Towards a theoretical clarification of biomimetics using conceptual tools from engineering design.

Many successful examples of biomimetic products are available, and most research efforts in this emerging field are directed towards the development of specific applications. The theoretical and conceptual underpinnings of the knowledge transfer between biologists, engineers and architects are, however, poorly investigated. The present article addresses this gap. We use a 'technomorphic' approach, i.e. the application of conceptual tools derived from engineering design, to better understand the processes operating during a typical biomimetic research project. This helps to elucidate the formal connections between functions, working principles and constructions (in a broad sense)-because the 'form-function-relationship' is a recurring issue in biology and engineering. The presented schema also serves as a conceptual framework that can be implemented for future biomimetic projects. The concepts of 'function' and 'working principle' are identified as the core elements in the biomimetic knowledge transfer towards applications. This schema not only facilitates the development of a common language in the emerging science of biomimetics, but also promotes the interdisciplinary dialogue among its subdisciplines.

Hindwings of insects as concept generator for hingeless foldable shading systems.

Hingeless shading systems inspired by nature are increasingly the focus of architectural research. In contrast to traditional systems, these compliant mechanisms can reduce the amount of maintenance-intensive parts and can easily be adapted to irregular, doubly curved, facade geometries. Previous mechanisms rely merely on the reversible material deformation of composite structures with almost homogeneous material properties. This leads to large actuation forces and an inherent conflict between the requirements of movement and the capacity to carry external loads. To enhance the performance of such systems, current research is directed at natural mechanisms with concentrated compliance and distinct hinge zones with high load-bearing capacity. Here, we provide insights into our biological findings and the development of a deployable structure inspired by the Flexagon model of hindwings of insects in general and the hierarchical structure of the wing cuticle of the shield bug (Graphosoma lineatum). By using technical fibre-reinforced plastics in combination with an elastomer foil, natural principles have been partially transferred into a multi-layered structure with locally adapted stiffness. Initial small prototypes have been produced in a vacuum-assisted hot press and sustain this functionality. Initial theoretical studies on test surfaces outline the advantages of these bio-inspired structures as deployable external shading systems for doubly curved facades.

First protein and peptide characterization of the tarsal adhesive secretions in the desert locust, Schistocerca gregaria, and the Madagascar hissing cockroach, Gromphadorhina portentosa.

Peptides and proteins have been largely neglected in the analysis of insect tarsal adhesives. After extraction of the protein fraction of the tarsal secretion of the desert locust, Schistocerca gregaria, and Madagascar hissing cockroach, Gromphadorhina portentosa, we combined Fourier transform infrared spectroscopy (FTIR), sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) analyses for protein mass detection. In both these insects, SDS-PAGE analysis revealed several protein bands ranging from 8-190 kDa in both the tarsal secretion and the tibia control sample. Two (S. gregaria) and one (G. portentosa) protein bands exclusively occurred in the tarsal secretion and can be considered to belong to peptides and proteins specific to this secretion. MALDI-TOF analyses revealed 83 different proteins/peptides of 1-7 kDa in S. gregaria, and 48 of 1-11 kDa in G. portentosa. 59 (S. gregaria) and 27 (G. portentosa) proteins exclusively occurred in the tarsal secretion. In G. portentosa, a characteristic series of signal peaks occurred in the range of c. 10-12 kDa, each peak being approximately 160 Da apart. Such a pattern is indicative of proteins modified by glycosylation. Our approach demonstrates that extensive sampling involving considerable time and manpower to sample the adhesive fluid directly from the tarsi opens up a perspective for extracting peptides and proteins in sufficient quantities. This makes them accessible to the field of proteomics and thus to elucidate their possible function in the adhesive process.

Bone healing of critical size defects of the rat femur after the application of bone marrow aspirate and two different rh-BMP7 concentrations.

BACKGROUND: It is known that the application of growth factors can enhance fracture healing in defect fractures. The role of bone marrow aspirate (BMA) in combination with BMP-7 and the dosage of rh BMP-7 are still under discussion. Our hypothesis was that the combination of rh-BMP-7 with BMA can heal bone defects more effectively than rh-BMP-7 alone. METHODS: Twenty-eight rats obtained a 5 mm critical size defect in the diaphysis of the right femur which was stabilized by a plate. Rh-BMP-7 was applied at 10 and 200 µg either with collagen or together with collagen and BMA. Collagen only and collagen with BMA served as control groups. Blood flow was assessed by laser Doppler flowmetry in regular time intervals until euthanasia. Callus formation and bone density were measured by micro-computed tomography and biomechanical stability was evaluated by torsional testing at 4 weeks, postoperatively. RESULTS: Blood flow increased at the operated side after surgery until the second postoperative week independent of treatment. Animals treated with high dose BMP-7 showed significantly (p = 0.001) increased mechanical stiffness independent of BMA treatment. Failure loads were lowest for the two control groups (p = 0.001). The reduction of the BMP-7 dose led to less callus tissue and lower biomechanical stability. BMA did not show significant influence on bone healing. CONCLUSION: The combination of an rhBMP-7 dose that would be equivalent to a dose used clinically in humans with bone marrow aspirate does not heal a critical bone defect more effectively than the same rhBMP-7 dose alone.

