Nanoparticles 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 ... 

The coprecipitation technique was based on the dropwise addition of a synthetic polymer solution, in a solvent mixture, into an aqueous protein solution under magnetic stirring. The progressive interaction between the water insoluble polymer and the protein gave rise to the microsphere formation. The glycolipid was then added as an aqueous dispersion to the nanoparticle suspension. No sedimentation was observed after several weeks of storage at room temperature. 

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... 

Recently, a miniaturized thermal apparatus, [t-ThFFF, was developed and applied to characterize the molar mass distribution of synthetic polymers in organic solvent as well to determine the particle size distribution of nanoparticles (PSs latex) in aqueous carrier. This 4-ThFFF proved to performed well in both macromolecule and particle analysis [48]. 

Even newer generations of nanomaterials are based on carbon nanotubes using the bottom-up approach. The materials are still very expensive, but the technology is evolving rapidly. Another type of nanotube has been prepared based on self-assembly of specific molecules such as chitosan-based nanoparticles of polypeptides, DNA or synthetic polymers. Phospholipids or dendrimer-coated particles are suitable for the entrapment of actives in very small vesicles. The current materials are still lacking in selectivity and yield (costs). 

Watanabe T, Kawasaki H, Yonezawa T, Arakawa R (2008) Surface-assisted laser desorption/ ionization mass spectrometry (SALDI-MS) of low molecular weight organic compounds and synthetic polymers using zinc oxide (ZnO) nanoparticles. J Mass Spectrom 43 1063-1071. doi 10.1002/jms.l385... 

Key Words shRNA RNAi Biodegradable polymer Natural polymer Synthetic polymer Non-viral gene delivery Drug delivery Nanoparticle Microparticle Tumor targeting. 

Gelatin, which is a simply denatured collagen, has shown promise in vitro and in vivo as an shRNA delivery vehicle. Cationized gelatin nanoparticles are relatively simple to produce when compared to synthetic polymers (61). They have been shown to have an in vitro transfection efficiency of approximately one order of magnitude less than PEI, but show approximately four-fold less cytotoxicity (62,63). 

Synthetic Polymers Physical Properties and Methods of Preparation of Nanoparticles... 

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. 

Nanoparticles of synthetic polymers are usually manufactured by dispersion of preformed polymers. Although many methods can be used, they may be classified as monomer polymerization, nanoprecipitation, emulsion diffusion/solvent evaporation, and salting out. An appropriate method is selected mainly depending on polymer and drug natures. Polymerization of polymer monomers has been developed usually using poly(alkyl cyanoacrylate) [96,97]. Organic solvents are usually used in polymerization. A detailed description of this method is not provided here. 

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. 

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. 

Chitosan is one of the most commonly studied polymers in nonviral gene delivery [106]. Indeed, its positive charges under slightly acidic conditions allow its interaction with nucleic acids such as DNA or siRNA and the condensation of the nucleic acids into nanoparticles. In addition, the biocompatibility and low toxicity of chitosan enable its in vivo use [107]. However, the poor buffering capacity and poor solubility in water [46] make chitosan less efficient than other catioiuc synthetic polymers, such as PEI or PEL. 

To increase the residence time of drug carriers in the blood, the carriers are modified with hydrophilic synthetic polymers, such as PEG [62-64]. Coating nanoparticles with PEG sterically disrupts the interactions of blood components with the carrier surface and subsequently decreases the binding of plasma proteins. This minimizes opsonin adsorption onto the carrier and carrier uptake rates by the reticuloendothelial system (RES) [65-67]. Repulsive interactions [68] and poor permeability of proteins through PEG coating [69] may contribute to this observation. 

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