An important prerequisite for the use of nanoparticles clinically is sterilization of the nanoparticle/drug complex. The possibility of sterilizing poly(butylcyanoacrylate) nano-particles was studied by Sabel et al. . Nanoparticle suspensions and nanoparticle powders were submitted to autoclaving (121° C for 20 min with or without cooling to 70° C afterward) or treated with formaldehyde (60° C). The nanoparticles were prepared using different stabilizers, such as dextran 70,000, poloxamer 188, and polysorbate 85. In most cases the authors detected a significant increase in particle size. For lyophilized nanoparticles no powder was suitable for preparing injectable suspensions. In particular, the resuspension of nanoparticle powders caused problems, which could not be overcome by intensified sonication. Under certain conditions poloxamer 188 suspensions and polysorbate 80 suspensions led to injectable nanoparticle suspensions. In summary, sterilization of nanoparticles after fabrication is possible under certain conditions, but the favored way to obtain aseptic material seems to be the production of nanoparticles under aseptic conditions.
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