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The main challenge in the development of bioreactors for tissue engineering is the delivery of a sufficient nutrient and oxygen supply for cell growth in a 3D environment. Thus, a new rotating bed system bioreactor for tissue engineering applications was developed. The system consists of a culture vessel as well as an integrated rotating bed of special porous ceramic discs and a process control unit connected with the reactor to ensure optimal culturing conditions. The aim of the project was the design and construction of a fully equipped rotating bed reactor, and in particular, the characterization and optimization of the system with regard to technical parameters such as mixing time and pH-control to guarantee optimal conditions for cell growth and differentiation. Furthermore, the applicability of the developed system was demonstrated by cultivation of osteoblast precursor cells. The porous structure of the ceramic discs and the external medium circulation loop provide an optimal environment for tissue generation in long-term cultivations. Mass transfer limitations were minimized by the slow rotation, which also provides the cells with sufficient nutrients and oxygen through alternate contact to air and medium. An osteoblast precursor cell line was successfully cultivated in this bioreactor for 28 days.

The development of bone tissue engineering depends on the availability of suitable biomaterials, a well-defined and controlled bioreactor system, and on the use of adequate cells. The biomaterial must fulfill chemical, biological, and mechanical requirements. Besides biocompatibility, the structural and flow characteristics of the biomaterial are of utmost importance for a successful dynamic cultivation of osteoblasts, since fluid percolation within the microstructure must be assured to supply to cells nutrients and waste removal. Therefore, the biomaterial must consist of a three-dimensional structure, exhibit high porosity and present an interconnected porous network. Sponceram, a ZrO(2) based porous ceramic, is characterized in the presented work with regard to its microstructural design. Intrinsic permeability is obtained through a standard Darcy's experiment, while Young's modulus is derived from a two plates stress-strain test in the linear range. Furthermore, the material is applied for the dynamic cultivation of primary osteoblasts in a newly developed rotating bed bioreactor.

Modern bioprocess control requires instantaneous data acquisition and in‐time evaluation of bioprocess variables. Optical sensor systems are of increasing interest in bioprocess monitoring because they are very sensitive and offer the possibility of on‐line, in situ , and noninvasive process monitoring. In this regard, on‐line fluorescence spectroscopy is a useful tool in the development of methods for bioprocess monitoring because many cellular substances and media components are biogenic fluorophors. This technique and the application of chemometric methods offer a deeper insight into biological processes and thus process monitoring, optimization, and control is accessible. In this review, an overview of the developments and applications of on‐line fluorescence techniques for bioprocess monitoring over the last 25 years is given with emphasis on 2D fluorescence spectroscopy.

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