High throughput viscoelastic particle focusing and separation in spiral microchannels

Passive particle manipulation using inertial and elasto-inertial microfluidics have received substantial interest in recent years and have found various applications in high throughput particle sorting and separation. For separation applications, elasto-inertial microfluidics has thus far been applied at substantial lower flow rates as compared to inertial microfluidics. In this work, we explore viscoelastic particle focusing and separation in spiral channels at two orders of magnitude higher Reynolds numbers than previously reported. We show that the balance between dominant inertial lift force, dean drag force and elastic force enables stable 3D particle focusing at dynamically high Reynolds numbers. Using a two-turn spiral, we show that particles, initially pinched towards the inner wall using an elasticity enhancer, PEO (polyethylene oxide), as sheath migrate towards the outer wall strictly based on size and can be effectively separated with high precision. As a proof of principle for high resolution particle separation, 15 µm particles were effectively separated from 10 µm particles. A separation efficiency of 98% for the 10 µm and 97% for the 15 µm particles was achieved. Furthermore, we demonstrate sheath-less, high throughput, separation using a novel integrated two-spiral device and achieved a separation efficiency of 89% for the 10 µm and 99% for the 15 µm particles at a sample flow rate of 1 mL/min—a throughput previously only reported for inertial microfluidics. We anticipate the ability to precisely control particles in 3D at extremely high flow rates will open up several applications, including the development of ultra-high throughput microflow cytometers and high-resolution separation of rare cells for point of care diagnostics.

Capturing structural changes of the S1 to S2 transition of photosystem II using time-resolved serial femtosecond crystallography

Photosystem II (PSII) catalyzes light-induced water oxidation through an S i -state cycle, leading to the generation of di-oxygen, protons and electrons. Pump–probe time-resolved serial femtosecond crystallography (TR-SFX) has been used to capture structural dynamics of light-sensitive proteins. In this approach, it is crucial to avoid light contamination in the samples when analyzing a particular reaction intermediate. Here, a method for determining a condition that avoids light contamination of the PSII microcrystals while minimizing sample consumption in TR-SFX is described. By swapping the pump and probe pulses with a very short delay between them, the structural changes that occur during the S1-to-S2 transition were examined and a boundary of the excitation region was accurately determined. With the sample flow rate and concomitant illumination conditions determined, the S2-state structure of PSII could be analyzed at room temperature, revealing the structural changes that occur during the S1-to-S2 transition at ambient temperature. Though the structure of the manganese cluster was similar to previous studies, the behaviors of the water molecules in the two channels (O1 and O4 channels) were found to be different. By comparing with the previous studies performed at low temperature or with a different delay time, the possible channels for water inlet and structural changes important for the water-splitting reaction were revealed.

High Throughput Viscoelastic Particle Focusing and Separation in Spiral Microchannels

Passive particle manipulation using inertial and elasto-inertial microfluidics have received substantial interest in recent years and have found various applications in high throughput particle sorting and separation. For separation applications, elasto-inertial microfluidics has thus far been applied at substantial lower flow rates as compared to inertial microfluidics. In this work, we explore viscoelastic particle focusing and separation in spiral channels at two orders of magnitude higher Reynolds numbers than previously reported. We show that the balance between dominant inertial lift force, dean drag force and elastic force enables stable 3D particle focusing at dynamically high Reynolds numbers. Using a two-turn spiral, we show that particles, initially pinched towards the inner wall using an elasticity enhancer, PEO (polyethylene oxide), as sheath migrate towards the outer wall strictly based on size and can be effectively separated with high precision. As a proof of principle for high resolution particle separation, 15 µm particles were effectively separated from 10 µm particles. A separation efficiency of 98% for the 10 µm and 97% for the 15µm particles was achieved. Furthermore, we demonstrate sheath-less, high throughput, separation using a novel integrated two-spiral device and achieved a separation efficiency of 89% for the 10 µm and 99% for the 15µm particles at a sample flow rate of 1 mL/ml – a throughput previously only reported for inertial microfluidics. We anticipate the ability to precisely control particles in 3D at extremely high flow rates will open up several applications, including the development of ultra-high throughput microflow cytometers and high-resolution separation of rare cells for point of care diagnostics.

Analysis of Multi-Hit Crystals in Serial Synchrotron Crystallography Experiments Using High-Viscosity Injectors

Serial Synchrotron Crystallography (SSX) is rapidly emerging as a promising technique for collecting data for time-resolved structural studies or for performing room temperature micro-crystallography measurements using micro-focused beamlines. SSX is often performed using high frame rate detectors in combination with continuous sample scanning or high-viscosity or liquid jet injectors. When performed using ultra-bright X-ray Free Electron Laser (XFEL) sources serial crystallography typically involves a process known as ’diffract-and-destroy’ where each crystal is measured just once before it is destroyed by the intense XFEL pulse. In SSX, however, particularly when using high-viscosity injectors (HVIs) such as Lipidico, the crystal can be intercepted multiple times by the X-ray beam prior to exiting the interaction region. This has a number of important consequences for SSX including whether these multiple-hits can be incorporated into the data analysis or whether they need to be excluded due to the potential impact of radiation damage. Here, we investigate the occurrence and characteristics of multiple hits on single crystals using SSX with lipidico. SSX data are collected from crystals as they tumble within a high viscous stream of silicone grease flowing through a micro-focused X-ray beam. We confirmed that, using the Eiger 16M, we are able to collect up to 42 frames of data from the same single crystal prior to it leaving the X-ray interaction region. The frequency and occurrence of multiple hits may be controlled by varying the sample flow rate and X-ray beam size. Calculations of the absorbed dose confirm that these crystals are likely to undergo radiation damage but that nonetheless incorporating multiple hits into damage-free data should lead to a significant reduction in the number of crystals required for structural analysis when compared to just looking at a single diffraction pattern from each crystal.

