Rapid prototyping of electrochemical lateral flow devices: stencilled electrodes.

A straightforward and very cost effective method is proposed to prototype electrodes using pressure sensitive adhesives (PSA) and a simple cutting technique. Two cutting methods, namely blade cutting and CO2 laser ablation, are compared and their respective merits are discussed. The proposed method consists of turning the protective liner on the adhesive into a stencil to apply screen-printing pastes. After the electrodes have been printed, the liner is removed and the PSA can be used as a backing material for standard lateral flow membranes. We present the fabrication of band electrodes down to 250 µm wide, and their characterization using microscopy techniques and cyclic voltammetry. The prototyping approach presented here facilitates the development of new electrochemical devices even if very limited fabrication resources are available. Here we demonstrate the fabrication of a simple lateral-flow device capable of determining glucose in blood. The prototyping approach presented here is highly suitable for the development of novel electroanalytical tools.

Critical contribution of mitochondria in the development of cardiomyopathy linked to desmin mutation.

BACKGROUND: Beyond the observed alterations in cellular structure and mitochondria, the mechanisms linking rare genetic mutations to the development of heart failure in patients affected by desmin mutations remain unclear due in part, to the lack of relevant human cardiomyocyte models. METHODS: To shed light on the role of mitochondria in these mechanisms, we investigated cardiomyocytes derived from human induced pluripotent stem cells carrying the heterozygous DESE439K mutation that were either isolated from a patient or generated by gene editing. To increase physiological relevance, cardiomyocytes were either cultured on an anisotropic micropatterned surface to obtain elongated and aligned cardiomyocytes, or as a cardiac spheroid to create a micro-tissue. Moreover, when applicable, results from cardiomyocytes were confirmed with heart biopsies of suddenly died patient of the same family harboring DESE439K mutation, and post-mortem heart samples from five control healthy donors. RESULTS: The heterozygous DESE439K mutation leads to dramatic changes in the overall cytoarchitecture of cardiomyocytes, including cell size and morphology. Most importantly, mutant cardiomyocytes display altered mitochondrial architecture, mitochondrial respiratory capacity and metabolic activity reminiscent of defects observed in patient's heart tissue. Finally, to challenge the pathological mechanism, we transferred normal mitochondria inside the mutant cardiomyocytes and demonstrated that this treatment was able to restore mitochondrial and contractile functions of cardiomyocytes. CONCLUSIONS: This work highlights the deleterious effects of DESE439K mutation, demonstrates the crucial role of mitochondrial abnormalities in the pathophysiology of desmin-related cardiomyopathy, and opens up new potential therapeutic perspectives for this disease.

Polysaccharide-Protein Multilayers Based on Chitosan-Fibrinogen Assemblies for Cardiac Cell Engineering.

The cell and tissue culture substrates play a pivotal role in the regulation of cell-matrix and cell-cell interactions. The surface properties of the materials control a wide variety of cell functions. Amongst various methods, layer-by-layer (LbL) assembly is a versatile surface coating technique for creating controllable bio-coatings. Here, polysaccharide/protein multilayers are proposed, which are fabricated by immersive LbL assembly and based on the chitosan/fibrinogen pair for improving the adhesion and spreading of cardiomyocytes. Two approaches in LbL assembly are employed for clarifying the effect of the bilayers order and their concentration on cardiomyocytes viability and morphology. Fourier transform infrared spectroscopy (FTIR) measurements show that the adsorption of the biopolymers is enhanced during the LbL deposition in a synergistic manner. Contact angle measurements indicate that the multilayers are alternating from less to more hydrophilic behavior depending on the biopolymer that is added last. Confocal microscopy with immunostained fibrinogen reveals that the amount of the protein is higher when the concentration of the immersion solution is increased, however, for low solution concentration it is speculated that interdigitation between the separate biopolymer layers takes place. This work motivates the use of fibrinogen in polysaccharide/protein multilayers for enhanced cytocompatibility in cardiac tissue engineering.

Cyto- and bio-compatibility assessment of plasma-treated polyvinylidene fluoride scaffolds for cardiac tissue engineering.

