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This article is about the particles. For the software company, see Microsphere (software company). For other uses, see microsphere (disambiguation). For the biological cell fragment, see Microvesicles.
IUPAC definition

Particle with dimensions between 1 × 10−7 and 1 × 10−4 m.

Note 1: The lower limit between micro- and nano-sizing is still a matter of debate.

Note 2: To be consistent with the prefix “micro” and the range imposed by the definition,
dimensions of microparticles should be expressed in μm.[1]

Microparticles are particles between 0.1 and 100 μm in size. Commercially available microparticles are available in a wide variety of materials, including ceramics, glass, polymers, and metals.[2] Microparticles encountered in daily life include pollen, sand, dust, flour, and powdered sugar. The study of microparticles has been called micromeritics,[3] although this term is not very common.

Microparticles have a much larger surface-to-volume ratio than at the macroscale, and thus their behavior can be quite different. For example, metal microparticles can be explosive in air.

Microspheres are spherical microparticles,[4] and are used where consistent and predictable particle surface area is important.

In biological systems, a microparticle is synonymous with a microvesicle, a type of extracellular vesicle (EV).

Applications

[edit]

Home pregnancy tests make use of gold microparticles. Many applications are also listed in the microsphere article.

A recent study showed that infused, negatively charged, immune-modifying microparticles could have therapeutic use in diseases caused or potentiated by inflammatory monocytes.[5]

Microparticles can also be used during minimally invasive embolization procedures, such as hemorrhoidal artery embolization.[6][7]

Microspheres

[edit]

Microspheres are small spherical particles, with diameters in the micrometer range (typically 1 μm to 1000 μm (1 mm). Microspheres are sometimes referred to as spherical microparticles. In general microspheres are solid or hollow and do not have a fluid inside, as opposed to microcapsules.

Microspheres can be made from various natural and synthetic materials. Glass microspheres, polymer microspheres, metal microspheres, and ceramic microspheres are commercially available.[8] Solid and hollow microspheres vary widely in density and, therefore, are used for different applications. Hollow microspheres are typically used as additives to lower the density of a material. Solid microspheres have numerous applications depending on what material they are constructed of and what size they are.

Polyethylene, polystyrene and expandable microspheres are the most common types of polymer microspheres.

IUPAC definition

Microparticle of spherical shape without membrane or any distinct outer layer.

Note: The absence of outer layer forming a distinct phase is important to distinguish
microspheres from microcapsules because it leads to first-order diffusion phenomena,
whereas diffusion is zero order in the case of microcapsules.[9]

Polystyrene microspheres are typically used in biomedical applications due to their ability to facilitate procedures such as cell sorting and immunoprecipitation. Proteins and ligands adsorb onto polystyrene readily and permanently, which makes polystyrene microspheres suitable for medical research and biological laboratory experiments.

Polyethylene microspheres are commonly used as a permanent or temporary filler. Lower melting temperature enables polyethylene microspheres to create porous structures in ceramics and other materials. High sphericity of polyethylene microspheres, as well as availability of colored and fluorescent microspheres, makes them highly desirable for flow visualization and fluid flow analysis, microscopy techniques, health sciences, process troubleshooting and numerous research applications. Charged polyethylene microspheres are also used in electronic paper digital displays.[10][11]

Expandable microspheres are polymer microspheres that are used as a blowing agent in e.g. puff ink, automotive underbody coatings and injection molding of thermoplastics. They can also be used as a lightweight filler in e.g. cultured marble, waterborne paints and crack fillers/joint compound. Expandable polymer microspheres can expand to more than 50 times their original size when heat is applied to them. The exterior wall of each sphere is a thermoplastic shell that encapsulates a low boiling point hydrocarbon. When heated, this outside shell softens and expands as the hydrocarbon exerts a pressure on the internal shell wall.

Glass microspheres are primarily used as a filler and volumizer for weight reduction, retro-reflector for highway safety, additive for cosmetics and adhesives, with limited applications in medical technology.

Microspheres made from highly transparent glass can perform as very high quality optical microcavities or optical microresonators.

Ceramic microspheres are used primarily as grinding media.

Hollow microspheres loaded with drug in their outer polymer shell were prepared by a novel emulsion solvent diffusion method and spray drying technique.

Microspheres vary widely in quality, sphericity, uniformity, particle size and particle size distribution. The appropriate microsphere needs to be chosen for each unique application.

