Combined Effects of Zeta-potential and Temperature of Nanopores on Diffusioosmotic Ion Transport.

Diffusioosmosis (DO) results from ion transport near charged surfaces in the presence of electrolyte gradients and is critical in nanofluidic systems. However, DO has not yet been comprehensively studied because nanofabrication materials have limitations of low throughput and difficult quantification. Herein, we describe a self-assembled particle membrane (SAPM)-integrated microfluidic platform that can modulate the material properties (e.g., zeta-potential) and transport flux of nanopores. We quantify the effect of the zeta-potential on DO by measuring the electrical signals across three different nanopores/nanochannels of the SAPM. We then empirically quantify the effects of the temperature and ionic strength of the electrolytes on DO and reveal a nonlinear relationship with DO-driven ion transport; the ionic strengths govern the DO- or diffusion-effective ion transport phenomena. Finally, we demonstrate DO-driven electric power generation with enhanced performance as a potential application under optimized experimental conditions.

Dynamic Culture and Selective Extraction of Target Microbial Cells in Self-Assembled Particle Membrane-Integrated Microfluidic Bioreactor Array.

Various microfluidic devices have overcome many disadvantages common to conventional bioreactor systems by enabling active manipulation of cell-culture conditions, monitoring of cellular responses in high-throughput mode, and extraction of target cells in a relatively rapid and low-cost manner. However, existing microfluidic devices still have limitations, including the complexity of their operation and a lack of availability of dynamic control of the chemical environment. Here, we present a novel microfluidic bioreactor array device capable of not only the stable and dynamic programing of cell-culture environments but also the selective extraction of target cells. This device comprises 64 microchambers in a 16 × 4 array format, and each microchamber is integrated with a robust and nanoporous membrane on one side and an H-shaped entrance on the other. The membrane made of self-assembled particles allowed continuous and sequential delivery of various nutrients containing gene inducers to compartmentalized microbial cells, thereby enabling dynamic cell culturing. Additionally, the H-shaped entrance was used for local and selective blocking of the microchamber by employing UV-curable material, thereby enabling the retrieval of target cells from the device while sequestering nontarget cells in the microchambers. Our results demonstrated that the targeted rare cells could be isolated and separated from a mixture of cells by repeating the extraction procedure. Therefore, we anticipate that this microfluidic bioreactor array device will be widely used for not only screening/extraction but also off-chip postanalyses of various microorganisms.

Novel chimeric peptide with enhanced cell specificity and anti-inflammatory activity.

An antimicrobial peptide (AMP), Hn-Mc, was designed by combining the N-terminus of HPA3NT3 and the C-terminus of melittin. This chimeric AMP exhibited potent antibacterial activity with low minimal inhibitory concentrations (MICs), ranging from 1 to 2 µM against four drug-susceptible bacteria and ten drug-resistant bacteria. Moreover, the hemolysis and cytotoxicity was reduced significantly compared to those of the parent peptides, highlighting its high cell selectivity. The morphological changes in the giant unilamellar vesicles and bacterial cell surfaces caused by the Hn-Mc peptide suggested that it killed the microbial cells by damaging the membrane envelope. An in vivo study also demonstrated the antibacterial activity of the Hn-Mc peptide in a mouse model infected with drug-resistant bacteria. In addition, the chimeric peptide inhibited the expression of lipopolysaccharide (LPS)-induced cytokines in RAW 264.7 cells by preventing the interaction between LPS and Toll-like receptors. These results suggest that this chimeric peptide is an antimicrobial and anti-inflammatory candidate as a pharmaceutic agent.

Microscale diffusion measurements and simulation of a scaffold with a permeable strut.

Electrospun nanofibrous structures provide good performance to scaffolds in tissue engineering. We measured the local diffusion coefficients of 3-kDa FITC-dextran in line patterns of electrospun nanofibrous structures fabricated by the direct-write electrospinning (DWES) technique using the fluorescence recovery after photobleaching (FRAP) method. No significant differences were detected between DWES line patterns fabricated with polymer supplied at flow rates of 0.1 and 0.5 mL/h. The oxygen diffusion coefficients of samples were estimated to be ~92%-94% of the oxygen diffusion coefficient in water based on the measured diffusion coefficient of 3-kDa FITC-dextran. We also simulated cell growth and distribution within spatially patterned scaffolds with struts consisting of either oxygen-permeable or non-permeable material. The permeable strut scaffolds exhibited enhanced cell growth. Saturated depths at which cells could grow to confluence were 15% deeper for the permeable strut scaffolds than for the non-permeable strut scaffold.

More than magnetic isolation: Dynabeads as strong Raman reporters towards simultaneous capture and identification of targets.

