Responsive polymer materials can adapt to surrounding environments, regulate transport of ions and molecules, change wettability and adhesion of different species on external stimuli, or convert chemical and biochemical signals into optical, electrical, thermal and mechanical signals, and vice versa. These materials are playing an increasingly important part in a diverse range of applications, such as drug delivery, diagnostics, tissue engineering and 'smart' optical systems, as well as biosensors, microelectromechanical systems, coatings and textiles. We review recent advances and challenges in the developments towards applications of stimuli-responsive polymeric materials that are self-assembled from nanostructured building blocks. We also provide a critical outline of emerging developments.

Emerging applications of stimuli-responsive polymer materials

Block copolymer (BCP) self-assembly has attracted considerable attention for many decades because it can yield ordered structures in a wide range of morphologies, including spheres, cylinders, bicontinuous structures, lamellae, vesicles, and many other complex or hierarchical assemblies. These aggregates provide potential or practical applications in many fields. The present tutorial review introduces the primary principles of BCP self-assembly in bulk and in solution, by describing experiments, theories, accessible morphologies and morphological transitions, factors affecting the morphology, thermodynamics and kinetics, among others. As one specific example at a more advanced level, BCP vesicles (polymersomes) and their potential applications are discussed in some detail.

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Self-assembly of block copolymers

Interaction of spherical particles with cells and within animals has been studied extensively, but the effects of shape have received little attention. Here we use highly stable, polymer micelle assemblies known as filomicelles to compare the transport and trafficking of flexible filaments with spheres of similar chemistry. In rodents, filomicelles persisted in the circulation up to one week after intravenous injection. This is about ten times longer than their spherical counterparts and is more persistent than any known synthetic nanoparticle. Under fluid flow conditions, spheres and short filomicelles are taken up by cells more readily than longer filaments because the latter are extended by the flow. Preliminary results further demonstrate that filomicelles can effectively deliver the anticancer drug paclitaxel and shrink human-derived tumours in mice. Although these findings show that long-circulating vehicles need not be nanospheres, they also lend insight into possible shape effects of natural filamentous viruses.

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Shape effects of filaments versus spherical particles in flow and drug delivery.

Since their discovery in the 1960s, liposomes have been studied in depth, and they continue to constitute a field of intense research. Liposomes are valued for their biological and technological advantages, and are considered to be the most successful drug-carrier system known to date. Notable progress has been made, and several biomedical applications of liposomes are either in clinical trials, are about to be put on the market, or have already been approved for public use. In this review, we briefly analyze how the efficacy of liposomes depends on the nature of their components and their size, surface charge, and lipidic organization. Moreover, we discuss the influence of the physicochemical properties of liposomes on their interaction with cells, half-life, ability to enter tissues, and final fate in vivo. Finally, we describe some strategies developed to overcome limitations of the "first-generation" liposomes, and liposome-based drugs on the market and in clinical trials.

https://www.dovepress.com/getfile.php?fileID=23533

Liposomes as nanomedical devices

Polymer-based nanocapsules for drug delivery

Polymer vesicles in vivo: correlations with PEG molecular weight.

Emerging Applications of Polymersomes in Delivery: from Molecular Dynamics to Shrinkage of Tumors.

Polymersomes are self-assembled polymer shells composed of block copolymer amphiphiles. These synthetic amphiphiles have a similar amphiphilicity to lipids, but they have much larger molecular weights and so for this reason, plus many others reviewed here, comparisons of polymersomes to viral capsids composed of large polypeptide chains seem increasingly more appropriate. The wide range of polymers being used to make polymersomes is summarized together with descriptions of physical properties such as stability and permeability. Emerging studies of in vivo stealthiness and programmed disassembly for controlled release are also elaborated here together with a summary of targeting in vitro. Comparisons of polymersomes to viral capsids are shown to encompass many aspects of current designs. Drug Dev. Res. 67:4–14, 2006. © 2006 Wiley-Liss, Inc.

Polymersomes as viral capsid mimics

A composition and method are disclosed The composition includes a carrier fluid and a solids mixture combined to form a slurry, wherein the solids mixture comprises a plurality of volume-averaged particle size distribution (PSD) modes, wherein a first PSD mode comprises solids having a volume-average median size at least three times larger than the volume-average median size of a second PSD mode such that a packed volume fraction of the solids mixture exceeds 075, and wherein the solids mixture comprises a degradable material and includes a reactive solid The method includes circulating the slurry through a wellbore to form a pack in a fracture and/or a screen-wellbore annulus; degrading the degradable material to increase porosity and permeability of the pack; and producing a reservoir fluid through the permeable pack

High solids content methods and slurries

The invention discloses a method of treating a subterranean formation of a well bore: providing a treatment fluid made of: a fluid; a particulate material, and a viscosifier material; wherein the viscosifier material is inactive in a first state and is able to increase viscosity of the treatment fluid when in a second state; introducing the treatment fluid into the wellbore; and providing a trigger able to activate the viscosifier material from first state to second state.

Peter J. Photos

Papers

Polymer vesicles in vivo: correlations with PEG molecular weight.

Emerging Applications of Polymersomes in Delivery: from Molecular Dynamics to Shrinkage of Tumors.

Polymersomes as viral capsid mimics

High solids content methods and slurries

Methods to reduce settling rate of solids in a treatment fluid