Applications

[edit]

New applications for microspheres are discovered every day. Below are just a few:

  • Assay - Coated microspheres provide measuring tool in biology and drug research
  • Buoyancy - Hollow microspheres are used to decrease material density in plastics (glass and polymer), neutrally-buoyant microspheres are frequently used for fluid flow visualization.
  • Particle image velocimetry - Solid or hollow microspheres used for flow visualization, density of the particle has to match that of the fluid.[12]
  • Ceramics - Used to create porous ceramics used for filters (microspheres melt out during firing, Polyethylene Microspheres) or used to prepare high strength lightweight concrete.[13]
  • Cosmetics - Opaque microspheres used to hide wrinkles and give color, Clear microspheres provide "smooth ball bearing" texture during application (Polyethylene Microspheres)
  • Deconvolution - Small fluorescent microspheres (<200 nanometers) are required to obtain an experimental Point spread function to characterise microscopes and perform image deconvolution
  • Drug delivery - As miniature time release drug capsule made of, for example, polymers. A similar use is as outer shells of microbubble contrast agents used in contrast-enhanced ultrasound.
  • Electronic paper - Dual Functional microspheres used in Gyricon electronic paper
  • Insulation – expandable polymer microspheres are used for thermal insulation and sound dampening.
  • Personal Care - Added to Scrubs as an exfoliating agent (Polyethylene Microspheres)
  • Spacers - Used in LCD screens to provide a precision spacing between glass panels (glass)
  • Standards - monodisperse microspheres are used to calibrate particle sieves, and particle counting apparatus.
  • Retroreflective - added on top of paint used on roads and signs to increase night visibility of road stripes and signs (glass)
  • Thickening Agent - Added to paints and epoxies to modify viscosity and buoyancy
  • Drugs can be formulated as HBS floating microsphere. Following are list of drugs which can formulated as microsphere: Repaglinide, Cimetidine, Rosiglitazone, Nitrendipine, Acyclovir, Ranitidine HCl, Misoprostol, Metformin, Aceclofenac, Diltiazem, L-Dopa and benserazide, Fluorouracil.

Biological protocells

[edit]

Some refer to microspheres or protein protocells as small spherical units postulated by some scientists as a key stage in the origin of life.

In 1953, Stanley Miller and Harold Urey demonstrated that many simple biomolecules could be formed spontaneously from inorganic precursor compounds under laboratory conditions designed to mimic those found on Earth before the evolution of life. Of particular interest was the substantial yield of amino acids obtained, since amino acids are the building blocks for proteins.

In 1957, Sidney Fox demonstrated that dry mixtures of amino acids could be encouraged to polymerize upon exposure to moderate heat. When the resulting polypeptides, or proteinoids, were dissolved in hot water and the solution allowed to cool, they formed small spherical shells about 2 μm in diameter—microspheres. Under appropriate conditions, microspheres will bud new spheres at their surfaces.

Although roughly cellular in appearance, microspheres in and of themselves are not alive. Although they do reproduce asexually by budding, they do not pass on any type of genetic material. However they may have been important in the development of life, providing a membrane-enclosed volume which is similar to that of a cell. Microspheres, like cells, can grow and contain a double membrane which undergoes diffusion of materials and osmosis. Sidney Fox postulated that as these microspheres became more complex, they would carry on more lifelike functions. They would become heterotrophs, organisms with the ability to absorb nutrients from the environment for energy and growth. As the amount of nutrients in the environment decreased at that period, competition for those precious resources increased. Heterotrophs with more complex biochemical reactions would have an advantage in this competition. Over time, organisms would evolve that used photosynthesis to produce energy.

Cancer research

[edit]

One useful discovery made from the research of microspheres is a way to fight cancer on a molecular level. According to Wake Oncologists, SIR-Spheres microspheres are radioactive polymer spheres that emit beta radiation. Physicians insert a catheter through the groin into the hepatic artery and deliver millions of microspheres directly to the tumor site. The SIR-Spheres microspheres target the liver tumors and spare healthy liver tissue. Cancer microsphere technology is the latest trend in cancer therapy[citation needed]. It helps the pharmacist to formulate the product with maximum therapeutic value and minimum or negligible range side effects. A major disadvantage of anticancer drugs is their lack of selectivity for tumor tissue alone, which causes severe side effects and results in low cure rates. Thus, it is very difficult to target abnormal cells by the conventional method of the drug delivery system. Microsphere technology is probably the only method that can be used for site-specific action (grossly overstated), without causing significant side effects on normal cells.[14]

Extracellular vesicles

[edit]

Microparticles can be released as extracellular microvesicles from red blood cells, white blood cells, platelets, or endothelial cells. These biological microparticles are thought to be shed from the plasma membrane of the cell as lipid bilayer-bound entities that are typically larger than 100 nm in diameter. "Microparticle" has been used most frequently in this sense in the hemostasis literature, usually as a term for platelet EVs found in the blood circulation. Because EVs retain the signature membrane protein composition of the parent cell, MPs and other EVs may carry useful information including biomarkers of disease. They can be detected and characterized by methods such as flow cytometry,[15] or dynamic light scattering.

