Effect of chain lengths of PEO–PPO–PEO on small unilamellar liposome morphology and stability: an AFM investigation

Liang, Xuemei; Mao, Guangzhao; Ng, Koon‐Kwan

doi:10.1016/j.jcis.2004.11.042

Cited by 70 publications

(53 citation statements)

References 35 publications

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“…The PEO-PPO-PEO chain can be modified by varying the length of each block so that the final chain exhibits the desired thermoresponsive gelation properties at physiological conditions for injectable delivery. 17,22 These gels can then dissolve slowly to release polymer micelles loaded with drugs. This base system can then be used as the central building block for further modification by adding various functional groups to both ends of the chain.…”

Section: Introductionmentioning

confidence: 99%

Thermoresponsive Reversible Behavior of Multistimuli Pluronic-Based Pentablock Copolymer at the Air−Water Interface

et al. 2006

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Surface behavior of the pH-and thermoresponsive amphiphilic ABCBA pentablock copolymer has been studied with respect to the environmental conditions. We demonstrate that the pentablock copolymer poly((diethylaminoethyl methacrylate)-b-(ethylene oxide)-b-(propylene oxide)-b-(ethylene oxide)-b-(diethylaminoethyl methacrylate)) possesses reversible temperature changes at the air-water interface in a narrow pH range of the water subphase. Significant diversity in the surface morphology of pentablock copolymer monolayers at different pH and temperatures observed were related to the corresponding reorganization of central and terminal blocks. Remarkable reversible variations of the surface pressure observed for the Langmuir monolayers at pH 7.4 in the course of heating and cooling between 27 and 50Â°C is associated with conformational transformations of terminal blocks crossing the phase line in the vicinity of the lower critical solution temperature point. The observed thermoresponsive surface behavior can be exploited for modeling of the corresponding behavior of pentablock copolymers adsorbed onto various biointerfaces for intracellular delivery for deeper understanding of stimuli-responsive transformations relevant to controlled drug and biomolecules release and retention. Surface behavior of the pH-and thermoresponsive amphiphilic ABCBA pentablock copolymer has been studied with respect to the environmental conditions. We demonstrate that the pentablock copolymer poly((diethylaminoethyl methacrylate)-b-(ethylene oxide)-b-(propylene oxide)-b-(ethylene oxide)-b-(diethylaminoethyl methacrylate)) possesses reversible temperature changes at the air-water interface in a narrow pH range of the water subphase. Significant diversity in the surface morphology of pentablock copolymer monolayers at different pH and temperatures observed were related to the corresponding reorganization of central and terminal blocks. Remarkable reversible variations of the surface pressure observed for the Langmuir monolayers at pH 7.4 in the course of heating and cooling between 27 and 50°C is associated with conformational transformations of terminal blocks crossing the phase line in the vicinity of the lower critical solution temperature point. The observed thermoresponsive surface behavior can be exploited for modeling of the corresponding behavior of pentablock copolymers adsorbed onto various biointerfaces for intracellular delivery for deeper understanding of stimuli-responsive transformations relevant to controlled drug and biomolecules release and retention.

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Section: Introductionmentioning

confidence: 99%

Thermoresponsive Reversible Behavior of Multistimuli Pluronic-Based Pentablock Copolymer at the Air−Water Interface

et al. 2006

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“…This formulation still exhibited increased aggregation as compared to singledrug loaded liposomes. The reduction in drug concentration did not improve liposome stability, and since a goal of the project was to make stabilized nanoliposomes, PLs were added to the bilayers in order to enhance vesicular stability (14). Pluronics® F-127 and F-108 have been shown to increase the mechanical stability of lipid-based vesicular systems, such as dioleoylphosphatidylethanolamine liposomes (23).…”

Section: Discussionmentioning

confidence: 99%

“…The stability of liposomes may be enhanced by steric hindrance of aggregation with the aid of poloxamer block copolymers (Pluronics® (PL)). As integral parts of liposomal membranes, PLs may enhance liposomal stability for an extended period of time (14,15).…”

