Influences of diatom frustule morphologies on protein adsorption behavior

Abstract

Diatom frustules are a potential protein adsorbent substitute for conventional silica to address synthesis limitations of synthetic silica particles such as high energy consumption, long synthesis duration, and usage of toxic compounds. Diatom frustules have been used in many applications including separation of heavy metals, enzyme immobilization, and drug delivery; however, research into diatom frustules as a substrate for selective protein adsorption is limited only to functionalized frustules as a general adsorbent. Hence, in this paper, the morphology of diatom frustules and their protein adsorption were studied. The protein adsorption experiments were conducted using three different diatom frustules, namely, Thalassiosira weissflogii, Navicula sp., and diatomaceous earth (DE). Bovine serum albumin and lysozyme were used as model proteins. The surface chemistry of diatom frustules and protein was manipulated to investigate the interplay between surface charge and adsorption capacity. The adsorption behavior was further evaluated and is discussed through isotherm model and kinetic fitting. The result revealed that among these three diatom frustules, the centric diatom, T. weissflogii frustules have the highest adsorption capability. This can be attributed to their morphology with larger surface area, pore volume, and the presence of silanol groups. Besides that, the kinetic and isotherm model fitting indicate that protein adsorption on these three diatom frustules is a monolayer chemisorption. These results indicate the possibility of diatom frustules as a potential substrate in immunoassay applications.