As part of applications dealing with cardiovascular tissue engineering, drop-cast polyvinylidene fluoride (PVDF) scaffolds have been treated by cold plasma to enhance their adherence to cardiac cells. The scaffolds were treated in a dielectric barrier device where cold plasma was generated in a gaseous environment combining a carrier gas (helium or argon) with/without a reactive gas (molecular nitrogen). We show that an Ar-N2 plasma treatment of 10 min results in significant hydrophilization of the scaffolds, with contact angles as low as 52.4° instead of 132.2° for native PVDF scaffolds. Correlation between optical emission spectroscopy and X-ray photoelectron spectroscopy shows that OH radicals from the plasma phase can functionalize the surface scaffolds, resulting in improved wettability. For all plasma-treated PVDF scaffolds, the adhesion and maturation of primary cardiomyocytes is increased, showing a well-organized sarcomeric structure (α-actinin immunostaining). The efficacy of plasma treatment was also supported by real-time PCR analysis to demonstrate an increased expression of the genes related to adhesion and cardiomyocyte function. Finally, the biocompatibility of the PVDF scaffolds was studied in a cardiac environment, after implantation of acellular scaffolds on the surface of the heart of healthy mice. Seven and 28 days after implantation, no exuberant fibrosis and no multinucleated giant cells were visible in the grafted area, hence demonstrating the absence of foreign body reaction and the biocompatibility of these scaffolds.

Integrated optical frequency-resolved Mach-Zehnder interferometers for label-free affinity sensing.

Integrated Optical Frequency-Resolved Mach-Zehnder Interferometry (IO FR-MZI) is introduced as an alternative, cost-efficient operation principle for integrated optical label-free affinity sensors that can combine high sensitivity with high versatility in terms of potential applications and experimental configurations. A detailed theoretical analysis of the method is presented followed by a semi-analytical approximation and numerical calculations in order to quantify the sensitivity and limits of detection of the FR-MZI over Single Wavelength MZI. The obtained results substantiate that IO FR-MZI- based sensors constitute a generic technological platform of high sensitivity that can be implemented into a plethora of detection schemes. For an optimized optical design well below 1mm in length the limit of detection can be as low as 0.025A in terms of adlayer effective thickness allowing for truly miniaturized integrated optical sensors fabricated with high yield with standard microfabrication techniques.

Design of Functional Electrospun Scaffolds Based on Poly(glycerol sebacate) Elastomer and Poly(lactic acid) for Cardiac Tissue Engineering.

Many works focus on the use of polyesters such as poly(lactic acid) (PLA) to produce nanofibrous scaffolds for cardiac tissue engineering. However, such scaffolds are hydrophobic and difficult to functionalize. Here, we show that adding 30% of poly(glycerol sebacate) (PGS) elastomer within PLA leads to PLA:PGS scaffolds with improved biological properties, depending on the processing parameters. Two categories of fibers were produced by blend electrospinning, with diameters of 600 and 1300 nm. The resulting fibers were cured at 90 or 120 °C to achieve two different cross-linking densities. The designed scaffolds were considered for cytocompatibility, biocompatibility, biodegradability, and chemical and mechanical properties. Our results demonstrated that the presence of PGS increases the hydrophilicity of the material and thus improves surface functionalization by Matrigel or laminin coating, commonly used cell culture matrices. PLA:PGS scaffolds associated with Matrigel or laminin allow an increased material-cell interaction. Moreover, the cardiomyocytes seeded on such scaffolds acquire a morphology similar to that observed in native tissue, the result being more remarkable on fibers having the smallest diameter and the highest PGS cross-linking density. In addition, these scaffolds induce neovascularization without an inflammatory response and foreign body giant cell response after grafting on a mouse heart. Hence, the improved biocompatibility and the ability to support cardiomyocyte development suggest that thin PLA:PGS scaffolds could be promising biomaterials for cardiac application.

A monolithic photonic microcantilever device for in situ monitoring of volatile compounds.

A monolithic photonic microcantilever device is presented comprising silicon light sources and detectors self-aligned to suspended silicon nitride waveguides all integrated into the same silicon chip. A silicon nitride waveguide optically links a silicon light emitting diode to a detector. Then, the optocoupler releases a localized formation of resist-silicon nitride cantilevers through e-beam lithography, dry etching and precisely controlled wet etching through a special microfluidic set-up. Fine micro-optical sensing functions are performed without the need for any off-chip optics. As the bimaterial microcantilevers are deflected by the stressed polymer film, the disrupted waveguide acts like a photonic switch. Cantilever deflections in the order of 1 A caused by thickness variations in the order of 0.005 A are detectable following changes in the physicochemical factors affecting the polymer film thickness. Such factors include the sorption of volatile compounds and through a proper set-up the response to certain vapor concentrations is monitored in real time.

