A Multiplex "Disposable Photonics" Biosensor Platform and Its Application to Antibody Profiling in Upper Respiratory Disease.

Photonic technologies promise to deliver quantitative, multiplex, and inexpensive medical diagnostic platforms by leveraging the highly scalable processes developed for the fabrication of semiconductor microchips. However, in practice, the affordability of these platforms is limited by complex and expensive sample handling and optical alignment. We previously reported the development of a disposable photonic assay that incorporates inexpensive plastic micropillar microfluidic cards for sample delivery. That system as developed was limited to singleplex assays due to its optical configuration. To enable multiplexing, we report a new approach addressing multiplex light I/O, in which the outputs of individual grating couplers on a photonic chip are mapped to fibers in a fiber bundle. As demonstrated in the context of detecting antibody responses to influenza and SARS-CoV-2 antigens in human serum and saliva, this enables multiplexing in an inexpensive, disposable, and compact format.

A photonic biosensor-integrated tissue chip platform for real-time sensing of lung epithelial inflammatory markers.

Tissue chip (TC) devices, also known as microphysiological systems (MPS) or organ chips (OCs or OoCs), seek to mimic human physiology on a small scale. They are intended to improve upon animal models in terms of reproducibility and human relevance, at a lower monetary and ethical cost. Virtually all TC systems are analyzed at an endpoint, leading to widespread recognition that new methods are needed to enable sensing of specific biomolecules in real time, as they are being produced by the cells. To address this need, we incorporated photonic biosensors for inflammatory cytokines into a model TC. Human bronchial epithelial cells seeded in a microfluidic device were stimulated with lipopolysaccharide, and the cytokines secreted in response sensed in real time. Sensing analyte transport through the TC in response to disruption of tissue barrier was also demonstrated. This work demonstrates the first application of photonic sensors to a human TC device, and will enable new applications in drug development and disease modeling.

Imaging of unusual perineal masses.

OBJECTIVE: The purpose of this article is to describe the radiologic features of unusual tumors that occur in the perineum. CONCLUSION: The perineal space is often overlooked because of the infrequency of abnormalities. Accurate image interpretation and visualization of extent of pathology is important for proper management. Trauma and infectious diseases occur in the acute setting, whereas tumors are common in the chronic setting. Cross-sectional imaging plays a crucial role in depicting perineal anatomy and evaluating the extent of disease.

Epstein-Barr Virus Causing Clinical Jaundice and Acute Acalculous Cholecystitis in a Previously Healthy 17-Year-Old Girl.

BACKGROUND Infectious mononucleosis secondary to Epstein-Barr Virus is a common infection in young adults. Infection usually involves a self-limiting course of fevers, sore throat, malaise, and myalgias. Transaminitis is a relatively common complication; clinical jaundice, however, is rare. This case report highlights an uncommon complication of Epstein-Barr Virus infection in which hepatocellular injury led to clinical jaundice as well as radiologic evidence of gallbladder pathology mimicking acute calculous cholecystitis. CASE REPORT A 17-year-old girl with no prior medical history presented to our Emergency Department 1 week after being diagnosed with infectious mononucleosis. She was hemodynamically stable and her physical exam was notable for scleral icterus with right upper quadrant tenderness and positive Murphy's sign. Multiple imaging modalities performed showed gallbladder wall thickening without common bile duct dilatation. A hepatobiliary iminodiacetic acid (HIDA) scan showed evidence of hepatocyte dysfunction with normal gallbladder filling. The imaging results obtained in conjunction with her laboratory testing and active infectious mononucleosis infection confirmed the patient's presentation was a result of her Epstein-Barr virus infection and did not require surgical intervention for cholecystectomy. CONCLUSIONS This case report highlights a rare complication of Epstein-Barr Virus infection and demonstrates the utility of interpreting hepatic function testing in conjunction with relevant imaging modalities in cases of clinical jaundice. By doing so, we were able to conclude the patient's gallbladder pathology was related to acute acalculous cholecystitis (AAC) and did not warrant surgical intervention. The patient was given supportive care measures and made a full recovery.

Multi-step synthesis of nanoparticles performed on millisecond time scale in a microfluidic droplet-based system.

This paper reports a plug-based, microfluidic method for performing multi-step chemical reactions with millisecond time-control. It builds upon a previously reported method where aqueous reagents were injected into a flow of immiscible fluid (fluorocarbons)(H. Song et al., Angew. Chem. Int. Ed., 2003, 42, 768). The aqueous reagents formed plugs--droplets surrounded and transported by the immiscible fluid. Winding channels rapidly mixed the reagents in droplets. This paper shows that further stages of the reaction could be initiated by flowing additional reagent streams directly into the droplets of initial reaction mixture. The conditions necessary for an aqueous stream to merge with aqueous droplets were characterized. The Capillary number could be used to predict the behavior of the two-phase flow at the merging junction. By transporting solid reaction products in droplets, the products were kept from aggregating on the walls of the microchannels. To demonstrate the utility of this microfluidic method it was used to synthesize colloidal CdS and CdS/CdSe core-shell nanoparticles.