Systematic investigation of the effect of lyophilizate collapse on pharmaceutically relevant proteins III: collapse during storage at elevated temperatures.

This study investigates the effect of lyophilizate collapse on the stability of pharmaceutical proteins. Recently, it was shown that collapse during freeze-drying has no major negative impact on protein stability during storage at elevated temperatures when compared to non-collapsed cakes [1,2]. In this part of the study, lyophilizates that collapsed during the freeze-drying process were compared to cakes that were initially non-collapsed but collapsed during subsequent storage under accelerated stress conditions. Collapsed and non-collapsed lyophilizates of identical formulation and comparable residual moisture levels, containing a monoclonal IgG antibody, were stored at 40 °C and 50 °C for up to 3 months. Protein stability was monitored using a comprehensive set of analytical techniques assessing the formation of soluble and insoluble aggregates as well as protein conformation. The properties of the freeze-dried cake, namely the glass transition temperature, excipient crystallinity, sucrose degradation, reconstitution behavior, and the residual moisture content, were analyzed as well. The incorporated protein was significantly better stabilized in cakes that collapsed during the freeze-drying process when compared to lyophilizates that collapsed during subsequent storage. This effect can be related to the onset of crystallization and hydrolysis of the stabilizer and non-enzymatic browning.

On the possibilities of hard X-ray imaging with high spatio-temporal resolution using polychromatic synchrotron radiation.

Time-resolved imaging with penetrating radiation has an outstanding scientific value but its realisation requires a high density of photons as well as corresponding fast X-ray image detection schemes. Bending magnets and insertion devices of third generation synchrotron light sources offer a polychromatic photon flux density which is high enough to perform hard X-ray imaging with a spatio-temporal resolution up to the µm-µs range. Existing indirect X-ray image detectors commonly used at synchrotron light sources can be adapted for fast image acquisition by employing CMOS-based digital high speed cameras already available on the market. Selected applications from life sciences and materials research underline the high potential of this high-speed hard X-ray microimaging approach.

Systematic investigation of the effect of lyophilizate collapse on pharmaceutically relevant proteins I: stability after freeze-drying.

The objective of this work was to investigate the effect of cake collapse during freeze-drying on the stability of protein lyophilizates containing a monoclonal IgG(1)-antibody or a second pharmaceutically relevant protein, referred to as PA01. In addition, L-lactic dehydrogenase was investigated because of its well-documented sensitivity towards freeze-drying stresses. Collapse was induced by two different means. First, by varying the ratio of the crystalline bulking agent mannitol to the amorphous stabilizer sucrose, different extents of collapsed cakes were generated. Second, formulations were freeze-dried using an aggressive collapse-cycle and a conventional freeze-drying protocol and collapsed and noncollapsed cakes of identical formulation were produced. Lyophilizates were analyzed using a comprehensive set of analytical techniques to monitor protein stability in terms of formation of soluble and insoluble aggregates, the biological activity and the conformational stability. The stability of excipients, namely the glass transition temperature, crystallinity, reconstitution behavior, and the residual moisture content was analyzed as well. In addition, the extent of collapse was quantified using the decrease of the specific surface area (SSA). Collapsed cakes had comparable residual moisture levels to noncollapsed lyophilizates. Reconstitution times were not increased. Protein stability was not relevantly different between collapsed and noncollapsed cakes.

Use of genetically modified muscle and fat grafts to repair defects in bone and cartilage.

We report a novel technology for the rapid healing of large osseous and chondral defects, based upon the genetic modification of autologous skeletal muscle and fat grafts. These tissues were selected because they not only possess mesenchymal progenitor cells and scaffolding properties, but also can be biopsied, genetically modified and returned to the patient in a single operative session. First generation adenovirus vector carrying cDNA encoding human bone morphogenetic protein-2 (Ad.BMP-2) was used for gene transfer to biopsies of muscle and fat. To assess bone healing, the genetically modified ("gene activated") tissues were implanted into 5mm-long critical size, mid-diaphyseal, stabilized defects in the femora of Fischer rats. Unlike control defects, those receiving gene-activated muscle underwent rapid healing, with evidence of radiologic bridging as early as 10 days after implantation and restoration of full mechanical strength by 8 weeks. Histologic analysis suggests that the grafts rapidly differentiated into cartilage, followed by efficient endochondral ossification. Fluorescence in situ hybridization detection of Y-chromosomes following the transfer of male donor muscle into female rats demonstrated that at least some of the osteoblasts of the healed bone were derived from donor muscle. Gene activated fat also healed critical sized defects, but less quickly than muscle and with more variability. Anti-adenovirus antibodies were not detected. Pilot studies in a rabbit osteochondral defect model demonstrated the promise of this technology for healing cartilage defects. Further development of these methods should provide ways to heal bone and cartilage more expeditiously, and at lower cost, than is presently possible.

