Introduction

Fluorescent particles are prepared by incorporating selected fluorophores into monodisperse PMMA particles through swelling process or copolymerizing PMMA with various organic fluorescent dyes, which produce fluorophores labeled PMMA particles with satisfactory properties. Functional groups or biological macromolecules (carboxyl, amino, streptavidin, biotin, etc.) can be quantitatively modified on the surface of microsphere as linking groups for immunoanalysis, making fluorescent PMMA microspheres have a wide range of applications, including lateral chromatography, cell imaging, microfluidics and fluorescence enzyme-related immunosorbent assay. Fluorescent particles with single or multiple fluorophores are available in various sizes, emission spectra and combinations.    Many are suitable for uses in flow cytometry, fluorescence microscopy, phagocytosis studies, and cell labeling[1-2].

Abvigen Inc. offers a wide range of Fluorescent PMMA Particles, including Green PMMA Fluorescent Particles, Blue PMMA Fluorescent Particles, Red PMMA Fluorescent Particles and Orange PMMA Fluorescent Particles. The product size is adjustable within the range of nanometers to micrometers, and can be further flexibly adjusted according to customer requirements and use conditions to achieve customized supply.

Preparation Method

Dispersion polymerization[3]: This work described a facile method to synthesize sterically stabilized monodisperse fluorescent poly(methyl methacrylate) (PMMA) colloids in the polar solvent mixture water/methanol with either a core-shell or a homogeneously cross-linked structure by dispersion polymerization. The particles were sterically stabilized by the polymer poly(vinylpyrrolidone) (PVP).   The morphology of the particles was controlled by varying the moment at which the gradual addition of cross-linker and dye was started. The absence of these extra agents at a time when the particle nuclei formed reduced the negative effects on this important process to a minimum and produced a core-shell structure, whereas an essentially homogeneously cross-linked fluorescent polymer colloid structure could be obtained by reducing the starting time of the addition of dye and cross-linker to zero. Three different dyes were chemically incorporated into the polymer network. Such dyes are important for the use of the particles in confocal scanning laser microscopy studies aimed at characterizing concentrated dispersions quantitatively in real space. A series of PMMA particles with different sizes were obtained through the variation of the weight ratio of solvents and the content of cross-linker. Furthermore, the swelling properties of the cross-linked PMMA particles in a good solvent (tetrahydrofuran) were investigated. The particles were stable in polar solvents (water and formamide) but could also successfully be transferred to apolar solvents such as decahydronaphthalene (decalin). The PVP stabilizer also allowed the particles to be permanently bonded in flexible strings by the application of an external electric field.

PMMA/PMMA Core–Shell Particles with Ellipsoidal, Fluorescent Cores[4]: A new class of core-shell particles was introduced, which can be used as rotational probes. The colloids described are composed of shape anisotropic, fluorescent cores covered with nonfluorescent PMMA shells. The core-shell particles are built up in four steps. In a first step, we produce fluorescent and photo-cross-linkable PMMA colloids. In the second step, these particles are thermomechanically elongated and fixed in defined ellipsoidal shapes by photo-cross-linking. Subsequently, we cover the cross-linked, fluorescent core with a nonfluorescent PMMA shell. The shape of the resulting core-shell colloids is tunable between the initial anisotropic and perfect spherical shape. For shaping, a simple solvent swelling procedure was applied. As one option, this method yields perfect PMMA spheres with ellipsoidal, fluorescent centers.

Batch emulsion polymerization (BEP) and monomer-starved semi-batch emulsion polymerization (MSSEP)-covalently bonded-copolymerized[5]: The synthesis of PMMA-based nanoparticles (NPs) covalently labeled with a fluorescent dye is investigated for imaging applications such as cell uptake and biodistribution. Batch emulsion polymerization (BEP) and monomer-starved semi-batch emulsion polymerization (MSSEP) are adopted using SDS. Fluorescent properties are added to these NPs using Rhodamine-B (RhB) as a fluorescent dye covalently bonded to 2-hyroxyethyl-acrylate. The resulting HEMA-RhB monomer is copolymerized with MMA via BEP and MSSEP to synthesize fluorescent NPs. Subsequently, SDS is substituted with a biocompatible surfactant, Tween80, through ionic-exchange resins.

