The HDI + ROPE decision rule is logically incoherent but we can fix it.

The Bayesian highest-density interval plus region of practical equivalence (HDI + ROPE) decision rule is an increasingly common approach to testing null parameter values. The decision procedure involves a comparison between a posterior highest-density interval (HDI) and a prespecified region of practical equivalence. One then accepts or rejects the null parameter value depending on the overlap (or lack thereof) between these intervals. Here, we demonstrate, both theoretically and through examples, that this procedure is logically incoherent. Because the HDI is not transformation invariant, the ultimate inferential decision depends on statistically arbitrary and scientifically irrelevant properties of the statistical model. The incoherence arises from a common confusion between probability density and probability proper. The HDI + ROPE procedure relies on characterizing posterior densities as opposed to being based directly on probability. We conclude with recommendations for alternative Bayesian testing procedures that do not exhibit this pathology and provide a "quick fix" in the form of quantile intervals. This article is the work of the authors and is reformatted from the original, which was published under a CC-BY Attribution 4.0 International license and is available at https://psyarxiv.com/5p2qt/. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Electrophoretic Microfluidic Characterization of mRNA- and pDNA-Loaded Lipid Nanoparticles.

Lipid nanoparticles (LNPs) are clinically advanced nonviral gene delivery vehicles with a demonstrated ability to address viral, oncological, and genetic diseases. However, the further development of LNP therapies requires rapid analytical techniques to support their development and manufacturing. The method developed and described in this paper presents an approach to rapidly and accurately analyze LNPs for optimized therapeutic loading by utilizing an electrophoresis microfluidic platform to analyze the composition of LNPs with different clinical lipid compositions (Onpattro, Comirnaty, and Spikevax) and nucleic acid (plasmid DNA (pDNA) and messenger RNA (mRNA)) formulations. This method enables the high-throughput screening of LNPs using a 96- or 384-well plate with approximate times of 2-4 min per sample using a total volume of 11 µL. The lipid analysis requires concentrations approximately between 109 and 1010 particles/mL and has an average precision error of 10.4% and a prediction error of 19.1% when compared to using a NanoSight, while the nucleic acid analysis requires low concentrations of 1.17 ng/µL for pDNA and 0.17 ng/µL for mRNA and has an average precision error of 4.8% and a prediction error of 9.4% when compared to using a PicoGreen and RiboGreen assay. In addition, our method quantifies the relative concentration of nucleic acid per LNP. Utilizing this approach, we observed an average of 263 ± 62.2 mRNA per LNP and 126.3 ± 21.2 pDNA per LNP for the LNP formulations used in this study, where the accuracy of these estimations is dependent on reference standards. We foresee the utility of this technique in the high-throughput characterization of LNPs during manufacturing and formulation research and development.

Assessment of pDNA isoforms using microfluidic electrophoresis.

The recent rise in nucleic acid-based vaccines and therapies has resulted in an increased demand for plasmid DNA (pDNA). As a result, there is added pressure to streamline the manufacturing of these vectors, particularly their design and construction, which is currently considered a bottleneck. A significant challenge in optimizing pDNA production is the lack of high-throughput and rapid analytical methods to support the numerous samples produced during the iterative plasmid construction step and for batch-to-batch purity monitoring. pDNA is generally present as one of three isoforms: supercoiled, linear, or open circular. Depending on the ultimate use, the desired isoform may be supercoiled in the initial stages for cell transfection or linear in the case of mRNA synthesis. Here, we present a high-throughput microfluidic electrophoresis method capable of detecting the three pDNA isoforms and determining the size and concentration of the predominant supercoiled and linear isoforms from 2 to 7 kb. The limit of detection of the method is 0.1 ng/µL for the supercoiled and linear isoforms and 0.5 ng/µL for the open circular isoform, with a maximum loading capacity of 10-15 ng/µL. The turnaround time is 1 min/sample, and the volume requirement is 10 µL, making the method suitable for process optimization and batch-to-batch analysis. The results presented in this study will enhance the understanding of electrophoretic transport in microscale systems dependent on molecular conformations and potentially aid technological advances in diverse areas relevant to microfluidic devices.

