Studies on visual sensor from self-assembled polypeptides

Abstract

A silane terminated poly (3-benzyloxycarbonyl-L-lysine) was synthesized and deposited as a self-assembled monolayer on the pre-colored silica substrate which was fabricated by Langmuir-Blodgett (LB) method. The monolayer was covalently attached to silica surface through terminal silane groups. The secondary structure of polymer, a-helix, was confirmed by circular dichroism spectroscopy. Furthermore, the conversion of the monolayer surface from non-ionic to cationic was accomplished by removal of 3-benzyloxycarbonyl group (Z group). The uniform monolayer on silica substrate and the changes occurring in the tethered monolayer were analyzed by atomic force microscopy (AFM). RNA aptamer with 72 sequences of nucleotides could be immobilized on the poly (L-lysine) cationic surface through electrostatic interaction. The superior recognition capability of RNA aptamer with specific microorganism is becoming a promising candidate in detection of bacteria. In this study, the binding of target bacteria, Sphingobium yanoikuyae, to the resulting RNA probe leads to a color change at the surface which is visually observed by real-time and confirmed through UV-reflective spectrophotometer. The RNA probes can be used as a high efficiency and versatile tool to visually sense the bacterial contamination in the food products. q

Functional Nucleic Acid Sensors

“…In the presence of the bacteria (1 × 10 5 cfu/mL), the film turned orange due to changes in the thickness of the film. 470…”

Visible detection of biotin by thin-film interference: thickness control through exchange reaction of biotin/dethiobiotin–avidin bonding

“…Previously, we have demonstrated that a silica thin-film constructed on a silicon substrate showed interference color change when bacteria and protein adsorbed on it. [13][14][15][16] Adsorption of bacteria of a sub-micron scale gave a visible color change, which was not only observed by spectrum measurement, but was also seen by the naked eye. On the other hand, adsorption of small molecules on the nanometre scale, such as antigens and peptides, gave little color change, which was only observed by spectrum measurement.…”

Nucleic Acids as Detection Tools

“…Another polymer-based approach uses artificial polypeptides as a color reporting group [167,168]. Peptides with modified groups (e.g.…”

“…This is known as structural color because light is reflected based on nanostructures and does not require color pigments. In a sensor reported by Yokogawa and co-workers, lysine-based polymers made from E-benzyloxycarbonyl-L-lysine are immobilized on a silica substrate [167,168]. To modulate the polymer structure, an RNA aptamer for Sphingobium bacteria is absorbed on the cationic polypeptide surface.…”