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Microparticle

View on Grokipedia
from Grokipedia
Microparticles are solid particles ranging in size from 1 to 1000 micrometers, composed of natural or synthetic materials such as polymers, , or inorganic substances, and serve as versatile carriers in applications including and . They are distinguished from nanoparticles (below 100 nm) and macroparticles (above 1000 μm) by their intermediate scale, which enables unique properties like controlled and surface interactions. In pharmaceutical sciences, microparticles are engineered as multi-unit systems—such as microspheres (homogeneous matrices dispersing active agents) or microcapsules (core-shell structures enclosing payloads)—to achieve sustained release, targeted delivery, and improved of therapeutics, with examples including poly(lactic-co-glycolic acid) () formulations approved for treatments like . These systems reduce dosing frequency and minimize side effects compared to conventional formulations. Beyond medicine, microparticles play critical roles in for applications in , paints, and , where their tunable surface chemistry facilitates adsorption of pollutants or enhancement of product stability. In , a distinct subclass encompasses cell-derived extracellular microparticles (0.1–1 μm), which are membrane-bound vesicles mediating intercellular signaling, , and pathological processes in conditions like and cancer. Overall, advances in fabrication techniques, such as and , continue to expand their utility across disciplines.

Fundamentals

Definition and Classification

Microparticles are defined as solid or semi-solid particles with diameters typically ranging from 1 to 1000 micrometers, serving as versatile carriers in various scientific and engineering applications. This size range distinguishes them from nanoparticles, which are generally smaller than 1 micrometer (often 1 to 100 nanometers), and from macroparticles, which exceed 1000 micrometers in diameter. The term encompasses a broad array of materials engineered or naturally occurring, enabling controlled interactions at the microscale. Early explorations of controlled release from matrices emerged in the within pharmaceutical contexts. A pivotal milestone occurred in the with the development of biodegradable polymeric microparticles, pioneered by and Robert Langer, who demonstrated sustained release of macromolecules such as proteins from ethylene-vinyl acetate copolymers and other polymers. Their work established foundational principles for using microparticles in long-term therapeutic delivery, influencing subsequent advancements in . Microparticles are classified according to several schemes, including origin, , and composition. By origin, they divide into synthetic types, produced via chemical or physical processes from non-biological materials, and biological types, often smaller (0.1-1 μm) and including membrane-bound vesicles derived from cellular fragments or aggregates of natural biomolecules like proteins. Structurally, they are categorized as matrix systems, such as microspheres where active components are uniformly dispersed throughout a solid core, or reservoir systems, like microcapsules featuring a distinct core enclosed by a polymeric shell. In terms of composition, common variants include polymeric (e.g., poly(lactic-co-glycolic acid) or ), lipid-based, ceramic, or protein-derived materials, each tailored for specific stability and release profiles. The size of microparticles significantly affects their physical behaviors and biological interactions. Smaller microparticles (around 1-5 micrometers) exhibit enhanced due to , facilitating deeper penetration into tissues or fluids, while larger ones (up to 1000 micrometers) are prone to under , influencing their settling in suspensions or deposition sites. These size-dependent traits also impact ; for instance, particles in the 1-5 micrometer range optimize respiratory deposition by balancing and , thereby improving absorption and retention in target areas like the lungs without rapid clearance.

Physical and Chemical Properties

Microparticles exhibit a range of physical properties that influence their handling, dispersion, and interaction with environments. typically ranges from 1 to 2 g/cm³ for polymeric microparticles, such as poly(lactic-co-glycolic acid) () with a true of approximately 1.3-1.4 g/cm³, while types can reach higher values around 3-4 g/cm³. varies from spherical to irregular or anisotropic forms, with often achieved through fabrication methods to optimize flow and packing. , which can reach 50-80% in engineered designs, significantly affects loading capacity for drugs or actives by providing internal void spaces. Surface area for non-porous polymeric microparticles typically ranges from 0.01 to 6 m²/g depending on size, while moderately porous variants can reach 10-100 m²/g or higher, enhancing reactivity and adsorption potential. Optical properties of microparticles include light scattering due to their size in the 1-1000 μm range, which contributes to visibility in suspensions and is exploited in applications. Mechanically, the base polymeric material in microparticles like has a of approximately 1-3 GPa, though assembled porous structures from such particles exhibit lower moduli around 1-10 MPa, rendering them flexible yet prone to deformation under , with fragility increasing in highly porous designs. Chemical properties encompass surface charge, quantified by , which is tunable from -30 to +30 mV through coatings or material selection to control colloidal stability and interactions. Hydrophilicity or hydrophobicity is characterized by contact angles ranging from 30° to 150°, with hydrophilic surfaces (below 90°) favoring aqueous dispersion and hydrophobic ones (above 90°) aiding encapsulation of non-polar compounds. Reactivity arises from functional groups such as carboxyl or , enabling conjugation for targeted modifications. Stability factors include degradation rates in aqueous environments, where biodegradable polymers like exhibit half-lives of 1-6 months depending on composition (e.g., 10 weeks for 75:25 :glycolide ratio). Thermal stability varies, with polymeric types stable up to 100-200°C and ceramics enduring beyond 200°C without structural compromise.

