No abstract

We report a label-free and simple approach for the detection of glycoprotein-120 (gp-120) using an aptamer-based liquid crystals (LCs) biosensing platform. The LCs are supported on the surface of a modified glass slide with a suitable amount of B40t77 aptamer, allowing the LCs to be homeotropically aligned. A pronounced topological change was observed on the surface due to a specific interaction between B40t77 and gp-120, which led to the disruption of the homeotropic alignment of LCs. This results in a dark-to-bright transition observed under a polarized optical microscope. With the developed biosensing platform, it was possible to not only identify gp-120, but obtained results were analyzed quantitatively through image analysis. The detection limit of the proposed biosensing platform was investigated to be 0.2 µg/mL of gp-120. Regarding selectivity of the developed platform, no response could be detected when gp-120 was replaced by other proteins, such as bovine serum albumin (BSA), hepatitis A virus capsid protein 1 (Hep A VP1) and immunoglobulin G protein (IgG). Due to attributes such as label-free, high specificity and no need for instrumental read-out, the presented biosensing platform provides the potential to develop a working device for the quick detection of HIV-1 gp-120.

Surface protein gp-120 of HIV-1 virus plays an important role in the infection of HIV-1, but detection of gp-120 during the early stage of infection is very difficult. Herein, we report a binding bioassay based on an RNA aptamer B40t77, which binds specifically to gp-120. The bioassay is built upon a hydrophobic glass slide with surface immobilized gp-120. When the glass surface is incubated in a solution containing B40t77, the aptamer is able to bind to gp-120 specifically and remove it from the surface after a short incubation time of 30 min. The result of the binding event can be amplified by using liquid crystal (LC) into optical signals in the final step. By using this bioassay, we are able to detect as low as 1 μg/ml of gp-120 with high specificity within 30 min. No response is obtained when gp-120 is replaced by other protein such as bovine serum albumin (BSA). This is the first qualitative bioassay which provides a simple way for the detection of gp-120 with the naked eye. The assay is robust, low-cost and does not require additional labeling. Thus, the bioassay is potentially useful for the early detection of HIV-1 in resources-limited regions.

In this study, Ag@In2O3 modified nickel foam (NF) was reported for its role as a non-enzymatic glucose sensor. Ag@In2O3 was prepared by a simple two-step method; preparation of a metal-organic framework (MOF) MIL-68(In) by solvothermal method, entrapment of Ag + by adding AgNO3 then drying it for 2 h to complete the entrapment process and subsequent calcination at 650°C for 3 h. The Ag@In2O3 modified NF was employed as a non-enzymatic glucose sensor to determine glucose concentrations in an alkaline medium. Two linear ranges were obtained from Ag@In2O3 modified electrode, i.e., 10 μM to 0.8 mM and 0.8–2.16 mM with a sensitivity of 3.31 mA mM−1 cm−2 and 1.51 mA mM−1 cm−2 respectively, with a detection limit of 0.49 µM. Ag@In2O3 modified NF exhibited high selectivity for glucose, among other interfering agents.

In the present study, a functional template made up of in situ synthesised gold nanoparticles (AuNPs) is prepared on polydimethylsiloxane (PDMS) for patterning of target protein onto the desired solid substrates. Unlike previous studies in which bioreceptor probes are randomly attached to the PDMS stamp through electrostatic interactions, herein, we propose an AuNPs–PDMS stamp, which provides a surface for the attachment of thiol-modified biorecognition probes to link to the stamp surface through a dative bond with a single anchoring point based on thiol chemistry. By using this platform, we have developed the ability for microcontact printing (µCP) to selectively capture and transfer target protein onto solid surfaces for detection purposes. After µCP, we also investigated whether liquid crystals (LCs) could be used as a label-free approach for identifying transfer protein. Our reported approach provides promise for biosensing of various analytes.