Dual-Channel Stretchable, Self-Tuning, Liquid Metal Coils and Their Fabrication Techniques

Flexible and stretchable radiofrequency coils for magnetic resonance imaging represent an emerging and rapidly growing field. The main advantage of such coil designs is their conformal nature, enabling a closer anatomical fit, patient comfort, and freedom of movement. Previously, we demonstrated a proof-of-concept single element stretchable coil design with a self-tuning smart geometry. In this work, we evaluate the feasibility of scaling this coil concept to a multi-element coil array and the associated engineering and manufacturing challenges. To this goal, we study a dual-channel coil array using full-wave simulations, bench testing, in vitro, and in vivo imaging in a 3 T scanner. We use three fabrication techniques to manufacture dual-channel receive coil arrays: (1) single-layer casting, (2) double-layer casting, and (3) direct-ink-writing. All fabricated arrays perform equally well on the bench and produce similar sensitivity maps. The direct-ink-writing method is found to be the most advantageous fabrication technique for fabrication speed, accuracy, repeatability, and total coil array thickness (0.6 mm). Bench tests show excellent frequency stability of 128 ± 0.6 MHz (0% to 30% stretch). Compared to a commercial knee coil array, the stretchable coil array is more conformal to anatomy and provides 50% improved signal-to-noise ratio in the region of interest.

Biomimetic Vasculatures by 3D-Printed Porous Molds

Despite recent advances in biofabrication, recapitulating complex architectures of cell-laden vascular constructs remains challenging. To date, biofabricated vascular models have not yet realized four fundamental attributes of native vasculatures simultaneously: freestanding, branching, multilayered, and perfusable. In this work, a microfluidics-enabled molding technique combined with coaxial bioprinting to fabricate anatomically relevant, cell-laden vascular models consisting of hydrogels is developed. By using 3D porous molds of poly(ethylene glycol) diacrylate as casting templates that gradually release calcium ions as a crosslinking agent, freestanding, and perfusable vascular constructs of complex geometries are fabricated. The bioinks can be tailored to improve the compatibility with specific vascular cells and to tune the mechanical modulus mimicking native blood vessels. Crucially, the integration of relevant vascular cells (such as smooth muscle cells and endothelial cells) in a multilayer and biomimetic configuration is highlighted. It is also demonstrated that the fabricated freestanding vessels are amenable for testing percutaneous coronary interventions (i.e., drug-eluting balloons and stents) under physiological mechanical states such as stretching and bending. Overall, a versatile fabrication technique with multifaceted possibilities of generating biomimetic vascular models that can benefit future research in mechanistic understanding of cardiovascular diseases and the development of therapeutic interventions is introduced.

Molecularly cleavable bioinks facilitate high-performance digital light processing-based bioprinting of functional volumetric soft tissues

Digital light processing bioprinting favors biofabrication of tissues with improved structural complexity. However, soft-tissue fabrication with this method remains a challenge to balance the physical performances of the bioinks for high-fidelity bioprinting and suitable microenvironments for the encapsulated cells to thrive. Here, we propose a molecular cleavage approach, where hyaluronic acid methacrylate (HAMA) is mixed with gelatin methacryloyl to achieve high-performance bioprinting, followed by selectively enzymatic digestion of HAMA, resulting in tissue-matching mechanical properties without losing the structural complexity and fidelity. Our method allows cellular morphological and functional improvements across multiple bioprinted tissue types featuring a wide range of mechanical stiffness, from the muscles to the brain, the softest organ of the human body. This platform endows us to biofabricate mechanically precisely tunable constructs to meet the biological function requirements of target tissues, potentially paving the way for broad applications in tissue and tissue model engineering.

Integration of a microfluidic multicellular coculture array with machine learning analysis to predict adverse cutaneous drug reactions