Microfluidic AAV Purity Characterization: New Insights into Serotype and Sample Treatment Variability.

Despite recent advances in nucleic acid delivery systems with the success of LNP vehicles, adeno-associated virus (AAV) remains the leading platform for targeted gene delivery due to its low immunogenicity to humans, high transduction efficiency, and range of serotypes with varying tropisms. Depending on the therapeutic goals and serotype used, different production conditions may be more amenable, generating an ever-growing need for rapid yet robust analytical techniques to support the high-quality manufacturing of AAV. A critical bottleneck exists for assessing full capsids where rapid, high-throughput techniques capable of analyzing a range of serotypes are needed. Here, we present a rapid, high-throughput analytical technique, microfluidic electrophoresis, for the assessment of full capsids compatible with AAV1, AAV2, AAV6, AAV8, and AAV9 without the need for assay modifications or optimizations, and AAV5 with some constraints. The method presented in this study uses a mathematical formulation we developed previously with a reference standard to combine the independently obtained capsid protein and single-stranded DNA (ssDNA) profiles to estimate the percentage of full capsids in a sample of unknown concentration. We assessed the ability to use a single serotype (AAV8) as the reference standard regardless of the serotype of the sample being analyzed so long as the melting temperature (Tm) of the capsids is within 12 °C from the Tm of AAV8. Using this method, we are able to characterize samples ±6.1% with an average analytical turnaround time of <5 min/sample, using only 10 µL/sample at a concentration of 2.5 × 1012 VG/mL.

Enzymatic isolation and microfluidic electrophoresis analysis of residual dsRNA impurities in mRNA vaccines and therapeutics.

The versatility, rapid development, and ease of production scalability of mRNA therapeutics have placed them at the forefront of biopharmaceutical research. However, despite their vast potential to treat diseases, their novelty comes with unsolved analytical challenges. A key challenge in ensuring sample purity has been monitoring residual, immunostimulatory dsRNA impurities generated during the in vitro transcription of mRNA. Here, we present a method that combines an enzyme, S1 nuclease, to identify and isolate dsRNA from an mRNA sample with a microfluidic electrophoresis analytical platform to characterize the impurity. After the method was developed and optimized, it was tested with clinically relevant, pseudouridine-modified 700 and 1800 bp dsRNA and 818-4451 nt mRNA samples. While the treatment impacted the magnitude of the fluorescent signal used to analyze the samples due to the interference of the buffer with the labeling of the sample, this signal loss was mitigated by 8.8× via treatment optimization. In addition, despite the mRNA concentration being up to 400× greater than that of the dsRNA, under every condition, there was a complete disappearance of the main mRNA peak. While the mRNA peak was digested, the dsRNA fragments remained physically unaffected by the treatment, with no change to their migration time. Using these samples, we detected 0.25% dsRNA impurities in mRNA samples using 15 µL with an analytical runtime of 1 min per sample after digestion and were able to predict their size within 8% of the expected length. The short runtime, sample consumption, and high throughput compatibility make it suitable to support the purity assessment of mRNA during purification and downstream.

A Rare Giant Nasofrontal Meningoencephalocele with Nasal and Visual Obstruction.

The encephalocele is a malformation that is manifested by the protrusion of brain tissue through a defect in the skull. The meningoencephalocele contains the meninges and brain tissue. Frontoethmoidal or nasal meningoencephalocele is rare; the frequency is approximately one in 40,000 live births. Three subtypes are currently known: nasoethmoid, nasofrontal, and nasoorbital. The authors report the clinical case of a 2-month-old girl with a very rare giant nasofrontal meningoencephalocele, which affected vision and breathing. The patient underwent surgery at an early age to avoid significant functional sequelae and promote the normal development and growth of the girl.

Identification, Formation, and Occurrence of Perlolyrine: A ß-Carboline Alkaloid with a Furan Moiety in Foods.

