Polymeric micro-and nanoparticles

Champion JA, Katare YK, Mitragotri S (2007) Making polymeric micro- and nanoparticles of complex shapes. Proc Natl Acad Sci USA 104 11901-11904. 

Barratt, G. et al. Polymeric micro- and nanoparticles as drug carriers. In Polymeric Biomaterials, 2nd edn. Dumitriu, S. (Ed.) Marcel Dekker, New York, 2002, p. 753. 

There are two main problems in obtaining polymeric micro- and nanoparticles, and these issues represent an obstacle when you want to scale up a product of its kind to be offered in the market. 

M.T. Chevalier, J.S. Gonzalez, and V.A. Alvarez, Polymeric micro and nanoparticles as drug carriers and controlled release devices New developments and future perspectives, in Advances in Materials Science Research. Vol. 17, M.C. Wythers, Ed., 2014, Nova Publishers. 

A large variety of drug delivery systems are described in the literature, such as liposomes (Torchilin, 2006), micro and nanoparticles (Kumar, 2000), polymeric micelles (Torchilin, 2006), nanocrystals (Muller et al., 2011), among others. Microparticles are usually classified as microcapsules or microspheres (Figure 8). Microspheres are matrix spherical microparticles where the drug may be located on the surface or dissolved into the matrix. Microcapsules are characterized as spherical particles more than Ipm containing a core substance (aqueous or lipid), normally lipid, and are used to deliver poor soluble molecules... 

Particulates are commonly classified into micro- and nanoparticles based on the size of the particles. Nanoparticles are colloidal particles ranging from 10 to 1,000 run, in which drag may be entrapped, encapsulated, and/or absorbed. Microparticulates are drag-containing small polymeric particles (erodible, non-erodible or ion-exchange resins) within the size of 1-10 /on, which are suspended in a liquid carrier medium. 

The combination of experimental evidence and computational modeling show conclusively that stable, homogeneously blended (bulk-immiscible) mixed-polymer composites can be formed in a single microparticle of variable size. To our knowledge, this represents a new method for suppressing phase-separation in polymer-blend systems without compatibilizers that allows formation of polymer composite micro- and nanoparticles with tunable properties such as dielectric constant. Conditions of rapid solvent evaporation (e.g. small (<10 pm) droplets or high vapor pressure solvents) and low polymer mobility must be satisfied in order to form homogeneous particles. While this work was obviously focused on polymeric systems, it should be pointed out that the... 

We expect that the proposed approach for the surface modification of polymeric membranes and the generation of the multilayered membrane assembUes can be straightforwardly employed as an efficient platform to fabricate breathable protective materials. The platform is highly tunable and upgradeable, since various parameters can be varied at will. First of all, membranes of different natures with different pore sizes can be employed. Second of all, various pre-modified (re)active/hydrophilic/hydrophobic membranes can be assembled together in a number of sequences. An additional advantage is the possibility of loading intermembrane space with functional micro- and nanoparticles, such as catalysts and/or adsorbents. Finally, in the assembly, protective elements are prefabricated and located at different levels and, thus, the compatibility issue can be resolved and multi-functionality can be achieved. 

Numerous synthetic or natural polymers have been used as matrices for micro- and nanoparticles or -capsules, most of which are biodegradable or bioerodible. Microparticles (or microspheres) are systems in which the drug is dispersed throughout the particle whereas capsules are vesicular systems in which the drug is contained in a cavity surrounded by the polymeric membrane (Couvreur and Puisieux, 1993). 

The nanostructured FSS consists of a dielectric matrix (polymeric or silicone resin) with micro- and nanoparticles embedded into it. For this composite nanostmctured material, it is required to have isotropy, homogeneity and continuity properties. In fact, when the nano-FSS works at high frequency. 

Enzyme-responsive polymers can be developed as enzyme-responsive polymeric assemblies, micro- and nanoparticles and hydrogels because of their similar properties to the extracellular matrix. Thus, a wide variety of hydrogels that suffer degradation in the presence of proteases for the release of encapsulated contents have been designed and tested for therapeutic purposes (Roy et al., 2010 de la Rica et al., 2012). 

Micro- and nanobeads with magnetic properties have recently become popular since these tools can be manipulated, e.g., collected in the region of interest. Magnetite nanoparticles are introduced in order to render the polymeric beads magnetic. Preparation and application of magnetic beads will be discussed in more detail in Sect 5.5. 

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