Adverse cutaneous reactions are potentially life-threatening skin side effects caused by drugs administered into the human body. The availability of a human-specific in vitro platform that can prospectively screen drugs and predict this risk is therefore of great importance to drug safety. However, since adverse cutaneous drug reactions are mediated by at least 2 distinct mechanisms, both involving systemic interactions between liver, immune and dermal tissues, existing in vitro skin models have not been able to comprehensively recapitulate these complex, multi-cellular interactions to predict the skin-sensitization potential of drugs. Here, we report a novel in vitro drug screening platform, which comprises a microfluidic multicellular coculture array (MCA) to model different mechanisms-of-action using a collection of simplistic cellular assays. The resultant readouts are then integrated with a machine-learning algorithm to predict the skin sensitizing potential of systemic drugs. The MCA consists of 4 cell culture compartments connected by diffusion microchannels to enable crosstalk between hepatocytes that generate drug metabolites, antigen-presenting cells (APCs) that detect the immunogenicity of the drug metabolites, and keratinocytes and dermal fibroblasts, which collectively determine drug metabolite-induced FasL-mediated apoptosis. A single drug screen using the MCA can simultaneously generate 5 readouts, which are integrated using support vector machine (SVM) and principal component analysis (PCA) to classify and visualize the drugs as skin sensitizers or non-skin sensitizers. The predictive performance of the MCA and SVM classification algorithm is then validated through a pilot screen of 11 drugs labelled by the US Food and Drug Administration (FDA), including 7 skin-sensitizing and 4 non-skin sensitizing drugs, using stratified 4-fold cross-validation (CV) on SVM. The predictive performance of our in vitro model achieves an average of 87.5% accuracy (correct prediction rate), 75% specificity (prediction rate of true negative drugs), and 100% sensitivity (prediction rate of true positive drugs). We then employ the MCA and the SVM training algorithm to prospectively identify the skin-sensitizing likelihood and mechanism-of-action for obeticholic acid (OCA), a farnesoid X receptor (FXR) agonist which has undergone clinical trials for non-alcoholic steatohepatitis (NASH) with well-documented cutaneous side effects.

Design and fabrication of micro/nanofluidics devices and systems

This chapter provides an overview of the science, engineering, and design methods required in the development of micro/nanofluidic devices. Section 2 provides the scientific background of fluid mechanics and physical phenomena in micro/nanoscale. Section 3 gives a brief overview of the existing fabrication techniques employed in micro/nanofluidics. The techniques are grouped into three categories: (1) subtractive manufacturing, (2) formative manufacturing, and (3) additive manufacturing. The advantages and disadvantages of each manufacturing technique are also discussed. Implementation of the fluidic devices beyond laboratory demonstrations is not trivial, which requires a good understanding of the problems of interest and the end-users. To that end, Section 4 introduces the design thinking approach and its application to develop micro/nanofluidic devices. Finally, Section 5 concludes the chapter with future outlooks.

Digital Light Processing Based Bioprinting with Composable Gradients

Recapitulation of complex tissues signifies a remarkable challenge and, to date, only a few approaches have emerged that can efficiently reconstruct necessary gradients in 3D constructs. This is true even though mimicry of these gradients is of great importance to establish the functionality of engineered tissues and devices. Here, a composable-gradient Digital Light Processing (DLP)-based (bio)printing system is developed, utilizing the unprecedented integration of a microfluidic mixer for the generation of either continual or discrete gradients of desired (bio)inks in real time. Notably, the precisely controlled gradients are composable on-the-fly by facilely by adjusting the (bio)ink flow ratios. In addition, this setup is designed in such a way that (bio)ink waste is minimized when exchanging the gradient (bio)inks, further enhancing this time- and (bio)ink-saving strategy. Various planar and 3D structures exhibiting continual gradients of materials, of cell densities, of growth factor concentrations, of hydrogel stiffness, and of porosities in horizontal and/or vertical direction, are exemplified. The composable fabrication of multifunctional gradients strongly supports the potential of the unique bioprinting system in numerous biomedical applications.

Highly-customizable 3D-printed peristaltic pump kit

Commercially available peristaltic pumps for microfluidics are usually bulky, expensive, and not customizable. Herein, we developed a cost-effective kit to build a micro-peristaltic pump (~ 50 USD) consisting of 3D-printed and off-the-shelf components. We demonstrated fabricating two variants of pumps with different sizes and operating flowrates using the developed kit. The assembled pumps offered a flowrate of 0.02 ~ 727.3 μL/min, and the smallest pump assembled with this kit was 20 × 50 × 28 mm. This kit was designed with modular components (i.e., each component followed a standardized unit) to achieve (1) customizability (users can easily reconfigure various components to comply with their experiments), (2) forward compatibility (new parts with the standardized unit can be designed and easily interfaced to the current kit), and (3) easy replacement of the parts experiencing wear and tear. To demonstrate the forward compatibility, we developed a flowrate calibration tool that was readily interfaced with the developed pump system. The pumps exhibited good repeatability in flowrates and functioned inside a cell incubator (at 37 °C and 95 % humidity) for seven days without noticeable issues in the performance. This cost-effective, highly customizable pump kit should find use in lab-on-a-chip, organs-on-a-chip, and point-of-care microfluidic applications.