ß-Carbolines are naturally occurring bioactive alkaloids found in foods and in vivo. This research reports the identification, characterization, mechanism of formation, and occurrence of perlolyrine (1-(5-(hydroxymethyl)furan-2-yl)-9H-pyrido[3,4-b]indole), a ß-carboline with a furan moiety. Perlolyrine did not arise from l-tryptophan and hydroxymethylfurfural but from the reaction of l-tryptophan with 3-deoxyglucosone, an intermediate of carbohydrate degradation. The mechanism of formation occurs through 3,4-dihydro-ß-carboline-3-carboxylic acid intermediates (imines), followed by the oxidation of C1'-OH to ketoimine and oxidative decarboxylation at C-3, along with dehydration and cyclization to afford the ß-carboline with a furan moiety. The formation of perlolyrine was favored in acidic conditions and temperatures in the range of 70-110 °C. Perlolyrine occurred in the reactions of tryptophan with carbohydrates. The formation rate from fructose was much higher than from glucose. Sucrose also gave perlolyrine under acidic conditions and heating. Perlolyrine was identified in many foods by HPLC-MS and analyzed by HPLC-fluorescence. It occurred in many processed foods such as tomato products including tomato puree, fried tomato, ketchups, tomato juices, and jams but also in soy sauce, beer, balsamic vinegar, fruit juices, dried fruits, fried onion, and honey. The concentrations ranged from an undetected amount to 3.5 µg/g with the highest average levels found in tomato concentrate (1.9 µg/g) and soy sauce (1.5 µg/mL). The results show that perlolyrine formed during the heating process of foods. It is concluded that perlolyrine is widely present in foods and it is daily ingested in the diet.

A microfluidic electrophoretic dual dynamic staining method for the identification and relative quantitation of dsRNA contaminants in mRNA vaccines.

mRNA vaccines (i.e., COVID-19 vaccine) offer various advantages over traditional vaccines in preventing and reducing disease and shortening the time between pathogen discovery and vaccine creation. Production of mRNA vaccines results in several nucleic acid and enzymatic by-products, most of which can be detected and removed; however, double-stranded RNA (dsRNA) contaminants pose a particular challenge. Current purification and detection platforms for dsRNA vary in effectiveness, with problems in scalability for mass mRNA vaccine production. Effectively detecting dsRNA is crucial in ensuring the safety and efficacy of the vaccines, as these strands can cause autoimmune reactions with length-symptom dependency and enhance mRNA degradation. We present a new microfluidics method to rapidly identify and quantify dsRNA fragments in mRNA samples. Our innovation exploits the differences in the dynamic staining behavior between mRNA and dsRNA molecules to detect dsRNA contaminants in a high throughput approach. The limit of detection of the system for dsRNA was estimated to be between 17.7-76.6 pg µL-1 with a maximum loading capacity of mRNA of 12.99 ng µL-1. Based on these estimated values, our method allows for the detection of dsRNA contaminants present in percentages as low as 0.14-0.59% compared to the total mRNA concentration. Here, we discuss the molecular mechanism of the dynamic staining behavior of dsRNA and mRNA for two different stains. We believe our method will accelerate the mRNA vaccine development from initial development to quality control workflows.

Reconstrucción escrotal con colgajo pediculado del músculo gracilis bilateral e injerto de piel parcial / Scrotal reconstruction with bilateral gracilis muscle pedicled flap and split-thickness skin graft

