Imaging Polymer Nanoparticles by Means of Transmission and Scanning Electron Microscopy Techniques
This chapter describes methods of imaging polymer nanoparticles by electron microscopy. Protocols for the preparation of nanoparticles for observations by transmission electron microscopy, scanning electron microscopy, and cryo-transmission electron micro
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Imaging Polymer Nanoparticles by Means of Transmission and Scanning Electron Microscopy Techniques Nicolas Tsapis
Abstract This chapter describes methods of imaging polymer nanoparticles by electron microscopy. Protocols for the preparation of nanoparticles for observations by transmission electron microscopy, scanning electron microscopy, and cryo-transmission electron microscopy are proposed. Possible artifacts are shown. Keywords Electron microscopy Negative staining Artifacts
Polymer nanoparticles Preparation methods
1 Introduction Nanomedicines consist of biodegradable or biocompatible colloidal particles with size below the micron encapsulating a drug (Fattal and Tsapis 2014). After the early work in the 1970s, nanomedicine technology has emerged as an attractive field and a tremendous number of nanometric novel delivery systems have been proposed (Fattal and Tsapis 2014). Advances in chemistry and engineering have yielded a large panel of biocompatible and biodegradable material nanomedicines can be built of. If the very first works focused on lipid-based nanomedicines (Gregoriadis and Ryman 1971; Gabizon et al. 1994; Joondeph et al. 1988; Lopez-Berestein et al. 1983), soon polymers started to attract some attention. However, the polymer nanoparticles first developed in the mid-1970 by Birrenbach and Speiser were not degradable (Birrenbach and Speiser 1976). As biodegradable polymers appeared, they were quickly used to design nanometric drug delivery systems suitable for human applications (Couvreur et al. 1979). Polymer nanoparticles were of interest as they could be more active than liposomes due to their better stability, leading to the encapsulation of many drugs (e.g., antibiotics, cytostatics, nucleic acids) (Fattal et al. 1991). Many different polymers were synthesized and formulated to yield nanomedicines N. Tsapis (&) Institut Galien Paris Sud, Faculty of Pharmacy, UMR CNRS 8612, Univ. Paris-Sud, Université Paris Saclay, 5 Rue J.B. Clément, 92296 Châtenay-Malabry, France e-mail: [email protected] © Springer International Publishing Switzerland 2016 C. Vauthier and G. Ponchel (eds.), Polymer Nanoparticles for Nanomedicines, DOI 10.1007/978-3-319-41421-8_8
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among which are polyesters such as poly-DL-lactide, poly(lactide-co-glycolide) or poly(ε-caprolactone), poly-alkylcyanoacrylates) and even polysaccharides. Biodegradable polymers can be formulated into nanospheres or nanocapsules according to different preparation processes: anionic emulsion polymerization (Couvreur et al. 1979) (see Chap. 5 by Vauthier from Xu and Khan), solvent emulsion-evaporation (Vanderhoff et al. 1979; Losa et al. 1993; Pisani et al. 2006) (see Chap. 4 by Mandoza-Muñoz et al.) or nanoprecipitation (Fessi et al. 1992) (see Chap. 2 by Miladi et al. and Chap. 3 by Tang and Prud’homme from Xu and Khan). Nanospheres are matrix systems in which the drug is dispersed throughout the whole matrix, whereas nanocapsules are vesicular systems in which the drug is confined to a cavity surrounded by a u
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