Dynabeads are superparamagnetic particles used for immunomagnetic purification of cells and biomolecules. Post-capture, however, target identification relies on tedious culturing, fluorescence staining and/or target amplification. Raman spectroscopy presents a rapid detection alternative, but current implementations target cells themselves with weak Raman signals. We present antibody-coated Dynabeads as strong Raman reporter labels whose effect can be considered a Raman parallel of immunofluorescent probes. Recent developments in techniques for separating target-bound Dynabeads from unbound Dynabeads makes such an implementation feasible with high specificity. We deploy Dynabeads anti-Salmonella to bind and identify Salmonella enterica, a major foodborne pathogen. Dynabeads present major peaks around 1000 and 1600 cm-1 from aliphatic and aromatic C-C stretching of the polystyrene coating and near 1350 cm-1 from the É£-Fe2O3 and Fe3O4 core, confirmed with electron dispersive X-ray (EDX) imaging. Minor to no contributions are made from the surface antibodies themselves as confirmed by Raman analysis of surface-activated, antibody-free beads. Dynabeads' Raman signature can be measured in dry and liquid samples even at single shot ~30 × 30 µm area imaging using 0.5 s, 7 mW laser acquisition with single and clustered beads providing a 44- and 68-fold larger Raman intensity compared to signature from cells. Higher polystyrene and iron oxide content in clusters yields larger signal intensity and conjugation to bacteria strengthens clustering as a bacterium can bind to more than one bead as observed via transmission electron microscopy (TEM). Our findings shed light on the intrinsic Raman reporter nature of Dynabeads. When combined with emerging techniques for the separation of target-bound Dynabeads from unbound Dynabeads such as using centrifugation through a density media bi-layer, they have potential to demonstrate their dual function for target isolation and detection without tedious staining steps or unique plasmonic substrate engineering, advancing their applications in heterogeneous samples like food, water, and blood.

Fabrication of patterned nanofibrous mats using direct-write electrospinning.

Due to the numerous advantages of nanofibers, there is a strong demand in various fields for nanofibrous structures fabricated by electrospinning. However, the process is currently beset by troublesome limitations with respect to geometric and morphological control of electrospun nanofibrous mats. This study presents a direct-write electrospinning process and apparatus with improved focusing and scanning functionalities for the fabrication of various patterned thick mats and nanofibrous patterns with high geometric fidelity, supported by a number of experimental results. Consequently, various patterned nanofibrous mats were fabricated using the developed method. Additionally, the fabricated mat was successfully used for cell patterning as a bioengineering application. The proposed method is expected to significantly improve the properties and functionalities of nanofibrous mats in a variety of applications.

Review on Multicomponent Hydrogel Bioinks Based on Natural Biomaterials for Bioprinting 3D Liver Tissues.

Three-dimensional (3D)-printed in vitro tissue models have been used in various biomedical fields owing to numerous advantages such as enhancements in cell response and functionality. In liver tissue engineering, several studies have been reported using 3D-printed liver tissue models with improved cellular responses and functions in drug screening, liver disease, and liver regenerative medicine. However, the application of conventional single-component bioinks for the printing of 3D in vitro liver constructs remains problematic because of the complex structural and physiological characteristics of the liver. The use of multicomponent bioinks has become an attractive strategy for bioprinting 3D functional in vitro liver tissue models because of the various advantages of multicomponent bioinks, such as improved mechanical properties of the printed tissue construct and cell functionality. Therefore, it is essential to review various 3D bioprinting techniques and multicomponent hydrogel bioinks proposed for liver tissue engineering to suggest future directions for liver tissue engineering. Accordingly, we herein review multicomponent bioinks for 3D-bioprinted liver tissues. We first describe the fabrication methods capable of printing multicomponent bioinks and introduce considerations for bioprinting. We subsequently categorize and evaluate the materials typically utilized for multicomponent bioinks based on their characteristics. In addition, we also review recent studies for the application of multicomponent bioinks to fabricate in vitro liver tissue models. Finally, we discuss the limitations of current studies and emphasize aspects that must be resolved to enhance the future applicability of such bioinks.

Noise, sign problems, and statistics.

We show how sign problems in simulations of many-body systems can manifest themselves in the form of heavy-tailed correlator distributions, similar to what is seen in electron propagation through disordered media. We propose an alternative statistical approach for extracting ground state energies in such systems, illustrating the method with a toy model and with lattice data for unitary fermions.

Low-electric-potential-assisted diffusiophoresis for continuous separation of nanoparticles on a chip.