Fabrication Methods

Synthesis Techniques

Microparticles are commonly synthesized using emulsion-based methods, which involve the dispersion of one phase into another to form droplets that solidify into particles upon or extraction. Single emulsion techniques, such as oil-in-water (O/W) processes, are particularly suited for encapsulating hydrophobic drugs, where the and active agent are dissolved in an organic (e.g., ) and emulsified into an aqueous phase containing a like (). Key parameters include concentrations of 1-2% to stabilize the and stirring speeds during ranging from 500 to 2000 rpm to control droplet size and prevent aggregation. These methods achieve encapsulation efficiencies up to 98% for certain hydrophobic compounds, though typical ranges are 20-90% depending on the drug- ratio. Double emulsion methods, such as water-in-oil-in-water (W/O/W), extend this approach for hydrophilic actives like proteins or peptides by first forming a primary water-in-oil , which is then dispersed into a secondary aqueous phase. This creates a barrier that enhances retention of water-soluble payloads, with processes involving ultrasonication or mechanical stirring for the initial emulsions followed by lower-speed stirring (500-1000 rpm) for solidification. levels of 1-5% PVA in the external phase are critical for stability, yielding encapsulation efficiencies of 28-100% and particle sizes tunable via phase volume ratios. Polymers like poly(lactic-co-glycolic acid) () are often employed in these techniques for biodegradable microparticles. Microfluidic approaches provide enhanced control over microparticle uniformity through droplet generation in flow-focusing or T-junction devices, where continuous and dispersed phase fluids meet to form monodisperse s. These methods produce particles with coefficients of variation (CV) below 5%, far surpassing batch emulsion polydispersity, by precisely regulating flow rates (typically 0.1-10 mL/h) and channel geometries. Advantages include reproducible composition and reduced material waste, with scalability improved via parallelization since the , enabling throughputs up to 100 times higher than single-channel systems. Other techniques include , where a feed solution or is atomized through nozzles (10-50 μm orifice size) into a hot gas stream, rapidly drying droplets into microparticles with yields of 70-90%. methods, such as antisolvent addition, involve rapid mixing of a solute solution with a non-solvent (e.g., at rates of 4 mL/min) under ultrasonication to induce and control size via concentration and flow dynamics. Mechanical grinding serves as a top-down approach for ceramics, using jet mills with high-velocity gas (300-500 m/s) to fracture bulk materials into micron-sized particles, with classifier speeds adjusting the size distribution. Across these methods, key parameters like encapsulation efficiency (20-90%) and (PSD) are optimized through variables such as flow rates in or precipitation and temperatures of 20-60°C in and steps, ensuring controlled production for targeted applications.

Materials and Composition

Microparticles are primarily composed of polymeric, , inorganic, or composite materials, selected based on their physical, chemical, and biological properties to suit specific fabrication and functional requirements. Polymeric materials dominate due to their versatility in encapsulation and release control. Biodegradable polymers like poly(lactic-co-glycolic acid) () are favored for their into non-toxic metabolites, such as lactic and glycolic acids, enabling safe degradation . variants typically feature lactic-to-glycolic acid ratios from 50:50 to 75:25 and molecular weights of 10,000–100,000 Da, influencing degradation rates—lower ratios accelerate while higher molecular weights prolong it. These properties offer advantages in and tunable erosion but can lead to burst release if not optimized, contrasting with non-degradable options like , which provide long-term stability without breakdown yet pose removal challenges post-use. Lipid-based compositions, particularly phospholipids forming liposomes, rely on amphiphilic structures for into bilayer vesicles. Common phospholipids exhibit temperatures of 40–50°C, ensuring fluidity at body temperature while maintaining integrity during fabrication. This allows high encapsulation efficiency for hydrophilic payloads but introduces sensitivity to environmental factors like and temperature, potentially limiting shelf-life compared to more rigid alternatives. Inorganic materials such as silica and impart mechanical strength and , with silica pores typically ranging from 2–50 nm to facilitate drug loading and release. , mimicking , offers bioactivity and rigidity for orthopedic applications, though its brittleness requires careful integration to avoid fragmentation. Composite materials combine these elements for enhanced functionality, such as polymer-coated cores (10–20 nm in size) that confer magnetic responsiveness for targeted delivery without compromising . The provides superparamagnetic behavior, while the shell (e.g., ) modulates and protects against aggregation. Material selection emphasizes , with receiving FDA approval for implants since the 1980s due to its inert degradation products. , quantified by logP values, guides incorporation of hydrophobic drugs (logP > 2 for optimal partitioning into matrices), and loading capacities reach up to 40% w/w for therapeutics, balancing payload efficiency with particle integrity.

