Trojan Microparticles

A disadvantage of nanoparticles is that their size range is too small to ensure retention in the deep lung. The particles can be inhaled, but these constructs are totally expelled during exhalation. The larger microparticles in micron size ensure their retention into the system for a longer period, but the constructs poorly penetrate cell and tissue relative to nanoparticles. The ideal particle sizes for pulmonary administration are between 2 and 5 pm, corresponding to the typical size of microparticles. Therefore such microparticles may be the optimal system for targeting the pulmonary alveoli. However, these particles are too large to diffuse and allow an efficient administration. This problem can be solved by combining the properties ofmicro- and nanoparticles through encapsulation of nanoparticles in microparticles. The multiscale nano-in-microparticle systems are known as Trojan particles [27]. Such particles as taken up by the target site can be retained for a fairly long time, especially in the pulmonary alveoli, and then the NPs are released, which can diffuse through the barriers.

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