Slow Flow Rate Research Articles

Sparged but not stirred: Rapid, ADH-NADH oxidase catalyzed deracemization of alcohols in a bubble column

We investigate in detail both the deracemization reaction rate and maximum conversion of (R,S)-1-phenylethanol in a bubble column and the deactivation rates of both enzymes involved, alcohol dehydrogenase (ADH) and NADH oxidase (nox2). Instead of the predicted ellipsoidal shape of the bubbles, we observe a spherical shape in all our experiments. Calculated values for the area-specific mass transfer coefficient kLa in sparged, but not stirred, solution ranged from 17 to 87 h−1. We find that minimizing the air–liquid interface over time results in the lowest rate of nox2 deactivation. The onset of nox2 dissociation beyond the initial 50 h correlates with a tenfold increase in the observed deactivation rate constant. The highest conversion (99%) for deracemizing 50 mM (R,S)-1-phenylethanol was reached in the shortest reaction time (6 h) if large air bubbles (diameter 2.6 mm) at slow flowrates (5 bubbles/s) were employed. A faster flowrate, which delivers more oxygen per unit time, increased the initial reaction rate but resulted in a slower rate at higher conversions and ultimately incomplete maximum conversion (94%). Reaction rates under sparging were 4–8 times faster than in quiescent solution. Lastly, stirring did not significantly aid conversion (41% vs 37% in quiescent solution after 12 h) but caused increased enzyme deactivation (44 h vs 136 h half-life quiescent solution).

A lateral flow immunoassay with self-sufficient microfluidic system for enhanced detection of thyroid-stimulating hormone

We report a self-sufficient microfluidic paper-based lateral flow immunoassay device (μLFD) for highly sensitive detection of the thyroid-stimulating hormone (TSH). Fabrication of the paper microchannels involves engraving the nitrocellulose membrane with a CO2 laser to create narrow flow paths, which constrain the fluid flow over the test zone. The proposed microchannel modified devices were studied for detection of the TSH using gold nanoparticles as labels. The effect of such microchannel modified LFDs has led to an improvement in sensitivity by nine times and the limit of detection by 6.6 times due to the slow flow rate of the sample compared with the traditional LFD. In addition, the binding of gold nanoparticles over the test line is more uniform in the case of the μLFD, thus minimizing leading-edge effects, resulting in more accurate quantitative analysis. The proposed strategy offers great potential for multiplex detection of biomarkers with increased sensitivity without introducing any hydrophobic materials to the LFD.

Combined use of rotational and excimer lASER coronary atherectomy (RASER) during complex coronary angioplasty-An analysis of cases (2006-2016) from the British Cardiovascular Intervention Society database.

Combining rotational (RA) and excimer laser coronary atherectomy (ELCA)-RASER atherectomy-is technique utilized in the percutaneous management of calcific coronary disease. The evidence base examining its safety and utility is sparse and limited to small case-series. This study examines the patterns and outcomes of RASER atherectomy use in the largest cohort to date. Using the British Cardiac Intervention Society database, data were analyzed on all PCI procedures in the UK between 2006 and 2016. Descriptive statistics and multivariate logistic regressions were used to examine baseline, procedural, and outcome associations with RASER. We identified 153 (0.02%) RASER atherectomy cases out of 686,358 PCI procedures. Baseline covariates associated with RASER use were age, BMI, diabetes, stable coronary disease, and previous CABG. Procedural co-variates associated with RASER were CTO-PCI, the use of more/longer stents, intravascular imaging, cutting balloons, and microcatheters. Adjusted rates of in-hospital major adverse cardiac/cerebrovascular events (MACCE) were not significantly different with RASER. However, there were higher odds of arterial complications (OR 3.23, 95% CI: 1.58-6.61), slow flow (OR 3.50, 95% CI: 1.29-9.55), and shock induction (OR 9.66, 95% CI: 3.44-27.06). RASER atherectomy use in complex PCI is associated with higher risk baseline and procedural characteristics. Although increased rates of shock induction, slow flow, and arterial complications were observed, RASER does not increase the likelihood of in-hospital MACCE, major bleeding, or death.

