Nanoparticle from synthetic polymers

Synthetic and natural polymers have been investigated which are biodegradable and biocompatible. The nanospheres are formed by precipitation of synthetic polymers or by denatu-ration/solidification of polymers of natural origin. Four techniques have been reported for preparing nanoparticles from synthetic preformed polymers. These include ... 

Polymer nanoparticles including nanospheres and nanocapsules (Fig. 1) can be prepared according to numerous methods that have been developed over the last 30 years. The development of these methods occurred in several steps. Historically, the first nanoparticles proposed as carriers for therapeutic applications were made of gelatin and cross-linked albumin. Then, to avoid the use of proteins that may stimulate the immune system and to limit the toxicity of the cross-linking agents, nanoparticles made from synthetic polymers were developed. At first, the nanoparticles were made by emulsion polymerization of acrylamide and by dispersion polymerization of methylmethacry-late.f These nanoparticles were proposed as adjuvants for vaccines. However, since they were made of non-biodegradable polymers, these nanoparticles were rapidly substituted by particles made of biodegradable... 

Nanoparticles, 10-1000 nm polymeric particles, are prepared from the same natural and synthetic biodegradable polymers as microspheres. ° Albumin nanoparticles are prepared by the cross-linking processes mentioned previously. For the preparation of particles from synthetic polymers, heterogeneous bulk polymerization techniques of suspension, emulsion, and micelle polymerization are often used. 

The self-assembling character of bilayer membranes is demonstrated by the formation of free-standing cast films from aqueous dispersions of synthetic bilayer membranes. The tendencies for association are sufficiently strong to allow the addition of guest molecules (nanoparticles, proteins, and various small molecules) to these films where the connective forces are secondary in nature and not primary. Synthetic polymer chemists have made use of these self-assembling tendencies to synthesize monolayer films. In particular, a monomer that contains both reactive groups and hydrophobic and hydrophilic areas is cast onto an appropriate template that self-assembles the monomer, holding it for subsequent polymerization. Thus, a bilayer structure is formed by... 

A detailed description of the methods of polymerization and variables employed in polymer synthesis are beyond the scope of this review and can be found in many texts and review articles. The focus of this section is to provide an overview of the properties and methods used to prepare nanoparticles from each class of synthetic polymer. 

The second strategy by which metal nanoparticles can be stabilized is the fixation of molecules by the particles surface atoms. The protecting molecules may consist of polymers, surfactants, or ligands, as they are known from traditional complex chemistry. The use of polymers is for their amphiphilic natiue, that is, they have not only to coordinate to the metal particle, but must simultaneously be solvated by the surrounding fluid. Gelatin, agar, cyclodextrins, cellulose acetate, and cellulose nitrate are used as well as synthetic polymers. Poly(vinylpyrrolidone) (PVP) and poly(vinylalcohol) have turned out to work perfectly in this respect. 

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