Design considerations for electrostatic microvalves with applications in poly(dimethylsiloxane)-based microfluidics.

Microvalves are critical in the operation of integrated microfluidic chips for a wide range of applications. In this paper, we present an analytical model to guide the design of electrostatic microvalves that can be integrated into microfluidic chips using standard fabrication processes and can reliably operate at low actuation potentials (<250 V). Based on the analytical model, we identify design guidelines and operational considerations for elastomeric electrostatic microvalves and formulate strategies to minimize their actuation potentials, while maintaining the feasibility of fabrication and integration. We specifically explore the application of the model to design microfluidic microvalves fabricated in poly(dimethylsiloxane), using only soft-lithographic techniques. We discuss the electrostatic actuation in terms of several microscale phenomena, including squeeze-film damping and adhesion-driven microvalve collapse. The actuation potentials predicted by the model are in good agreement with experimental data obtained with a microfabricated array of electrostatic microvalves actuated in air and oil. The model can also be extended to the design of peristaltic pumps for microfluidics and to the prediction of actuation potentials of microvalves in viscous liquid environments. Additionally, due to the compact ancillaries required to generate low potentials, these electrostatic microvalves can potentially be used in portable microfluidic chips.

Splenic lacerations and return to play: case report of 2 professional hockey players.

BACKGROUND: Several sports medicine reviews have highlighted a 3- to 6-month time frame for return to play after splenic lacerations. These reviews are based on several well-defined grading scales for splenic injury based on computed tomography (CT). None of the articles suggest that serial CT scanning is necessary for follow-up; some even indicate that it has no role in the management of these injuries. HYPOTHESIS: With proper follow-up and possibly the use of serial CT scanning or other imaging modalities, it may be possible for athletes to safely return to play sooner than what current guidelines recommend. STUDY DESIGN: The authors present 2 cases of professional hockey players who both suffered grade III splenic lacerations while playing. METHODS: Both players were treated conservatively and monitored with serial CT scanning until radiographic and clinical findings suggested complete healing. RESULTS: Both players were able to return to full-contact professional hockey within 2 months after suffering grade III splenic lacerations. Neither athlete suffered any complications after his return. CONCLUSIONS: With CT scanning, 2 athletes were able to return to play earlier (2 months) than previously recommended (3-6 months) without compromising their safety. CLINICAL RELEVANCE: Additional cases must be examined before outlining more definitive recommendations regarding splenic lacerations in sports, but it is possible that elite athletes may return to play sooner than what the current literature recommends.

Reduction of radiation exposure in pediatric patients with trauma: cephalic stabilization improves adequacy of lateral cervical spine radiographs.

INTRODUCTION: Plain radiographs continue to play a role in cervical spine clearance. Inadequate radiographs commonly necessitate repeat x-rays or computed tomography imaging (10 × radiation dose). We have used the technique of cephalic stabilization (CS) to improve the results of plain radiographs. Cephalic stabilization lateral radiographs are obtained, with one assistant applying traction to the arms while another placing fingers in the patient's ears and stabilizing the head. This study tests the hypothesis that CS improves visualization of the cervicothoracic junction during lateral cervical spine radiographs. METHODS: A 2-year review of institutional pediatric trauma registry identified 46 patients with CS, matched 1:3 with controls. Randomized lateral radiographs were evaluated independently by 2 pediatric radiologists to determine adequate visualization of the craniocervical and cervicothoracic junctions. Reviewers were blinded to CS through image cropping. RESULTS: The proportion of adequate visualization of the cervicothoracic junction was 0.85 for cases with stabilization and 0.60 for controls. Odds of obtaining adequate visualization with stabilization are 3.8 times those without stabilization (P = .001) and were even greater for patients younger than 13 years. CONCLUSIONS: Cephalic stabilization improves visualization of the cervicothoracic junction in lateral cervical spine radiographs and can reduce radiation exposure in patients who would otherwise require further imaging.

Microfluidic Generation of Lipidic Mesophases for Membrane Protein Crystallization.

We report on a microfluidic method for the formation of aqueous/lipid mesophases to enable screening of suitable crystallization conditions of membrane proteins from a membrane-like phase in sub-20 nanoliter volumes. This integrated microfluidic chip and the employed mixing strategy address the specific challenges associated with the mixing of fluids of highly different viscosities (here a factor of 30) as well as the non-Newtonian character of the resulting mesophases. The chip requires less than 20 nL of material per condition screened whereas typically on the order of 10 µL or more is needed for a batch preparation in the present screening methods. We validated our approach with the successful crystallization of the membrane protein bacteriorhodopsin.

Nanoliter microfluidic hybrid method for simultaneous screening and optimization validated with crystallization of membrane proteins.