Tuning Size and Morphology of mPEG-b-p(HPMA-Bz) Copolymer Self-Assemblies Using Microfluidics.

The careful design of nanoparticles, in terms of size and morphology, is of great importance to developing effective drug delivery systems. The ability to precisely tailor nanoparticles in size and morphology during polymer self-assembly was therefore investigated. Four poly(ethylene glycol)-b-poly(N-2-benzoyloxypropyl methacrylamide) mPEG-b-p(HPMA-Bz) block copolymers with a fixed hydrophilic block of mPEG 5 kDa and a varying molecular weight of the hydrophobic p(HPMA-Bz) block (A: 17.1, B: 10.0, C: 5.2 and D: 2.7 kDa) were self-assembled into nanoparticles by nanoprecipitation under well-defined flow conditions, using microfluidics, at different concentrations. The nanoparticles from polymer A, increased in size from 55 to 90 nm using lower polymer concentrations and slower flow rates and even polymer vesicles were formed along with micelles. Similarly, nanoparticles from polymer D increased in size from 35 to 70 nm at slower flow rates and also formed vesicles along with micelles, regardless of the used concentration. Differently, polymers B and C mainly self-assembled into micelles at the different applied flow rates with negligible size difference. In conclusion, this study demonstrates that the self-assembly of mPEG-b-p(HPMA-Bz) block copolymers can be easily tailored in size and morphology using microfluidics and is therefore an attractive option for further scaled-up production activities.

Oiling‐Out Crystallization of Beta‐Alanine on Solid Surfaces Controlled by Solvent Exchange

AbstractIn this work, the solvent‐exchange crystallization processes of beta‐alanine in mixture of isopropanol and water on solid surfaces are reported. As the antisolvent isopropanol displaces the alanine solution pre‐filled in a microchamber, liquid–liquid phase separation occurs at the mixing front. The alanine‐rich subphase forms surface microdroplets that subsequently crystallize with during the solvent exchange. It is found that the flow rates and solid surfaces have significant influence on the droplet size, growth rate, and crystal size and morphology. At fast flow rates, the droplets solidify rapidly, forming spherical‐cap structures resembling the shape of droplets, in contrast to crystal microdomains or thin films formed at slow flow rates. On a highly hydrophilic surface, the crystals form thin film without droplets formation. It is further demonstrated that by the solvent exchange, the crystals, generated by using a stock solution with a very low concentration of the precursor, can be used as seeds to facilitate crystallization in bulk solution. The results suggest that the solvent exchange has the potential to be an effective approach for controlling oiling‐out crystallization, and to be wider applied in, such as, separation and purification of many food, medical, and therapeutic ingredients.

