Protein-polymer nanoreactors

Palivan CG, Fischer-Onaca O, Delcea M, Itel F, Meier W. Protein-polymer nanoreactors for medical applications. Chem Soc Rev 2012 41(7) 2800-23. 

Fig. 16 a-d Schematic representation of polymer nanoreactors, a Cross section of triblock copolymer vesicle, b Polymersome with encapsulated enzyme and membrane-embedded channel protein. In the case described in the text, the substrate entering the vesicle is ampicillin, and the product of the hydrolysis is ampicillinoic acid, c Polymersome with embedded ionophores allowing Ca2+ ions to enter the vesicle ere they react with phosphate ions to form calcium phosphate crystals, d The LamB protein serves as a receptor to the 1 phage virus which can inject its DNA through the channel into the polymersome [259]. Reproduced with permission of The Royal Society of Chemistry... 

The polymer self-assembly can be considered as a template-free approach to produce nanomaterials. In contrast, the template-assisted approaches make use of a sacrificial template, which is initially covered by a polymeric layer and afterwards removed thus yielding polymeric capsules or containers. The latter are structures, composed of a hollow core and a polymeric shell (membrane), tiiat have shown potential as dmg and vaccine carriers as weU as in applications such as gene and protein delivery, nanoreactors, and artificial organelles. 

One particular asset of structured self-assemblies is their ability to create nano- to microsized domains, snch as cavities, that could be exploited for chemical synthesis and catalysis. Many kinds of organized self-assemblies have been proved to act as efficient nanoreactors, and several chapters of this book discnss some of them such as small discrete supramolecular vessels (Chapter Reactivity In Nanoscale Vessels, Supramolecular Reactivity), dendrimers (Chapter Supramolecular Dendrlmer Chemistry, Soft Matter), or protein cages and virus capsids (Chapter Viruses as Self-Assembled Templates, Self-Processes). In this chapter, we focus on larger and softer self-assembled structures such as micelles, vesicles, liquid crystals (LCs), or gels, which are made of surfactants, block copolymers, or amphiphilic peptides. In addition, only the systems that present a high kinetic lability (i.e., dynamic) of their aggregated building blocks are considered more static objects such as most of polymersomes and molecularly imprinted polymers are discussed elsewhere (Chapters Assembly of Block Copolymers and Molecularly Imprinted Polymers, Soft Matter, respectively). Finally, for each of these dynamic systems, we describe their functional properties with respect to their potential for the promotion and catalysis of molecular and biomolecu-lar transformations, polymerization, self-replication, metal colloid formation, and mineralization processes. 

The design of bionanoreactors is based on encapsulation/insertion of active compounds (proteins, enzymes, mimics) inside polymeric supramolecular assemblies, such as dendrimers, capsules, and vesicles, in which they can act in situ while being protected from proteolytic attack [3,6]. These supramolecular assemblies should allow the passage of products or substrates to the inner spaces where the active compounds are located in order to support reactions confined within their structures. Various approaches to providing accessibility to the inner reaction space of the polymer assemblies are presented, even though not all have been used in the design of nanoreactors, in order to give an overview of the variety of solutions that can be expected to advance this field of science. 

In order to combine a polymer 3D supramolecular assembly with proteins and/ or enzymes to form a confined reaction space at the nanoscale, a complex system of requirements must be fulfilled. The aiteria used to design nanoreactors... 

The ability to design water-in-SCF micioemulsions offers new opportunities for protein and polymer chemistry, separation science, reaction engineering science such as providing a nanoreactor for the synthesis of nanoparticles and conducting chemical reactions [14]. 

Another bio-inspired approach is to design polymersomes as enclosed reaction compartments for the development of nanoreactors, nanodevices, or artificial organelles, in which active compounds are not only protected from the environment, but also allowed to act in situ. For such function, membrane permeability is of crucial importance, since it allows the exchange of substrates/products with the environment of the pol)maersomes. Various methods have been reported to generate polymersomes with permeable membranes (i) polymers forming intrinsically porous membranes, (ii) polymer membranes that are permeable to ions as e.g. specific oxygen species, (iii) pore formation in pH responsive polymer membranes by chemical treatment, (iv) polymer membrane permeabilization by UV-irradiation, and (v) biopores or membrane proteins inserted into polymer membranes. ... 

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