Types

Microspheres and Microcapsules

Microspheres and microcapsules represent two primary structural subtypes of synthetic microparticles, distinguished by their internal and release profiles. Microspheres are matrix systems in which active agents are uniformly dispersed throughout a polymeric matrix, enabling controlled release primarily through or matrix erosion. In contrast, microcapsules feature a core-shell configuration, where the active is encapsulated within a distinct core protected by a surrounding shell, allowing for more targeted or triggered release mechanisms. Microspheres typically range from 1 to 1000 μm in and are fabricated using methods such as emulsification-solvent evaporation, where the and active are dissolved in an organic , emulsified in an aqueous phase, and the is evaporated to form solid particles. This technique, widely adopted since the , produces homogeneous structures suitable for sustained release over weeks to months, as the actives dissolve or gradually from the degrading matrix. A common characteristic is an initial burst release of 10-30% of the within the first day, attributed to surface-associated molecules, followed by prolonged or erosion-controlled delivery. Microcapsules, typically 1 to 1000 μm in size, employ core-shell designs with wall thicknesses typically ranging from 0.1 to 10 μm, providing a barrier that isolates the core material from the environment. Fabrication commonly involves coacervation, where induces deposition around the core, or interfacial , in which reactive monomers at the oil-water interface form a polymeric shell. These structures facilitate triggered release, such as in response to changes or enzymatic degradation, by exploiting shell permeability alterations. An key advantage of microcapsules is the protection of sensitive payloads, including proteins, from degradation during storage or transit, minimizing premature exposure.

Biological Microparticles

Biological microparticles, also known as cell-derived microparticles or microvesicles, are small membrane-bound vesicles released from various cell types, including platelets, endothelial cells, and leukocytes. They originate from the outward and vesiculation of the plasma membrane during cellular activation or early , processes often triggered by increased intracellular calcium levels that lead to cytoskeletal reorganization and membrane blebbing. Unlike synthetic microparticles designed for controlled , these natural entities form spontaneously as part of cellular stress responses or physiological signaling. Their typical size ranges from 100 to 1000 nm, which overlaps with certain synthetic classifications but distinguishes them by their biological derivation. In terms of composition, biological microparticles are enclosed by a phospholipid bilayer derived from the parent , incorporating lipids such as (), which becomes exposed on the outer leaflet to serve as a recognition signal for by immune cells like macrophages. They also contain bioactive cargos, including membrane proteins (e.g., and selectins), cytoplasmic proteins, enzymes, and nucleic acids such as mRNA and , enabling the transfer of functional molecules between cells. This heterogeneous makeup reflects the originating cell's identity, with surface markers like CD41 for platelet-derived microparticles or for endothelial-derived ones. Detection of biological microparticles relies on techniques that account for their small size and low . is widely used, employing (FSC) to estimate by measuring deflection proportional to , often calibrated with standardized beads to gate events between 100-1000 nm, combined with fluorescent labeling of surface markers for specificity. Electron microscopy provides high-resolution visualization of morphology and confirms vesicular structure through transmission or scanning modes. For isolation, differential ultracentrifugation is standard, involving initial low-speed spins to remove cells and debris, followed by high-speed centrifugation at approximately 100,000 g for 1 hour to pellet the microparticles. In , biological microparticles play a key role in intercellular communication by acting as vectors that deliver signaling molecules, , and genetic material to recipient cells, thereby modulating functions such as , , and vascular tone without requiring direct cell-cell contact. For instance, they can transfer functional proteins or to reprogram target cells, facilitating coordinated responses in tissues like the vasculature or . This contrasts with synthetic microparticles, which primarily serve structural or delivery purposes rather than endogenous signaling.

