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Controlling Self-Assembly, Ordering, and Stability in Poloxamer/Oil Formulations Using Reverse Poloxamers
Charles T Knisely1, Grace M Heinecke1, Michael F Coleman1
1Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave SE, Minneapolis, Minnesota 55455, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|March 3, 2026
Summary
Reverse poloxamers (RPs) improve the stability of Poloxamer 407 (P407) and methyl laurate (ML) formulations for drug delivery. The hydrophilic 17R4 RP effectively controls P407 self-assembly and rheology, enhancing formulation properties.
Area of Science:
- Materials Science
- Polymer Chemistry
- Biomedical Engineering
Background:
- Poloxamer 407 (P407) is a versatile ABA triblock polymer used in drug delivery, known for temperature-dependent self-assembly.
- Incorporating additives like methyl laurate (ML) can enhance drug permeation but often compromises formulation stability and mechanical integrity.
- P407/ML formulations exhibit poor emulsion stability, leading to phase separation, limiting their therapeutic potential.
Purpose of the Study:
- To investigate the use of reverse poloxamers (RPs), specifically BAB triblock polymers, as additives to stabilize P407/ML formulations.
- To understand how RPs influence the self-assembly, ordering behavior, and rheological properties of P407/ML systems.
- To establish a framework for selecting optimal RPs for developing P407-based drug delivery vehicles with tailored properties.
Main Methods:
- Differential scanning calorimetry (DSC) was employed to analyze thermal transitions.
- Rheology measurements were used to assess mechanical properties and viscoelastic behavior.
- Small-angle X-ray scattering (SAXS) was utilized to probe self-assembly structures and ordering.
Main Results:
- Methyl laurate (ML) induces ordering in P407 at low concentrations by encapsulation within micelles.
- Addition of RPs (17R2 and 17R4) enhances emulsion stability and increases the maximum modulus of P407/ML formulations.
- The hydrophilic 17R4 RP significantly alters P407 self-assembly and rheological transitions by delaying ordering through micelle corona interactions.
Conclusions:
- Reverse poloxamers effectively stabilize P407/ML formulations, improving emulsion stability and mechanical properties.
- The solubility and incorporation mechanism of RPs dictate their impact on P407 self-assembly and rheology.
- RPs offer a tunable strategy for controlling the properties of P407 drug delivery systems for specific applications.
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