Permanently hydrophilic, piezoelectric PVDF nanofibrous scaffolds promoting unaided electromechanical stimulation on osteoblasts.

Biomimetic functional scaffolds for tissue engineering should fulfil specific requirements concerning structural, bio-chemical and electro-mechanical characteristics, depending on the tissue that they are designed to resemble. In bone tissue engineering, piezoelectric materials based on poly(vinylidene fluoride) (PVDF) are on the forefront, due to their inherent ability to generate surface charges under minor mechanical deformations. Nevertheless, PVDF's high hydrophobicity hinders sufficient cell attachment and expansion, which are essential in building biomimetic scaffolds. In this study, PVDF nanofibrous scaffolds were fabricated by electrospinning to achieve high piezoelectricity, which was compared with drop-cast membranes, as it was confirmed by XRD and FTIR measurements. Oxygen plasma treatment of the PVDF surface rendered it hydrophilic, and surface characterization revealed a long-term stability. XPS analysis and contact angle measurements confirmed an unparalleled two-year stability of hydrophilicity. Osteoblast cell culture on the permanently hydrophilic PVDF scaffolds demonstrated better cell spreading over the non-treated ones, as well as integration into the scaffold as indicated by SEM cross-sections. Intracellular calcium imaging confirmed a higher cell activation on the piezoelectric electrospun nanofibrous scaffolds. Combining these findings, and taking advantage of the self-stimulation of the cells due to their attachment on the piezoelectric PVDF nanofibers, a 3D tissue-like functional self-sustainable scaffold for bone tissue engineering was fabricated.

Fibers for hearts: A critical review on electrospinning for cardiac tissue engineering.

Cardiac cell therapy holds a real promise for improving heart function and especially of the chronically failing myocardium. Embedding cells into 3D biodegradable scaffolds may better preserve cell survival and enhance cell engraftment after transplantation, consequently improving cardiac cell therapy compared with direct intramyocardial injection of isolated cells. The primary objective of a scaffold used in tissue engineering is the recreation of the natural 3D environment most suitable for an adequate tissue growth. An important aspect of this commitment is to mimic the fibrillar structure of the extracellular matrix, which provides essential guidance for cell organization, survival, and function. Recent advances in nanotechnology have significantly improved our capacities to mimic the extracellular matrix. Among them, electrospinning is well known for being easy to process and cost effective. Consequently, it is becoming increasingly popular for biomedical applications and it is most definitely the cutting edge technique to make scaffolds that mimic the extracellular matrix for industrial applications. Here, the desirable physico-chemical properties of the electrospun scaffolds for cardiac therapy are described, and polymers are categorized to natural and synthetic.Moreover, the methods used for improving functionalities by providing cells with the necessary chemical cues and a more in vivo-like environment are reported.

Quantitative self-powered electrochromic biosensors.

Self-powered sensors are analytical devices able to generate their own energy, either from the sample itself or from their surroundings. The conventional approaches rely heavily on silicon-based electronics, which results in increased complexity and cost, and prevents the broader use of these smart systems. Here we show that electrochromic materials can overcome the existing limitations by simplifying device construction and avoiding the need for silicon-based electronics entirely. Electrochromic displays can be built into compact self-powered electrochemical sensors that give quantitative information readable by the naked eye, simply controlling the current path inside them through a combination of specially arranged materials. The concept is validated by a glucose biosensor coupled horizontally to a Prussian blue display designed as a distance-meter proportional to (glucose) concentration. This approach represents a breakthrough for self-powered sensors, and extends the application of electrochromic materials beyond smart windows and displays, into sensing and quantification.

Nanofibrous clinical-grade collagen scaffolds seeded with human cardiomyocytes induces cardiac remodeling in dilated cardiomyopathy.