Los defectos en la región escrotal son producidos en la mayoría de los casos por la gangrena de Fournier, y en ocasiones por traumatismo o patologías oncológicas. Estas heridas generan mucha dificultad para el desarrollo de una vida normal a los pacientes que lo padecen; por lo general producen dolor, los testículos quedan desprotegidos y la espermatogénesis puede verse alterada. Actualmente no existe un método estándar de reconstrucción escrotal, y las técnicas tradicionalmente utilizadas no ofrecen una cobertura funcional ni estética. Generalmente producen mucho abultamiento en la región genital, que puede dificultar el movimiento de las piernas y el uso de pantalones. En este trabajo se expone una opción quirúrgica para reconstruir el escroto, por medio del colgajo pediculado de músculo gracilis bilateral e injerto de piel parcial. Para tal efecto, se presenta un caso clínico de un paciente de 64 años con secuelas en la región perineal, posterior a una gangrena de Fournier. El paciente presentaba una pérdida total del escroto y exposición de ambos testículos. El método arriba mencionado es una opción válida para reconstruir el escroto y en este trabajo se describe la técnica empleada de forma detallada, donde se puede apreciar que presenta escasas complicaciones y es fácil de reproducir por un cirujano plástico entrenado.

Defects in the scrotal region are caused in most cases by Fournier's gangrene, and sometimes by trauma or oncological pathologies. These wounds generate difficulties for the development of a normal life; They usually produce pain; the testicles are unprotected and spermatogenesis can be altered. Currently there is no standard method of scrotal reconstruction, and the techniques traditionally used do not offer functional or aesthetic coverage. They generally produce a big bulge in the genital region, which can make it hard to move the legs and wear pants. A surgical option is exposed to reconstruct the scrotum, by means of the bilateral gracilis muscle pedicled flap and split-thickness skin graft. For this purpose, a clinical case of a 64-year-old patient with sequelae in the perineal region, after Fournier's gangrene, is presented. The patient presented a total loss of the scrotum and exposure of both testicles. The method mentioned above is a valid option to reconstruct the scrotum and the technique used is described in detail, where it can be seen that it is easy to reproduce by a trained plastic surgeon.

An Optimized CoBRA Method for the Microfluidic Electrophoresis Detection of Breast Cancer Associated RASSF1 Methylation.

Although breast cancer screening assays exist, many are inaccessible and have high turnaround times, leaving a significant need for better alternatives. Hypermethylation of tumor suppressor genes is a common epigenetic marker of breast cancer. Methylation tends to occur most frequently in the promoter and first exon regions of genes. Preliminary screening tests are crucial for informing patients whether they should pursue more involved testing. We selected RASSF1, previously demonstrated to be aberrantly methylated in liquid biopsies from breast cancer patients, as our gene of interest. Using CoBRA as our method for methylation quantification, we designed unique primer sets that amplify a portion of the CpG island spanning the 5' end of the RASSF1 first exon. We integrated the CoBRA approach with a microfluidics-based electrophoresis quantification system (LabChip) and optimized the assay such that insightful results could be obtained without post-PCR purification or concentration, two steps traditionally included in CoBRA assays. Circumventing these steps resulted in a decreased turnaround time and mitigated the laboratory machinery and reagent requirements. Our streamlined technique has an estimated limit of detection of 9.1 ng/µL of input DNA and was able to quantify methylation with an average error of 4.3%.

Electrophoresis-Mediated Characterization of Full and Empty Adeno-Associated Virus Capsids.

Adeno-associated virus (AAV) has shown great potential in gene therapy due to its low immunogenicity, lack of pathogenicity to humans, and ability to provide long-term gene expression in vivo. However, there is currently a need for fast, high-throughput characterization systems that require low volumes for the determination of its sample composition in terms of full and empty capsids since empty capsids are a natural byproduct of AAV synthesis. To address this need, the following study proposes a high-throughput electrophoresis-mediated microfluidics approach that is independent of sample input concentration to estimate the composition of a given sample by combining its protein and ssDNA information relative to a standard. Using this novel approach, we were able to estimate the percentage of full capsids of six AAV8 samples with an average deviation from the actual percentage of 4%. The experiments used for these estimations were conducted with samples of varying percentages of full capsids (21-75%) and varying concentrations (5 × 1011-1 × 1012 VP/mL) with a total volume requirement of 3-10 µL for triplicate analysis of the sample. This method offers a rapid way to evaluate the quality and purity of AAV products. We believe that our method addresses the critical need as recognized by the gene and molecular therapy community.

