Paper Number
PO42 

Session
Poster Session

Title
Controlling the temperature-dependent gelation of injectable poloxamer hydrogels via reverse poloxamer addition

Presentation Date and Time
October 12, 2022 (Wednesday) 6:30

Track / Room
Poster Session / Riverwalk A

Authors (Click on name to view author profile)

  1. White, Joanna M. (University of Minnesota, Chemical Engineering and Materials Science)
  2. Bates, Frank S. (University of Minnesota, Chemical Engineering and Materials Science)
  3. Calabrese, Michelle A. (University of Minnesota, Chemical Engineering and Materials Science)

Author and Affiliation Lines (in printed abstract book)
Joanna M. White, Frank S. Bates and Michelle A. Calabrese
Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455

Speaker / Presenter 
White, Joanna M.

Keywords
biomaterials; gels; polymer blends; polymer solutions

Text of Abstract
Poloxamer 407 (P407) is a commercially available ABA triblock polymer that is widely utilized for its thermoresponsive behavior in aqueous solutions. Room temperature solutions behave as liquids composed of disordered spherical micelles with a poly(propylene oxide) (PPO) core. With increasing temperature, the volume fraction of micelles increases, reaching a critical fraction that results in ordering with face-centered cubic packing. Ordering is accompanied by an increase in the dynamic moduli by many orders of magnitude due to gelation. While such a transition is promising for injectable therapeutics, the tunability of this transition in neat P407 solutions is limited. For example, increasing P407 concentration increases the dynamic moduli, but also significantly decreases the gelation temperature. In this work, we show that BAB reverse poloxamers (RPs) can be used as an additive to change the polymer assembly and thus individually tune gelation properties. Addition of low-molecular weight (< 3.2 kDa) RPs with a high PPO fraction (xPPO > 0.8) leads to formation of mixed micelles with P407, associating near the core and affecting micelle packing and gel structure, often with limited impact on the gelation temperature. In contrast, similar molecular weight RPs with lower PPO fractions (xPPO = 0.6) can form multi-chain bridges across P407 micelles, affecting both gelation temperature and gel moduli. The fundamental understanding of these micellization mechanisms provides general design guidelines for formulating poloxamer solutions with ideal properties for targeted delivery.