Model-based analysis of biocatalytic processes and performance of microbioreactors with integrated optical sensors.

Design and development of scale-down approaches, such as microbioreactor (µBR) technologies with integrated sensors, are an adequate solution for rapid, high-throughput and cost-effective screening of valuable reactions and/or production strains, with considerably reduced use of reagents and generation of waste. A significant challenge in the successful and widespread application of µBRs in biotechnology remains the lack of appropriate software and automated data interpretation of µBR experiments. Here, it is demonstrated how mathematical models can be usedas helpful tools, not only to exploit the capabilities of microfluidic platforms, but also to reveal the critical experimental conditions when monitoring cascade enzymatic reactions. A simplified mechanistic model was developed to describe the enzymatic reaction of glucose oxidase and glucose in the presence of catalase inside a commercial microfluidic platform with integrated oxygen sensor spots. The proposed model allowed an easy and rapid identification of the reaction mechanism, kinetics and limiting factors. The effect of fluid flow and enzyme adsorption inside the microfluidic chip on the optical sensor response and overall monitoring capabilities of the presented platform was evaluated via computational fluid dynamics (CFD) simulations. Remarkably, the model predictions were independently confirmed for µL- and mL- scale experiments. It is expected that the mechanistic models will significantly contribute to the further promotion of µBRs in biocatalysis research and that the overall study will create a framework for screening and evaluation of critical system parameters, including sensor response, operating conditions, experimental and microbioreactor designs.

Microfluidic reprogramming to pluripotency of human somatic cells.

Human induced pluripotent stem cells (hiPSCs) have a number of potential applications in stem cell biology and regenerative medicine, including precision medicine. However, their potential clinical application is hampered by the low efficiency, high costs, and heavy workload of the reprogramming process. Here we describe a protocol to reprogram human somatic cells to hiPSCs with high efficiency in 15 d using microfluidics. We successfully downscaled an 8-d protocol based on daily transfections of mRNA encoding for reprogramming factors and immune evasion proteins. Using this protocol, we obtain hiPSC colonies (up to 160 ± 20 mean ± s.d (n = 48)) in a single 27-mm2 microfluidic chamber) 15 d after seeding ~1,500 cells per independent chamber and under xeno-free defined conditions. Only ~20 µL of medium is required per day. The hiPSC colonies extracted from the microfluidic chamber do not require further stabilization because of the short lifetime of mRNA. The high success rate of reprogramming in microfluidics, under completely defined conditions, enables hundreds of cells to be simultaneously reprogrammed, with an ~100-fold reduction in costs of raw materials compared to those for standard multiwell culture conditions. This system also enables the generation of hiPSCs suitable for clinical translation or further research into the reprogramming process.

Simvastatin Rapidly and Reversibly Inhibits Insulin Secretion in Intact Single-Islet Cultures.

INTRODUCTION: Epidemiological studies suggest that statins may promote the development or exacerbation of diabetes, but whether this occurs through inhibition of insulin secretion is unclear. This lack of understanding is partly due to the cellular models used to explore this phenomenon (cell lines or pooled islets), which are non-physiologic and have limited clinical transferability. METHODS: Here, we study the effect of simvastatin on insulin secretion using single-islet cultures, an optimal compromise between biological observability and physiologic fidelity. We develop and validate a microfluidic device to study single-islet function ex vivo, which allows for switching between media of different compositions with a resolution of seconds. In parallel, fluorescence imaging provides real-time analysis of the membrane voltage potential, cytosolic Ca2+ dynamics, and insulin release during perfusion under 3 or 11 mM glucose. RESULTS: We found that simvastatin reversibly inhibits insulin secretion, even in high-glucose. This phenomenon is very rapid (<60 s), occurs without affecting Ca2+ concentrations, and is likely unrelated to cholesterol biosynthesis and protein isoprenylation, which occur on a time span of hours. CONCLUSIONS: Our data provide the first real-time live demonstration that a statin inhibits insulin secretion in intact islets and that single islets respond differently from cell lines on a short time scale. FUNDING: University of Padova, EASD Foundation.

[Changes in patient survival and quality of life after heart transplantation]. / Come sono cambiate la sopravvivenza e la qualità di vita del paziente trapiantato?

Heart transplantation was performed firstly in 1967, but it became a valuable option in the 1980s, due to the availability of cyclosporine and of the technique for rejection monitoring by means of serial endomyocardial biopsies. Post-transplant survival improved over the years, mainly due to a reduction in early mortality for infection or acute rejection. Expected 1-year and 5-year survivals are around 85% and 70%, respectively. During the past 20-30 years, better therapies for heart failure have been developed, leading to restriction of heart transplant candidacy to truly refractory heart failure. On the contrary, the criteria for donor acceptance have been liberalized, due to the discrepancy between heart transplant candidates and available organs. It must be kept in mind that renal and/or hepatic insufficiency that may be a consequence of heart failure, pulmonary hypertension, and donor age, all remain risk factors for mortality after transplantation. In order to maintain and possibly improve the results of heart transplantation, effective strategies to increase safely the donor pool are of utmost importance. Moreover, long-term post-transplant recipients present new challenges to research and clinical practice. Mechanical circulatory support devices represent a surgical bridge or an alternative to transplantation; their expansion is limited by costs, organizational burden, and by patient difficulties in accepting this therapy.