DIALYSIS DISEQUILIBRIUM SYNDROME: A RARE CAUSE OF DELIRIUM IN THE ICU

SESSION TITLE: Medical Student/Resident Critical Care Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Delirium is common in the hospital setting with rates up to 70% in the medical intensive care unit. It can be due to multiple etiologies. Here we describe a case of dialysis disequilibrium syndrome (DDS) associated with hemodialysis for acute hyperkalemia. CASE PRESENTATION: A 55 year-old male with past medical history of heart failure, diabetes mellitus and end-stage renal disease presented to the emergency room after a mechanical fall. His last hemodialysis was 2 days prior. On examination, he was alert and oriented to time, place, and person without headache, nausea or vomiting. Laboratory values were notable for a sodium of 140 mEq/L, potassium of 7.3 mEq/L, BUN 114 mg/dL. EKG showed peaked T waves. He was admitted to the MICU for acute hyperkalemia and urgent hemodialysis at a blood flow rate of 400ml/minute for 3.5 hours with 1.6L of ultrafiltration. Three hours after completion of dialysis, he became confused and delirious. Over the next few hours, he became more agitated with incomprehensible speech and inability to answer questions appropriately. Repeat labs showed a sodium of 136 mEq/L, BUN of 25 mg/dL, Ammonia of 36 umol/L and glucose of 125 mg/dl. CT head was performed to rule out subdural hematoma in the setting of a fall, however, it was normal. Toxicology screen as well as infectious work up were negative. Given the acute onset of mental status changes after hemodialysis with a drastic decrease in BUN, and excluding all possible causes, a working diagnosis of Dialysis Disequilibrium Syndrome was made. Dialysis was held for one day with improvement in patient's mental status. He was able to follow commands without any delirium. BUN showed a steady increase from 25 to 64 mg/dL. Hemodialysis was re-initiated at a slower blood flow rate of 200 ml/minute which the patient tolerated without any complications and no further episodes of delirium. DISCUSSION: DDS is caused by water movement into the brain due to a transient osmotic gradient from the rapid removal of small solutes such as urea, which causes cerebral edema. It is generally seen in patients undergoing dialysis for the first time or if they are undergoing dialysis after a long period of time. Most of the symptoms are self-limited. However, one must be cautious to restart hemodialysis at a slower flow rate since there have been cases that resulted in death. CONCLUSIONS: DDS is an increasingly rare syndrome and one must consider this after excluding all other causes of acute delirium. Early detection and management is associated with favorable outcomes. Reference #1: Mistry K. Dialysis disequilibrium syndrome prevention and management. Int J Nephrol Renovasc Dis. 2019;12:69-77 DISCLOSURES: No relevant relationships by Hung-I Liao, source=Web Response No relevant relationships by Avantika Nathani, source=Web Response

The Guarani Aquifer System – from regional reserves to local use

The Guarani Aquifer System is a massive groundwater body underlying large areas of Brazil, Paraguay, Uruguay and Argentina, with a thickness of 50–600 m (averaging about 250 m). It is one of the world's largest sandstone aquifers. The mainly weakly-cemented sandstones were formed by aeolian, fluvial and lacustrine continental deposition during the Triassic–Jurassic period and are overlain by extensive Cretaceous basalt lava-flows. The system is totally storage-dominated, with recharge amounting to only about 0.2% of the estimated 30 000 km 3 of water stored. Using 14 C and 81 Kr techniques, it was possible to confirm extremely slow flow rates, with groundwater older than 730 000 years BP in some parts of São Paulo State, Brazil. The vast regional freshwater storage contrasts sharply with localized active flow systems of recharge areas, which are strongly impacted by land-use change. The aquifer is the best known and most exploited in São Paulo State (80% of total extraction) and the experience of groundwater use for the supply of Ribeirão Preto and São José do Rio Preto (both with populations of over 0.5 million), together with one transboundary urban area, will be summarized. Thematic collection: This article is part of the Hydrogeology of Sandstone collection available at: https://www.lyellcollection.org/cc/hydrogeology-of-sandstone

In silico optimization of targeted aerosol delivery in upper airways via Inhaled Volume Tracking

BackgroundDespite the widespread use of aerosol inhalation as a drug delivery method, targeted delivery to the upper airways remains an ongoing challenge in the quest for improved clinical response in respiratory disease. MethodsHere, we examine in silico flow and particle dynamics when using an oral Inhaled Volume Tracking manoeuvre. A short pulsed aerosol bolus is injected during slow inhalation flow rates followed by clean air, and a breath-hold is initiated once it reaches the desired depth. We explore the fate of a broad particle size range (1–40 μm) for both upright and supine positions. FindingsOur findings illustrate that despite attempts to mitigate dispersion using slower flow rates, the laryngeal jet disperses the aerosol bolus and thus remains a hurdle for efficient targeted delivery. Nevertheless, we show a decrease in extra-thoracic deposition; large aerosols in the range of 10–30 μm potentially outperform existing inhalation methods, showing deposition fractions of up to 80% in an upright orientation. InterpretationThe improved deposition during Inhaled Volume Tracking shows promise for clinical applications and could be leveraged to deliver larger payloads to the upper airways.