Formation, Characterization, and Occurrence of ß-Carboline Alkaloids Derived from α-Dicarbonyl Compounds and l-Tryptophan.

ß-Carbolines (ßCs) are naturally occurring bioactive alkaloids, whereas α-dicarbonyl compounds are reactive substances generated in foods and in vivo. In this work, l-tryptophan reacted with α-dicarbonyl compounds affording new ß-carbolines. Glyoxal afforded 1-hydroxymethyl-ß-carboline (HME-ßC) and its 3-carboxylic acid, and methylglyoxal afforded 1-(1-hydroxyethyl)-ß-carboline (HET-ßC) and its 3-carboxylic acid. 3-Deoxyglucosone afforded 1-(1,3,4,5-tetrahydroxypent-1-yl)-ß-carboline isomers (1a/b), 1-(1,4,5-trihydroxypent-1-yl)-ß-carboline (2), and 1-(1,5-dihydroxypent-3-en-1-yl)-ß-carboline (3). The formation of these ßCs increased under acidic conditions and with increasing temperature. A mechanism is proposed explaining the conversion of a carbonyl into a hydroxy group based on tautomerism and cyclization to the dihydro-ßC-3-COOH intermediates, which were isolated and gave the ßCs. These α-dicarbonyl-derived ßCs occurred in model reactions of l-tryptophan with fructose or glucose incubated under heating and can be considered as advanced glycation end products (AGEs). They were also present in foods and formed during heating processes. HET-ßC appeared in processed foods, reaching up to 309 ng/g, with the highest amount found in dried tomato, fried onion, toasted bread, and Manuka honey. HME-ßC was only detected in some foods with lower amounts than HET-ßC. HET-ßC appeared in foods as a racemic mixture of enantiomers suggesting the same mechanism of formation as the synthetized product. α-Dicarbonyl-derived ßCs (HET-ßC, HME-ßC, and 1a/b-3) occur in foods and food processing and, therefore, they are ingested during diet.

Endolymphatic Sac Tumor as a Ménière-Like Vertiginous Syndrome: A Case Report.

Endolymphatic sac tumors are rare benign neoplasms with locally aggressive behavior located in the posterior petrous ridge of the temporal bone. They cause sensorineural hearing loss and may develop vestibular damage. A 24-year-old male patient arrived at our office with a history of acute vertiginous syndrome, left hearing loss, and tinnitus 1-year ago. His chief complaint was an increase in auditory symptoms. A CT scan and MRI showed an endolymphatic sac tumor. Complete resection of the lesion was achieved by a transmastoid and translabyrinthine approach. Low-grade adenocarcinoma was confirmed by histopathology. The patient remained without clinical vestibular symptoms. However, a small residual tumor was addressed by gamma-ray radiosurgery. Postoperative deep left sensorineural hearing loss was identified, without any vestibular sequelae. Radiologic imaging is the most useful tool for this diagnosis. Endolymphatic sac tumors should be in the differential diagnosis of recalcitrant audio-vestibular symptoms. Complete surgical resection is the most appropriate management.

Reconstrucción de defecto de órbita con colgajo prelaminado de fascia temporal superficial / Orbit defect reconstruction with pre-laminated temporal superficial fascia flap

El colgajo de fascia temporal superficial es muy versátil para la reconstrucción de defectos tisulares localizados en los tercios superior y medio de la cara, en la región orbito-palpebral, en la cavidad oral, en la base del cráneo y a nivel mandibular. En nuestra experiencia, constituye una opción segura para reconstrucciones complejas de cavidades. En el presente artículo los autores exponen el caso de una paciente en quien se reconstruyó un defecto de órbita con un colgajo de fascia temporal superficial prelaminado

The superficial temporal fascia flap is versatile for the reconstruction of tissue defects located in the upper and middle thirds of the face, in the orbital-palpebral region, in the oral cavity, at the base of the skull and at the mandibular level. In our experience, it is a safe option for complex cavity reconstructions. In this article the authors present the case of a patient in whom an orbit defect was reconstructed with a pre-laminated superficial temporal fascia flap

Grifola frondosa (Maitake) Extract Reduces Fat Accumulation and Improves Health Span in C. elegans through the DAF-16/FOXO and SKN-1/NRF2 Signalling Pathways.

