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Self-Aggregation of Sodium Ibuprofenate in Water. II. Equilibrium Modeling and Structural Characterization from
Paula Y Steinberg1,2, Javier M Abbas1, Patricia C Rivas-Rojas3
1Gerencia Química, Centro Atómico Constituyentes, Comisión Nacional de Energía Atómica and CONICET, Av. General Paz 1499, San Martín, Buenos Aires 1650, Argentina.
Langmuir : the ACS Journal of Surfaces and Colloids
|October 2, 2025
Summary
Sodium ibuprofenate (NaIbu) self-aggregation in water forms stable micelles. Molecular dynamics and scattering experiments determined micelle size, aggregation number, and ionization degree, providing insights into drug behavior in solution.
Area of Science:
- Physical Chemistry
- Materials Science
- Biophysics
Background:
- Understanding the self-aggregation of pharmaceutical compounds like sodium ibuprofenate (NaIbu) in aqueous solutions is crucial for drug formulation and delivery.
- Micellization influences drug solubility, stability, and bioavailability.
Purpose of the Study:
- To comprehensively characterize the self-aggregation process of NaIbu in water.
- To determine microscopic details of micelle formation, including aggregation number and degree of ionization.
- To correlate micellar properties with the behavior of ibuprofenate within the micellar environment.
Main Methods:
- Molecular dynamics (MD) simulations to probe micelle structure and dynamics.
- Small-angle X-ray scattering (SAXS) experiments to analyze aggregate characteristics.
- Integration of simulation and experimental data within the Burchfield and Woolley model.
Main Results:
- MD simulations revealed stable, ellipsoidal micelles with lengths ~20 Å, an average aggregation number of 45 ibuprofenate molecules, and ionization degree α = 0.63.
- SAXS experiments confirmed similar structural characteristics and low polydispersity across various NaIbu concentrations.
- The equilibrium aggregation model yielded In(K_Agg) = 41, n = 45, α = 0.64, and a critical micellar concentration of 0.185 m.
Conclusions:
- Combined MD simulations and SAXS experiments provide a robust characterization of NaIbu micellization.
- The determined parameters (aggregation number, ionization, CMC) are essential for understanding NaIbu behavior in solution.
- The micellar environment modulates ibuprofenate's dynamical modes, potentially affecting its photochemical response.