Ex vivo adenoviral transfer of bone morphogenetic protein 12 (BMP-12) cDNA improves Achilles tendon healing in a rat model.

The aim of our study was to evaluate the histological and biomechanical effects of BMP-12 gene transfer on the healing of rat Achilles tendons using a new approach employing a genetically modified muscle flap. Biopsies of autologous skeletal muscle were transduced with a type-five, first-generation adenovirus carrying the human BMP-12 cDNA (Ad.BMP-12) and surgically implanted around experimentally transected Achilles tendons in a rat model. The effect of gene transfer on healing was evaluated by mechanical and histological testing after 1, 2, 4 and 8 weeks. One week after surgery, the maximum failure load of the healing tendons was significantly increased in the BMP-12 group, compared with the controls, and the tendon stiffness was significantly higher at 1, 2 and 4 weeks. Moreover, the size of the rupture callus was increased in the presence of BMP-12 and there was evidence of accelerated remodeling of the lesion in response to BMP-12. Histological examination showed a much more organized and homogeneous pattern of collagen fibers at all time points in lesions treated with the BMP-12 cDNA muscle graft. Both single fibrils and the collagen fibers had a greater diameter, with a higher degree of collagen crimp than the collagen of the control groups. This was confirmed by sirius red staining in conjunction with polarized light microscopy, which showed a higher shift of small yellow-green fibers to strong yellow-orange fibers after 2, 4 and 8 weeks in the presence of BMP-12 cDNA. There was also an earlier shift from fibroblasts to fibrocytes within the healing tendon, with less fat cells present in the tendons of the BMP-12 group compared with the controls. Treatment with BMP-12 cDNA-transduced muscle grafts thus produced a promising acceleration and improvement of tendon healing, particularly influencing early tissue regeneration, leading to quicker recovery and improved biomechanical properties of the Achilles tendon. Further development of this approach could have clinical applications.

BMP-silk composite matrices heal critically sized femoral defects.

Clinical drawbacks of bone grafting prompt the search for alternative bone augmentation technologies such as use of growth and differentiation factors, gene therapy, and cell therapy. Osteopromotive matrices are frequently employed for the local delivery and controlled release of these augmentation agents. Some matrices also provide an osteoconductive scaffold to support new bone growth. In this study, silkworm-derived silk fibroin was evaluated as an osteoconductive matrix for healing critical sized mid-femoral segmental defects in nude rats. Four treatment groups were assessed over eight weeks: silk scaffolds (SS) with recombinant human BMP-2 (rhBMP-2) and human mesenchymal stem cells (HMSC) that had been pre-differentiated along an osteoblastic lineage ex vivo (Group I; pdHMSC/rhBMP-2/SS); SS with rhBMP-2 and undifferentiated HMSCs (Group II; udHMSC/rhBMP-2/SS); SS and rhBMP-2 alone (Group III; rhBMP-2/SS); and empty defects (Group IV). Bi-weekly radiographs revealed a progressive and similar increase in Group I-III mean defect mineralization through post-operative week (POW) 8. Radiographs, dual energy x-ray absorptiometry, and micro-computed tomography confirmed that Groups I-III exhibited similar substantial and significantly (p<0.05) greater defect mineralization at POW 8 than the unfilled Group IV defects which remained void of bone. No significant differences in Groups I-III defect healing at POW 8 were apparent using these same assays or mechanical testing. Histology at POW 8 revealed moderately good bridging of the parent diaphyseal cortices with woven and lamellar bone bridging islands of silk matrix in Groups I and III. Group II defects possessed comparatively less new bone which was most abundant adjacent to the parent bone margins. Elsewhere the silk matrix was more often enveloped by poorly differentiated loose fibrous connective tissue. Group IV defects showed minimal new bone formation. None of the treatment groups attained the mean mineralization or the mean biomechanical strength of identical defects implanted with SS and pdHMSCs alone in a previous study. However, addition of rhBMP-2 to SS prompted more bone than was previously generated using udHMSC/SS or SS alone. These data imply the clinical potential of silk scaffolds and rhBMP-2 as composite osteopromotive implants when used alone or with select stem cell populations. Additional studies in larger species are now warranted.

Delayed administration of adenoviral BMP-2 vector improves the formation of bone in osseous defects.