Nanoparticle separation techniques are of significant importance in nanoscience and nanotechnological applications and different concentration gradients, electric/dielectric forces, flow/pressure fields, and acoustic waves have been intensively investigated. However, precise separation of nanoparticles has many technical challenges in terms of sizes, shapes, and material properties, limiting the separation resolution, capability, applicability, throughput and so on. In this study, we present a microfluidic device for continuous separation of nanoparticles by combining diffusiophoresis (DP) and electrophoresis (EP) to achieve high separation performance. Concentration gradients formed from sodium chloride (NaCl) and potassium acetate (K-acetate) passively drive the diffusiophoretic migration of nanoparticles. Simultaneously, a low electric potential is additionally applied to impose a synergistic effect on nanoparticle migration by size and surface charge, which is called low-electric-potential-assisted DP (LEPDP). Using a LEPDP-based separation device, we demonstrate the separation of nanoparticles having different sizes (diameters of 500, 200, and 50 nm) and under different surface-charge conditions (carboxylated polystyrene, silica, and polylactide). The resulting separation performance exceeded 95%, in terms of size uniformity, which is about two times better than that obtained using DP alone. We also emphasize that the enhancement of separation performance only needs a small voltage (<1 V), thereby demonstrating that our multiphysical approach could be utilized for high-resolution and portable nanoparticle separation on a chip without the side effects associated with high electric fields. Lastly, we ensure that rapid and precise bio/chemical sensing and analysis of various nanosized particles would be envisioned by strategically combining two nonlinear but synergistic migration effects.

Micro-/Nanofluidics for Liquid-Mediated Patterning of Hybrid-Scale Material Structures.

Various materials are fabricated to form specific structures/patterns at the micro-/nanoscale, which exhibit additional functions and performance. Recent liquid-mediated fabrication methods utilizing bottom-up approaches benefit from micro-/nanofluidic technologies that provide a high controllability for manipulating fluids containing various solutes, suspensions, and building blocks at the microscale and/or nanoscale. Here, the state-of-the-art micro-/nanofluidic approaches are discussed, which facilitate the liquid-mediated patterning of various hybrid-scale material structures, thereby showing many additional advantages in cost, labor, resolution, and throughput. Such systems are categorized here according to three representative forms defined by the degree of the free-fluid-fluid interface: free, semiconfined, and fully confined forms. The micro-/nanofluidic methods for each form are discussed, followed by recent examples of their applications. To close, the remaining issues and potential applications are summarized.

Effect of Black Rice Powder on the Quality Properties of Pork Patties.

Physicochemical properties of pork patties formulated with black rice powder were investigated. Moisture contents of samples containing black rice powder were significantly higher than that of the control (p<0.05). Protein, fat, and ash contents increased with increasing black rice powder content. Uncooked and cooked pH values of samples increased with increasing black rice powder content. Lightness and yellowness of samples decreased with increasing concentration of black rice powder. Redness of cooked samples containing black rice powder was significantly lower than that of the control (p<0.05). Water holding capacity and cooking yield of samples increased with increasing black rice powder concentration. Diameter and thickness reduction ratio of samples decreased with increasing black rice powder content. Sensory evaluation of samples showed no significant difference between samples. Thus, black rice powder improved the quality of pork patties.

A cracking-assisted micro-/nanofluidic fabrication platform for silver nanobelt arrays and nanosensors.

Nanowires (NWs) with a high surface-to-volume ratio are advantageous for bio- or chemical sensor applications with high sensitivity, high selectivity, rapid response, and low power consumption. However, NWs are typically fabricated by combining several nanofabrication and even microfabrication processes, resulting in drawbacks such as high fabrication cost, extensive labor, and long processing time. Here, we show a novel NW fabrication platform based on "crack-photolithography" to produce a micro-/nanofluidic channel network. Solutions were loaded along the microchannel, while chemical synthesis was performed in the nanoslit-like nanochannels for fabricating silver nanobelts (AgNBs). In addition, the NW/NB fabrication platform not only made it possible to produce AgNBs in a repeatable, high-throughput, and low-cost manner but also allowed the simultaneous synthesis and alignment of AgNBs on a chip, eliminating the need for special micro- and/or nanofabrication equipment and dramatically reducing the processing time, labor, and cost. Finally, we demonstrated that the AgNBs can be used as chemical sensors, either as prepared or when integrated in a flexible substrate, to detect target analytes such as hydrogen peroxide.

Fabrication of Microfiber Patterns with Ivy Shoot-Like Geometries Using Improved Electrospinning.

Fibers and fibrous structures are used extensively in various fields due to their many advantages. Microfibers, as well as nanofibers, are considered to be some of the most valuable forms of advanced materials. Accordingly, various methods for fabricating microfibers have been developed. Electrospinning is a useful fabrication method for continuous polymeric nano- and microfibers with attractive merits. However, this technique has limitations in its ability to control the geometry of fibrous structures. Herein, advanced electrospinning with direct-writing functionality was used to fabricate microfiber patterns with ivy shoot-like geometries after experimentally investigating the effects of the process conditions on the fiber formation. The surface properties of the fibers were also modified by introducing nanoscale pores through the use of higher levels of humidity during the fabrication process.

