Optimization of Porous Silicon Conditions for DNA-based Biosensing via Reflectometric Interference Spectroscopy

• Published in: Cell journal (Yakhteh) Vol. 20; no. 4; pp. 584 - 591
• Main Authors: Rahimi, Fereshteh, Fardindoost, Somayeh, Ansari-Pour, Naser, Sepehri, Fatemeh, Makiyan, Farideh, Shafiekhani, Azizollah, Rezayan, Ali Hossein
• Format: Journal Article
• Language: English
• Published: Iran Royan Institute of Iran 2019; Royan Institute; Royan Institute (ACECR), Tehran
• Subjects: Biosensor; Biosensors; BRCA1 Gene; BRCA1 protein; Breast cancer; Complementary DNA; Deoxyribonucleic acid; DNA; Electrolytes; Etching; Ethanol; Fabrication; Field emission microscopy; Gene expression; Gene sequencing; Hybridization; Interference; Morphology; Mutation; Nanochip Analytical Device; Nonaqueous electrolytes; Nucleotide sequence; Nucleotides; Oligonucleotides; Optimization; Original; Ovarian cancer; Porous silicon; Scanning electron microscopy; Silicon; Silicon wafers; Sodium hydroxide; Solid phases; Spectroscopy; Spectrum analysis; Surface roughness; United States > US; BRCA1 Gene; Nanochip Analytical Device; Biosensor
• DOI: 10.22074/cellj.2019.5598
• ISSN: 2228-5806

Substantial effort has been put into designing DNA-based biosensors, which are commonly used to detect presence of known sequences including the quantification of gene expression. Porous silicon (PSi), as a nanostructured base, has been commonly used in the fabrication of optimally transducing biosensors. Given that the function of any PSi-based biosensor is highly dependent on its nanomorphology, we systematically optimized a PSi biosensor based on reflectometric interference spectroscopy (RIS) detecting the high penetrance breast cancer susceptibility gene, BRCA1. In this experimental study, PSi pore sizes on the PSi surface were controlled for optimum filling with DNA oligonucleotides and surface roughness was optimized for obtaining higher resolution RIS patterns. In addition, the influence of two different organic electrolyte mixtures on the formation and morphology of the pores, based on various current densities and etching times on doped p-type silicon, were examined. Moreover, we introduce two cleaning processes which can efficiently remove the undesirable outer parasitic layer created during PSi formation. Results of all the optimization steps were observed by field emission scanning electron microscopy (FE-SEM). DNA sensing reached its optimum when PSi was formed in a two-step process in the ethanol electrolyte accompanied by removal of the parasitic layer in NaOH solution. These optimal conditions, which result in pore sizes of approximately 20 nm as well as a low surface roughness, provide a considerable RIS shift upon complementary sequence hybridization, suggesting efficient detectability. We demonstrate that the optimal conditions identified here makes PSi an attractive solid-phase DNA-based biosensing method and may be used to not only detect full complementary DNA sequences, but it may also be used for detecting point mutations such as single nucleotide substitutions and indels.