Search

Cardiac tissue engineering holds great promise for the treatment of myocardial infarction. However, insufficient cell migration into the scaffolds used and inflammatory reactions due to scaffold biodegradation remain as issues to be addressed. Engineered heart tissue (EHT) grafts fabricated by means of a cell encapsulation technique provide cells with a tissue-like environment, thereby potentially enhancing cellular processes such as migration, proliferation, and differentiation, and tissue regeneration. This paper presents a study on the fabrication and characterization of EHT grafts from novel alginate/collagen composite microbeads by means of cell encapsulation. Specifically, the microbeads were fabricated from alginate and collagen by barium ion cross-linking, with neonatal rat cardiomyocytes encapsulated in the composite microbeads during the fabrication of the EHT grafts. To evaluate the suitablity of these EHT grafts for heart muscle repair, the growth of cardiac cells in the microbeads was examined by means of confocal microscopy and staining with DAPI and F-actin. The EHT grafts were analyzed by scanning electron microscopy and transmission electron microscopy, and the contractile function of the EHT grafts monitored using a digital video camera at different time points. The results show the proliferation of cardiac cells in the microbeads and formation of interconnected multilayer heart-like tissues, the presence of well-organized and dense cell structures, the presence of intercalated discs and spaced Z lines, and the spontaneous synchronized contractility of EHT grafts (at a rate of 20-30 beats min(-1) after two weeks in culture). Taken together, these observations demonstrate that the novel alginate/collagen composite microbeads can provide a tissue-like microenvironment for cardiomyocytes that is suitable for fabricating native heart-like tissues.

International audience; Side-channel and fault injection attacks are renown techniques to extract keys from cryptographic devices. Fortunately, leakage reduction and fault detection countermeasures exist and can be implemented right in the source-code. However, source-code level countermeasures might be altered during the compilation process. Design simulation is an effective means to detect such harmful simplifications. This is a well-known methodology to analyze regressions in terms of side-channel leakage. In this chapter, we explain that protections against fault injection attacks are no exception. First of all, we show that vulnerabilities to those attacks can be easily detected by simulation methods. Second, we highlight that simulation techniques are also highly efficient in detecting logic simplifications which destroy (fully or partly) the countermeasures. Thus, the simulation-based methodology we present in this chapter shows that it is possible to decide quickly which compilation options are safe and which ones are detrimental to the security.