Self-assembled particle membranes for in situ concentration and chemostat-like cultivation of microorganisms on a chip.

Recently, microparticles have been used as nanoporous membranes in microfluidic devices, contributing to various bioassays on a chip. Here, we report a self-assembled particle membrane (SAPM) integrated microfluidic device that concentrates particles into an aimed microchamber array by using evaporation-driven capillary forces, and manipulates the chemical environment of the microchamber array by sequentially introducing different solutions. We demonstrate that the SAPM-integrated microchamber array can concentrate microparticles and microbial cells up to 120-fold for 2 h and 35-fold for 1 h, respectively, resulting in remarkably high concentration factors. Additionally, we demonstrate that the microchamber array has high potential as a chemostat-like bioreactor because it can actively manipulate the initial seeding number of bacterial cells and continuously supply and sequentially switch fresh nutrients to them. As an example of various applications, the chemostat-like bioreactor was used as a microbial biosensor platform that enabled microbial sensor cells to respond more efficiently and rapidly to external stimuli, such as heavy metal ions. This was made possible by almost eliminating the initial lag phase that dramatically shortened the whole assay time. Notably, the SAPM-integrated microchamber array not only facilitates various bioassays on a chip but also provides unprecedented experimental platforms to study microorganisms in a simple and convenient manner.

Review of micro/nanotechnologies for microbial biosensors.

A microbial biosensor is an analytical device with a biologically integrated transducer that generates a measurable signal indicating the analyte concentration. This method is ideally suited for the analysis of extracellular chemicals and the environment, and for metabolic sensory regulation. Although microbial biosensors show promise for application in various detection fields, some limitations still remain such as poor selectivity, low sensitivity, and impractical portability. To overcome such limitations, microbial biosensors have been integrated with many recently developed micro/nanotechnologies and applied to a wide range of detection purposes. This review article discusses micro/nanotechnologies that have been integrated with microbial biosensors and summarizes recent advances and the applications achieved through such novel integration. Future perspectives on the combination of micro/nanotechnologies and microbial biosensors will be discussed, and the necessary developments and improvements will be strategically deliberated.

Quality Evaluation of Chicken Nugget Formulated with Various Contents of Chicken Skin and Wheat Fiber Mixture.

This study aimed to investigate the effects of various mixtures of the chicken skin and wheat fiber on the properties of chicken nuggets. Two skin and fiber mixtures (SFM) were prepared using the following formulations; SFM-1: chicken skin (50%), wheat fiber (20%), and ice (30%); and SFM-2: chicken skin (30%), wheat fiber (20%), and ice (50%). Chicken nugget samples were prepared by adding the following amounts of either SFM-1 or SFM-2: 0%, 2.5%, 5%, 7.5%, and 10%. The water content for samples formulated with SFM-1 or SFM-2 was higher than in the control (p<0.05), and increased with increasing the concentrations of SFM-1 and SFM-2. The addition of SFM-1 and SFM-2 had no significant effect on the pH of the samples. The lightness value of uncooked chicken nuggets was higher than that of cooked chicken nuggets for all the samples tested. Chicken nuggets formulated with SFM-1 and SFM-2 displayed higher cooking yields than the control sample. The hardness of the control sample was also lower than the samples containing SFM-1 and SFM-2. The sensory evaluation showed no significant differences between the control and the samples containing SFM. Therefore, the incorporation of a chicken skin and wheat fiber mixture improved the quality of chicken nuggets.

Quality Characteristics of Marinated Chicken Breast as Influenced by the Methods of Mechanical Processing.

The aim of this study was to investigate the effects of various marination processes on the quality characteristics of chicken breast prepared with chicken feet gelatin and wheat fiber. The chicken feet gelatin was swollen with hydrochloric solution (0.1 N HCl, pH 1.31±0.02) and dehydrated by freeze-drying. The composition (w/w) of the marinade was water (10%), soy sauce (12%), phosphate (0.3%), wheat fiber (1.5%), and chicken feet gelatin (1.5%). Three samples of chicken breast were manufactured with Tumbler (only tumbler), Tenderizer (tenderizer and tumbler), and Injector (injector and tumbler). The water content of the Injector sample was significantly higher than those of the Tumbler and Tenderizer samples (p<0.05). During heating, the lightness of all chicken breasts increased and the redness decreased. The tumbling and cooking yield of the Injector sample were significantly higher than those of the Tumbler and Tenderizer samples (p<0.05). The shear force of the Tenderizer sample was significantly lower than that of the Tumbler and Injector samples (p<0.05). No significant differences, except for color, were observed in the sensory analysis of the samples. Thus, the proper selection of mechanical processing is important to improve the quality characteristics of marinated chicken breast, considering the types of final products.