Dynamic Behavior of the Structural Phase Transition of Hydrogel Formation Induced by Temperature Ramp and Addition of Ibuprofen

Abstract

Understanding the dynamic behavior of hydrogel formation induced by a temperature ramp is essential for the design of gel-based injectable formulation as drugdelivery vehicles. In this study, the dynamic behavior of the hydrogel formation of Pluronic F108 aqueous solutions within different heating rates was explored in both macroscopic and microscopic views. It was discovered that when the heating rate is increased, the gelation temperature window (hard gel region) shrinks and the mechanical strength of the hydrogel decreases. A given system at different heating rates would lead to different crystalline structural evolutions. The time-resolved small-angle X-ray scattering (SAXS) experiments at a heating rate of 10 °C/min disclose that the crystalline structure of micelle packing in the hydrogel exhibits a series of transitions: hexagonal close-packed (HCP) to face-centered cubic (FCC) and body-centered cubic (BCC) structures coexisting and then to the BCC structure along with the increasing temperature. For the system at equilibrium, the BCC structure exclusively dominates the system. Furthermore, the addition of a hydrophobic model drug (ibuprofen) to the F108 aqueous solution promotes hard gel formation at even lower temperatures and concentrations of F108. The SAXS results for the system with ibuprofen at a heating rate of 10 °C/min demonstrate a mixture of FCC and BCC structures coexisting over the whole gelation window compared to the BCC structure that exclusively dominates the system at equilibrium. The addition of ibuprofen would alter the structural evolution to change the delivery path of the encapsulated drug, which is significantly related to the performance of drug release.

Wood-based electrolyte with reversible phase transition for smart thermal-shutdown self-protection

“…4i). 39 When the temperature increased to the phase transition point (∼60 °C), the circular arc became higher and the aspect ratio decreased to 1.24 in 2D SAXS patterns, thereby exhibiting less anisotropy. Also, the signal at 0.9 nm −1 became smaller while a new signal appeared at ∼0.4 nm −1 , indicating that FCC and body-centered cubic (BCC) structures were present.…”

Fate of Photoinduced Electron Transfer Reactions with Temperature- and pH-Induced Assembly/Disassembly of Star Block Copolymer Micelles

“…The self-assembly and structural versatility of amphiphilic block copolymers are active areas of research with extensive technological applications. − Micelles formed with block copolymers have several advantages over those formed with conventional low-molecular weight surfactants. Some of the favorable attributes of polymeric micelles include lower critical micelle concentration (CMC), greater stability, core–shell structures with enhanced drug loading capacity, and better therapeutic potential and stimulus response. − The poloxamine copolymers (Tetronics) consisting of an ethylene diamine group linked to four arms of repeating ethylene oxide (EO) and propylene oxide (PO) units are especially an interesting class of amphiphiles. − Micelles formed with these star-shaped block copolymers are not only susceptible to temperature changes but also sensitive to pH of the medium. − The central diamine group in Tetronic copolymers allows introduction of positive charges in these nonionic surfactants by protonation.…”