Transparent Electromechanical Stimulation System for Stem Cell Applications

Functionalities of cells and tissues in the human body depend greatly on their specific microenvironment created by a variety of biochemical, electrical and mechanical cues. Current standard in vitro cell cultivation technologies fail to mimic the cellular microenvironment in its full complexity, which makes them unsuitable as physiological models for example in drug development. Therefore, the development of a controlled, biomimetic cell cultivation technology that combines and recreates all features of the cellular microenvironment is of high importance especially in stem cell research. This study introduces two optional system design approaches for a transparent electromechanical cell stimulation device usable for in vitro cell stimulation. The device is aimed as a modular expansion of an earlier introduced mechanical cell stimulation platform. Hereby, it is of high importance that the new electrical-stimulative module expands the functionalities of the existing device, without affecting its original capabilities and benefits. This is realized through incorporation of a stretchable, transparent, electrical-stimulative component in the existing system. The first approach focuses on direct electrical stimulation of cells through transparent conductive polymers, which allows flexible electrical stimulation independent from mechanical stimulation. In the second approach, a system design that utilizes indirect electrical stimulation coupled to the mechanical stimulus created by an embedded piezoelectric layer of cellulose nanocrystals is studied. Various structural integration strategies for the fabrication of stretchable conductive electrodes and nanocomposites containing cellulose nanocrystals thin-films are presented. Their success is evaluated in regards to their structural properties, mechanical durability, electro-stimulative functionality as well as biocompatibility. Stretchable conductive electrodes could only be introduced to the mechanical stimulation system in the form of channel casted electrodes, with limited equiaxial stretchability. However, the fabricated structures were highly transparent and expressed beneficial biological properties. The experimental work also resulted in a new technical approach to create thin, transparent nanocellulose composite, based on surface integration technologies. The achieved structure is easily integrable in the existing mechanical stimulation device, without limiting its transparency, stretchability or biocompatibility

Pneumatic unidirectional cell stretching device for mechanobiological studies of cardiomyocytes

In this paper, we present a transparent mechanical stimulation device capable of uniaxial stimulation, which is compatible with standard bioanalytical methods used in cellular mechanobiology. We validate the functionality of the uniaxial stimulation system using human-induced pluripotent stem cells-derived cardiomyocytes (hiPSC-CMs). The pneumatically controlled device is fabricated from polydimethylsiloxane (PDMS) and provides uniaxial strain and superior optical performance compatible with standard inverted microscopy techniques used for bioanalytics (e.g., fluorescence microscopy and calcium imaging). Therefore, it allows for a continuous investigation of the cell state during stretching experiments. The paper introduces design and fabrication of the device, characterizes the mechanical performance of the device and demonstrates the compatibility with standard bioanalytical analysis tools. Imaging modalities, such as high-resolution live cell phase contrast imaging and video recordings, fluorescent imaging and calcium imaging are possible to perform in the device. Utilizing the different imaging modalities and proposed stretching device, we demonstrate the capability of the device for extensive further studies of hiPSC-CMs. We also demonstrate that sarcomere structures of hiPSC-CMs organize and orient perpendicular to uniaxial strain axis and thus express more maturated nature of cardiomyocytes

Challenges and capabilities of conductive polymeric materials for electromechanical stimulation of stem cells : A case study

Cell cultivation devices that mimic the complex microenvironment of cells in the human body are of high importance for the future of stem cell research. This paper introduces a prototype of an electromechanical stimulation platform as a modular expansion of an earlier developed mechanical stimulation device for stem cell research. A solution processable ink from PEDOT:PSS and graphene is studied as a suitable material for fabrication of transparent stretchable electrodes. Challenges of electrode integration on a flexible membrane using this material are critically discussed.acceptedVersionPeer reviewe

Nanopillar-Assisted SERS Chromatography

Practical implementation of surfaced enhanced Raman spectroscopy (SERS) sensing is hindered by complexity of real-life samples, which often requires long and costly pretreatment and purification. Here, we present a novel nanopillar-assisted SERS chromatography (NPC-SERS) method for simultaneous quantitation of target molecules and analysis of complex, multicomponent fluids, e.g., human urine spiked with a model drug paracetamol (PAR). Gold-coated silicon nanopillar (AuNP) SERS substrates and a centrifugal microfluidic platform are tactfully combined, which allows (i) a precise and fully automated sample manipulation and (ii) spatial separation of different molecular species on the AuNP substrate. The NPC-SERS technique provides a novel approach for wetting the stationary phase (AuNP) using the “wicking effect”, and thus minimizes dilution of analytes. Separation of PAR and the main human urine components (urea, uric acid, and creatinine) has been demonstrated. Quantitative detection of PAR with ultrawide linear dynamic range (0–500 ppm) is achieved by analyzing the spreading profiles of PAR on the AuNP surface. NPC-SERS transforms SERS into a sensing technique with general applicability, facilitating rapid and quantitative detection of analytes in complex biofluids, such as saliva, blood, and urine

Pneumatically actuated elastomeric device for simultaneous mechanobiological studies & live-cell fluorescent microscopy

In this study, we demonstrate the functionality and usability of a compact, pneumatically actuated, elastomeric stimulation device for mechanobiological studies. The soft mechatronic device enables high-resolution live-cell confocal fluorescent imaging during equiaxial stretching. Several single cells can be tracked and imaged repeatedly after stretching periods. For demonstration, we provide image based analysis of dynamic change of the cell body and the nucleus area and actin fiber orientation during mechanical stimulation of mouse embryonic fibroblast (MEF) cells. Additionally, we present the characteristics of the device utilizing computational simulations and experimental validation using a particle tracking method for strain field analysis.acceptedVersionPeer reviewe