Biogenic silica as a novel carrier to encapsulate isorhamnetin using a microfluidic device

Diatoms have the peculiarity to synthesize amorphous silica around the cell wall. Frustules (empty silica shells) have the advantages of being biocompatible, biodegradable, nontoxic and rich with OH groups on the surface. Frustules have been used in diverse fields, but recently their application in the biomedical field has been investigated. Drug delivery systems (DDS) have been studied to improve the therapeutic effect of different drugs, especially hydrophobic drugs. Different encapsulation methodologies have been used to load the drug in a carrier such as drop-wise methodology or solvent evaporation. However, a reproducible methodology that reduces handling error must be explored. In the present work, a microfluidic device is used as a novel encapsulation technique for solid particles and hydrophobic drugs. A novel microfluidic device fabrication technique was used: ESCARGOT (Embedded SCAffold RemovinG Open Technology). Isorhamnetin was used as a model drug which has a hydrophobic nature. Three different concentrations were studied: 20, 60 and 100 μg/mL, and three different resident times in the device (0.4, 1 and 2 minutes). The highest encapsulation efficiency (EE%) and loading capacity (LC%) were 17.92% and 1.63% respectively. According to the statistical analysis, the optimum conditions to obtain a maximum (EE%) were 2 minutes and 20 μg/mL. The isorhamnetin release behavior was observed with a burst release in the first hour with 48.26%, while the total amount of drug was delivered in three hours. The feasibility of frustules as carriers and the microfluidic device as a mixer was successfully accessed. This methodology could be used as a standardization technique to obtain reproducible results. Further studies with frustule surface functionalization need to be performed to improve EE%.