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Understanding how immune cells such as monocytes or macrophages within our blood and tissue engulf and destroy foreign organisms is important for developing new therapies. The process undertaken by these cells, called phagocytosis, has yet to be observed in real-time at the single cell level. Microfluidic-based imaging platforms offer a wide range of tools for precise fluid control and biomolecule manipulation that makes regulating long term experiments and data collection possible. With the compatibility between acoustofluidics and light-sheet fluorescent microscopy (LSFM) previously demonstrated, here an acousto-optfluidic device with on-chip fluid flow direction control was developed. The standing surface acoustic waves (SSAWs) were used to trap, load and safeguard individual cells within a highly controllable fluid loop, created via the triggering of on-chip PDMS valves, to demonstrate multiple rounds of live single cell imaging. The valves allowed for the direction of the fluid flow to be changed (between forward and reverse operation) without altering the inlet flow rate, an important factor for performing reproducible and comparable imaging of samples over time. With this high-resolution imaging system, volumetric reconstructions of phagocytosed bacteria within macrophages could be resolved over a total of 9 rounds of imaging: totalling 19 reconstructed images of the cell membrane with visible intracellular bacteria. [ABSTRACT FROM AUTHOR]

The induced quenching in fluorescence upon addition of copper (Cu2+) ions and subsequent regain with aqueous hydrogen sulphide (HS−) was studied with a series of coumarin di(picolyl)amine-based compounds, with varying electron withdrawing/donating abilities. The coumarin analogue with an amino group at the 7-position was the most emissive, followed by the methoxy-variant with both the t-butyl- and difluoro-variants being weakly emissive. The amino-variant was also most responsive to quenching upon the addition of Cu2+ ions and was the most responsive to the subsequent addition of HS− ions. All compounds were shown to form predominately a 1:1 copper(II) complex, supported by mass spectral studies and X-ray crystallography. This investigation sheds light on the structural aspects of the copper-sensor interactions and subsequent copper sequestration, contributing to the understanding of their fluorescence properties and potential applications in sensing and imaging. [ABSTRACT FROM AUTHOR]

The ability to create complex three-dimensional cellular models that can effectively replicate the structure and function of human organs and tissues in vitro has the potential to revolutionize medicine. Such models could facilitate the interrogation of developmental and disease processes underpinning fundamental discovery science, vastly accelerate drug development and screening, or even be used to create tissues for implantation into the body. Realization of this potential, however, requires the recreation of complex biochemical, biophysical, and cellular patterns of 3D tissues and remains a key challenge in the field. Recent advances are being driven by improved knowledge of tissue morphogenesis and architecture and technological developments in bioengineering and materials science that can create the multidimensional and dynamic systems required to produce complex tissue microenvironments. In this article, we discuss challenges for in vitro models of tissues and organs and summarize the current state-of-the art in biomaterials and bioengineered systems that aim to address these challenges. This includes both top-down technologies, such as 3D photopatterning, magnetism, acoustic forces, and cell origami, as well as bottom-up patterning using 3D bioprinting, microfluidics, cell sheet technology, or composite scaffolds. We illustrate the varying ways that these can be applied to suit the needs of different tissues and applications by focussing on specific examples of patterning the bone-tendon interface, kidney organoids, and brain cancer models. Finally, we discuss the challenges and future prospects in applying materials science and bioengineering to develop high-quality 3D tissue structures for in vitro studies. [ABSTRACT FROM AUTHOR]

The precise manipulation of individual cells is a key capability for the study of single cell physiological characteristics or responses to stimuli. Currently, only large cell populations can be transferred with certainty using expensive and laborious flow cytometry platforms. However, when approaching small populations of cells, this task becomes increasingly challenging. Here, we report an effective acoustofluidic micro-dispenser, utilising surface acoustic waves (SAWs), with the ability to trap and release cells on demand, which when combined with an external valve can guide the trajectory of individual cells. We demonstrate single cell trap and release with a single cell trapping effectiveness of 74%, enabling the capability of dispensing a highly controlled amount of cells without any harmful effects. This device has the potential to be easily integrated into a wide range of analytical platforms for applications such as single cell fluorescent imaging and single cell proteomic studies. [ABSTRACT FROM AUTHOR]

