A High Efficiency, Low Resistance Antibacterial Filter Formed by Dopamine-Mediated In Situ Deposition of Silver onto Glass Fibers.

The coating of filter media with silver is typically achieved by chemical deposition and aerosol processes. Whilst useful, such approaches struggle to provide uniform coating and are prone to blockage. To address these issues, an in situ method for coating glass fibers is presented via the dopamine-mediated electroless metallization method, yielding filters with low air resistance and excellent antibacterial performance. It is found that the filtration efficiency of the filters is between 94 and 97% and much higher than that of silver-coated filters produced using conventional dipping methods (85%). Additionally, measured pressure drops ranged between 100 and 150 Pa, which are lower than those associated with dipped filters (171.1 Pa). Survival rates of Escherichia coli and Bacillus subtilis bacteria exposed to the filters decreased to 0 and 15.7%±1.49, respectively after 2 h, with no bacteria surviving after 6 h. In contrast, survival rates of E. coli and B. subtilis bacteria on the uncoated filters are 92.5% and 89.5% after 6 h. Taken together, these results confirm that the in situ deposition of silver onto fiber surfaces effectively reduces pore clogging, yielding low air resistance filters that can be applied for microbial filtration and inhibition in a range of environments.

Ultrahigh-Throughput, Real-Time Flow Cytometry for Rare Cell Quantification from Whole Blood.

We present an ultrahigh-throughput, real-time fluorescence cytometer comprising a viscoelastic microfluidic system and a complementary metal-oxide-semiconductor (CMOS) linear image sensor-based detection system. The flow cytometer allows for real-time quantification of a variety of fluorescence species, including micrometer-sized particles and cells, at analytical throughputs in excess of 400,000 species per second. The platform integrates a custom C++ control program and graphical user interface (GUI) to allow for the processing of raw signals, adjustment of processing parameters, and display of fluorescence intensity histograms in real time. To demonstrate the efficacy of the platform for rare event detection and its utility as a basic clinical tool, we measure and quantify patient-derived circulating tumor cells (CTCs) in peripheral blood, realizing that detection has a sensitivity of 6 CTCs per million blood cells (0.000006%) with a volumetric throughput of over 3 mL/min.

Direct isolation of small extracellular vesicles from human blood using viscoelastic microfluidics.

Small extracellular vesicles (sEVs; <200 nm) that contain lipids, nucleic acids, and proteins are considered promising biomarkers for a wide variety of diseases. Conventional methods for sEV isolation from blood are incompatible with routine clinical workflows, significantly hampering the utilization of blood-derived sEVs in clinical settings. Here, we present a simple, viscoelastic-based microfluidic platform for label-free isolation of sEVs from human blood. The separation performance of the device is assessed by isolating fluorescent sEVs from whole blood, demonstrating purities and recovery rates of over 97 and 87%, respectively. Significantly, our viscoelastic-based microfluidic method also provides for a remarkable increase in sEV yield compared to gold-standard ultracentrifugation, with proteomic profiles of blood-derived sEVs purified by both methods showing similar protein compositions. To demonstrate the clinical utility of the approach, we isolate sEVs from blood samples of 20 patients with cancer and 20 healthy donors, demonstrating that elevated sEV concentrations can be observed in blood derived from patients with cancer.

Plasmofluidic-Based Near-Field Optical Trapping of Dielectric Nano-Objects Using Gold Nanoislands Sensor Chips.

Near-field optical manipulation has been widely used for guiding and trapping nanoscale objects close to an optical-active interface. This near-field manipulation opens opportunities for next-generation biosensing with the capability of large-area trapping and in situ detection. In this article, we used the finite element method (FEM) to analyze the motion mechanism of nano-objects (50-500 nm) in the near-field optics, especially localized surface plasmon resonance (LSPR). The size-dependent optical forces and hydrodynamic forces of subwavelength nanoparticles (<500 nm) in different hydrodynamic velocity fields were calculated. When the strength of the local electric field was increased, LSPR with two-dimensional gold nanoislands (AuNIs) showed improved capability for manipulating nano-objects near the vicinity of the AuNI interface. Through the experiments of in situ interferometric testing 50-500 nm nano-objects with constant number concentration or volume fraction, it was confirmed that the local plasmonic near-field was able to trap the dielectric polystyrene beads smaller than 200 nm. The plasmofluidic system was further verified by testing biological nanovesicles such as exosomes (40-200 nm) and high- and low-density lipoproteins (10-200 nm). This concept of direct dielectric nano-objects manipulation enables large-scale parallel trapping and dynamic sensing of biological nanovesicles without the need of molecular binding tethers or labeling.

DropCRISPR: A LAMP-Cas12a based digital method for ultrasensitive detection of nucleic acid.

Since their discovery, CRISPR/Cas systems have been extensively exploited in nucleic acid biosensing. However, the vast majority of contemporary platforms offer only qualitative detection of nucleic acid, and fail to realize ultrasensitive quantitative detection. Herein, we report a digital droplet-based platform (DropCRISPR), which combines loop-mediated isothermal amplification (LAMP) with CRISPR/Cas12a to realize ultrasensitive and quantitative detection of nucleic acids. This is achieved through a novel two-step microfluidic system which combines droplet LAMP with a picoinjector capable of injecting the required CRISPR/Cas12a reagents into each droplet. This method circumvents the temperature incompatibilities of LAMP and CRISPR/Cas12a and avoids mutual interference between amplification reaction and CRISPR detection. Ultrasensitive detection (at fM level) was achieved for a model plasmid containing the invA gene of Salmonella typhimurium (St), with detection down to 102 cfu/mL being achieved in pure bacterial culture. Additionally, we demonstrate that the DropCRISPR platform is capable of detecting St in raw milk samples without additional nucleic acid extraction. The sensitivity and robustness of the DropCRISPR further demonstrates the potential of CRISPR/Cas-based diagnostic platforms, particularly when combined with state-of-the-art microfluidic architectures.

Automatic detection of particle size distribution by image analysis based on local adaptive canny edge detection and modified circular Hough transform.

To obtain size distribution of nanoparticles, scanning electron microscope (SEM) and transmission electron microscopy (TEM) have been widely adopted, but manual measurement of statistical size distributions from the SEM or TEM images is time-consuming and labor-intensive. Therefore, automatic detection methods are desirable. This paper proposes an automatic image processing algorithm which is mainly based on local adaptive Canny edge detection and modified circular Hough transform. The proposed algorithm can utilize the local thresholds to detect particles from the images with different degrees of complexity. Compared with the results produced by applying global thresholds, our algorithm performs much better. The robustness and reliability of this method have been verified by comparing its results with manual measurement, and an excellent agreement has been found. The proposed method can accurately recognize the particles with high efficiency.