Enantioselective Circular Dichroism Sensing of Cysteine and Glutathione with Gold Nanorods

Enantioselective analysis of biological thiols, including cysteine (Cys) and glutathione (GSH), is extremely important because of their unique role in bioentities. Here we demonstrated that the end-to-end assemblies of plasmonic gold nanorods with chiral Cys or GSH can be used as a distinctive chiroptical sensor for reliable determination of the absolute configuration of Cys and GSH at the visible light region. The end-to-end assemblies of Au nanorods induced by Cys or GSH exhibit strong circular dichroism (CD) signals in the region of 500–850 nm, which is attributed to chiral current inside Au nanorods induced by the mixed biothiols. The CD intensity of the assemblies shows good linearity with the amount of Cys and GSH. The limit of detection for Cys and GSH using end-to-end assemblies is at micromolar concentrations. In addition, the sensing system exhibits good selectively toward Cys and GSH in the presence of other amino acids

Commercial flow cytometer counting results for the mixed RBC and HepG2 cells.

<p>The absolute counts of RBC and HepG2 are 1054 and 978 with the ratio of RBC/HepG2 by 51.9%:48.1% = 1.08: 1.</p

Paper-Based Analytical Devices Relying on Visible-Light-Enhanced Glucose/Air Biofuel Cells

A strategy that combines visible-light-enhanced biofuel cells (BFCs) and electrochemical immunosensor into paper-based analytical devices was proposed for sensitive detection of the carbohydrate antigen 15-3 (CA15-3). The gold nanoparticle modified paper electrode with large surface area and good conductibility was applied as an effective matrix for primary antibodies. The glucose dehydrogenase (GDH) modified gold–silver bimetallic nanoparticles were used as bioanodic biocatalyst and signal magnification label. Poly­(terthiophene) (pTTh), a photoresponsive conducting polymer, served as catalyst in cathode for the reduction of oxygen upon illumination by visible light. In the bioanode, electrons were generated through the oxidation of glucose catalyzed by GDH. The amount of electrons is determined by the amount of GDH, which finally depended on the amount of CA15-3. In the cathode, electrons from the bioanode could combine with the generated holes in the HOMO energy level of cathode catalysts pTTh. Meanwhile, the high energy level photoexcited electrons were generated in the LUMO energy level and involved in the oxygen reduction reaction, finally resulting in an increasing current and a decreasing overpotential. According to the current signal, simple and efficient detection of CA15-3 was achieved

Different contact imaging systems without optical lens.

<p>(A) Static contact imaging system. (B) Microfluidic contact imaging system with capillary flow. (C) The proposed microfluidic contact-imaging cytometer system with continuous flow: (C1) bonding process; (C2) overall system structure.</p

Comparison of counting results of different microbead concentration solutions between the developed microfluidic cytometer and the commercial flow cytometer.

<p>(A) Measurement results correlate well between the developed system and the commercial one (y = 0.97x-8, correlation coefficient = 0.996). (B) The Bland-Altman analysis of the measurement results between the developed one and the commercial one show a mean bias of −13.6 uL⁻¹, the lower 95% limit of agreement by −61.0 uL⁻¹, and the upper 95% limit of agreement by 33.8 uL⁻¹.</p

Comparison of concentration measurement results for 6 µm microbead solution between the developed microfluidic cytometer and the commercial flow cytometer.

<p>The average counting result of the developed microfluidic cytometer matched well with that of the commercial cytometer with 8% error.</p

ELM-SR on-line testing results for HepG2 and RBC cells.

<p>The resolution is improved by 4× after ELM-SR processing. (A) The HepG2 on-line testing image and the recovered SR image. (B) The RBC on-line testing image and the recovered SR image. (C) The comparison of MSSIM for different SR images obtained under different training models. The detected HepG2 and RBC can be correctly categorized to its type as the SR image recovered by corresponding ELM-SR model produces a larger MSSIM when compared to each cell HR library. The scale bar indicates 5 µm.</p

Metal-Enhanced Ratiometric Fluorescence/Naked Eye Bimodal Biosensor for Lead Ions Analysis with Bifunctional Nanocomposite Probes

A novel metal-enhanced ratiometric fluorescence/naked eye bimodal biosensor based on ZnFe₂O₄@Au–Ag bifunctional nanocomposite and DNA/CeO₂ complex for lead ions (Pb²⁺) has been successfully developed. The nanocomposite probe was composed of a magnetic ZnFe₂O₄ core and a Au–Ag hollow nanocube shell. Upon bioconjugation, bifunctional magnetic nanocomposites could not only make the probe possess excellent recyclability but also provide an enrichment of “hot spots” for surface enhanced fluorescence detection of Pb²⁺ by a metal-enhanced fluorescence effect. Typically, the bifunctional nanocomposites conjugated with double-stranded DNA (included Pb²⁺-specific DNAzyme strand and corresponding substrate strand) to form a Pb²⁺ biosensor. Nanoceria as a fluorescence quencher strongly adsorbed DNA. Therefore, the formation of double-stranded DNA brought the labeled nitrogen sulfur doped carbon dots (N,S-CDs) and CeO₂ into close proximity, which significantly quenched the fluorescence of N,S-CDs. The presence of Pb²⁺ led to the breakage of the DNAzyme strand, resulting in the fluorescence signal of Cy3 decreasing, while the fluorescence intensity of N,S-CDs aggrandized. First, a preliminary test of Pb²⁺ was performed by the naked eye. The disengaged DNA/CeO₂ complex could result in color change after adding H₂O₂ because of autocatalysis of CeO₂, resulting in real-time visual detection of Pb²⁺. If further accurate determination was required, the fluorescence intensity ratio of these two fluorescence indicators was measured at 562 and 424 nm (<i>I</i>₅₆₂/<i>I</i>₄₂₄). A good linear correlation exists between the log­(<i>I</i>₅₆₂/<i>I</i>₄₂₄) and the logarithm of Pb²⁺ concentrations ranging from 10^–12 to 3 × 10^–6 M. Remarkably, the detection limit of this ratiometric biosensor was 3 × 10^–13 M, which ascribed to its superior fluorescence enhancement. Interestingly, the developed bifunctional nanocomposite probe manifests good recyclability and selectivity. More importantly, the biosensor provided potential application of on-site and real-time unknown Pb²⁺ ions in real systems

Measured RBC and HepG2 counting results of the developed microfluidic cytometer with ELM-SR based cell recognition.

<p>Measured RBC and HepG2 counting results of the developed microfluidic cytometer with ELM-SR based cell recognition.</p

Microfluidic contact-imaging cytometer system for flowing cell detection, recognition and counting.

<p>(A) Cell shadow image by contact imaging. (B) Captured video of flowing cells. (C) CMOS image sensor board schematic with external controls. (D) System board of the developed microfluidic cytometer.</p