Physicochemical Characteristics of Nanosystems Based on Endogenous Polymers

2 Physicochemical Characteristics of Nanosystems Based on Endogenous Polymers 

Although a detailed description of the main physicochemical characterization techniques used in polymer characterization is clearly beyond the scope of this chapter, we have included specific details to be considered when such characterization is specifically for nanoparticles for the purpose of gene therapy. In such a situation we should take into consideration the following parameters and details  

In the case of proteins, low polydispersity and well-defined values for the molecular weight are expected as compared with polysaccharides. On the other hand, the molecular weight distribution of polysaccharides can be strongly influenced by their source and method of obtention. 

Ideally, for the formation of a nanoparticulate system by complexation/ionic gelation, the polymeric solution should be in one semi-diluted regimen, the optimal concentration being  

Microscopy techniques may also be used to perform size estimations and to corroborate the size homogeneity in a population. Transmission electronic microscopy (TEM), scanning electronic microscopy (SEM) and atomic force microscopy (AFM) are the most used. Nevertheless, these techniques are more often applied for visual characterization of size and distribution in order to corroborate data obtained with other techniques. This is because the theory behind most of the techniques used for size determination relies on the use of monodisperse and spherical particles. Any deviation from this condition may give unrealistic results that consequently may affect the efficacy of the system. In TEM measurements, a contrast agent is normally necessary for proper visualization, such as uranyl acetate, osmium tetroxide, ammonium molybdate or phosphotungstic acid. Because of its high resolution, AFM can also be useful to detect interactions between plasmids and nanostructures [77]. 

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