The first absorbance biosensor based on pure silicon hollow integrated waveguides is presented in this work. With the use of horseradish peroxidase (HRP) as a model recognition element, an enzymatic sensor for the measurement of hydrogen peroxide was fabricated, numerically simulated, and experimentally characterized. Waveguides with widths ranging from 50 to 80 [micro]m, having a depth of 50 [micro]m and lengths up to 5 mm were easily fabricated by just one photolithographic step. These were further modified by covalent immobilization of HRP using silanization chemistry. Simulation studies of the proposed approach showed a sensor linear behavior up to 300 [micro]M [H.sub.2][O.sub.2] and a sensitivity of 2.7 x [10.sup.-3] AU/[micro]M. Experimental results were in good agreement with the simulated ones. A linear behavior between 10 and 300 [micro]M [H.sub.2][O.sub.2], a sensitivity of 3 x [10.sup.-3] AU/[micro]M, and a signal-to-noise ratio around 20 dB were attained. Also, kinetic studies of the activity of the immobilized enzyme on the silicon waveguide surface gave an apparent Michaelis-Menten constant of 0.44 mM. The simple technology proposed in this work enables the fabrication of cost-effective, easy-to-use, miniaturized biosensor generic platforms, these being envisioned as excellent candidates for the development of lab-on-a-chip systems.

Sperm motility is a significant predictor of male fertility potential and is directly linked to fertilization success in both natural and some forms of assisted reproduction. Sperm motility can be impaired by both genetic and environmental factors, with asthenozoospermia being a common clinical presentation. Moreover, in the setting of assisted reproductive technology clinics, there is a distinct absence of effective and noninvasive technology to increase sperm motility without detriment to the sperm cells. Here, a new method is presented to boost sperm motility by increasing the intracellular rate of metabolic activity using high frequency ultrasound. An increase of 34% in curvilinear velocity (VCL), 10% in linearity, and 32% in the number of motile sperm cells is shown by rendering immotile sperm motile, after just 20 s exposure. A similar effect with an increase of 15% in VCL treating human sperm with the same setting is also identified. This cell level mechanotherapy approach causes no significant change in cell viability or DNA fragmentation index, and, as such, has the potential to be applied to encourage natural fertilization or less invasive treatment choices such as in vitro fertilization rather than intracytoplasmic injection. [ABSTRACT FROM AUTHOR]

Cells can perceive complex mechanical cues across both the micro‐ and nanoscale which can influence their development. While causative effects between surface topography and cellular function can be demonstrated, the variability in materials used in this screening process makes it difficult to discern whether the observed phenotypic changes are indeed a result of topographical cues alone or the inherent difference in material properties. A novel approach to directly imprint micro‐ and nanoscaled topographical features into the base of conventional cell cultureware is thus developed, facilitating its compatibility with standard biological techniques and methods of analysis. The utility of this technology is demonstrated by performing high‐throughput screening across five distinct cell types to interrogate the effects of 12 surface topographies, exemplifying unique cell‐specific responses to both behavior and cell morphological characteristics. The ability of this technology to underpin new insights into how surface topographies can regulate key image descriptors to drive cell fate determination is further demonstrated. These findings will inform the future development of advanced micro‐ and nanostructured cell culture substrates that can regulate cell behavior and fate determination across the life sciences, including fundamental cell biology, drug screening, and cell therapy. [ABSTRACT FROM AUTHOR]

