Self-assembling polymer amphiphiles

Recently, many studies have focused on self-assembled biodegradable nanoparticles for biomedical and pharmaceutical applications. Nanoparticles fabricated by the self-assembly of amphiphilic block copolymers or hydrophobically modified polymers have been explored as drug carrier systems. In general, these amphiphilic copolymers consisting of hydrophilic and hydrophobic segments are capable of forming polymeric structures in aqueous solutions via hydrophobic interactions. These self-assembled nanoparticles are composed of an inner core of hydrophobic moieties and an outer shell of hydrophilic groups [35, 36]. 

Fig. 10.2 Nanoparticles formed via polymer micelles by self-assembly of amphiphilic block copolymers...

Shapes of vesicular aggregates range from tubular to spherical, from more exotic large compound (LCV) and starfish vesicles to simpler extended lamellae. Both unilamellar [75] and multilamellar ( onions ) [47,76] vesicles have been observed. One of the possible morphologies formed in solution are tubular vesicles, also known as tubes (rods) [77,78], Soft, water-filled polymer tubes of nanometer-range diameters and several tens of millimeters in length have been prepared via self-assembly of amphiphilic ABA triblock copolymer in aqueous media (Fig. 4). The tubes were mechanically and chemically stable and could be loaded with water-soluble substances [23],... 

Polymersomes, self-assembled polymer shells composed of block copolymer amphiphiles. These synthetic amphiphiles with amphiphilicity similar to lipids constitute a new class of drug carriers. They are spontaneously formed in aqueous media, as unilamellar vesicles up to tens of microns in diameter. Amphiphilic block copolymers form a range of self-assembled aggregates including spherical, rod-like, tubular micelles, lamellae, or vesicles, depending on polymer architectnre and preparation conditions. Polymers having low hydrophobicity (less than 50%) favor the formation of micelles, however, intermediate level of hydrophobicity (50%-80%) favors the formation of vesicles. Polymeric vesicles, which have a liposome-like structure with a hydrophobic polymer membrane and hydrophilic inner cavity, are called polymersomes. 

The preparation of nanogels from polymer precursor is based on the simply locking of self-assembled amphiphilic copolymers. This versatile methodology is discussed in detail based on cross-linking reaction types employed to fix the self-assembled polymer in this entry. 

Y. Yang, J. Cai, X. Zhuang, Z. Guo, X. Jing, X. Chen, pH-dependent self-assembly of amphiphilic poly (l-glutamic acid)-block-poly (lactic-co-glycolic acid) copolymers. Polymer 51 (2010) 2676-2682. 

We can also mention the use of bio-sourced building blocks based on cellulose or dextran. Kadla et al. described value-added materials from naturally abundant polymers for system that may serve as a platform for the design and development of biosensors [197]. A hierarchically strucmred honeycomb film from dextran-ft-PS amphiphilic linear diblock copolymers has also been described by Chen et al. leading to ordered porous bio-hybrid films. [198] Honeycomb patterned surfaces functionalized with biomolecules for specific recognition of proteins or bacteria have been also achieved either by self-assembly of amphiphilic copolymers based on galactose moieties [155] or by post-modification with peptide sequences [199]. 

Jia L, Liu M, Di Cicco A, Albouy PA, Brissault B, Penelle J, et al. Self-assembly of amphiphilic hquid crystal polymers obtained from a cyclopropane-1,1-dicarboxylate bearing a cholester-yl mesogen. Langmuir 2012 28(30) 11215-24. 

The segregated core-shell microstmctures, consisting of a hydrophobic core surrounded by a hydrophilic shell, are of great praaical interest as their mechanical properties are mainly influenced by the core polymer and the chemical properties and solubility mainly by the shell monomer units. These materials have attracted increased attention because they not only maintain the funaions of both the core and shell components but also exhibit additional excellent optical, electrical, and magnetic properties. Polymeric core-shell microstmctures can be obtained through phase separation, which is realized by inductive polymerization," solvent extraction and evaporation,"" self-assembly of amphiphilic block copolymers,"" or sequential predpitation,"" which is intrinsically a self-assembly and phase-separation process. However, these methodologies are usually complicated and tedious. 

Gheybi, H. and Entezami, AA. (2013) Nanosized micelles self-assembled from amphiphilic poly(citric acid)—poly(e-caprolactone)—poly(citric acid) copolymers. Polym. Bull, 70, 1875. 

The approach of encapsulating NIR fluorophores by micelles formed by the self-assembly of amphiphilic polymers or block copolymers stems from the application of this kind of nanoparticle as a drug delivery vehicle, which has been eonsidered to be of great potential over the past decades. Generally, it involves the self-assembly of amphiphilie polymers or block copolymers upon interaction with water, spontaneously generating micelles with a hydrophobic core and a hydrophilic surface (Figure 5.14). ... 

In recent years there has been significant progress in the preparation of stable polymer vesicles over a size range of tens of nanometers to tens of micrometers by either polsunerization of lipid vesicles or self-assembly of amphiphilic block... 

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