Complex sentence: With the aid of nanoparticle delivery systems, studies have shown that certain drugs cannot only cross the BBB, but they can also exhibit lower toxicity throughout the body, which is an importnat concept for pharmacology because high toxicity levels could be detrimental to the patient.
Split into simpler sentences: With the aid of nanoparticle delivery systems, studies have shown that certain drugs cannot only cross the BBB, but they can also exhibit lower toxicity throughout the body. The concept of toxicity is important for pharmacology because high toxicity levels could be detrimental to the patient.