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Updated: Sep 29, 2026
Study of Phagolysosome Biogenesis in Live Macrophages
Published on: March 11, 2014
Synthesis and application of submicrometer fluorescence sensing particles for lysosomal pH measurements in murine
J Ji1, N Rosenzweig, C Griffin
1University of New Orleans, Department of Chemistry, Louisiana 70148, USA.
Abstract:
Phagocytosis of bioparticles such as bacteria and viruses by macrophages is a critical component of the immune response against infections. In this paper we describe the synthesis of submicrometer fluorescent particles with pH sensing capability. The particles are used to measure the pH and to monitor the effect of chloroquine, an antimalarial drug, on the pH in the lysosome, the cellular organelle involved in the phagocytosis process. The synthesis of the pH sensing particles is realized by the covalent attachment of amine reactive forms of Oregon Green (pH sensitive dye) and Texas Red (pH insensitive dye) to the surface of amino-modified submicrometer polystyrene particles. The particles are absorbed by J774 Murine Macrophages through phagocytosis and directed to lysosomes. Despite the high lysosomal levels of digestive enzymes and acidity, the absorbed particles remain stable for 12 h in the cells when they are stored in a PBS buffer solution at pH 7.4. The pH dynamic range of the sensing particles is between pH 4.5 and 7 with a sensitivity of 0.1 pH units. Exposure of the cells to chloroquine increases the lysosomal pH from 4.8 to 6.5. The effect is concentration-dependent.
Insights
Researchers developed pH-sensing fluorescent particles to monitor macrophage lysosomes. These particles revealed chloroquine, an antimalarial drug, increases lysosomal pH in a concentration-dependent manner.
Area of Science:
- Immunology
- Cell Biology
- Biomedical Engineering
Background:
- Phagocytosis by macrophages is crucial for immune response against pathogens.
- Lysosomes are key organelles in phagocytosis, characterized by acidic environments.
- Monitoring lysosomal pH is vital for understanding cellular processes and drug effects.
Purpose of the Study:
- To synthesize novel submicrometer fluorescent particles capable of sensing pH.
- To utilize these particles to measure lysosomal pH dynamics.
- To investigate the impact of chloroquine on lysosomal pH within macrophages.
Main Methods:
- Covalent attachment of pH-sensitive (Oregon Green) and pH-insensitive (Texas Red) dyes to amino-modified polystyrene particles.
- Phagocytosis of synthesized particles by J774 Murine Macrophages, with subsequent lysosomal localization.
- Measurement of lysosomal pH using fluorescence properties of the particles and assessing stability in cellular environments.
- Evaluating the effect of varying chloroquine concentrations on lysosomal pH.
Main Results:
- Stable fluorescent pH-sensing particles were successfully synthesized and remained intact in lysosomes for 12 hours.
- The particles demonstrated a pH dynamic range of 4.5-7 with 0.1 pH unit sensitivity.
- Chloroquine treatment led to a concentration-dependent increase in lysosomal pH, from 4.8 to 6.5.
Conclusions:
- Synthesized fluorescent particles are effective tools for monitoring lysosomal pH in live cells.
- Chloroquine significantly alters lysosomal pH, providing insights into its mechanism of action.
- This methodology offers a valuable approach for studying drug effects on cellular organelle function.
