MatriGrid® Based Biological Morphologies: Tools for 3D Cell Culturing.

Recent trends in 3D cell culturing has placed organotypic tissue models at another level. Now, not only is the microenvironment at the cynosure of this research, but rather, microscopic geometrical parameters are also decisive for mimicking a tissue model. Over the years, technologies such as micromachining, 3D printing, and hydrogels are making the foundation of this field. However, mimicking the topography of a particular tissue-relevant substrate can be achieved relatively simply with so-called template or morphology transfer techniques. Over the last 15 years, in one such research venture, we have been investigating a micro thermoforming technique as a facile tool for generating bioinspired topographies. We call them MatriGrid®s. In this research account, we summarize our learning outcome from this technique in terms of the influence of 3D micro morphologies on different cell cultures that we have tested in our laboratory. An integral part of this research is the evolution of unavoidable aspects such as possible label-free sensing and fluidic automatization. The development in the research field is also documented in this account.

Thermoforming techniques for manufacturing porous scaffolds for application in 3D cell cultivation.

Within the scientific community, there is an increasing demand to apply advanced cell cultivation substrates with increased physiological functionalities for studying spatially defined cellular interactions. Porous polymeric scaffolds are utilized for mimicking an organ-like structure or engineering complex tissues and have become a key element for three-dimensional (3D) cell cultivation in the meantime. As a consequence, efficient 3D scaffold fabrication methods play an important role in modern biotechnology. Here, we present a novel thermoforming procedure for manufacturing porous 3D scaffolds from permeable materials. We address the issue of precise thermoforming of porous polymer foils by using multilayer polymer thermoforming technology. This technology offers a new method for structuring porous polymer foils that are otherwise available for non-porous polymers only. We successfully manufactured 3D scaffolds from solvent casted and phase separated polylactic acid (PLA) foils and investigated their biocompatibility and basic cellular performance. The HepG2 cell culture in PLA scaffold has shown enhanced albumin secretion rate in comparison to a previously reported polycarbonate based scaffold with similar geometry.

Nerve cell response to inhibitors recorded with an aluminum-galliumnitride/galliumnitride field-effect transistor.

Experiments based on neuronal cell-transistor couplings were made from some groups during the last years. Pioneering work in this field was carried out by Fromherz and his group (Fromherz, 2003; Schmidtner and Fromherz, 2006). We were interested of the interaction of nerve cells to serine hydrolase inhibitor diisopropylfluorophosphate (DFP), monitored by using an aluminum-galliumnitride/galliumnitride (AlGaN/GaN) electrolyte gate field effect transistor (EGFET). The biocompatibility study of our sensor materials with nerve cells shows a proliferation rate of at least 95%. The inhibitors were added to the medium and the source-drain current of the EGFET was recorded as a function of time. The inhibitor was added to the NG108-15 nerve cells growing directly on the sensor surface, resulting in a fast decrease in the drain current, I(DS). Control measurements show that this response is associated with cationic fluxes pumped through ionic channels present in the cellular membrane. The sensor enables analysis of the ion channel activity without cell destruction and simultaneously allows visual observation due to the optical transparency of the sensor material.

Thrombin inhibitors identified by computer-assisted multiparameter design.

Here, we present a series of thrombin inhibitors that were generated by using powerful computer-assisted multiparameter optimization process. The process was organized in design cycles, starting with a set of randomly chosen molecules. Each cycle combined combinatorial synthesis, multiparameter characterization of compounds in a variety of bioassays, and algorithmic processing of the data to devise a set of compounds to be synthesized in the next cycle. The identified lead compounds exhibited thrombin inhibitory constants in the lower nanomolar range. They are by far the most selective synthetic thrombin inhibitors, with selectivities of >100,000-fold toward other proteases such as Factor Xa, Factor XIIa, urokinase, plasmin, and Plasma kallikrein. Furthermore, these compounds exhibit a favorable profile, comprising nontoxicity, high metabolic stability, low serum protein binding, good solubility, high anticoagulant activity, and a slow and exclusively renal elimination from the circulation in a rat model. Finally, x-ray crystallographic analysis of a thrombin-inhibitor complex revealed a binding mode with a neutral moiety in the S1 pocket of thrombin.