A physiologically relevant environment is essential for successful long-term cell culturing in vitro. Precise control of temperature, one of the most crucial environmental parameters in cell cultures, increases the fidelity and repeatability of the experiments. Unfortunately, direct temperature measurement can interfere with the cultures or prevent imaging of the cells. Furthermore, the assessment of dynamic temperature variations in the cell culture area is challenging with the methods traditionally used for measuring temperature in cell culture systems. To overcome these challenges, we integrated a microscale cell culture environment together with live-cell imaging and a precise local temperature control that is based on an indirect measurement. The control method uses a remote temperature measurement and a mathematical model for estimating temperature at the desired area. The system maintained the temperature at 37±0.3 °C for more than 4 days. We also showed that the system precisely controls the culture temperature during temperature transients and compensates for the disturbance when changing the cell cultivation medium, and presented the portability of the heating system. Finally, we demonstrated a successful long-term culturing of human induced stem cell–derived beating cardiomyocytes, and analyzed their beating rates at different temperatures.

Cell culture in-vitro is a well-known method to develop cell and disease models for studying physiologically relevant mechanisms and responses for various applications in life sciences. Conventional methods for instance, using static culture flasks or well plates, have limitations, as these cannot provide accurate tractable models for advanced studies. However, microscale systems can overcome this since they mimic the cells' natural microenvironment adequately. We have developed a portable live-cell imaging system with an invert-upright-convertible architecture and a mini-bioreactor for long-term simultaneous cell imaging and analysis, chemical sensing and electrophysiological recording. Our system integrates biocompatible cell-friendly materials with modular measurement schemes and precise environment control, and can be automated. High quality time-lapse cell imaging is hugely useful in cell/disease models. However, integration of advanced in-vitro systems into benchtop microscopes for in-situ imaging is tricky and challenging. This is especially true with device based biological systems such as lab/organ/body-on-chips, or mini-bioreactors/microfluidic systems. They face, issues ranging from optical and physical geometry incompatibilities to difficulties in connectivity of flow and perfusion systems. However, our novel modular system either as an inverted or as an upright system can easily accommodate virtually any in-vitro devices. Furthermore, it can accept additional sensor or measurement devices quite freely. Cell characterization, differentiation, chemical sensing, drug screening, microelectrode-array-electrophysiological recordings and cell stimulation can be carried out with simultaneous in-situ imaging and analysis. Moreover, our system can be configured to capture images from regions that are otherwise inaccessible by conventional microscopes, for example, cells cultured on physical or biochemical sensor systems. We demonstrate the system for video-based beating analysis of cardiomyocytes, cell orientation analysis on nanocellulose, and simultaneous long-term in-situ microscopy with pO2 and temperature sensing. The compact microscope as such is comparable to standard phase-contrast-microscopes without any detectable aberrations and is useful practically for any in-situ microscopy demands.

Cell culture in stem cell research is on the rise, not only for basic research but also for its potential medical and therapeutic applications. Monitoring culture process using sensors throughout the culture helps to optimize culture conditions for optimal growth and maximize yield from the cells. Further, the sensor data gives insight into developing better cell culture systems. Typical stem cell culture platforms, e.g. well plates or flasks, cannot be easily equipped with sensors and impose many challenges in periodic process measurements in a CO ₂ incubator. We present an incubator compatible modular measurement system with three sensors, to monitor pH, temperature and humidity continuously throughout the culture. Sensors are assembled around a flow through cuvette for highly sterile non-contact measurements. No sample preparation or sample extraction from the incubator is needed and the measurements are carried out in a closed flow loop without wasting any medium. The modular assembly is novel, reusable and feasible for humid incubator environments. The system has been tested, validated and used in mesenchymal stem cell expansion and differentiation, for periods ranging from two to three weeks. Once the measurement has commenced at the beginning of culture, continuous measurements without sensor recalibration or special manual attention are carried out till the end of the culture. Measurement data clearly show the interplay between measured parameters, indicating a few stress sources present all through the culture. Additionally, it gives an overall picture of behavior of critical control parameters in an incubator and points out the need for bioprocess systems with automatic process monitoring and smart control for maximum yield, optimal growth and maintenance of the cells.

Luminescence-based oxygen sensing is a widely used tool in cell culture applications. In a typical configuration, the luminescent oxygen indicators are embedded in a solid, oxygen-permeable matrix in contact with the culture medium. However, in sensitive cell cultures even minimal leaching of the potentially cytotoxic indicators can become an issue. One way to prevent the leaching is to immobilize the indicators covalently into the supporting matrix. In this paper, we report on a method where platinum(II)-5,10,15,20-tetrakis-(2,3,4,5,6-pentafluorphenyl)-porphyrin (PtTFPP) oxygen indicators are covalently immobilized into a polymer matrix consisting of polystyrene and poly(pentafluorostyrene). We study how the covalent immobilization influences the sensing material’s cytotoxicity to human induced pluripotent stem cell-derived (hiPSC-derived) neurons and cardiomyocytes (CMs) through 7–13 days culturing experiments and various viability analyses. Furthermore, we study the effect of the covalent immobilization on the indicator leaching and the oxygen sensing properties of the material. In addition, we demonstrate the use of the covalently linked oxygen sensing material in real time oxygen tension monitoring in functional hypoxia studies of the hiPSC-derived CMs. The results show that the covalently immobilized indicators substantially reduce indicator leaching and the cytotoxicity of the oxygen sensing material, while the influence on the oxygen sensing properties remains small or nonexistent.