Section: Introductionmentioning

confidence: 99%

Radio Frequency-Activated Nanoliposomes for Controlled Combination Drug Delivery

et al. 2015

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Abstract. This work was conducted in order to design, characterize, and evaluate stable liposomes containing the hydrophobic drug raloxifene HCl (RAL) and hydrophilic doxycycline HCl (DOX), two potentially synergistic agents for treating osteoporosis and other bone lesions, in conjunction with a radio frequency-induced, hydrophobic magnetic nanoparticle-dependent triggering mechanism for drug release. Both drugs were successfully incorporated into liposomes by lipid film hydration, although combination drug loading compromised liposome stability. Liposome stability was improved by reducing the drug load and by including Pluronics® (PL) in the formulations. DOX did not appear to interact with the phospholipid membranes comprising the liposomes, and its release was maximized in the presence of radio frequency (RF) heating. In contrast, differential scanning calorimetry (DSC) and phosphorus-31 nuclear magnetic resonance ( 31 P-NMR) analysis revealed that RAL developed strong interactions with the phospholipid membranes, most notably with lipid phosphate head groups, resulting in significant changes in membrane thermodynamics. Likewise, RAL release from liposomes was minimal, even in the presence of RF heating. These studies may offer useful insights into the design and optimization of multidrug containing liposomes. The effects of RAL on liposome characteristics and drug release performance underscore the importance of appropriate physical-chemical analysis in order to identify and characterize drug-lipid interactions that may profoundly affect liposome properties and performance early in the formulation development process.

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“…Micelle formation and interfacial properties of this surfactant type have been investigated elsewhere. [22,23] In all of the experiments, at the first step, the epoxy resin and the surfactant were mixed together at a constant emulsifier concentration of 5% (of the epoxy resin), above their melting temperature (75 8C), and then the phase inversion was brought about by the addition of deionized water to the system (increasing f W ) in a drop wise manner at a fixed rate of 80 drops/min (roughly equal to 3 mL/min) at the reaction temperature using a thermostatic pump. The phase inversions were indicated by measuring changes in the stirring speed of the stirrer from its initial value since as discussed in more detail in the results and discussion section, the inversion point is usually associated with a minimum in the viscosity of the emulsifying system.…”

Section: Experimental Partmentioning

confidence: 99%

Particle Formation by Emulsion Inversion Method: Effect of the Stirring Speed on Inversion and Formation of Spherical Particles

Aravand

Semsarzadeh

2008

Macromolecular Symposia

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Summery: Phase inversion emulsification technique was employed in this work as a practical method to form epoxy particles. The effect of stirring speed on the inversion behaviour and the morphological aspects of the resulting solid epoxy particles are investigated. Emulsion inversion was induced by increasing the amount of initially dispersed deionized water in the presence of a non-ionic block copolymer surfactant at a fixed concentration. The process of inversion was followed by monitoring the variations in the rotational speed of the stirrer caused by the viscosity variations of the emulsifying system throughout the process. It was shown that the mixing speed plays an important role in controlling the size and size distribution of the resulting emulsion particles. Below a critical stirring speed, spherical particles could not be formed and the inversion process resulted in macroscopically non-homogeneous multi shape structures. Fully spherical particles were formed above this critical speed. Further increase in the rotational speed of the mixer, significantly reduced the size of these spherical particles with a wide and random size distributions controlled and considerably narrowed by the stirring speed. Dynamic light scattering analysis and scanning electron microscopy were used to study the particle size and size distributions. In addition, study of the rotational speed variations of the stirrer, which is directly related to the viscosity changes of the emulsifying system, revealed that a correlation between the physical aspects of the inversion behaviour and the viscosity changes during the emulsion inversion process could be established.

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Effect of chain lengths of PEO–PPO–PEO on small unilamellar liposome morphology and stability: an AFM investigation

Cited by 70 publications

References 35 publications

Thermoresponsive Reversible Behavior of Multistimuli Pluronic-Based Pentablock Copolymer at the Air−Water Interface

Thermoresponsive Reversible Behavior of Multistimuli Pluronic-Based Pentablock Copolymer at the Air−Water Interface

Radio Frequency-Activated Nanoliposomes for Controlled Combination Drug Delivery

Particle Formation by Emulsion Inversion Method: Effect of the Stirring Speed on Inversion and Formation of Spherical Particles

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