce unnecessary wash steps.

• Leave a controlled residual volume above the pellet.

Microfluidic Blockage

Possible causes:

• Channel dimensions are too small

• Particle aggregation

• Excessive particle concentration

• Narrow connectors

• Incompatible valves or filters

• Insufficient device flushing

Recommended actions:

• Confirm the minimum channel dimension.

• Reduce particle concentration.

• Remove aggregates before loading.

• Increase the flow-path dimensions.

• Validate the complete device with plain 50µm particles first.

Frequently Asked Questions

What is SAPS50UM-10?

SAPS50UM-10 is a 50µm streptavidin-coated microsphere suspension supplied at 1% solids for capturing biotinylated biomolecules in biological research and particle-based assays.

What is the SHBC brand?

SHBC is the microsphere and biotechnology material brand of Shanghai SanYu Biotechnology Co., Ltd.

What is the nominal particle diameter?

The nominal particle diameter is 50µm.

The measured diameter, size range, and particle-size distribution should be confirmed using lot-specific documentation.

What is the solids content?

SAPS50UM-10 is supplied at 1% solids.

Are SAPS50UM-10 microspheres magnetic?

The product should not be assumed to be magnetic unless magnetic properties are specifically stated in the technical specification.

For magnetic separation, select a product specifically described as streptavidin magnetic beads.

Are the microspheres fluorescent?

The standard SAPS50UM-10 product should not be assumed to contain an internal fluorescent dye unless fluorescence is specifically stated.

A fluorescently encoded version may be discussed as a customized product.

Which molecules can bind to SAPS50UM-10?

The streptavidin surface can capture biotinylated antibodies, antigens, proteins, peptides, enzymes, receptors, lectins, oligonucleotides, DNA, RNA, aptamers, and other biotin-containing molecules.

Can an unmodified antibody bind directly?

An unmodified antibody will not specifically attach through the streptavidin–biotin interaction unless it is biotinylated or connected through another compatible reagent.

Is EDC/NHS activation required?

EDC/NHS activation is normally not required when loading a biotinylated molecule onto streptavidin-coated microspheres.

What is the biotin-binding capacity?

Binding capacity should be confirmed using the product specification or lot-specific Certificate of Analysis.

It should not be estimated from solids content or particle diameter alone.

Why choose 50µm microspheres?

The 50µm particles provide a large surface per individual particle, excellent microscopy visibility, easy individual-particle identification, and dimensions suitable for large-particle biological and microfluidic research.

Do 50µm particles provide more total surface area?

Each 50µm particle has more surface area than each smaller particle.

However, smaller particles normally provide more particles and greater collective surface area per unit mass.

Why do the particles settle quickly?

Large particles generally settle more quickly than smaller microspheres.

Mix the stock immediately before sampling and maintain gentle mixing during incubation and repeated dispensing.

Can SAPS50UM-10 be used for microscopy?

Yes. The particle size is suitable for evaluation by optical, fluorescence, and confocal microscopy.

Can SAPS50UM-10 be used in flow cytometry?

It may be used only when the flow cytometer fluidics, nozzle, flow cell, sample probe, and internal pathways are compatible with 50µm particles.

Can SAPS50UM-10 be used as a cell model?

The 50µm diameter may be relevant to selected large-cell, spheroid, embryo, or synthetic biological particle research.

Synthetic microspheres do not reproduce all optical, mechanical, chemical, or biological properties of living cells.

Can the microspheres be used for immunoassays?

Yes. A biotinylated capture antibody may be immobilized on the particle, followed by target capture and detection with a compatible reporter.

Can the particles be used for nucleic acid capture?

Yes. Biotinylated oligonucleotides, DNA, RNA, PCR products, and aptamers may be evaluated for immobilization and target capture.

Can SAPS50UM-10 be used in multiplex assays?

Yes, provided that the 50µm population can be distinguished from other microsphere populations.

Size coding, fluorescence coding, or visible color coding may be considered.

How should the particles be washed?

The washing method depends on particle material, density, buffer, volume, and required recovery.

Centrifugation, filtration, mesh-based recovery, or controlled sedimentation may be evaluated.

How can non-specific binding be reduced?

Optimize the blocking reagent, capture-ligand concentration, detection-reagent concentration, washing conditions, detergent level, sample dilution, and incubation time.

Can buffers containing free biotin be used?

Free biotin may occupy streptavidin-binding sites and should generally be avoided during capture-ligand loading.

Should SAPS50UM-10 be diluted before use?

Yes. Prepare a working concentration according to the required particle number, reaction volume, and detection method.

Can SAPS50UM-10 be frozen?

Freezing is generally not recommended unless freeze–thaw stability has been specifically validated.

Can the concentration be customized?

Alternative solids concentrations may be discussed according to project requirements and manufacturing feasibility.

Can the binding capacity be customized?

Project-specific streptavidin coating levels or binding-capacity targets may be evaluated.

Can fluorescent 50µm streptavidin microspheres be produced?

Fluorescently encoded or visibly colored 50µm streptavidin microspheres may be discussed for qualified imaging, microfluidic, and multiplex projects.

Is bulk production available?

Yes. Shanghai SanYu Biotechnology Co., Ltd. supports samples, pilot batches, repeated orders, OEM projects, and bulk manufacturing.

What information is required for a quotation?

Please provide:

• Catalog number SAPS50UM-10

• Required quantity

• Expected annual purchasing volume

• Preferred package size

• Intended biological application

• Type of biotinylated ligand

• Required binding capacity

• Required particles per test

• Detection method

• Buffer restrictions

• Preservative restrictions

• Quality-control requirements

• Documentation requirements

• Delivery destination

Request a Sample or Bulk Quotation

SHBC SAPS50UM-10 50µm Streptavidin Microspheres provide a large and clearly identifiable particle platform for immobilizing biotinylated antibodies, proteins, peptides, enzymes, receptors, lectins, oligonucleotides, DNA, RNA, aptamers, and other biotin-labeled molecules.

The product is suitable for:

• Biological assay development

• Bead-based immunoassays

• Antibody immobilization

• Protein interaction research

• Nucleic acid capture

• Hybridization assays

• Cell–particle interaction research

• Microscopy and high-content imaging

• Microfluidic research

• Particle agglutination

• Size-coded multiplex systems

• Particle-based biosensors

• Individual-particle analysis

• Research reagent manufacturing

SAPS50UM-10 provides:

• 50µm nominal particle diameter

• Streptavidin-functional surface

• 1% solids suspension

• Large surface per individual particle

• Excellent microscopic visibility

• Compatibility with biotinylated biomolecules

• Sample and pilot-batch supply

• Bulk manufacturing capability

• OEM and custom-development support

For sample evaluation or bulk purchasing, provide the intended application, required quantity, biotinylated ligand, desired binding capacity, detection platform, packaging requirements, and quality-control specifications.

Product Name: 50µm Streptavidin Microspheres
Catalog Number: SAPS50UM-10
Brand: SHBC
Manufacturer: Shanghai SanYu Biotechnology Co., Ltd.
Nominal Particle Diameter: 50µm
Surface Modification: Streptavidin
Solids Content: 1%
Primary Application: Biological Research and Particle-Based Assays
Supply Capability: Samples, Pilot Batches, and Bulk Production
Intended Use: Research Use Only. Not for diagnostic or therapeutic use.