Abstract
Resonant glassy nanostrings have been employed for the detection of biomolecules. These devices offer high sensitivity and amenability to large array integration and multiplexed assays. Such a concept has however been impaired by the lack of stable and biocompatible linker chemistries. Diazonium salt reduction-induced aryl grafting is an aqueous-based process providing strong chemical adhesion. In this work, diazonium-based linker chemistry was performed for the first time on glassy nanostrings, which enabled the bio-functionalization of such devices. Large arrays of nanostrings with ultra-narrow widths down to 10 nm were fabricated employing electron beam lithography. Diazonium modification was first developed on SiCN surfaces and validated by X-ray photoelectron spectroscopy. Similarly modified nanostrings were then covalently functionalized with anti-rabbit IgG as a molecular probe. Specific enumeration of rabbit IgG was successfully performed through observation of downshifts of resonant frequencies. The specificity of this enumeration was confirmed through proper negative control experiments. Helium ion microscopy further verified the successful functionalization of nanostrings.
Highlights
Biological analysis technologies play an important role in many fields such as disease biomarker diagnosis and monitoring, drug discovery, and molecular analysis [1,2,3,4,5,6,7]
With the developed HSQ serving as a protection mask, the SiCN film was selectively etched by reactive ion etching (RIE) using 4:1 SF6:O2
A critical point drying (CPD) step usually required in most MEMS/NEMS device fabrication was not needed in this process
Summary
Biological analysis technologies play an important role in many fields such as disease biomarker diagnosis and monitoring, drug discovery, and molecular analysis [1,2,3,4,5,6,7]. Nanostring biosensors have received increased attention in terms of their sensitivity and amenability to large scale integration [19,29,30,31,32,33] Such devices assess the addition or loss of bound analytes through monitoring of their resonance frequency. Significant research involving diazonium-induced surface modification of biosensors has been conducted in recent years Most of these reports were limited to electrochemical sensors and surfaces such as carbon and metals [39,42,43,44,45,46,47,48,49].To the best of our knowledge, diazonium salt linker chemistry has neither been applied to glassy sensor surfaces nor exploited to functionalize nanostrings of the type described here. Helium ion microscopy (HIM) was conducted on the functionalized and pristine nanostrings to further observe the immobilized analytes
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