Limited data are available on the effects of stem cells in non-ischemic dilated cardiomyopathy (DCM). Since the diffuse nature of the disease calls for a broad distribution of cells, this study investigated the scaffold-based delivery of human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CM) in a mouse model of DCM. Nanofibrous scaffolds were produced using a clinical grade atelocollagen which was electrospun and cross-linked under different conditions. As assessed by scanning electron microscopy and shearwave elastography, the optimum crosslinking conditions for hiPS-CM colonization proved to be a 10% concentration of citric acid crosslinking agent and 150 min of post-electrospinning baking. Acellular collagen scaffolds were first implanted in both healthy mice and those with induced DCM by a cardiac-specific invalidation of serum response factor (SRF). Seven and fourteen days after implantation, the safety of the scaffold was demonstrated by echocardiography and histological assessments. The subsequent step of implantation of the scaffolds seeded with hiPS-CM in DCM induced mice, using cell-free scaffolds as controls, revealed that after fourteen days heart function decreased in controls while it remained stable in the treated mice. This pattern was associated with an increased number of endothelial cells, in line with the greater vascularity of the scaffold. Moreover, a lesser degree of fibrosis consistent with the upregulation of several genes involved in extracellular matrix remodeling was observed. These results support the interest of the proposed hiPS-CM seeded electrospun scaffold for the stabilization of the DCM outcome with potential for its clinical use in the future.

At-line bioprocess monitoring by immunoassay with rotationally controlled serial siphoning and integrated supercritical angle fluorescence optics.

In this paper we report a centrifugal microfluidic "lab-on-a-disc" system for at-line monitoring of human immunoglobulin G (hIgG) in a typical bioprocess environment. The novelty of this device is the combination of a heterogeneous sandwich immunoassay on a serial siphon-enabled microfluidic disc with automated sequential reagent delivery and surface-confined supercritical angle fluorescence (SAF)-based detection. The device, which is compact, easy-to-use and inexpensive, enables rapid detection of hIgG from a bioprocess sample. This was achieved with, an injection moulded SAF lens that was functionalized with aminopropyltriethoxysilane (APTES) using plasma enhanced chemical vapour deposition (PECVD) for the immobilization of protein A, and a hybrid integration with a microfluidic disc substrate. Advanced flow control, including the time-sequenced release of on-board liquid reagents, was implemented by serial siphoning with ancillary capillary stops. The concentration of surfactant in each assay reagent was optimized to ensure proper functioning of the siphon-based flow control. The entire automated microfluidic assay process is completed in less than 30 min. The developed prototype system was used to accurately measure industrial bioprocess samples that contained 10 mg mL(-1) of hIgG.

Monolithically integrated Mach-Zehnder biosensors for real-time label-free monitoring of biomolecular reactions.

Arrays of monolithically integrated Mach-Zehnder interferometers were fabricated by standard silicon technology and applied to the label-free real-time monitoring of biomolecular interactions. Chips accommodating 10 MZIs were functionalized with recognition biomolecules and encapsulated in wafer scale. Detection is based on Frequency-Resolved Mach-Zehnder Interferometry, a new concept that takes advantage of the broad-band input spectrum by monitoring the changes for every input frequency. The sensitivity of the device in terms of refractive index changes (Δn) was calculated using isopropanol/water solutions. A detection limit of Δn = 4 × 10(-6) was calculated. The bioanalytical capabilities of the device there demonstrated through model binding assays (biotin/streptavidin) as well as the detection of total prostate specific antigen in serum samples using devices coated with antigen-specific monoclonal antibody. Detection limits at the pM range were determined.

Monolithically integrated biosensors based on Frequency-Resolved Mach-Zehnder Interferometers for multi-analyte determinations.

The application of fully monolithically-integrated Mach-Zehnder interferometer arrays fabricated by standard silicon technology to the label-free detection of analytes is introduced. Detection with the presented biosensor is based on a novel concept, the Frequency-Resolved Mach-Zehnder Interferometry (FR-MZI). In addition, a smart encapsulation based on an appropriately designed microfluidic system and performed at the wafer scale scheme for the easy delivery of the samples to be analyzed is demonstrated. Testing of the FR-MZI biosensors with model binding assays demonstrated the detection of streptavidin binding to immobilized biotin at concentrations in the sub nM range. This is the first experimental demonstration of the FR-MZI concept as well as the first demonstration of a monolithically fully-integrated MZI biosensor.