Microencapsulation of Clostridium tyrobutyricum by Spray drying Method and Its Characteristics in-vitro

Present study was conducted to improve microencapsulation process of Clostridium tyrobutyricum (Ct) by optimizing process parameters to improve its in-vitro characteristics over that of free cells. All process parameters including wall material (w/v concentration: modified starch 3-7%; gelatin 2-6%; maltodextrin 3-7%), sample flow rate (250-450 mLh-1) and inlet air temperature (105-145°C) were analysed through single factor analysis. Response surface design test was used to develop multiple quadratic regression equations to fit the functional relationship between factors and response values and to choose the optimal conditions. The optimal conditions for maximum survival rate (82.030%) of encapsulated Ct were: 4% gelatin, 5% modified starch and 5% maltodextrin concentration with sample flow rate of 350 mLh-1 at inlet air temperature of 105°C. Encapsulation reduced the survival loss of Ct from 1.990 to 1.080 lgCFUg-1 under strong acidic condition (pH1) than free Ct. Survival loss of free Ct was 31.914% more than encapsulated Ct under high temperature treatment (90°C). Similarly, protected Ct showed higher survival rate under simulated gastric condition with long storage life. Encapsulation of Ct through optimized spray drying method efficiently improved its survival rate under strong acidic or high temperature environment with safe transit through gastrointestinal tract and also eradicates the technological limitations which preventing the use of many probiotic strains

Simultaneous Extraction and Determination of Allura Red (E129) and Brilliant Blue FCF (E133) in Foodstuffs by Column Solid-Phase Spectrophotometry

Background: Allura Red (AR) and Brilliant Blue FCF (BB) are highly water-soluble synthetic food dyes used to color baked goods, beverages, candies, jellies, sausages, etc. Although AR and BB are not entirely toxic, they can lead to health problems in humans. Objective: The aim of the study was to develop a column solid-phase extraction (SPE) and preconcentration method based on the adsorption on a Diaion HP-20 polymeric resin for simultaneous spectrophotometric determination of AR and BB. Methods: The column SPE method was used, and the analytical parameters of the SPE method, such as pH, sample flow rate, sample volume, etc., were systematically investigated and optimized. Results: The detection limits of AR and BB ranged between 0.90 and 0.19 μg/L and quantification limits between 2.59 and 0.53 μg/L, respectively. Preconcentration factors were obtained at 80 and 100 for AR and BB, respectively. The RSDs of the method were lower than 4% for both dyes. The method was successfully applied to foodstuffs. AR and BB contents in foodstuffs were determined between 9.48–407.34 and 2.96–137.12 μg/g, respectively, for solid samples; 52.28 and 5.91 μg/mL of dye contents of liquid samples were determined for AR and BB, respectively. Conclusions: Satisfactory recoveries show that the method will be more useful for future food quality and control applications. Highlights: The developed method exhibited simplicity and reliable, simultaneous determination of AR and BB in foodstuffs.

DESENVOLVIMENTO DE METODOLOGIA EM SISTEMA EM FLUXO PARA DETERMINAÇÃO DE CD USANDO ERVA MATE E CHÁ PRETO COMO ADSORVENTE E ESPECTROMETRIA DE ABSORÇÃO ATÔMICA EM CHAMA

In this study new methods for determination of cadmium in certified biological samples using mate (llex paraguariensis) and black tea (Camellia sinensis, L.) as biosorbents in an on-line preconcentration system coupled to flame atomic absorption spectrometry was developed. Flow and chemical variables of the proposed system were optimized through multivariate designs. Sample pH, buffer concentration, sample flow rate and biosorbents mass were the selected variables. The limit of detection for cadmium was 0.98 μg L-1 with a precision below 3.6% (35 μg L-1, n=6) for mate biosorbent and 0.97 μg L-1 with a precision below 4.4% (35 μg L-1, n=7) for black tea biosorvent. For both biosorbents the analytical curves were linear from 5 to 50 μg L-1, with a correlation coefficient of 0.9995. The developed methods were successfully applied to certified reference materials (pig kidney and human hair).

Dynamic Absorption and Desorption Properties of HPD722 Macroporous Resin for Flavonoids in Emilia sonchifolia Extract

The impact of HPD722 macroporous resin on the dynamic adsorption and desorption of flavonoids in Emilia Sonchifolia extract is studied. The diameter-height ratio of macroporous resin column is 1:10; the mass concentration of the sample solution is selected to be 50.00 mg•mL-1; while the sample flow rate is 3.00mL min-1; upon dynamic absorption for once, the absorption rate reaches 81.11%; with adoption of 50mL ethanol at a volume ratio of 60% as the desorption agent, the desorption flow rate comes to 3.00mL•min-1; and the desorption rate of flavonoids attains 85.26%. Under optimal conditions, the content of flavonoids increases from 6.05% to 32.65% upon purification by HPD722 macroporous resin.

Purification of Total Flavonoids from Buddleja officinalis by AB-8 Macroporous Adsorption Resin

The separation and purification of total flavonoids from Buddleja officinalis were carried out by AB-8 macroporous adsorption resin. The optimum adsorption conditions for sample flow rate, pH value and feeding concentration were 2.0 mL/min, 4.5 and 1.6 mg/mL, respectively, and the optimum desorption conditions were obtained by using 2.0 BV of 70% ethanol as desorption solvent at a flow rate of 1.0 mL/min. Under these conditions, the flavonoids content of the final product was 90.43%, increased by 1.7 times than unpurified sample (53.09%).