Effect of electrospinning parameters on the morphology of polyurethane/polycaprolactone fibers

Introduction: Electrospinning is now being widely used as a potential tool for tissue engineering to manufacturing tissue grafts, wound dressings, medical fabrics, and drug delivery systems. Regarding biomaterials, polyurethane (PU) and polycaprolactone (PCL) and their combination are prospective candidates for the fabrication of electrospun membranes used in tissue engineering due to their suitable biocompatibility, biodegradability, and mechanical properties. Thus, this study investigates how to manipulate the electrospinning process of PU/PCL to obtain nanofibers with desired features.
 Methods: PU/PCL dissolved in N,N-Dimethylformamide, and tetrahydrofuran were electrospun with various applied voltages, tip-to-collector distances, and flow rates. The collected membranes were observed using a scanning electron microscope to evaluate the effect of electrospinning conditions on their morphology and fiber diameters.
 Results: Slower flow rate, longer tip-to-collector distance, and higher voltage all led to smaller, more uniform fibers. By manipulating these factors, the study yielded a non-woven, porous membrane with uniform, separated nanofibers at the condition set of 12 cm tip-to-collector, 20 kV applied, and 0.5 mL/h flow rate.
 Conclusion: The study determined the effect of electrospinning parameters on the morphology of polycaprolactone/polyurethane fibers and obtained membrane with suitable properties for further research.

Evaluation of the van Deemter equation in terms of open-ended flow to chromatography.

Plate theory and adsorption theory are the main tools available for understanding chromatographic experiments. Both theories predict a Gaussian distribution of solute molecules within the tubular system. However, Gaussian concentration distributions are observed predominantly at slow linear flow rates, while asymmetric concentration distributions are observed at the linear flow rates most used in chromatography. Allegedly, this asymmetry originates from an inhomogeneous distribution of grain sizes in the column and column overload. However, it is an experimental fact that the distribution of chemicals within an injected volume of solute changes as a function of time, while the response is measured simultaneously. Accordingly, the obtained signal cannot be compared to the theory before some type of time-based deconvolution of the data has been performed. Adjustments to high-performance liquid chromatography data were thus proposed through empirical equations that describe the relevant time values, peak height, peak area, and parameters of the van Deemter equation. It was proposed that the transfer of solute from the front to the rear part of the pulse during laminar open-ended flow occurs at rate that depends on the linear flow rate, and to a lesser extent, on properties of the response function.

Coupled effect of flow velocity and structural heterogeneity on transport and release of kaolinite colloids in saturated porous media.

Understanding the behavior and fate of clay colloids in water-saturated porous media is critical to assess its environmental impact and potential risk since clay is commonly a carrier of many contaminants. Column experiments with four-packing configurations were designed to understand the coupled effects of column structural heterogeneity and the flow velocity on the transport and fate of kaolinite colloids in the saturated porous media. The results showed that the structural heterogeneity could have facilitated the transport of kaolinite colloids in saturated porous media. For the columns with strong heterogeneity, the preferential flow paths led to an early breakthrough of kaolinite. Only few kaolinite colloids were released with slow flow rate; however, the released peak concentration and release percentage of kaolinite colloids had further increased with the high flow velocity. In the layered column, there was significant kaolinite's retention at the interface where water passed from fine to coarse quartz sand. All results indicated that both flow rates and media characteristics played an important role in controlling kaolinite's fate and transport in porous media. A thorough understanding of these processes had an important significance for pollution control in subsurface natural environment where heterogeneous soil and variation in flow pattern are usually common.