Applications

Biomedical and Pharmaceutical Uses

Microparticles have revolutionized in by enabling sustained release formulations that maintain therapeutic drug levels over extended periods, reducing dosing frequency and improving patient compliance. A seminal example is Lupron Depot, a poly(lactic-co-glycolic acid) () microsphere formulation encapsulating leuprolide acetate for treating hormone-dependent conditions such as and . Approved by the FDA in 1989, this system provides controlled release over 1 to 6 months depending on the formulation (e.g., 3.75 mg for 1 month or 45 mg for 6 months), achieved through and mechanisms that sustain plasma concentrations between 0.4 and 1.4 μg/L. Targeted therapies leverage surface-modified microparticles to enhance specificity and efficacy, particularly in , by directing payloads to tumor sites via ligand-receptor interactions. For instance, microspheres conjugated with antibodies such as enable tumor homing by binding to (EGFR)-overexpressing cancer cells, facilitating uptake through . This approach improves drug accumulation at the , minimizing off-target effects and enhancing therapeutic indices in preclinical models of colorectal and tumors. In and , microparticles serve as adjuvants and carriers to amplify immune responses and facilitate . Alum-based microparticles, such as aluminum formulations, adsorb to promote uptake by antigen-presenting cells, enhancing humoral and cellular immunity by up to 100-fold in titers compared to antigen alone, as demonstrated in studies with synthetic particles. For , cationic microparticles complexed with DNA enable efficient of mesenchymal stromal cells, supporting applications in and DNA vaccines by protecting payloads from degradation and promoting endosomal escape. Diagnostic imaging benefits from gas-filled microparticles, particularly microbubbles, which act as contrast agents to improve visualization of vascular structures and tissues. These perfluorocarbon or sulfur hexafluoride-filled shells exhibit high echogenicity through and nonlinear oscillation under ultrasound waves, enabling real-time detection of tumors and abnormalities with enhanced sensitivity over traditional methods. Clinical agents like SonoVue, introduced in the early 2000s, have established this for and imaging, providing safe, non-ionizing contrast without renal clearance issues.

Industrial and Environmental Applications

Microparticles serve as essential fillers in and paints, enhancing texture, opacity, and durability. In , silica microparticles, typically ranging from 5 to 50 μm in size, are incorporated to provide a matte finish and oil absorption, improving product spreadability and aesthetic appeal without compromising skin feel. These particles scatter light for a soft-focus effect, commonly used in and powders. In paints and coatings, silica and similar fillers, often under 5 μm, act as extenders to boost opacity and mechanical properties, such as and weather resistance, while reducing formulation costs and improving application smoothness. In environmental remediation, chitosan-based microparticles and beads are widely employed as adsorbents for heavy metal pollutants in wastewater. These materials, derived from natural polymers, exhibit high adsorption capacities of 120–420 mg/g for metals like lead (Pb²⁺) and cadmium (Cd²⁺), facilitated by chelation through amino and hydroxyl groups. Composites such as chitosan-Fe₃O₄ microparticles enable magnetic separation post-adsorption, achieving 80–95% removal efficiency in industrial effluents from mining and textiles, promoting sustainable water purification. Microparticles play a key role in food and agriculture through encapsulation for controlled release of active ingredients. In the , starch-based microparticles, such as those from (10–200 μm), encapsulate flavors via , protecting volatiles and enabling gradual release through or swelling, which enhances stability in products like beverages and baked goods. In , microparticles loaded with pesticides, like or isoproturon, provide sustained delivery over weeks, significantly reducing leaching—down to about 10% after multiple irrigations—while minimizing environmental contamination and application frequency. In additive manufacturing, microparticles function as sacrificial porogens to create hierarchical in 3D-printed scaffolds. Poly(ethylene glycol) (PEG) microparticles are blended into polymer filaments, such as , and extruded via ; subsequent leaching in solvents like removes the porogens, yielding micropores around 1 μm and overall up to 75%. This approach enhances structural permeability and mechanical integrity, supporting scalable production of porous components for industrial filters and lightweight composites.

Research Developments

Extracellular Vesicles

Extracellular vesicles (EVs) are small, membrane-bound particles released by cells into the extracellular space, serving as key mediators of intercellular communication. They encompass several subtypes based on biogenesis and size, including exosomes, which range from 30 to 150 nm in diameter and originate from the endosomal pathway through intraluminal vesicle formation in multivesicular endosomes, and microvesicles, which are larger at 100 to 1000 nm and form via direct budding from the plasma membrane. These structures were first identified in the 1980s during studies of maturation, where vesicles carrying receptors were observed as a mechanism for protein disposal.48095-7/fulltext) EVs transport a diverse cargo of bioactive molecules, including microRNAs (miRNAs), proteins, lipids, and nucleic acids, enabling them to modulate recipient cell functions through signaling pathways. In particular, EV-associated miRNAs and proteins facilitate intercellular signaling, such as in inflammatory responses, where EVs from immune cells can transfer anti- or pro-inflammatory mediators to alter production and immune activation. During states involving , EV concentrations can increase by 10- to 100-fold compared to baseline levels, amplifying these signaling effects and contributing to pathological progression. Isolation of EVs typically employs protocols, starting with low-speed spins (e.g., 300–2000 g) to remove cells and debris, followed by intermediate at 10,000–20,000 g to pellet microvesicles, and ultracentrifugation at 100,000–120,000 g for exosomes. Characterization often involves (NTA), which measures and concentration, revealing typical plasma levels of 10^8 to 10^10 particles per mL in healthy individuals. These methods ensure high purity and enable detailed analysis of EV heterogeneity. As biomarkers, EVs hold promise due to their stability in biofluids and ability to reflect disease-specific changes; for instance, elevated neuronal EV levels carrying proteins like matrix metalloproteinase-9 are observed in , correlating with neurodegeneration. This elevation underscores their potential for non-invasive diagnostics, though further validation is needed for clinical translation.