Stable, fluorescent polymethylmethacrylate particles[6]: Produce PMMA colloidal particles that employ polymerizable and photostable cyanine-based fluorescent monomers spanning the range of visible wavelengths and a polymeric stabilizer prepared from polydimethylsiloxane, PDMS-graft-PMMA. Using microcalorimetry, we characterize the thermodynamics of an accelerated equilibration process for these dispersions in the buoyancy- and refractive-index-matching solvents. We use confocal differential dynamic microscopy to demonstrate that they behave as hard spheres. The suspended particles are stable for months to years, maintaining fixed particle size and density, and do not leak dye.

Preparation of highly fluorescent PMMA nanoparticles[7]: Methacrylate monomers were functionalized with a 4-hydroxythiazole chromophore and copolymerized with methyl methacrylate via RAFT. Nanoparticles of 120 and 500 nm in size were prepared without using stabilizers/surfactants.

A two-step method (dispersion polymerization-swelled-heat-induced polymerization)[8]: The fabrication of fluorescent snowman-like poly(methyl methacrylate) (PMMA) colloidal microbeads using a two-step method. The fluorescent cross-linked PMMA seeds were first synthesized by dispersion polymerization and then swelled in a monomer solution containing the methyl methacrylate monomer, a secondary cross-linker and initiator, followed by heat-induced polymerization.

One-step method (a variation of the methods of Barrett and Campbell and Bartlett)[9]: A lipophilic fluorescent dye, 1,1‘-dioctadecyl-3,3,3‘,3‘-tetramethylindodicarbocyanine perchlorate, is directly incorporated into PMMA particles through dispersion polymerization. A poly(hydroxystearic acid) graft (poly) methyl methacrylate (MM) and methacrylic acid (MA) copolymer is used as a stabilizer to prevent the particles from aggregating and flocculating in the nonaqueous solvents. The fluorescent PMMA particles are very uniform in size, bleach at very low rate, and behave like hard spheres in their ordering on substrates.

Soap-free emulsion polymerization[10]: Soap-free emulsion polymerization was extended to preparation of monodisperse poly(methyl methacrylate) (PMMA) particles incorporating rhodamine 6G (R6G) fluorescent molecules. The polymerization was conducted in the presence of an anionic monomer, p-styrenesulfonate (NaSS), which improved dispersion stability of the polymer particles.  NaSS concentrations was ranged up to 2 mol/m3 H2O in the polymerization at 0.5 kmol/m3 H2O methyl methacrylate (MMA) monomer and 5 mol/m3 H2O potassium persulfate (KPS) initiator for R6G concentrations from 0.1 to 10 mol/m3-polymer. At R6G concentrations lower than 1.0 mol/m3-polymer, PMMA particles were highly monodisperse and incorporated most R6G molecules. The average sizes of PMMA particles were in a rage of 160-300 nm, and decreased with the concentration of NaSS. The high monodispersity of the particles enabled the fabrication of colloidal crystals of the particles with a vertical deposition method.

Application

Phagocytosis studies;

Cell imaging;

Tracking;

Calibration of flow cytometry;

Lateral chromatography;

Microfluidics;

Fluorescence enzyme-related immunosorbent assay;

Fluorescence microscopy

Advantages

Monodisperse Particles;

High particle size uniformity;

High-intensity fluorescence;

Available with red, green orange and blue fluorescence;

Designed with carboxylic acid groups (COOH) and amino groups (NH2) on the particle surface for the covalent binding of proteins, antibodies or other molecules;

Offered with streptavidin on the surface for binding of biotinylated molecules;

Outstanding long-term stability under proper storage conditions (both color and fluorescence);

Spherical shape;

Great resistance to photobleaching;

Minimized dye leaching