A Smartphone-Enabled Portable Digital Light Processing 3D Printer

3D printing has emerged as an enabling approach in a variety of different fields. However, the bulk volume of printing systems limits the expansion of their applications. In this study, a portable 3D Digital Light Processing (DLP) printer is built based on a smartphone-powered projector and a custom-written smartphone-operated app. Constructs with detailed surface architectures, porous features, or hollow structures, as well as sophisticated tissue analogs, are successfully printed using this platform, by utilizing commercial resins as well as a range of hydrogel-based inks, including poly(ethylene glycol)-diacrylate, gelatin methacryloyl, or allylated gelatin. Moreover, due to the portability of the unique DLP printer, medical implants can be fabricated for point-of-care usage, and cell-laden tissues can be produced in situ, achieving a new milestone for mobile-health technologies. Additionally, the all-in-one printing system described herein enables the integration of the 3D scanning smartphone app to obtain object-derived 3D digital models for subsequent printing. Along with further developments, this portable, modular, and easy-to-use smartphone-enabled DLP printer is anticipated to secure exciting opportunities for applications in resource-limited and point-of-care settings not only in biomedicine but also for home and educational purposes.

Bridging the academia-to-industry gap: organ-on-a-chip platforms for safety and toxicology assessment

Some organ-on-a-chip (OoC) systems for drug evaluation show better predictive capabilities than planar, static cell cultures and animal models. One of the ongoing initiatives led by OoC developers is to bridge the academia-to-industry gap in the hope of gaining wider adoption by end-users - academic biological researchers and industry. We discuss several recommendations that can help to drive the adoption of OoC systems by the market. We first review some key challenges faced by OoC developers before highlighting current advances in OoC platforms. We then offer recommendations for OoC developers to promote the uptake of OoC systems by the industry.

Ultra-Deformable and Tissue-Adhesive Liquid Metal Antennas with High Wireless Powering Efficiency

Flexible and stretchable antennas are important for wireless communication using wearable and implantable devices to address mechanical mismatch at the tissue-device interface. Emerging technologies of liquid-metal-based stretchable electronics are promising approaches to improve the flexibility and stretchability of conventional metal-based antennas. However, existing methods to encapsulate liquid metals require monolithically thick (at least 100 µm) substrates, and the resulting devices are limited in deformability and tissue-adhesiveness. To overcome this limitation, fabrication of microchannels by direct ink writing on a 7 µm-thick elastomeric substrate is demonstrated, to obtain liquid metal microfluidic antennas with unprecedented deformability. The fabricated wireless light-emitting device is powered by a standard near-field-communication system (13.56 MHz, 1 W) and retained a consistent operation under deformations including stretching (>200% uniaxial strain), twisting (180° twist), and bending (3.0 mm radius of curvature) while maintaining a high quality factor (q > 20). Suture-free conformal adhesion of the polydopamine-coated device to ex vivo animal tissues under mechanical deformations is also demonstrated. This technology offers a new capability for the design and fabrication of wireless biomedical devices requiring conformable tissue-device integration toward minimally invasive, imperceptible medical treatments.

[Russian version of PEACH scale (validation and normative data)]

PEACH is an important tool for evaluation of children's hearing development, used in age 2-7 years. It is also appropriate for amplification outcomes measurements. PEACH scale includes 13 questions. Parents fill the questionnaire after week observation of child's hearing behavior in different situations. The goal of the study was validation of Russian version of PEACH scale. Translation and cross-cultural adaptation were performed following international guidelines. 50 children with normal hearing and 50 hearing impaired children were involved in the validation process. All of the hearing-impaired children used hearing aids or cochlear implants. PEACH scores of the children with normal hearing have strong correlation with data of original version (ρ=0.998; p<0.05) and can be used as a normative data for Russian version. PEACH scores of the hearing-impaired children were worse in higher degrees of hearing loss, which shows sensitivity of the method. Test-retest reliability in children with normal hearing was ρ=1.0 (p<0.05), in hearing impaired children ρ=0.976 (p<0.05). Russian PEACH scale is free available at the official site of Center of Pediatric Audiology: https://dgsc.kzdrav.gov.spb.ru.