In recent years, food ingredients rich in bioactive compounds have emerged as candidates to prevent excess adiposity and other metabolic complications characteristic of obesity, such as low-grade inflammation and oxidative status. Among them, fungi have gained popularity for their high polysaccharide content and other bioactive components with beneficial activities. Here, we use the C. elegans model to investigate the potential activities of a Grifola frondosa extract (GE), together with the underlying mechanisms of action. Our study revealed that GE represents an important source of polysaccharides and phenolic compounds with in vitro antioxidant activity. Treatment with our GE extract, which was found to be nongenotoxic through a SOS/umu test, significantly reduced the fat content of C. elegans, decreased the production of intracellular ROS and aging-lipofuscin pigment, and increased the lifespan of nematodes. Gene expression and mutant analyses demonstrated that the in vivo anti-obesity and antioxidant activities of GE were mediated through the daf-2/daf-16 and skn-1/nrf-2 signalling pathways, respectively. Taken together, our results suggest that our GE extract could be considered a potential functional ingredient for the prevention of obesity-related disturbances.

On the potential of microscale electrokinetic cascade devices.

Phages used for phage therapy of multidrug resistant bacteria must be highly purified prior to use. There are limited purification approaches that are broadly applicable to many phage types. Electrokinetics has shown great potential to manipulate phages, but obstructions from the cell debris produced during phage propagation can severely diminish the capacity of an electrokinetic device to concentrate and purify phage samples. A multipart insulator-based electrokinetic device is proposed here to remove the larger, undesirable components of mixtures from phage preparations while transferring the freshly purified and concentrated sample to a second stage for downstream analysis. By combining the large debris prescreen and analysis stages in a streamlined system, this approach simultaneously reduces the impact of clogging and minimizes the sample loss observed during manual transferring of purified samples. Polystyrene particles were used to demonstrate a diminished sample loss of approximately one order of magnitude when using the cascade device as opposed to a manual transfer scheme. The purification and concentration of three different phage samples were demonstrated using the first stage of the cascade device as a prescreen. This design provides a simple method of purifying and concentrating valuable samples from a complex mixture that might impede separation capacity in a single channel.

Prelaminated Temporoparietal Osteofascial Flap: A Novel Nasal Reconstruction Technique.

Nasal reconstruction can be a difficult task to perform. It is a challenge when the defect to be reconstructed is extensive and involves the entire thickness of the nose. The difficulty is further increased when a recurrent tumor is removed, where other flaps were previously used to reconstruct the initial defect. A therapeutic option is microsurgical reconstruction; however, sometimes this cannot be performed. Furthermore, free flaps such as the anterolateral thigh or the antebrachialis radial tend to be very thick for the integuments of the face. Therefore, it is important to think of another reconstructive option to solve this problem. We present a case of nasal reconstruction with a prelaminated temporoparietal osteofascial flap, after full-thickness excision for recurrent carcinoma.

Electrokinetic characterization of synthetic protein nanoparticles.

The application of nanoparticle in medicine is promising for the treatment of a wide variety of diseases. However, the slow progress in the field has resulted in relatively few therapies being translated into the clinic. Anisotropic synthetic protein nanoparticles (ASPNPs) show potential as a next-generation drug-delivery technology, due to their biocompatibility, biodegradability, and functionality. Even though ASPNPs have the potential to be used in a variety of applications, such as in the treatment of glioblastoma, there is currently no high-throughput technology for the processing of these particles. Insulator-based electrokinetics employ microfluidics devices that rely on electrokinetic principles to manipulate micro- and nanoparticles. These miniaturized devices can selectively trap and enrich nanoparticles based on their material characteristics, and subsequently release them, which allows for particle sorting and processing. In this study, we use insulator-based electrokinetic (EK) microdevices to characterize ASPNPs. We found that anisotropy strongly influences electrokinetic particle behavior by comparing compositionally identical anisotropic and non-anisotropic SPNPs. Additionally, we were able to estimate the empirical electrokinetic equilibrium parameter (eE EEC) for all SPNPs. This particle-dependent parameter can allow for the design of various separation and purification processes. These results show how promising the insulator-based EK microdevices are for the analysis and purification of clinically relevant SPNPs.