Volumetric, sub-micron to micron level resolution imaging is necessary to assay phenotypes or characteristics at the sub-cellular/organelle scale. However, three-dimensional fluorescence imaging of cells is typically low throughput or compromises on the achievable resolution in space and time. Here, we capitalise on the flow control capabilities of microfluidics and combine it with microoptics to integrate light-sheet based imaging directly into a microfluidic chip. Our optofluidic system flows suspended cells through a sub-micrometer thick light-sheet formed using micro-optical components that are cast directly in polydimethylsiloxane (PDMS). This design ensures accurate alignment, drift-free operation, and easy integration with conventional microfluidics, while providing sufficient spatial resolution, optical sectioning and volumetric data acquisition. We demonstrate imaging rates of 120 ms per cell at sub-μm resolution, that allow extraction of complex cellular phenotypes, exemplified by imaging of cell clusters, receptor distribution, and the analysis of endosomal size changes. [ABSTRACT FROM AUTHOR]

Cells are able to perceive complex mechanical cues from their microenvironment, which in turn influences their development. Although the understanding of these intricate mechanotransductive signals is evolving, the precise roles of substrate microtopography in directing cell fate is still poorly understood. Here, UV nanoimprint lithography is used to generate micropillar arrays ranging from 1 to 10 µm in height, width, and spacing to investigate the impact of microtopography on mechanotransduction. Using mesenchymal stem cells (MSCs) as a model, stark pattern‐specific changes in nuclear architecture, lamin A/C accumulation, chromatin positioning, and DNA methyltransferase expression, are demonstrated. MSC osteogenesis is also enhanced specifically on micropillars with 5 µm width/spacing and 5 µm height. Intriguingly, the highest degree of osteogenesis correlates with patterns that stimulated maximal nuclear deformation which is shown to be dependent on myosin‐II‐generated tension. The outcomes determine new insights into nuclear mechanotransduction by demonstrating that force transmission across the nuclear envelope can be modulated by substrate topography, and that this can alter chromatin organisation and impact upon cell fate. These findings have potential to inform the development of microstructured cell culture substrates that can direct cell mechanotransduction and fate for therapeutic applications in both research and clinical sectors. [ABSTRACT FROM AUTHOR]

The number of studies conducted about nonenzymatic electrochemical sensors has increased in recent years due to the development of more stable and robust electrodes using noble metals. One of the key aspects for achieving high sensing performance including detection limit and sensitivity is the design of electrode architecture. Herein, we report a new electrochemical sensing platform featuring ultrathin standing gold nanowires (AuNWs) for nonenzymatic detection of hydrogen peroxide (H2O2). The use of AuNWs resulted in an increased electron transfer efficiency due to the higher active surface area compared to traditional gold film electrodes. This sensor demonstrates good selectivity, reproducibility, a linear range up to 49.5 mM of H2O2 with a sensitivity of 0.185±0.003 mAmM−1cm−2 and a limit of detection of 111 μM. The biological relevance of this sensor was tested in cell culture media to illustrate the performance of the proposed sensing electrode in complex biological media. [ABSTRACT FROM AUTHOR]

To assist the transition of 3D bioprinting technology from simple lab-based tissue fabrication, to fully functional and implantable organs, the technology must not only provide shape control, but also functional control. This can be accomplished by replicating the cellular composition of the native tissue at the microscale, such that cell types interact to provide the desired function. There is therefore a need for precise, controllable, multi-material printing that could allow for high, possibly even single cell, resolution. This paper aims to draw attention to technological advancements made in 3D bioprinting that target the lack of multi-material, and/or multi cell-type, printing capabilities of most current devices. Unlike other reviews in the field, which largely focus on variations in single-material 3D bioprinting involving the standard methods of extrusion-based, droplet-based, laser-based, or stereolithographic methods; this review concentrates on sophisticated multi-material 3D bioprinting using multi-cartridge printheads, co-axial nozzles and microfluidic-enhanced printing nozzles. [ABSTRACT FROM AUTHOR]

