Abstract: Over the past decade, tissue engineering in the field of medicine has proven to provide alternative therapies for tissue or organ implants, especially providing a functional implantation and avoiding immune rejection of tissues and organs. [...]
Abstract: Anaerobic digestion (AD) is an efficient and sustainable way of using organic carbon from residual biomass and organic waste for the production of renewable energy, while simultaneously recycling nutrients and cleaning up waste streams. The process relies on complex microbial communities comprised of diverse functional guilds; these communities have manifold metabolic pathways and interactions. In contrast to the conventional view of an anaerobic digester as a black box, advanced microbiological methods have paved the way for understanding and even controlling complex microbial networks. Nowadays, microbial resource management is crucial for technological progress in AD, and offers new perspectives concerning sustainable waste management, renewable energy production, resource efficiency, and advanced bio-refineries; these perspectives lead to novel applications of AD processes that go beyond biogas as the main product. [...]
Abstract: The dual responsive Electrochemical Cell-on-a-Chip Microdisc Electrode Array (ECC MDEA 5037) is a recently developed electrochemical transducer for use in a wireless, implantable biosensor system for the continuous measurement of interstitial glucose and lactate. Fabrication of the biorecognition membrane via pyrrole electropolymerization and both in vitro and in vivo characterization of the resulting biotransducer is described. The influence of EDC-NHS covalent conjugation of glucose oxidase with 4-(3-pyrrolyl) butyric acid (monomerization) and with 4-sulfobenzoic acid (sulfonization) on biosensor performance was examined. As the extent of enzyme conjugation was increased sensitivity decreased for monomerized enzymes but increased for sulfonized enzymes. Implanted biotransducers were examined in a Sprague-Dawley rat hemorrhage model. Resection after 4 h and subsequent in vitro re-characterization showed a decreased sensitivity from 0.68 (±0.40) to 0.22 (±0.17) µA·cm−2·mM−1, an increase in the limit of detection from 0.05 (±0.03) to 0.27 (±0.27) mM and a six-fold increase in the response time from 41 (±18) to 244 (±193) s. This evidence reconfirms the importance of biofouling at the bio-abio interface and the need for mitigation strategies to address the foreign body response.
Abstract: The application of freeze-dried gelatin sponges as alternative bone grafting substitutes has many advantages, including the ability to swell, high porosity, tailorable degradation, and versatility to incorporate multiple components such as growth factors and nanofillers. The purpose of this study was to mineralize (M) and further characterize 1-Ethyl-3-[3-dimethylaminopropyl]carbodiimide hydrochloride (EDC) cross-linked gelatin sponges enhanced with preparations rich in growth factors, hydroxyapatite, and chitin whiskers (PHCE). Sponges were characterized for their swelling and in vitro mineralization potential, surface characteristics, protein release, mechanical properties, and MG-63 cell attachment and infiltration. All sponges swelled up to 50% of their original volume upon hydration. Scanning electron microscopy showed sparse mineral deposition for gelatin-M scaffolds while PHCE-M scaffolds exhibited more uniform mineral nucleation. Over 21 days, PHCE-M scaffolds cumulatively released significantly more (30%) of its initial protein content than all other scaffolds. PHCE-M scaffolds reported lower modulus values (1.3–1.6 MPa) when compared to gelatin control scaffolds (1.6–3.2 MPa). Increased cell attachment and infiltration was noticed on PHCE and PHCE-M scaffolds. The results of the study demonstrate the enhanced performance of PHCE and PHCE-M scaffolds to serve as bone healing scaffolds. Their potential to release incorporated factors, comparable composition/mechanical properties to tissues developed in the early stages of bone healing, and enhanced initial cellular response make them suitable for further studies evaluating more complex cellular interactions.
Abstract: Pichia pastoris is an attractive candidate platform for recombinant protein production. Dissolved oxygen is one of the most important factors in the cultivation of P. pastoris. However, the effect of oxygen on triggering productivity led to ambivalent results. In our earlier work, a two-compartment system, consisting of a single reactor coupled with a plug flow reactor (PFR), has been proposed as a tool to improve protein quantity and quality. The goal of this work was to investigate the effects of frequency (the residence time of broth in the PFR) and amplitude (the dissolved oxygen level in the reactor) of the stress on productivity, titer and physiology. A recombinant P. pastoris strain, which expressed horseradish peroxidase, was used as the model system. Thirteen experiments were performed. Multivariate data analysis was done and the results showed that the residence time did not influence titer, productivity and physiology over the range of residence time studied while dissolved oxygen influenced titer and specific productivity in a quadratic function. In other words, an intermediate level of dissolved oxygen (25%) showed the highest specific productivity and titter, irrespective of the residence time in the PFR. In turn, the variation of the residence time and dissolved oxygen did not influence growth physiology, as quantified in biomass and carbon dioxide yields.
Abstract: The current paper presents a methodology for the derivation of optimal operating strategies for turbo dynamic ventricular assist devices (tVADs). In current clinical practice, tVADs are typically operated at a constant rotational speed, resulting in a blood flow with a low pulsatility. Recent research in the field has aimed at optimizing the interaction between the tVAD and the cardiovascular system by using predefined periodic speed profiles. In the current paper, we avoid the limitation of using predefined profiles by formulating an optimal-control problem based on a mathematical model of the cardiovascular system and the tVAD. The optimal-control problem is solved numerically, leading to cycle-synchronized speed profiles, which are optimal with respect to an arbitrary objective. Here, an adjustable trade-off between the maximization of the flow through the aortic valve and the minimization of the left-ventricular stroke work is chosen. The optimal solutions perform better than constant-speed or sinusoidal-speed profiles for all cases studied. The analysis of optimized solutions provides insight into the optimized interaction between the tVAD and the cardiovascular system. The numerical approach to the optimization of this interaction represents a powerful tool with applications in research related to tVAD control. Furthermore, patient-specific, optimized VAD actuation strategies can potentially be derived from this approach.