Embedded Ink Writing (EIW) of Polysiloxane Inks

Polysiloxane is a desirable material for the fabrication of devices in microfluidics, lab-on-a-chip, and microelectromechanical systems, but direct patterning of microstructures using liquid polysiloxane resins would require adequate rheological and chemical properties of the resins. In this work, we developed a simple method to fabricate planar microstructures consisting of polysiloxane using commercially available liquid polysiloxane resins without changing their properties. We used a direct ink writing (DIW) printer to dispense curable liquid polysiloxane (with the viscosity in the range of 1-100 Pa·s) in a liquid immiscible with the resins (such as methanol, ethanol, and isopropanol). The contact angle (θ) of the dispensed polysiloxane on the Petri dish increased from 20° in air to 100° in methanol, ethanol, and isopropanol. The increase in the contact angles allowed maintaining the structures of patterned polysiloxane until curing, and the embedding liquid was readily removed by evaporation. We termed this method as embedded ink writing (EIW). The effects of curing time (τ) and nozzle speed (v) on the width of the printed filament (w) were evaluated. EIW achieved the minimum width of the printed filament of 65 μm. EIW enabled direct writing of polysiloxane resins and should find applications in fabricating microfluidic devices, flexible wearables, and soft actuators.

Self-aligning Tetris-Like (TILE) modular microfluidic platform for mimicking multi-organ interactions

Multi-organ perfusion systems offer the unique opportunity to mimic different physiological systemic interactions. However, existing multi-organ culture platforms have limited flexibility in specifying the culture conditions, device architectures, and fluidic connectivity simultaneously. Here, we report a modular microfluidic platform that addresses this limitation by enabling easy conversion of existing microfluidic devices into tissue and fluid control modules with self-aligning magnetic interconnects. This enables a 'stick-n-play' approach to assemble planar perfusion circuits that are amenable to both bioimaging-based and analytical measurements. A myriad of tissue culture and flow control TILE modules were successfully constructed with backward compatibility. Finally, we demonstrate applications in constructing recirculating multi-organ systems to emulate liver-mediated bioactivation of nutraceuticals and prodrugs to modulate their therapeutic efficacies in the context of atherosclerosis and cancer. This platform greatly facilitates the integration of existing organs-on-chip models to provide an intuitive and flexible way for users to configure different multi-organ perfusion systems.

Rastreamento anterior para câncer de colo uterino em mulheres com alterações citológicas ou histológicas

OBJETIVO: Analisar a história de rastreamento citológico anterior em mulheres que apresentaram alterações citológicas e confirmação histológica para câncer cervical. MÉTODOS: Estudo transversal com 5.485 mulheres (15-65 anos) que se submeteram a rastreamento para o câncer cervical entre fevereiro de 2002 a março de 2003, em São Paulo e Campinas, SP. Aplicou-se questionário comportamental e foi feita a coleta da citologia oncológica convencional ou em base líquida. Para as participantes com alterações citológicas indicou-se colposcopia e, nos casos anormais, procedeu-se à biópsia cervical. Para investigar a associação entre as variáveis qualitativas e o resultado da citologia, utilizou-se o teste de qui-quadrado de Pearson com nível de significância de 5%. RESULTADOS: Dentre os resultados citológicos, 354 (6,4%) foram anormais, detectando-se 41 lesões intra-epitelial escamosa de alto grau e três carcinomas; em 92,6% revelaram-se normais. De 289 colposcopias realizadas, 145 (50,2%) apresentaram alterações. Dentre as biópsias cervicais foram encontrados 14 casos de neoplasia intra-epitelial cervical grau 3 e quatro carcinomas. Referiram ter realizado exame citológico prévio: 100% das mulheres com citologia compatível com carcinoma, 97,6% das que apresentaram lesões intra-epiteliais de alto grau, 100% daquelas com confirmação histológica de carcinoma cervical, e 92,9% das mulheres com neoplasia intra-epitelial cervical grau 3. A realização de citologia anterior em período inferior a três anos foi referida, respectivamente, por 86,5% e 92,8% dessas participantes com alterações citológicas e histológicas. CONCLUSÕES: Entre as mulheres que apresentaram confirmação histológica de neoplasia intra-epitelial cervical grau 3 ou carcinoma e aquelas que não apresentaram alterações histológicas não houve diferença estatisticamente significante do número de exames citológicos realizados, bem como o tempo do último exame citológico anterior.