High-throughput screening and optimization experiments are critical to a number of fields, including chemistry and structural and molecular biology. The separation of these two steps may introduce false negatives and a time delay between initial screening and subsequent optimization. Although a hybrid method combining both steps may address these problems, miniaturization is required to minimize sample consumption. This article reports a "hybrid" droplet-based microfluidic approach that combines the steps of screening and optimization into one simple experiment and uses nanoliter-sized plugs to minimize sample consumption. Many distinct reagents were sequentially introduced as approximately 140-nl plugs into a microfluidic device and combined with a substrate and a diluting buffer. Tests were conducted in approximately 10-nl plugs containing different concentrations of a reagent. Methods were developed to form plugs of controlled concentrations, index concentrations, and incubate thousands of plugs inexpensively and without evaporation. To validate the hybrid method and demonstrate its applicability to challenging problems, crystallization of model membrane proteins and handling of solutions of detergents and viscous precipitants were demonstrated. By using 10 microl of protein solution, approximately 1,300 crystallization trials were set up within 20 min by one researcher. This method was compatible with growth, manipulation, and extraction of high-quality crystals of membrane proteins, demonstrated by obtaining high-resolution diffraction images and solving a crystal structure. This robust method requires inexpensive equipment and supplies, should be especially suitable for use in individual laboratories, and could find applications in a number of areas that require chemical, biochemical, and biological screening and optimization.

Formation of droplets of alternating composition in microfluidic channels and applications to indexing of concentrations in droplet-based assays.

For screening the conditions for a reaction by using droplets (or plugs) as microreactors, the composition of the droplets must be indexed. Indexing here refers to measuring the concentration of a solute by addition of a marker, either internal or external. Indexing may be performed by forming droplet pairs, where in each pair the first droplet is used to conduct the reaction, and the second droplet is used to index the composition of the first droplet. This paper characterizes a method for creating droplet pairs by generating alternating droplets, of two sets of aqueous solutions in a flow of immiscible carrier fluid within PDMS and glass microfluidic channels. The paper also demonstrates that the technique can be used to index the composition of the droplets, and this application is illustrated by screening conditions of protein crystallization. The fluid properties required to form the steady flow of the alternating droplets in a microchannel were characterized as a function of the capillary number Ca and water fraction. Four regimes were observed. At the lowest values of Ca, the droplets of the two streams coalesced; at intermediate values of Ca the alternating droplets formed reliably. At even higher values of Ca, shear forces dominated and caused formation of droplets that were smaller than the cross-sectional dimension of the channel; at the highest values of Ca, coflowing laminar streams of the two immiscible fluids formed. In addition to screening of protein crystallization conditions, understanding of the fluid flow in this system may extend this indexing approach to other chemical and biological assays performed on a microfluidic chip.

Formation of Arrayed Droplets by Soft Lithography and Two-Phase Fluid Flow, and Application in Protein Crystallization.

This paper presents an overview of our recent work on the use of soft lithography and two-phase fluid flow to form arrays of droplets. The crucial issues in the formation of stable arrays of droplets and alternating droplets of two sets of aqueous solutions include the geometry of the microchannels, the capillary number, and the water fraction of the system. Glass capillaries could be coupled to the PDMS microchannels and droplets could be transferred into glass capillaries for long-term storage. The arrays of droplets have been applied to screen the conditions for protein crystallization with microbatch and vapor diffusion techniques.

Experimental test of scaling of mixing by chaotic advection in droplets moving through microfluidic channels.

This letter describes an experimental test of a simple argument that predicts the scaling of chaotic mixing in a droplet moving through a winding microfluidic channel. Previously, scaling arguments for chaotic mixing have been described for a flow that reduces striation length by stretching, folding, and reorienting the fluid in a manner similar to that of the baker's transformation. The experimentally observed flow patterns within droplets (or plugs) resembled the baker's transformation. Therefore, the ideas described in the literature could be applied to mixing in droplets to obtain the scaling argument for the dependence of the mixing time, t~(aw/U)log(Pe), where w [m] is the cross-sectional dimension of the microchannel, a is the dimensionless length of the plug measured relative to w, U [m s(-1)] is the flow velocity, Pe is the Péclet number (Pe=wU/D), and D [m(2)s(-1)] is the diffusion coefficient of the reagent being mixed. Experiments were performed to confirm the scaling argument by varying the parameters w, U, and D. Under favorable conditions, submillisecond mixing has been demonstrated in this system.

Microfluidic systems for chemical kinetics that rely on chaotic mixing in droplets.

This paper reviews work on a microfluidic system that relies on chaotic advection to rapidly mix multiple reagents isolated in droplets (plugs). Using a combination of turns and straight sections, winding microfluidic channels create unsteady fluid flows that rapidly mix the multiple reagents contained within plugs. The scaling of mixing for a range of channel widths, flow velocities and diffusion coefficients has been investigated. Due to rapid mixing, low sample consumption and transport of reagents with no dispersion, the system is particularly appropriate for chemical kinetics and biochemical assays. The mixing occurs by chaotic advection and is rapid (sub-millisecond), allowing for an accurate description of fast reaction kinetics. In addition, mixing has been characterized and explicitly incorporated into the kinetic model.