Unexpected and Successful “One-Step” Formation of Porous Polymeric Particles Only by Mixing Organic Solvent and Water under “Low-Energy-Input” Conditions

Abstract

We found that porous particles were unexpectedly obtained in a "one-step" manner only by mixing an organic solvent and water under "low-energy-input" (i.e., low-homogenization-rate) conditions. This phenomenon was attributable to the unexpected formation of the spontaneously formed water-in-oil (w/o) emulsions in the droplets of o/w emulsions. The unexpected formation resulted in the successful formation of water-in-oil-in-water (w/o/w) emulsions instead of o/w emulsions, although the mixed solution containing both an organic solvent and water were simply emulsified in the presence of block copolymers. The present study clarifies the effects of the various preparation conditions on the morphology of unexpected w/o/w emulsions and resulting particles. The porous particles are expected to be suitable drug carriers for pulmonary delivery. The results obtained in the present study show that a newly developed one-step emulsification can be a powerful and facile technique for preparing porous polymeric particles.

Electrospray loading and release of hydrophobic gramicidin in polyester microparticles

“…This distribution pattern is closely related to the structure and stability of water-in-oil emulsions. 35,36 The polar phase composed of GA dissolved in ethanol was dispersed into the organic phase, composed of PE44 dissolved in chloroform during the own electrospraying process. As a consequence, the drug was close to the surface the microparticles.…”

The Horizon of the Emulsion Particulate Strategy: Engineering Hollow Particles for Biomedical Applications

“…[24] In this work, the hydrophilicity and hydrophobicity of the stabilizers were balanced by the asymmetric ratio (the fraction of block length between PS and PEG). [26] For amphiphilic block copolymers, poly(ethylene glycol)-b-polylactide (PEG-b-PLA), stable W/O/W emulsion were formed under "low-energy-input." At higher toluene ratio (80%), a typical catastrophic phase inversion occurred, which left the toluene in the continuous phase to form stable W/O emulsion ( Figure 3e).…”

“…To illustrate this, Takami and co-workers reported "one-step" procedure to trigger the phase inversion via changing the homogenization rates. [26] For amphiphilic block copolymers, poly(ethylene glycol)-b-polylactide (PEG-b-PLA), stable W/O/W emulsion were formed under "low-energy-input." But, under "high-energyinput" (i.e., high-homogenization-rate) conditions, W/O/W emulsions were converted to O/W emulsions.…”

“…And, this phenomenon was intensified by the electrostatic attractions between stabilizers and the polymers, such as cetyltrimethyl ammonium bromide and PLA. [26] Collectively, by controlling the phase inversion, multiple emulsions can be prepared by single step. Nonetheless, phase inversion was typically the intermediate state in emulsion evolution.…”

Chitosan Gel Sheet Containing Polymeric Micelles: Synthesis and Gelation Properties of PEG-Grafted Chitosan

“…The controlled sustained release of compounds from hydrogels is difficult because the release mechanism depends mainly on two phenomena: the degradation of polymeric networks and the diffusion of compounds through the hydrogel medium. In these regards, we have developed a novel ‘hybrid’ approach: the incorporation of functional block copolymers and/or their self-assembly (polymeric micelles) into base materials (such as gel [ 3 , 4 , 5 , 6 , 7 ], sheets [ 8 , 9 , 10 ], and particles [ 11 , 12 , 13 , 14 , 15 ]) for the construction of biomaterials for drug delivery systems. Polymeric micelles have a core that can incorporate either hydrophobic [ 16 , 17 , 18 , 19 , 20 , 21 ] or hydrophilic [ 22 , 23 ] compounds and release drugs by means of either the dilution-induced collapse or the degradation of micelle-forming polymers.…”