**11. Release profile**

Obtaining constant drug release is considered an urgent necessity to obtain sustained drug level in tumor tissue which can lead to a lower dose requirement. For example, paclitaxel gelatin nanoparticles are highly effective in the treatment of bladder cancer because the rate of paclitaxel release from paclitaxel gelatin nanoparticles is limited by the drug solubility in aqueous medium. So the drug concentration remains constant and does not dilute when urine production is increased [58].

Sometimes, a fast release rate is desired, accompanied with enhanced solubility and penetra‐ tion of non polar drugs. For example, *Hibiscus rosa-sinensis* and *Murraya koenigii* extracts are acclaimed to prevent hair loss and promoting its growth. However, proving such claims scientifically was hindered by many limitations, especially the poor solubility of the extracts in water. Since the desired formulation is intended to be used as a topical treatment with fast release rate to study its effectiveness, microemulsions were the ideal choice for improving the solubility and systemically study the extracts of these plants [72].
