Immunoassay of Glomalin by Quartz Crystal Microbalance Biosensor Containing Iron Oxide Nanoparticles.

Miroslav Pohanka,Vitezslav Vlcek

doi:10.1155/2020/8844151

Abstract

Glomalin is a soil protein resembling heat shock protein (HSP) 60 and exerting high affinity to metals, causing retention of water in the environment and improving mechanical stability of soil. Currently, glomalin is determined in the soil or other samples by combination of autoclaving extraction and total protein determination typically by the Bradford method. In this paper, a piezoelectric biosensor was prepared to determine glomalin in a label-free measurement. The biosensor contained antibodies immobilized on quartz crystal microbalance (QCM), and the recognition layer was stabilized by iron oxide nanoparticles. The assay was tested on real soil samples and compared with the standard Bradford assay. Limit of detection of the assay was equal to 2.4 µg/g for a soil extract with a volume of 50 µl. The assay takes approximately half of an hour and was fully correlated to the Bradford assay. The biosensor had significant advantages than the other methods: it worked in a label-free mode and was fully applicable for practical samples.

Highlights

Presence of free proteins in the environment has been underestimated for a long time
Glomalin exerts high homologies with health shock protein 60 (HSP 60) including the human type, but the soil glomalin is of a fungal origin and it is a product of arbuscular mycorrhizal fungi [1,2,3]
While preparation of self-assembled monolayer by cysteamine and glutaraldehyde had no effect on oscillation frequency, binding of antibodies caused decrease in the frequency equal to 753 ± 44 Hz, and binding of iron oxide nanoparticles further dropped the frequency of 958 ± 67 Hz

Summary

Introduction

Presence of free proteins in the environment has been underestimated for a long time. Assay of this proteins can help in various processes and may be helpful, for instance, in the criminalistics, archeology, agronomy, ecology, and other disciplines. Glomalin is extensively studied, and its presence in the nature appears to have a significant role for water and metals retaining mechanical stability of soil, ability of microorganism surviving in the environment, and so on. It exerts high stability which is in a good correspondence with knowledge about HSP 60

Methods

Results

Conclusion