title: Sucrose Diffusion in Decellularized Heart Valves for Freeze-Drying.
abstract: Decellularized heart valves can be used as starter matrix implants for heart valve replacement therapies in terms of guided tissue regeneration. Decellularized matrices ideally need to be long-term storable to assure off-the-shelf availability. Freeze-drying is an attractive preservation method, allowing storage at room temperature in a dried state. However, the two inherent processing steps, freezing and drying, can cause severe damage to extracellular matrix (ECM) proteins and the overall tissue histoarchitecture and thus impair biomechanical characteristics of resulting matrices. Freeze-drying therefore requires a lyoprotective agent that stabilizes endogenous structural proteins during both substeps and that forms a protective glassy state at room temperature. To estimate incubation times needed to infiltrate decellularized heart valves with the lyoprotectant sucrose, temperature-dependent diffusion studies were done using Fourier transform infrared spectroscopy. Glycerol, a cryoprotective agent, was studied for comparison. Diffusion of both protectants was found to exhibit Arrhenius behavior. The activation energies of sucrose and glycerol diffusion were found to be 15.9 and 37.7 kJ·mol(-1), respectively. It was estimated that 4 h of incubation at 37°C is sufficient to infiltrate heart valves with sucrose before freeze-drying. Application of a 5% sucrose solution was shown to stabilize acellular valve scaffolds during freeze-drying. Such freeze-dried tissues, however, displayed pores, which were attributed to ice crystal damage, whereas vacuum-dried scaffolds in comparison revealed no pores after drying and rehydration. Exposure to a hygroscopic sucrose solution (80%) before freeze-drying was shown to be an effective method to diminish pore formation in freeze-dried ECMs: matrix structures closely resembled those of control samples that were not freeze-dried. Heart valve matrices were shown to be in a glassy state after drying, suggesting that they can be stored at room temperature.
authors: 1 Institute of Multiphase Processes, Leibniz Universität Hannover , Hannover, Germany .
authors: Shangping
authors: S
authors: Wang
authors: 2 Clinic for Horses-Unit for Reproductive Medicine, University of Veterinary Medicine Hannover , Hannover, Germany .
authors: Harriëtte
authors: H
authors: Oldenhof
authors: 3 Leibniz Research Laboratories for Biotechnology and Artificial Organs, Hannover Medical School , Hannover, Germany .
authors: Tobias
authors: T
authors: Goecke
authors: 3 Leibniz Research Laboratories for Biotechnology and Artificial Organs, Hannover Medical School , Hannover, Germany .
authors: Robert
authors: R
authors: Ramm
authors: 4 Corlife GbR , Hannover, Germany .
authors: Michael
authors: M
authors: Harder
authors: 3 Leibniz Research Laboratories for Biotechnology and Artificial Organs, Hannover Medical School , Hannover, Germany .
authors: Axel
authors: A
authors: Haverich
authors: 3 Leibniz Research Laboratories for Biotechnology and Artificial Organs, Hannover Medical School , Hannover, Germany .
authors: Andres
authors: A
authors: Hilfiker
authors: 1 Institute of Multiphase Processes, Leibniz Universität Hannover , Hannover, Germany .
authors: Willem Frederik
authors: WF
authors: Wolkers
mesh_terms: D000818:Animals; D002152:Calorimetry, Differential Scanning; D003451:Cryoprotective Agents / Q000494:pharmacology; D004058:Diffusion; D005612:Freeze Drying; D005898:Glass; D006351:Heart Valves / Q000166:cytology* / Q000187:drug effects; D011664:Pulmonary Valve / Q000166:cytology / Q000187:drug effects; D017550:Spectroscopy, Fourier Transform Infrared; D013395:Sucrose / Q000494:pharmacology*; D034421:Sus scrofa; D013696:Temperature; D054457:Tissue Scaffolds / Q000737:chemistry; D014867:Water
chemical_list: D003451:Cryoprotective Agents; D014867:Water; D013395:Sucrose