P1055REMARKABLE REMOVALS OF BETA-2-MICROGLOBULIN AND PHOSPHATE WITH SHORT-DAILY HOME HEMODIALYSIS USING LOW DIALYSATE FLOW RATE

Abstract Background and Aims Short-daily hemodialysis (HD) with low-dialysate volume is an appealing portable dialysis approach for home use. Although this type of HD has proved being effective for the volume control and the clearance of low molecular-weight uremic toxins, limited data are available on the impact on the removal rates of other uremic toxins like β2-microglobulin (β2M) or phosphate (P), whose clearance is limited by sequestration into compartments, poor diffusion, high time-dependency, or protein binding. We evaluated the impact of short-daily HD with slow dialysate flow rate on the removal of solutes of different molecular weights and distribution volumes. Method Single-session and weekly balances of β2M, P, urea, and creatinine were prospectively assessed with total dialysate collection and serum measurements before and after 341 dialysis sessions (mean dialysate volume: 30963 ± 862 mL; mean length of dialysis session: 153 ± 8 min) in 31 stable patients (female; 9, 29 %; mean age: 55.6 ± 13.6 y; dry weight: 74.9 ± 13.3 kg) undergoing short-daily home HD with NxStage cycler, between July 2014 and October 2019. The mean blood flow rate was 365 ± 17 mL/min, whereas the mean dialysate flow rate was 194 ± 12 mL/min. Results Single-session β2M, P, urea, and creatinine removals were 0.138 ± 0.050 g, 0.610 ± 0.161 g, 18.89 ± 6.07 g and 1.07 ± 0.31 g, respectively, whereas the reduction rates (%) were 38.0 ± 13.0, 46.8 ± 8.6, 48.2 ± 7.0 and 46.6 ± 6.6, for β2M, P, urea and creatinine, respectively. The estimated weekly β2M, P, urea and creatinine removals in HDD patients dialyzing 5-6 days per week were comparable with 4-h in-center thrice-weekly on-line hemodiafiltration according to previous studies (Table 1). Conclusion Treating patients with short-daily HD with low-dialysate volume at a 5-6 days per week prescription may achieve an efficient weekly β2M and P removal.

Chemiluminescence imaging immunoassay for simultaneous determination of TBBPA-DHEE and TBBPA-MHEE in aquatic environments.

The environmental concentration of tetrabromobisphenol A bis(2-hydroxyethyl) ether (TBBPA-DHEE) and tetrabromobisphenol A mono(hydroxyethyl) ether (TBBPA-MHEE), as some of themain derivatives and byproducts of tetrabromobisphenol A (TBBPA), are obscure due to lacking available analytical methods. In the present study, a multiplexed competitive chemiluminescent imaging immunoassay (CLIIA) based on specific monoclonal antibody respectively against TBBPA-MHEE and TBBPA-DHEE has been developed for the simultaneous detection of the two targets. To improve the sensitivity of immunoassay, Au nanoparticles (AuNPs) were utilized as solid support for loading horseradish peroxidase, labeled to obtain the multi-enzyme particles. Under the optimized conditions, the limits of detection (LODs) for TBBPA-MHEE and TBBPA-DHEE were 1.85ng/mL and 2.05ng/mL, respectively. After estimating its accuracy and precision, the established method was applied for investigation of the contaminants at the inner rivers in Zhenjiang, Jiangsu Province. Our results indicated that no TBBPA-MHEE was found in all 11 water samples and two samples of TBBPA-DHEE were detectedup to 6.34ng/mL, possibly ascribed to the dense population and slow flow rate around the sampling site. Graphical abstract.

Inflammatory and Hematological Indices as Simple, Practical Severity Predictors of Microdysfunction Following Coronary Intervention: A Systematic Review and Meta-Analysis.

