Silicon nanowire (SiNW) field-effect transistors (FETs) have been developed as very sensitive and label-free biomolecular sensors. The detection principle operating in a SiNW biosensor is indirect. The biomolecules are detected by measuring the changes in the current through the transistor. Those changes are produced by the electrical field created by the biomolecule. Here, we have combined nanolithography, chemical functionalization, electrical measurements and molecular recognition methods to correlate the current measured by the SiNW transistor with the presence of specific molecular recognition events on the surface of the SiNW. Oxidation scanning probe lithography (o-SPL) was applied to fabricate sub-12 nm SiNW field-effect transistors. The devices were applied to detect very small concentrations of proteins (500 pM). Atomic force microscopy (AFM) single-molecule force spectroscopy (SMFS) experiments allowed the identification of the protein adsorption sites on the surface of the nanowire. We detected specific interactions between the biotin-functionalized AFM tip and individual avidin molecules adsorbed to the SiNW. The measurements confirmed that electrical current changes measured by the device were associated with the deposition of avidin molecules.
DNA has excellent features such as the presence of functional and targeted molecular recognition motifs, tailorable, defined material source, multifunctionality, high–precision molecular self–assembly, synthetic preparation, hydrophilicity and outstanding biocompatibility. Due...
Regulation of enzyme activity is key to dynamic processes in biology but is difficult to achieve with synthetic systems. We here report molecularly imprinted nanoparticles with strong binding for the...
Covalent organic materials (COMs) are a class of ideal platform in various areas, such as biomedical and analytical purpose. However, it is still a challenge to construct COMs with both...
The formation of inclusion complexes between alkylsulfonate guests and a cationic pillar[5]arene receptor in water was investigated by NMR and ITC techniques. The results show the formation of host-guest complexes stabilized by electrostatic interactions and hydrophobic effects with binding constants of up to 107 M−1 for the guest with higher hydrophobic character. Structurally, the alkyl chain of the guest is included in the hydrophobic aromatic cavity of the macrocycle while the sulfonate groups are held in the multicationic portal by ionic interactions.
Ways of creating new generation biosensors for multiparametric express diagnostics based on molecular recognition and direct fluorimetric registration of a peptide aptamer — protein marker complex were considered. The biosensor platform comprises a microfluidic channel for delivery sample solutions, coupled with flow-through zones containing covalently attached arrays of peptide probes — aptamers. An outer glass window of the biochip assembly contains a layer of luminophore ZnS:Cu, bound on it via an acrylic lacquer and intended for the re-emitting native fluorescence of bound proteins into the longer wavelength range, more efficient in registering signals with CMOS sensors. The aptamers were designed using "Protein 3D" program for analysis of spatial complementarity of protein structures. The peptide, complementary to Troponin T, was modified by replacement of aromatic amino acid residue while maintaining the spatial configuration. The complementarity of peptide and Troponin T was confirmed using a capillary electrophoresis-on-a-chip. Biosensors are manufactured using thick-film technology and photolithography. The fluorescence of marker proteins was excited using UV-LED with a radiation wavelength of 275 nm. The limit of detection achieved for Troponin T was 6 ng/ml.
Families of quasiracemic materials constructed from 3- and 4-substituted chiral diarylamide molecular frameworks were prepared, where the imposed functional group differences systematically varied from H to CF3–9 unique components for each isomeric framework. Cocrystallization from the melt via hot stage thermomicroscopy using all possible racemic and quasiracemic combinations probed the structural boundaries of quasiracemate formation. The crystal structures and lattice energies (differential scanning calorimetry and lattice energy calculations) for many of these systems showed that quasienantiomeric components organize with near inversion symmetry and lattice energetics closely resembling those found in the racemic counterparts. This study also compared the shape space of pairs of quasienantiomers using an in silico alignment-based method to approximate the differences in molecular shape and provide a diagnostic tool for quasiracemate prediction. Comparing these results to our recent report on related 2-substituted diarylamide quasiracemates shows that functional group position can have a marked effect on quasiracemic behavior and provide critical insight to a more complete shape space, essential for defining molecular recognition processes.
Molecular Recognition by Silicon Nanowire Field-Effect Transistor and Single-Molecule Force Spectroscopy