Cancer Research and Protocells

In , microparticles have emerged as promising drug carriers for targeted delivery, particularly to mitigate systemic toxicities associated with agents like . For instance, -based nanoparticles loaded with have demonstrated reduced in preclinical models through controlled release and localized tumor accumulation, as shown in studies post-2015. Tumor-derived microparticles further play a critical role in by facilitating signaling; these vesicles, shed from cancer cells, are internalized by macrophages in distant organs like the lungs, inducing metabolic reprogramming and pro-metastatic inflammation through pathways such as activation and release. Protocells, synthetic microparticles designed to mimic primitive cellular structures, consist of -based membranes typically ranging from 1 to 10 μm in size and exhibit under neutral to slightly alkaline conditions ( 7-9), facilitating the encapsulation and replication of genetic material like . Research on protocells since the early has focused on their relevance to the origins of life, where vesicles support non-enzymatic replication and division, providing a model for how prebiotic compartments could have sustained proto-metabolic cycles. Recent advancements from 2023 to 2025 have integrated extracellular vesicle (EV)-mimicking microparticles into , particularly for PD-L1 blockade, where engineered nanoparticles emulate natural EVs to enhance inhibition and tumor infiltration. For example, immunocyte-derived small EVs carrying PD-1 and have been shown to redistribute PD-L1 on tumor cells, boosting T-cell responses in preclinical models. Additionally, microfluidic platforms enable high-throughput evolution of arrays, allowing rapid screening of variants for improved functionality in applications. Despite these progresses, key challenges in translating microparticles and protocells to clinical use include of production and stability, where uncoated structures often exhibit times under 24 hours due to rapid clearance and degradation in physiological environments. Surface coatings, such as , have been explored to extend circulation, but achieving consistent long-term viability remains a barrier.

