Revealing the Binding Events of Single Proteins on Exosomes Using Nanocavity Antennas beyond Zero-Mode Waveguides.

Exosomes (EXOs) play a crucial role in biological action mechanisms. Understanding the biological process of single-molecule interactions on the surface of the EXO membrane is essential for elucidating the precise function of the EXO receptor. However, due to dimensional incompatibility, monitoring the binding events between EXOs of tens to hundreds of nanometers and biomolecules of nanometers using existing nanostructure antennas is difficult. Unlike the typical zero-mode waveguides (ZMWs), this work presents a nanocavity antenna (λvNAs) formed by nanocavities with diameters close to the visible light wavelength dimensions. Effective excitation volumes suitable for observing single-molecule fluorescence were generated in nanocavities of larger diameters than typical ZMWs; the optimal signal-to-noise ratio obtained was 19.5 when the diameter was 300 nm and the incident angle was ∼50°. EXOs with a size of 50-150 nm were loaded into λvNAs with an optimized diameter of 300-500 nm, resulting in appreciable occupancy rates that overcame the nanocavity size limitation for large-volume biomaterial loading. Additionally, this method identified the binding events between the single transmembrane CD9 proteins on the EXO surface and their monoclonal antibody anti-CD9, demonstrating that λvNAs expanded the application range beyond subwavelength ZMWs. Furthermore, the λvNAs provide a platform for obtaining in-depth knowledge of the interactions of single molecules with biomaterials ranging in size from tens to hundreds of nanometers.

Integrated microdevice with a windmill-like hole array for the clog-free, efficient, and self-mixing enrichment of circulating tumor cells.

Circulating tumor cells (CTCs) have tremendous potential to indicate disease progression and monitor therapeutic response using minimally invasive approaches. Considering the limitations of affinity strategies based on their cost, effectiveness, and simplicity, size-based enrichment methods that involve low-cost, label-free, and relatively simple protocols have been further promoted. Nevertheless, the key challenges of these methods are clogging issues and cell aggregation, which reduce the recovery rates and purity. Inspired by the natural phenomenon that the airflow around a windmill is disturbed, in this study, a windmill-like hole array on the SU-8 membrane was designed to perturb the fluid such that cells in a fluid would be able to self-mix and that the pressure acting on cells or the membrane would be dispersed to allow a greater velocity. In addition, based on the advantages of fluid coatings, a lipid coating was used to modify the membrane surface to prevent cell aggregation and clogging of the holes. Under the optimal conditions, recovery rates of 93% and 90% were found for A549 and HeLa cells in a clinical simulation test of our platform with a CTC concentration of 20-100 cells per milliliter of blood. The white blood cell (WBC) depletion rate was 98.7% (n = 15), and the CTC detection limit was less than 10 cells per milliliter of blood (n = 6). Moreover, compared with conventional membrane filtration, the advantages of the proposed device for the rapid (2 mL/min) and efficient enrichment of CTCs without clogging were shown both experimentally and theoretically. Due to its advantages in the efficient, rapid, uniform, and clog-free enrichment of CTCs, our platform offers great potential for metastatic detection and therapy analyses.

Correction: Design and fabrication of a microfluidic chip to detect tumor markers.

[This corrects the article DOI: 10.1039/D0RA06693A.].

A simple and rapid method for blood plasma separation driven by capillary force with an application in protein detection.

Blood plasma separation is a vital sample pre-treatment procedure for microfluidic devices in blood diagnostics, and it requires reliability and speediness. In this work, we propose a novel and simple method for microvolume blood plasma separation driven by capillary force. Flat-shaped filter membranes combined with hydrophilic narrow capillaries are introduced into devices, in order to reduce the residual volumes of blood plasma. An interference fit is used to ensure no leakage of blood or cells. There is desired trapping efficiency of blood cells in the devices. The method provides high efficiency with a plasma extraction yield of 71.7% within 6 min, using 60 µL of undiluted whole human blood with 45% haematocrit. The influence from structural parameters on the separation kinetics and the dependence of the haematocrit levels on the separation efficiency are also investigated. The total protein detection shows considerable protein recovery of 82.3% in the extracted plasma. Thus, the plasma separation unit with a very simple structure is suitable for integrating into microfluidic devices, presenting promising prospects for clinical diagnostics as well as for point-of-care testing applications.

Design and fabrication of a microfluidic chip to detect tumor markers.

A microfluidic chip based on capillary infiltration was designed to detect tumor markers. Serum samples flowed along a microchannel that used capillary force to drive sample injection, biochemical reactions and waste liquid collection. This permitted us to realize rapid qualitative detection of tumor markers and other biological molecules. The chip integrated a number of microfluidic functions including blood plasma separation, microvalve operation, and antibody immobilization. Using antigen-antibody reaction principles, the chip provided highly selective and sensitive detection of markers. Combining a microfluidic chip with immunoassays not only improved the antigen-antibody reaction speed, but also reduced the consumption of samples and reagents. The experimental results showed that the chip can achieve separation of trace whole blood, control of sample flow rate, and detection of alpha fetoprotein, thus providing preliminary verification of its feasibility and potential for clinical use. In summary, in this paper a cheap, mass-produced, and portable microfluidic chip for cancer detection, which has good prospects for practical use during disease diagnosis and screening is reported.

Fabrication and improved photoelectrochemical properties of a transferred GaN-based thin film with InGaN/GaN layers.

Herein, a lift-off mesoporous GaN-based thin film, which consisted of a strong phase-separated InGaN/GaN layer and an n-GaN layer, was fabricated via an electrochemical etching method in a hydrofluoric acid (HF) solution for the first time and then transferred onto quartz or n-Si substrates, acting as photoanodes during photoelectrochemical (PEC) water splitting in a 1 M NaCl aqueous solution. Compared to the as-grown GaN-based film, the transferred GaN-based thin films possess higher and blue-shifted light emission, presumably resulting from an increase in the surface area and stress relaxation in the InGaN/GaN layer embedded on the mesoporous n-GaN. The properties such as (i) high photoconversion efficiency, (ii) low turn-on voltage (-0.79 V versus Ag/AgCl), and (iii) outstanding stability enable the transferred films to have excellent PEC water splitting ability. Furthermore, as compared to the film transferred onto the quartz substrate, the film transferred onto the n-Si substrate exhibits higher photoconversion efficiency (2.99% at -0.10 V) due to holes (h+) in the mesoporous n-GaN layer that originate from the n-Si substrate.