Improving the selectivity by using different blocking agents in DNA hybridization assays for SiGe bio-molecular sensors

•Functionalized SiGe MEM resonators are promising devices for label-free biosensing.•No dependence on the oxidation method on the degree of immobilized bioreceptors.•Hexylamine is a promising blocking agent as it has the advantages of BSA.

In this work minimizing the non-specific binding onto the sensor surface was carried out using different blocking agents to obtain a specific detection (1–125 nM). Bovine Serum Albumin (BSA) is considered. However, its serious disadvantage is that it has been shown to cause stiction of the Micro-Electro-Mechanical Systems (MEMS). In addition, it does not strongly bind to the underlying layer causing detachment that may lead to a weight calculation error, after the target DNA hybridization. To address both requirements mentioned above, we have tested different oxidation methods which are wet and dry to explore the impact of the SiGe oxide quality on the amount of attached bioreceptors and tested alternatives to BSA as blocking agent. Oxidized SGe samples were then exposed to different blocking agents, i.e. hexylamine, hydroxylamine, ethanolamine hydrochloride and 1,3-propyldiamine, as an alternative for BSA. It was found that there is no dependence of the probe immobilization on the type of the oxidation methods. Hexaylamine as a blocking agent was found to be the best blocking agent for SiGe MEMS.

Graphical abstractA schematic representation of the bio-layers deposited on SiGe (a), BSA blocking agent for the unreacted sites within the different chemical layers on the SiGe substrate (b).Figure optionsDownload full-size imageDownload as PowerPoint slide