Single Plasmon-Active Optical Fiber Probe for Instantaneous Chiral Detection

Water Evaporation-Driven Arginine Enantiomer Recognition on a Self-Powered Flexible Chip with High Specificity

Chiral recognition is a crucial issue in the biomedical and pharmaceutical research communities. Due to the need for expensive equipment, reagents, and external energy, enantiomer identification is difficult to perform outside of a laboratory. Based on water evaporation-induced hydrovoltaic effect, a power-free sensing platform with sensitive chiral recognition capability is proposed for the discrimination of enantiomers. The chiral recognizer was bovine serum albumin (BSA), a naturally occurring protein. Using arginine (Arg) enantiomers as the sensing targets, the difference in enantioselectivity between l-Arg and d-Arg on a BSA-modified porous carbon substrate can be measured directly from the output voltage. By combining the cyclization reaction between NO and O-phenylenediamine (OPD), it has been discovered that the sensitivity and specificity of enantioselective identification can be significantly enhanced based on the surface charges. The limit of detection (LOD) could be as low as 76.0 nM. In addition, the proposed chips are extremely flexible and can function under deformation without sacrificing output performance. This self-powered chiral recognition chip paves a new path for the detection of chiral molecules at any time, any place, and it also has excellent potential for use in flexible wearable technology.

Construction of an enzyme-based all-fiber SPR biosensor for detection of enantiomers

Chiral analysis of amino acids (AAs) is of great importance in medical science due to the distinctive effect of AA isomers on human health. Although various chiral recognition techniques have been developed, the quantitative chiral recognition of low-level AA isomers remains challenging. Here, we combined the fiber optic SPR with an enzyme-substrate recognition mechanism to construct a direct-assay-type chiral AA biosensor. As a proof-of-concept attempt, a recently discovered Rasamsonia emersonii D-amino acid oxidase (ReDAAO) with a wide substrate spectrum and high stability was immobilized on the graphene oxide and gold nanorods composites (GO-AuNRs), using both EDC/NHS coupling and the gold-binding peptide (GBP) method. Such a biosensor can distinguish two AA isomers at the same concentration. It achieved specific detection of D-amino acids (D-AAs) with a linear range from 5x10^-4 mM to 30 mM. Furthermore, it showed good resistance to enantiomeric interference. When the percentage of D-AA increases in the isomer mixture, a good linear relationship between the D/(D + L)-AA ratio and SPR spectral shift was obtained. This unique combination of the enzyme, nanocomposite, and SPR taps into the rich reservoir of proteins for chiral receptors. It lays the foundation for protein-based chiral recognition of other clinically important small molecules in future biosensor designs.

High-performance plasmonic lab-on-fiber sensing system constructed by universal polymer assisted transfer technique

Plasmonic lab-on-fiber (LOF) system has become an emerging sensing platform for the realization of miniaturized and portable plasmonic sensors. Herein, a facile and efficient polymer assisted transfer technique was reported for the preparation of plasmonic LOF systems. The proposed plasmonic LOF system was constructed through transferring plasmonic arrays to the end surface of optical fibers using polylactic acid as the sacrificial layer. The morphology of the transferred plasmonic arrays maintains excellent consistency with the original arrays. Importantly, the as-prepared plasmonic LOF system also possesses outstanding sensing performance in refractive index sensing and quantitative label-free biosensing applications. Additionally, the proposed polymer assisted transfer technique shows broad universality for various plasmonic arrays. Together with the above features, it is believed that the polymer assisted transfer technique will show great potential for the application of future plasmonic LOF systems.

Conceptual Developments of Aryldiazonium Salts as Modifiers for Gold Colloids and Surfaces

Modified colloids and flat surfaces occupy an important place in materials science research due to their widespread applications. Interest in the development of modifiers that adhere strongly to surfaces relates to the need for stability under ambient conditions in many applications. Diazonium salts have evolved as the primary choice for the modification of surfaces. The term "diazonics" has been introduced in the literature to describe "the science and technology of aryldiazonium salt-derived materials". The facile reduction of diazonium salts via chemical or electrochemical processes, irradiation stimuli, or spontaneously results in the efficient modification of gold surfaces. Robust gold-aryl nanoparticles, where gold is connected to the aryl ring through bonding to carbon and films modified by using diazonium salts, are critical in electronics, sensors, medical implants, and materials for power sources. Experimental and theoretical studies suggest that gold-carbon interactions constructed via chemical reactions with diazonium salts are stronger than nondiazonium surface modifiers. This invited feature article summarizes the conceptual development of recent studies of diazonium salts in our laboratories and others with a focus on the surface modification of gold nanostructures, flat surfaces and gratings, and their applications in nanomedicine engineering, sensors, energy, forensic science, and catalysis.