What is SLN in nanotechnology?

Could you please explain what the term "SLN" stands for in the context of nanotechnology? As someone who is new to this field, I'm curious to know if it refers to a specific type of nanoparticle, a method of synthesis, or perhaps a technique used in the application of nanomaterials. I'd appreciate it if you could provide a concise yet informative answer that helps me understand the role of SLN in nanotechnology.