Product Overview and Principle

SLC core-shell Monodispersed Magnetic Silica Microspheres (SKU: M120220) are engineered particles consisting of a superparamagnetic iron oxide core encapsulated within a uniform silica shell. This architecture combines the rapid magnetic responsiveness of iron oxide with the chemically versatile and biocompatible surface properties of silica.

The monodispersed size distribution ensures reproducible binding kinetics, low non-specific adsorption, and consistent batch-to-batch performance—critical attributes for quantitative assay development and automated workflows. The silica surface presents abundant silanol (Si–OH) groups that serve as anchoring points for downstream functionalization with a broad range of silane coupling agents.

Upon application of an external magnetic field, the microspheres migrate rapidly to the vessel wall, enabling supernatant removal and washing steps without centrifugation. Once the field is removed, the particles readily resuspend due to their superparamagnetic character and absence of magnetic remanence.

Materials Required

• SLC core-shell Monodispersed Magnetic Silica Microspheres (M120220), supplied as aqueous suspension
• Appropriate binding/wash buffer (e.g., PBS pH 7.4, or buffer suited to specific application)
• Magnetic separation rack or permanent magnet compatible with tube format in use
• Microcentrifuge tubes (1.5 mL or 2.0 mL) or appropriate reaction vessels
• Micropipettes and low-binding pipette tips
• Vortex mixer and/or rotary end-over-end mixer
• Temperature-controlled incubator or heat block (if required by application)
• Target biomolecule (antibody, oligonucleotide, or other ligand) for conjugation if performing functionalization
• Coupling reagents appropriate to chosen surface chemistry (e.g., EDC/NHS for –COOH surfaces, glutaraldehyde for –NH₂ surfaces)

Step-by-Step Protocol

Step 1 – Preparation of Microsphere Suspension

1. Remove the product vial from storage (4 °C) and allow it to equilibrate to room temperature for approximately 10 minutes.
2. Resuspend the microspheres thoroughly by vortexing for 30 seconds followed by gentle end-over-end rotation for 2 minutes. Ensure no visible aggregates remain.
3. Transfer the required volume of microsphere suspension to a fresh microcentrifuge tube.

Step 2 – Magnetic Wash (Pre-Equilibration)

1. Place the tube on the magnetic rack for 2–3 minutes until the microspheres are fully captured against the tube wall and the supernatant is clear.
2. Carefully aspirate and discard the supernatant without disturbing the microsphere pellet.
3. Remove the tube from the magnet and immediately add the appropriate working buffer (e.g., 500 µL PBS pH 7.4).
4. Resuspend by vortexing briefly (5–10 seconds) and end-over-end rotation for 1 minute.
5. Repeat the magnetic wash step once more for a total of two pre-equilibration washes.

Step 3 – Binding / Functionalization

1. After the final wash, remove the supernatant magnetically and resuspend the microspheres in the binding buffer at the desired concentration.
2. Add the target biomolecule or coupling reagent according to the requirements of the specific application or functionalization chemistry.
3. Incubate under appropriate conditions (temperature, time, and agitation as dictated by the application). End-over-end rotation is recommended to maintain particle suspension during incubation.
4. Following incubation, place on the magnetic rack for 2–3 minutes and remove the supernatant.

Step 4 – Washing and Elution

1. Resuspend the microspheres in wash buffer and mix for 1–2 minutes.
2. Apply magnetic separation (2–3 minutes) and aspirate the wash supernatant.
3. Repeat washing 2–3 times or as optimised for the specific application.
4. For elution of captured target molecules, resuspend the washed microspheres in elution buffer (composition dependent on application, e.g., low-pH glycine buffer for antibody–antigen systems, heated water or low-salt buffer for nucleic acids).
5. After elution incubation, magnetically separate the microspheres and collect the eluate containing the target analyte.

Step 5 – Storage of Used or Unused Microspheres

1. Unused microspheres should be stored as received at 4 °C in their original aqueous suspension. Do not freeze.
2. If the microspheres are to be reused (application-dependent), wash thoroughly in storage buffer and store at 4 °C. Assess performance before reuse in critical assays.

Troubleshooting

Safety, Handling, and Regulatory Notes

General Handling: SLC core-shell Monodispersed Magnetic Silica Microspheres are intended for research use only (RUO). They are not approved for diagnostic, therapeutic, or clinical use in humans or animals.

Physical Hazards: The product contains iron oxide nanoparticles. Avoid inhalation of any dried particulate. Work in a well-ventilated area and wear appropriate personal protective equipment (lab coat, gloves, and eye protection) when handling.

Magnetic Precautions: When using strong external magnets, keep away from electronic devices, implanted medical devices (e.g., pacemakers), and magnetic storage media.

Disposal: Dispose of all waste in accordance with local institutional and governmental regulations for chemical and biological waste.

SDS: Consult the Safety Data Sheet (SDS) for M120220 available from Aladdin Scientific prior to use. The SDS contains current information on hazard classification, first-aid measures, and emergency contacts.