A versatile modular bioreactor platform for Tissue Engineering

Tissue Engineering (TE) bears potential to overcome the persistent shortage of donor organs in transplantation medicine. Additionally, TE products are applied as human test systems in pharmaceutical research to close the gap between animal testing and the administration of drugs to human subjects in clinical trials. However, generating a tissue requires complex culture conditions provided by bioreactors. Currently, the translation of TE technologies into clinical and industrial applications is limited due to a wide range of different tissue‐specific, non‐disposable bioreactor systems. To ensure a high level of standardization, a suitable cost‐effectiveness, and a safe graft production, a generic modular bioreactor platform was developed. Functional modules provide robust control of culture processes, e.g. medium transport, gas exchange, heating, or trapping of floating air bubbles. Characterization revealed improved performance of the modules in comparison to traditional cell culture equipment such as incubators, or peristaltic pumps. By combining the modules, a broad range of culture conditions can be achieved. The novel bioreactor platform allows using disposable components and facilitates tissue culture in closed fluidic systems. By sustaining native carotid arteries, engineering a blood vessel, and generating intestinal tissue models according to a previously published protocol the feasibility and performance of the bioreactor platform was demonstrated.     

微流控芯片技术在细胞生物学研究中的应用进展

20世纪90年代以来,微流控芯片技术得到了快速发展。由于具有小型化、集成化、高通量、低消耗、分析快速等特点,微流控芯片作为一种新型的生物学研究平台,能够提供传统方法不具备的精细和可控制的细胞研究条件,在细胞生物学研究领域中得到了广泛关注。该文主要介绍其在细胞培养、分选、裂解、计数、凋亡检测、迁移、单细胞捕获、细胞间作用等方面的研究进展。     

Integrated analysis of multiple data sources reveals modular structure of biological networks

It has been a challenging task to integrate high-throughput data into investigations of the systematic and dynamic organization of biological networks. Here, we presented a simple hierarchical clustering algorithm that goes a long way to achieve this aim. Our method effectively reveals the modular structure of the yeast protein-protein interaction network and distinguishes protein complexes from functional modules by integrating high-throughput protein-protein interaction data with the added subcellular localization and expression profile data. Furthermore, we take advantage of the detected modules to provide a reliably functional context for the uncharacterized components within modules. On the other hand, the integration of various protein-protein association information makes our method robust to false-positives, especially for derived protein complexes. More importantly, this simple method can be extended naturally to other types of data fusion and provides a framework for the study of more comprehensive properties of the biological network and other forms of complex networks.     

Design and characterization of a prototype enzyme microreactor: Quantification of immobilized transketolase kinetics

In this work, we describe the design of an immobilized enzyme microreactor (IEMR) for use in transketolase (TK) bioconversion process characterization. The prototype microreactor is based on a 200‐μm ID fused silica capillary for quantitative kinetic analysis. The concept is based on the reversible immobilization of His₆‐tagged enzymes via Ni‐NTA linkage to surface derivatized silica. For the initial microreactor design, the mode of operation is a stop‐flow analysis which promotes higher degrees of conversion. Kinetics for the immobilized TK‐catalysed synthesis of L ‐erythrulose from substrates glycolaldehyde (GA) and hydroxypyruvate (HPA) were evaluated based on a Michaelis–Menten model. Results show that the TK kinetic parameters in the IEMR (V_max(app) = 0.1 ± 0.02 mmol min^–1, K_m(app) = 26 ± 4 mM) are comparable with those measured in free solution. Furthermore, the k_cat for the microreactor of 4.1 × 10⁵ s^?1 was close to the value for the bioconversion in free solution. This is attributed to the controlled orientation and monolayer surface coverage of the His₆‐immobilized TK. Furthermore, we show quantitative elution of the immobilized TK and the regeneration and reuse of the derivatized capillary over five cycles. The ability to quantify kinetic parameters of engineered enzymes at this scale has benefits for the rapid and parallel evaluation of evolved enzyme libraries for synthetic biology applications and for the generation of kinetic models to aid bioconversion process design and bioreactor selection as a more efficient alternative to previously established microwell‐based systems for TK bioprocess characterization. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Analysis of Developing Tooth Germ Innervation Using Microfluidic Co-culture Devices

Innervation plays a key role in the development, homeostasis and regeneration of organs and tissues. However, the mechanisms underlying these phenomena are not well understood yet. In particular, the role of innervation in tooth development and regeneration is neglected.Several in vivo studies have provided important information about the patterns of innervation of dental tissues during development and repair processes of various animal models. However, most of these approaches are not optimal to highlight the molecular basis of the interactions between nerve fibres and target organs and tissues.Co-cultures constitute a valuable method to investigate and manipulate the interactions between nerve fibres and teeth in a controlled and isolated environment. In the last decades, conventional co-cultures using the same culture medium have been performed for very short periods (e.g., two days) to investigate the attractive or repulsive effects of developing oral and dental tissues on sensory nerve fibres. However, extension of the culture period is required to investigate the effects of innervation on tooth morphogenesis and cytodifferentiation.Microfluidics systems allow co-cultures of neurons and different cell types in their appropriate culture media. We have recently demonstrated that trigeminal ganglia (TG) and teeth are able to survive for a long period of time when co-cultured in microfluidic devices, and that they maintain in these conditions the same innervation pattern that they show in vivo.On this basis, we describe how to isolate and co-culture developing trigeminal ganglia and tooth germs in a microfluidic co-culture system.This protocol describes a simple and flexible way to co-culture ganglia/nerves and target tissues and to study the roles of specific molecules on such interactions in a controlled and isolated environment.     

A high‐throughput all‐optical laser‐scanning imaging flow cytometer with biomolecular specificity and subcellular resolution

Image‐based cellular assay advances approaches to dissect complex cellular characteristics through direct visualization of cellular functional structures. However, available technologies face a common challenge, especially when it comes to the unmet need for unraveling population heterogeneity at single‐cell precision: higher imaging resolution (and thus content) comes at the expense of lower throughput, or vice versa. To overcome this challenge, a new type of imaging flow cytometer based upon an all‐optical ultrafast laser‐scanning imaging technique, called free‐space angular‐chirp‐enhanced delay (FACED) is reported. It enables an imaging throughput (>20 000 cells s^?1) 1 to 2 orders of magnitude higher than the camera‐based imaging flow cytometers. It also has 2 critical advantages over optical time‐stretch imaging flow cytometry, which achieves a similar throughput: (1) it is widely compatible to the repertoire of biochemical contrast agents, favoring biomolecular‐specific cellular assay and (2) it enables high‐throughput visualization of functional morphology of individual cells with subcellular resolution. These capabilities enable multiparametric single‐cell image analysis which reveals cellular heterogeneity, for example, in the cell‐death processes demonstrated in this work—the information generally masked in non‐imaging flow cytometry. Therefore, this platform empowers not only efficient large‐scale single‐cell measurements, but also detailed mechanistic analysis of complex cellular processes.