Diatom microparticles for drug delivery applications: Impact of surface functionalisation

Abstract

Nature has developed an elegant biologically based self-assembling synthetic route to produce silica biomaterials with complex 3-dimensional (3-d) porous structures, offering great potential to replace synthetic mesoporous materials as suitable drug carriers for the development of cost-effective drug delivery systems. This work presents the application of a porous silica material derived from diatoms, also known as diatomaceous earth (DE), as a drug carrier with the aim to explore the impact of surface functionalization on drug loading and release characteristics of water insoluble drugs. The surface modification on DE was performed with two silanes: 3-aminopropyltriethoxy silane (APTES) and N-(3-(trimethoxysilyl) propyl) ethylene diamine (AEAPTMS) and phosphonic acids (PA), i.e. 2-carboxyethyl-phosphonic acid (2-phos), 16-phosphono-hexadecanoic acid (16-phos), providing organic surface hydrophilic and hydrophobic properties. Differences in the loading capacity of DE (15-24%) and release time (6-15 days) were observed as results of the presence of different functional groups on the surface.