C-reactive protein (CRP) and high-sensitivity CRP (hsCRP), along with a series of hematological indices, platelet to lymphocyte ratio (PLR), neutrophil to lymphocyte ratio (NLR), mean platelet volume (MPV), platelet distribution width (PDW), and red blood cell distribution width (RDW), are regarded to be related to the incidence of no-reflow or slow flow. Clinical studies were retrieved from the electronic databases of PubMed, EMBASE, Google Scholar, Clinical Trials, and science direct from their inception to August 24, 2019. A total of 21 studies involving 7403 patients were included in the meta-analysis. Pooled analysis results revealed patients with higher hsCRP (odds ratio [OR] = 1.03, 95% confidence interval [CI], 1.01-1.05, P = .006), hsCRP (OR = 1.04, 95% CI: 1.0-1.08, P = .012), NLR (OR = 1.23, 95% CI: 1.11-1.37, P < .0001), PLR (OR = 1.13, 95% CI: 1.07-1.20, P < .0001), and MPV (OR = 2.13, 95% CI: 1.57-2.90, P < .0001) all exhibited significantly higher no-reflow incidence, but there was no significant association between no-reflow risk and RDW or PDW. Patients with higher CRP/hsCRP also performed higher rate of slow flow (OR = 1.06, 95% CI: 1.01-1.11, P = .018). Preangiographic CRP/hsCRP could independently predict no-reflow and slow flow. Moreover, some hematological indices are associated with no-flow.

Characterization of a river at risk: the case of Sapangdaku River in Toledo City, Cebu, Philippines

Sapangdaku River in Toledo City, Cebu is a freshwater source found near a copper mine operating for more than 50 years. The river has been one of the major rivers identified by the Environmental Management Bureau to be at risk, that needs monitoring and more empirical studies. This paper assessed the water quality of the Sapangdaku River through physicochemical, metal, and microbial analyses. Five (5) samples were collected from the downstream, midstream, and upstream sites, and were immediately tested in a water laboratory. Findings revealed that the pH, DO, BOD and COD registered within the acceptable range. Conductivity, turbidity, TDS, and TSS have fluctuating results where the midstream area recorded the highest measurement for the first three and upstream for the latter. Hg and Pb are present in little amounts while Cu in high concentrations. Total coliform counts are low in midstream and upstream while fecal coliform counts are high in all sites. Higher conductivity, higher turbidity, slower flow rate, and cooler condition in the midstream, as well as the presence of more pathogenic bacteria and Cu across sites, indicate poor water quality. Though there is poor quality, the DO, BOD, and COD levels of the river show promising results that aquatic life can still thrive. Educating communities, decreasing means of erosion, and establishing strict policies and ordinances on the use of river resources are recommended.

Development and evaluation of a dynamic powder splitting system for the directed energy deposition (DED) process

A dynamic powder splitting system (DPSS) was developed to overcome a slow powder flow rate (PFR) response in conventional powder delivery systems used in the Directed Energy Deposition (DED) additive manufacturing process. Complementary to the main powder delivery system, the DPSS uses a custom valve to split powder flow and cyclone separator to redirect powder flow that is not used in the cladding process. Its potential applications are compensation for clad height inconsistencies caused by machine feed rate errors and increase of powder usage efficiency via a powder recycling system. Various tests were performed to verify performance and cladding.

Production of 28 μm zirconium carbide kernels using the internal gelation process and microfluidics

Studies using internal gelation and microfluidics have shown that the production of sintered spheres with diameters below 200 μm is possible. The addition of carbon can be problematic because of slow flow rates (100 μL/min) and long run times (4 h). However, a solution of dispersed carbon, Cabot’s TPX-101, was successfully used with solutions of zirconyl nitrate, urea, and hexamethylenetetramine to make zirconium microspheres with carbon. A simple carbothermic reduction using a maximum temperature of 2073 K and ultrahigh purity argon produced zirconium carbide kernels with an average diameter of 28 μm and a standard deviation of 2.3 μm.

