Surface functionalization of germanium ATR devices for use in FTIR-biosensors

Abstract

Biosensors based on intrinsic detection methods have attracted growing interest. The use of Fourier transform infra-red (FTIR) spectroscopy with the attenuated internal total reflection (ATR) mode, in the biodetection context, requires appropriate surface functionalization of the ATR optical element. Here, we report the direct grafting of a thin organic layer (about 20 Å depth) on the surface of a germanium crystal. This covering, constructed with novel amphiphilic molecules 2b (namely, 2,5,8,11,14,17,20-heptaoxadocosan-22-yl-3-(triethoxysilyl) propylcarbamate), is stable for several hours under phosphate buffered saline (PBS) flux and features protein-repulsive properties. Photografting of molecule 5 (namely, O-succinimidyl 4-(p-azidophenyl)butanoate) affords the activated ATR element, ready for the covalent fixation of receptors, penicillin recognizing proteins BlaR-CTD for instance. The different steps of the previous construction have been monitored by water contact angle (θ w ) measurements, spectroscopic ellipsometry (covering depth), X-ray photoelectron spectroscopy (XPS) by using a fluorinated tag for the control of surface reactivity, and FTIR-ATR spectroscopy for the structural analysis of grafted molecules. Indeed, contrarily to silicon device, germanium device offers a broad spectral window (1000-4000 cm −1 ) and thus amide I and II absorption bands can be recorded. This work lays the foundations for the construction of novel FTIR biosensors.

Synthesis of tri-, penta-, and heptasaccharides, functionalized with orthogonally N-protected amino residues at the reducing and non-reducing ends

“…biosensing strongly depends on the cross linker. We have demonstrated the synthesis of oligosaccharides, with variable lengths and flexibility, as possible bifunctional cross-linking structures (1)(2)(3)(4). Common problems associated with the synthesis of the traditionally used PEGs/OEGs are purification and low crystallinity.…”

Protein attachment to silane-functionalized porous silicon: A comparison of electrostatic and covalent attachment

“…1a), that proves the right functionalization, is the characteristic vibration from the carbonyl group (C@O) at 1644 cm À1 [54]. Besides this peak, other visible peaks in the spectrum corresponding to this linker are the vibrations from ACAHA at 1410 cm À1 and ASiACA at 1430 cm À1 , also present for APTMS and APTMS-GTA [61]. Furthermore, ASiAOA vibrations at 880 cm À1 from the underlying oxidized silicon can also be observed [55,56].…”

“…In the high-wavenumber spectrum of silane-PEG-NHS (Fig. 2b) wide stretching vibrations from ANAHA together with environment vibrations in the range between 3000 and 3500 cm À1 also confirm the correct attachment of the linker [54,61]. Table 1 reports all the observed vibrational peaks summarizing, for every functional group, its characteristic absorption range, the sample and the technique where it has been recognized and the corresponding citation.…”

Adsorption Selectivities between Hydroxypyridine and Pyridone Adsorbed on the Ge(100) Surface: Conjugation and Geometric Configuration Effects on Adsorption Structures

“…It is clear that these technologies which have a direct correlation to the interactions between biomolecules and semiconductor surfaces can play a significant role in promising applications in biosensors, molecular electronics and immunoassay sensors. [1][2][3][4][5][6][7][8][9][10] Among many different kinds of bio-molecules, we present the results of the adsorption energies, optimized structures and geometric configurations using DFT calculation method and high-resolution photoemission spectroscopy (HRPES) when 4-pyridone, 4-hydroxypyridine, 2-pyridone and 2-hydroxypyridine are adsorbed on Ge(100) surfaces. The Ge(100) surface, which is one of the Group IV semiconductor surfaces, possesses a strong  bond and a weak  bond resulting in the formation of surface dimers.…”