Structuring SU-8 based superparamagnetic polymer composite (SPMPC) containing Fe3O4 nanoparticles by photolithography is limited in thickness due to light absorption by the nanoparticles. Hence, obtaining thicker structures requires alternative processing techniques. This paper presents a method based on inkjet printing and thermal curing for the fabrication of much thicker hemispherical microstructures of SPMPC. The microstructures are fabricated by inkjet printing the nanoparticle-doped SU-8 onto flat substrates functionalized to reduce the surface energy and thus the wetting. The thickness and the aspect ratio of the printed structures are further increased by printing the composite onto substrates with confinement pedestals. Fully crosslinked microstructures with a thickness up to 88.8 μm and edge angle of 112° ± 4° are obtained. Manipulation of the microstructures by an external field is enabled by creating lines of densely aggregated nanoparticles inside the composite. To this end, the printed microstructures are placed within an external magnetic field directly before crosslinking inducing the aggregation of dense Fe3O4 nanoparticle lines with in-plane and out-of-plane directions. [ABSTRACT FROM AUTHOR]

A volume hologram recorded with a lens array is proposed as a color transflective screen for Head Worn Display (HWD) systems. Design, fabrication as well as proof of concept are reported. Light from a single MEMS-based projector is efficiently diffracted towards the eye with an angular spread given by the numerical aperture of the lenses forming the lens array. Using a dual-focus contact lens, full color high-resolution images are added to the HWD user's normal vision. A full color system with a 55 degrees lateral field of view is demonstrated. This screen offers the possibility for small footprint and large field of view HWD's. [ABSTRACT FROM PUBLISHER]

We describe design and miniaturization of a polymeric optical interface for flow monitoring in biomicrofluidics applications based on polydimethylsiloxane technology, providing optical transparency and compatibility with biological tissues. Design and ray tracing simulation are presented as well as device realization and optical analysis of flow dynamics in microscopic blood vessels. Optics characterization of this polymeric microinterface in dynamic experimental conditions provides a proof of concept for the application of the device to two-phase flow monitoring in both in vitro experiments and in vivo microcirculation investigations. This technology supports the study of in vitro and in vivo microfluidic systems. It yields simultaneous optical measurements, allowing for continuous monitoring of flow. This development, integrating a well-known and widely used optical flow monitoring systems, provides a disposable interface between live mammalian tissues and microfluidic devices making them accessible to detection/processing technology, in support or replacing standard intravital microscopy. [ABSTRACT FROM AUTHOR]

Lab-on-a-chip sensing technologies have changed how cell biology research is conducted. This review summarises the progress in the lab-on-a-chip devices implemented for the detection of cellular metabolites. The review is divided into two subsections according to the methods used for the metabolite detection. Each section includes a table which summarises the relevant literature and also elaborates the advantages of, and the challenges faced with that particular method. The review continues with a section discussing the achievements attained due to using lab-on-a-chip devices within the specific context. Finally, a concluding section summarises what is to be resolved and discusses the future perspectives. [ABSTRACT FROM AUTHOR]

Nowadays, there is increasing number of electrochemical biosensors which utilize chitosan (Ch); as an enzyme immobilization matrix, and conductive nanomaterials; as electron carriers improving sensitivity of the biosensor. However, the challenge these sensors face is the lack of uniform dispersion of nanomaterials throughout the Ch film, which can negatively affect analytical performance of the biosensor. In this study, we report the development of an enzyme immobilization matrix that displays enhanced electrochemical performance thanks to a novel conductive thin film prepared via in situ electrocopolymerization of pyrrole (Py) and thiophene-grafted chitosan (Th-Ch). This is a simple thin film preparation method that can help overcome aforementioned challenges by providing a uniformly distributed conductive layer on the electrode. We are also for the first time reporting the synthesis and characterization of Th-Ch, where grafted Th plays an essential role as a linking group between Ch and Py. The resulting conductive Ch-based thin film was modified with glucose oxidase (GOx) which served as a model enzyme. In situ electrocopolymerization of Py with Th-Ch resulted in a highly conductive thin film enabling approximately 40% higher sensitivity when compared to a Py-Ch composite. This new type of composite thin film is promising in biosensor technology due to its biocompatibility, the chemically and physically modifiable structure, as well as its electrical conductivity. Unlabelled Image [ABSTRACT FROM AUTHOR]