Determination of the Empirical Electrokinetic Equilibrium Condition of Microorganisms in Microfluidic Devices.

The increased concern regarding emerging pathogens and antibiotic resistance has drawn interest in the development of rapid and robust microfluidic techniques to analyze microorganisms. The novel parameter known as the electrokinetic equilibrium condition (EEEC) was presented in recent studies, providing an approach to analyze microparticles in microchannels employing unique electrokinetic (EK) signatures. While the EEEC shows great promise, current estimation approaches can be time-consuming or heavily user-dependent for accurate values. The present contribution aims to analyze existing approaches for estimating this parameter and modify the process into an accurate yet simple technique for estimating the EK behavior of microorganisms in insulator-based microfluidic devices. The technique presented here yields the parameter called the empirical electrokinetic equilibrium condition (eEEEC) which works well as a value for initial approximations of trapping conditions in insulator-based EK (iEK) microfluidic systems. A total of six types of microorganisms were analyzed in this study (three bacteria and three bacteriophages). The proposed approach estimated eEEEC values employing images of trapped microorganisms, yielding high reproducibility (SD 5.0-8.8%). Furthermore, stable trapping voltages (sTVs) were estimated from eEEEC values for distinct channel designs to test that this parameter is system-independent and good agreement was obtained when comparing estimated sTVs vs. experimental values (SD 0.3-19.6%). The encouraging results from this work were used to generate an EK library of data, available on our laboratory website. The data in this library can be used to design tailored iEK microfluidic devices for the analysis of microorganisms.

Simultaneous Determination of Linear and Nonlinear Electrophoretic Mobilities of Cells and Microparticles.

Direct-current insulator-based electrokinetics (DC-iEK) is a branch of microfluidics that has demonstrated to be an attractive and efficient technique for manipulating micro- and nano- particles, including microorganisms. A unique feature of DC-iEK devices is that nonlinear EK effects are enhanced by the presence of regions of higher field intensity between the insulating structures. Accurate computational models, describing particle and cell behavior, are crucial to optimize the design and improve the performance of DC-iEK devices. The electrokinetic equilibrium condition (EEEC) is a recently introduced fundamental concept that has radically shifted the perspective behind the analysis of particle manipulation in these microfluidic devices. The EEEC takes into consideration previously neglected nonlinear effects on particle migration and indicates that these effects are central to control particle motion in DC-iEK devices. In this study, we present a simultaneous experimental characterization of linear and nonlinear electrokinetic (EK) parameters, that is, the electrophoretic mobility (µEP(1)), the particle zeta potential (ζP), the EEEC, and the electrophoretic mobility of the second kind (µEP(3)), for four types of polystyrene microparticles and four cell strains. For this, we studied the electromigration of polystyrene microparticles ranging in size from 2 to 6.8 µm, three bacteria strains (B. cereus, E. coli, and S. enterica) and a yeast cell (S. cerevisiae), ranging in size from 1 to 6.3 µm, in a polydimethylsiloxane (PDMS) microfluidic channel with a rectangular cross-section. The results illustrated that electrokinetic particle trapping can occur by linear and nonlinear electrophoresis and electroosmosis reaching an equilibrium, without the presence of insulating posts. The experimentally measured parameters reported herein will allow optimizing the design of future DC-iEK devices for a wide range of applications (e.g., to separate multiple kinds of particles and microorganisms) and for developing computational models that better represent reality.