NAL-NL1 procedure for fitting nonlinear hearing aids: characteristics and comparisons with other procedures

A new procedure for fitting nonlinear hearing aids (National Acoustic Laboratories' nonlinear fitting procedure, version 1 [NAL-NL1]) is described. The rationale is to maximize speech intelligibility while constraining loudness to be normal or less. Speech intelligibility is predicted by the Speech Intelligibility Index (SII), which has been modified to account for the reduction in performance associated with increasing degrees of hearing loss, especially at high frequencies. Prescriptions are compared for the NAL-NL1, desired sensation level [input/output], FIG6, and a threshold version of the Independent Hearing Aid Fitting Forum procedures. For an average speech input level, the NAL-NL1 prescriptions are very similar to those of the well-established NAL-Revised, Profound procedure. Compared with the other procedures, NAL-NL1 prescribes less low-frequency gain for flat and upward sloping audiograms. It prescribes less high-frequency gain for steeply sloping high-frequency hearing losses. NAL-NL1 tends to prescribe less compression than the other procedures. All procedures differ considerably from one another for some audiograms.

Oxyleghemoglobin-mediated Hydrogen Oxidation by Rhizobium japonicum USDA 122 DES Bacteroids

Oxyleghemoglobin was used to supply low concentrations of O(2) to H(2)-oxidizing bacteroids from Rhizobium japonicum USDA 122 DES. The H(2) oxidation system of these bacteroids was capable of effectively utilizing O(2) at the low concentrations of O(2) expected to be found in soybean nodules. Apparent K(m) values of approximately 10 nanomolar O(2) have been calculated for the oxyhydrogen reaction. These values include the K(m) values for both H(2) oxidation and endogenous substrate oxidation. Even in the presence of oxyleghemoglobin, H(2) additions stimulated C(2)H(2) reduction, reduced the rate of endogenous respiration and maintained the ATP contents of bacteroids. In our reconstituted oxyleghemoglobin and bacteriod system, we estimate that the H(2) oxidation system is capable of recycling all of the H(2) evolved during the N(2) fixation process.

Thyroid surgery in children and teenagers

From 1961 to 1976 62 patients under age 20 underwent thyroidectomy for various thyroid disorders. Twenty-four thyroid lobectomies and eight subtotal or near-total thyroidectomies were performed for benign nodular goiter. Eight near-total thyroidectomies and two thyroid lobectomies were performed for carcinoma. Two patients also had a radical neck dissection. Twenty patients with hyperthyroidism underwent near-total thyroidectomy. Postoperative complications occurred in six patients-all with hyperthyroidism. Operative mortality was zero. Two indications for thyroidectomy in our series were nodular goiter (to rule out carcinoma), and hyperthyroidism (that was not well-controlled medically or where surgery was chosen as primary therapy). In patients with nodular goiters that required surgery, a minimal complication rate occurred. By contrast, surgery for hyperthyroidism was associated with a high postoperative complication rate, six of 20 patients or 30%, which must be anticipated by the surgeon.

Enzymes of the glyoxylate cycle in rhizobia and nodules of legumes

The relatively high level of fatty acids in soybean nodules and rhizobia from soybean nodules suggested that the glyoxylate cycle might have a role in nodule metabolism. Several species of rhizobia in pure culture were found to have malate synthetase activity when grown on a number of different carbon sources. Significant isocitrate lyase activity was induced when oleate, which presumably may act as an acetyl CoA precursor, was utilized as the principle carbon source. Malate synthetase was active in extracts of rhizobia from nodules of bush bean (Phaseolus vulgaris L.), cowpea (Vigna sinensis L.), lupine (Lupinus angustifolius L.) and soybean (Glycine max L. Merr.). Activity of malate synthetase was, however, barely detectable in rhizobia from alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.) and pea (Pisum sativum L.) nodules. Appreciable isocitrate lyase activity was not detected in rhizobia from nodules nor was it induced by depletion of endogenous substrates by incubation of excised bush bean nodules. Although rhizobia has the potential for the formation of the key enzymes of the glyoxylate cycle, the absence of isocitrate lyase activity in bacteria isolated from nodules indicated that the glyoxylate cycle does not operate in the symbiotic growth of rhizobia and that the observed high content of fatty acids in nodules and nodule bacteria probably is related to a structural role.