References

  1. https://www.sciencedirect.com/topics/pharmacology-toxicology-and-pharmaceutical-science/microparticle
  2. https://www.sigmaaldrich.com/US/en/applications/materials-science-and-engineering/nanoparticle-and-microparticle-synthesis
  3. https://pmc.ncbi.nlm.nih.gov/articles/PMC6224484/
  4. https://www.sciencedirect.com/topics/chemistry/microparticle
  5. https://www.mdpi.com/2218-0532/87/3/20
  6. https://pmc.ncbi.nlm.nih.gov/articles/PMC10049314/
  7. https://pmc.ncbi.nlm.nih.gov/articles/PMC4000927/
  8. https://pubs.acs.org/doi/10.1021/acsami.9b04769
  9. https://pmc.ncbi.nlm.nih.gov/articles/PMC1167690/
  10. https://www.nature.com/articles/263797a0
  11. https://pmc.ncbi.nlm.nih.gov/articles/PMC4386009/
  12. https://www.sigmaaldrich.com/US/en/product/aldrich/805114
  13. https://pmc.ncbi.nlm.nih.gov/articles/PMC3600995/
  14. https://www.sciencedirect.com/science/article/pii/S1742706114003511
  15. https://openresearch.newcastle.edu.au/articles/journal_contribution/Tailoring_elastic_properties_of_PLGA_TiO2_biomaterials/29004479/1/files/54391676.pdf
  16. https://pmc.ncbi.nlm.nih.gov/articles/PMC9230634/
  17. https://www.sciencedirect.com/science/article/abs/pii/S0168365998001916
  18. https://www.researchgate.net/publication/227834591_Factors_affecting_the_degradation_and_drug-release_mechanism_of_polylactic_acid_and_polylactic_acid-co-glycolic_acid
  19. https://www.nature.com/articles/s41586-022-04784-0
  20. https://www.researchgate.net/publication/368967195_Review_emulsion_techniques_for_producing_polymer_based_drug_delivery_systems
  21. https://pmc.ncbi.nlm.nih.gov/articles/PMC4106449/
  22. https://www.mdpi.com/2227-9717/13/5/1409
  23. https://pmc.ncbi.nlm.nih.gov/articles/PMC3744931/
  24. https://pubs.acs.org/doi/10.1021/la403220p
  25. https://pmc.ncbi.nlm.nih.gov/articles/PMC6189904/
  26. https://pmc.ncbi.nlm.nih.gov/articles/PMC2292490/
  27. https://www.researchgate.net/publication/355063964_Preparation_of_Daidzein_Microparticles_through_Liquid_Antisolvent_Precipitation_Under_Ultrasonication
  28. https://www.onlinepharmacytech.info/docs/vol3issue8/JPST11-03-08-02.pdf
  29. https://pmc.ncbi.nlm.nih.gov/articles/PMC4140625/
  30. https://pmc.ncbi.nlm.nih.gov/articles/PMC3347861/
  31. https://pmc.ncbi.nlm.nih.gov/articles/PMC7718366/
  32. https://www.sciencedirect.com/science/article/abs/pii/S0168365903000300
  33. https://www.sciencedirect.com/science/article/pii/S240584402200682X
  34. https://pmc.ncbi.nlm.nih.gov/articles/PMC6321143/
  35. https://www.sciencedirect.com/science/article/abs/pii/S0272884216304394
  36. https://pubs.acs.org/doi/abs/10.1021/cm020126q
  37. https://pmc.ncbi.nlm.nih.gov/articles/PMC7374157/
  38. https://pmc.ncbi.nlm.nih.gov/articles/PMC3093624/
  39. https://pubmed.ncbi.nlm.nih.gov/10837563/
  40. https://www.nature.com/articles/s41467-022-28787-7
  41. https://patents.google.com/patent/US11071878B2/en
  42. https://www.microcapsules-technologies.com/en/our-technologies/microencapsulation-par-polymerisation-interfaciale/
  43. https://www.ahajournals.org/doi/10.1161/circresaha.110.226456
  44. https://pmc.ncbi.nlm.nih.gov/articles/PMC3757826/
  45. https://journals.physiology.org/doi/10.1152/ajplung.00058.2017
  46. https://www.ahajournals.org/doi/10.1161/atvbaha.111.244616
  47. https://pmc.ncbi.nlm.nih.gov/articles/PMC3004516/
  48. https://www.accessdata.fda.gov/drugsatfda_docs/nda/pre96/019943_LupronTOC.cfm
  49. https://pubmed.ncbi.nlm.nih.gov/12083977/
  50. https://pmc.ncbi.nlm.nih.gov/articles/PMC4261190/
  51. https://pmc.ncbi.nlm.nih.gov/articles/PMC9848416/
  52. https://pmc.ncbi.nlm.nih.gov/articles/PMC3263514/
  53. https://pmc.ncbi.nlm.nih.gov/articles/PMC10397127/
  54. https://pmc.ncbi.nlm.nih.gov/articles/PMC2963573/
  55. https://www.nature.com/articles/s41598-020-71129-0
  56. https://www.pnas.org/doi/10.1073/pnas.97.2.811
  57. https://pmc.ncbi.nlm.nih.gov/articles/PMC6319889/
  58. https://pmc.ncbi.nlm.nih.gov/articles/PMC2720159/
  59. https://pmc.ncbi.nlm.nih.gov/articles/PMC4584939/
  60. https://www.agcchem.com/blog/skin-care-additives-top-6-benefits-of-using-silica-microspheres-in-personal-care-products/
  61. https://www.sciencedirect.com/science/article/pii/S2590123025016135
  62. https://www.sciencedirect.com/science/article/pii/S2666523925001126
  63. https://ifst.onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2621.2005.00980.x
  64. https://www.sciencedirect.com/science/article/pii/S0014305723008480
  65. https://pubs.acs.org/doi/10.1021/acsomega.3c09035
  66. https://pmc.ncbi.nlm.nih.gov/articles/PMC6678302/
  67. https://www.nature.com/articles/s41392-024-01735-1
  68. https://pmc.ncbi.nlm.nih.gov/articles/PMC9235439/
  69. https://pmc.ncbi.nlm.nih.gov/articles/PMC5486107/
  70. https://www.tandfonline.com/doi/full/10.1080/20013078.2018.1535750
  71. https://www.nature.com/articles/s41598-020-78422-y
  72. https://www.nature.com/articles/s44400-024-00002-y
  73. https://pubs.rsc.org/en/content/articlehtml/2024/nr/d3nr06269d
  74. https://pubmed.ncbi.nlm.nih.gov/37261951/
  75. https://aacrjournals.org/cancerimmunolres/article/6/9/1046/469475/Circulating-Tumor-Microparticles-Promote-Lung
  76. https://pmc.ncbi.nlm.nih.gov/articles/PMC2890201/
  77. https://pmc.ncbi.nlm.nih.gov/articles/PMC6120706/
  78. https://pubs.acs.org/doi/10.1021/ja900919c
  79. https://jeccr.biomedcentral.com/articles/10.1186/s13046-025-03403-w
  80. https://www.nature.com/articles/s41467-024-48200-9
  81. https://pmc.ncbi.nlm.nih.gov/articles/PMC6899980/
  82. https://www.sciencedirect.com/science/article/pii/S2590006425002820
  83. https://www.nature.com/articles/s41467-024-46732-8
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