SCIGRIP 4 10308 Acrylic Solvent Cement will, I repeat, WILL dissolve PLA from your clogged nozzles.
I purchased mine here:
I print a lot of PLA. I occasionally get partially clogged nozzles, usually due to something causing extrusion to stop. Leaving PLA at 225C for a few hours tends to cause partial clogs that ruin print quality. Now I can clean up that row of plugged up brass I have sitting on my shelf!!!