Adjuvant Hepatic Arterial Infusion Pump Chemotherapy After Resection of Colorectal Liver Metastases: Results of a Safety and Feasibility Study in The Netherlands

BackgroundThe 10-year overall survival with adjuvant hepatic arterial infusion pump (HAIP) chemotherapy after resection of colorectal liver metastases (CRLMs) was 61% in clinical trials from Memorial Sloan Kettering Cancer Center. A pilot study was performed to evaluate the safety and feasibility of adjuvant HAIP chemotherapy in patients with resectable CRLMs.Study DesignA phase II study was performed in two centers in The Netherlands. Patients with resectable CRLM without extrahepatic disease were eligible. All patients underwent complete resection and/or ablation of CRLMs and pump implantation. Safety was determined by the 90-day HAIP-related postoperative complications from the day of pump placement (Clavien–Dindo classification, grade III or higher) and feasibility by the successful administration of the first cycle of HAIP chemotherapy.ResultsA total of 20 patients, with a median age of 57 years (interquartile range [IQR] 51–64) were included. Grade III or higher HAIP-related postoperative complications were found in two patients (10%), both of whom had a reoperation (without laparotomy) to replace a pump with a slow flow rate or to reposition a flipped pump. No arterial bleeding, arterial dissection, arterial thrombosis, extrahepatic perfusion, pump pocket hematoma, or pump pocket infections were found within 90 days after surgery. After a median of 43 days (IQR 29–52) following surgery, all patients received the first dose of HAIP chemotherapy, which was completed uneventfully in all patients.ConclusionPump implantation is safe, and administration of HAIP chemotherapy is feasible, in patients with resectable CRLMs, after training of a dedicated multidisciplinary team.

Dimensional analysis and parametric studies of the microwell for particle trapping

Recently, the microwell has been widely used for cell trapping due to its simple design and enclosed microenvironment for on-chip cell culture and stimulation. In this paper, we investigated the effect of various geometrical factors on microwells for efficient particle analysis. We used the Arbitrary Lagrangian–Eulerian method to calculate the trajectory of particles entering circular and triangular microwells under various geometrical factors, particle size, and flow conditions. Our simulation results show that the W/L = 2 triangular microwell provides the best trapping efficiency due to a stronger recirculation vortex. A smaller particle size or slower flow rate also enhances particle trapping efficiency. To validate simulation results, we flowed 4.5, 6, and 10 µm diameter polystyrene beads into W/L = 1 circular, W/L = 1 and W/L = 2 triangular microwells under various flow rates. The experimental results agreed well with simulation results, showing that the occupancy of W/L = 2 triangular microwell was sevenfold and twofold higher than W/L = 1 circular and W/L = 1 triangular microwells, respectively. Overall, the above results can provide a useful guideline to design the microwell device for efficient hydrodynamic particle trapping, which can be applied to single cell analysis or rare cell capture.

Separation of monoclonal antibody charge variants using cation exchange chromatography: Resins and separation conditions optimization

The separation of charge variants is a challenge for the production of monoclonal antibodies (mAbs). Cation exchange chromatography (CEX) is normally used to accomplish this task. In this study, with IgG1-type mAb as the model protein, charge variants separation was investigated under various conditions including resins, elution mode, gradient slope and flow rate. The trade-off between main peak purity and recovery was focused to evaluate the separation performance. The results indicated that the diameter of resin particles was the critical factor. For SP Sepharose Fast Flow (90 μm diameter resin), the overlap between main peak and charge variants was too serious to meet the separation requirements. For Monomix MC30 SP (30 μm diameter resin), the purity of main peak was improved to 93.4% under 0.05 pH/CV and 100 cm/h. For Nano SP-15L (15 μm diameter resin), near 100% purity of main peak could be obtained with a recovery of 56.5% under 0.05 pH/CV and 100 cm/h. Two types of elution gradient, salt gradient and pH gradient, were compared and it was found that there was no obvious difference after the optimization and both showed some improvements with a shallower gradient. In addition, slower flow rate could improve the separation of main peak. In general, smaller resin particle size, shallower gradient slope and slower flow rate could improve the separation performance of main peak and charge variants under both salt gradient and pH gradient elution, which should be selected according to the actual requirements.