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Effect of size, concentration, surface area, and volume of polymethylmethacrylate particles on human macrophages in
O González1, R L Smith, S B Goodman
1Orthopaedic Research Laboratory, Stanford University School of Medicine, CA 94305, USA.
Abstract:
This study investigated effects of different sizes, concentrations, volumes, and surface areas of polymethylmethacrylate (PMMA) particles on human macrophages. Adherent peripheral blood monocytes isolated from five healthy individuals were exposed for 48 h to phagocytosable (0.325 micron and 5.5 microns) and nonphagocytosable (200 microns) spherical particles. Each particle size was tested over a range of concentrations (10(4)-10(11) particles per milliliter [0.325 micron], 10(2)-10(7) particles per milliliter [5.5 microns], 10(1)-10(4) particles per milliliter [200 microns]) to provide overlap in number, volume, and surface area. Primary human monocyte/macrophages were cultured in macrophage serum-free medium and 5% fetal calf serum. Macrophage viability was assessed by 3H-thymidine uptake and activation was quantified by release of interleukin-1 beta, interleukin-6, tumor necrosis factor-alpha, prostaglandin E2 (PGE2), and the lysosomal enzyme hexosaminidase. Medium alone served as a negative control; lipopolysaccharide (10 micrograms/mL) was also tested. PMMA particles were not toxic to human macrophages at any concentration tested. The smallest phagocytosable particles (0.325 micron) stimulated the release of interleukin-1 beta, interleukin-6, prostaglandin E2, and hexosaminidase at concentrations of 10(10)-10(11) particles/mL. The release of cytokines, PGE2, and hexosaminidase depended on the size, concentration, surface area, and volume of the phagocytosable particles. This study demonstrates that PMMA particle load Mi.e., the concentration of phagocytosable particles per tissue volume, characterized by size, surface area, and volume, rather than simply particle number-determines the degree of macrophage activation.
Insights
Polymethylmethacrylate (PMMA) particle size, surface area, and volume, not just number, dictate human macrophage activation. Smaller, phagocytosable PMMA particles stimulate cytokine and enzyme release without toxicity.
Area of Science:
- Biomaterials Science
- Immunotoxicology
- Cellular Biology
Background:
- Polymethylmethacrylate (PMMA) is widely used, necessitating understanding its biological interactions.
- Human macrophages are key immune cells involved in foreign particle response.
- Previous studies lack comprehensive analysis of PMMA particle characteristics on macrophage activation.
Purpose of the Study:
- To investigate the impact of varying PMMA particle sizes, concentrations, volumes, and surface areas on human macrophages.
- To determine if PMMA particles induce toxicity or modulate macrophage activation markers.
- To elucidate the relationship between PMMA particle load and macrophage response.
Main Methods:
- Isolation and culture of primary human monocytes/macrophages.
- Exposure to different sizes (0.325, 5.5, 200 microns) of spherical PMMA particles at various concentrations.
- Assessment of macrophage viability (3H-thymidine uptake) and activation (cytokine, PGE2, hexosaminidase release).
Main Results:
- PMMA particles demonstrated no toxicity to human macrophages across all tested concentrations.
- Phagocytosable PMMA particles (0.325 and 5.5 microns) stimulated release of IL-1β, IL-6, PGE2, and hexosaminidase.
- Macrophage activation was dependent on particle size, concentration, surface area, and volume, not solely particle number.
Conclusions:
- PMMA particle load, defined by size, surface area, and volume, is the critical determinant of macrophage activation.
- The findings highlight the importance of considering multiple particle characteristics in biomaterial safety assessments.
- This study provides crucial insights into the immunomodulatory potential of PMMA particles in a human macrophage model.