The direct, local, administration of adenovirus carrying human BMP-2 cDNA (Ad.BMP-2) heals critical-sized femoral bone defects in rabbit and rat models. However, the outcome is suboptimal and the technology needs to provide a more reliable and uniform outcome. To this end, we investigated whether the timing of Ad.BMP-2 administration influenced the formation of mineralized tissue within the defect. Critical-sized defects were created in the femora of 28 Sprague-Dawley rats. Animals were injected intralesionally with a single, percutaneous injection of Ad.BMP-2 (4 x 10(8) plaque-forming units) either intraoperatively (day 0) or 24 h (day 1), 5 days or 10 days after surgery. The femora were evaluated 8 weeks after surgery by X-ray, microcomputed tomography, dual-energy X-ray absorptiometry and biomechanical testing. The incidence of radiological union was markedly increased when administration of Ad.BMP-2 was delayed until days 5 and 10, at which point 86% of the defects healed. These time points also provided greater bone mineral content within the defect site and improved the average mechanical strength of the healed bone. Thus, delaying the injection of Ad.BMP-2 until 5 or 10 days after surgery enables a greater percentage of critical-sized, segmental defects to achieve radiological union, producing a repair tissue with enhanced mineralization and greater mechanical strength.

Silk based biomaterials to heal critical sized femur defects.

Bone auto- and allografts have inherent drawbacks, therefore the treatment of non-unions and critical size defects in load bearing long bones would benefit from the use of osteopromotive biodegradable, biocompatible and mechanically durable matrices to enhance migration or delivery of cell populations and/or morphogens/cytokines. Silk fibroin biomaterial scaffolds were evaluated as osteopromotive matrices in critical sized mid-femoral segmental defects in nude rats. Four treatment groups were assessed over 8 weeks in vivo: silk scaffolds (SS) with human mesenchymal stem cells (hMSCs) that had previously been differentiated along an osteoblastic lineage in vitro (group I; pdHMSC/SS); SS with undifferentiated hMSCs (group II; udHMSC/SS); SS alone (group III; SS); and empty defects (group IV). When hMSCs were cultured in vitro in osteogenic medium for 5 weeks, bone formation was characterized with bimodal peak activities for alkaline phosphatase at 2 and 4 weeks. Calcium deposition started after 1 week and progressively increased to peak at 4 weeks, reaching cumulative levels of deposited calcium at 16 mug per mg scaffold wet weight. In vivo osteogenesis was characterized by almost bridged defects with newly formed bone after 8 weeks in group I. Significantly (P < 0.01) greater bone volumes were observed with the pdHMSC/SS (group I) implants than with groups II, III or IV. These three groups failed to induce substantial new bone formation and resulted in the ingrowth of cells with fibroblast-like morphology into the defect zone. The implantation of pdHMSC/SS resulted in significantly (P < 0.05) greater maximal load and torque when compared to the other treatment regimens. The pdHMSC/SS implants demonstrated osteogenic ability in vitro and capacity to thrive towards the healing of critical size femoral segmental defects in vivo. Thus, these new constructs provide an alternative protein-based biomaterial for load bearing applications.

[Is ginger a relevant antiemetic for postoperative nausea and vomiting?]. / Ist Ingwer ein sinnvolles Antiemetikum für die postoperative Phase? Eine Metaanalyse randomisierter kontrollierter Studien.-

OBJECTIVE: Ginger (Zingiber officinale) has traditionally been used in China for gastrointestinal symptoms, including nausea and vomiting. A recent systematic review on the possible antiemetic effect of ginger for various indications, including PONV, morning sickness, and motion sickness, concluded that ginger was a promising antiemetic herbal remedy, but the clinical data were insufficient to draw firm conclusions. Since that publication, additional data has accumulated and thus an updated meta-analysis was performed. METHODS: A systematic search of the literature was performed using different search strategies in MEDLINE, EMBASE, and the Cochrane Library. Six randomized controlled trials including 538 patients were identified investigating ginger to prevent postoperative nausea and vomiting (PONV). Data on the incidences of PONV, nausea, vomiting, and the need for rescue antiemetics within the first 24 postoperative hours were extracted and the pooled relative risk and the numbers needed to treat (NNT) were calculated using a random effects model. RESULTS: The pooled relative risk to suffer from PONV after pre-treatment with ginger was 0.84 (95 %-confidence interval 0.69 - 1.03). About 11 patients must be treated with ginger for one additional patient remaining free from PONV (NNT: 11; 95 %-CI: 6 - 250). Results for nausea, vomiting, and need for antiemetic rescue treatment are similar. CONCLUSION: Ginger is not a clinically relevant antiemetic in the PONV setting.

Gene delivery to cartilage defects using coagulated bone marrow aspirate.

The long-term goal of the present study is to develop a clinically applicable approach to enhance natural repair mechanisms within cartilage lesions by targeting bone marrow-derived cells for genetic modification. To determine if bone marrow-derived cells infiltrating osteochondral defects could be transduced in situ, we implanted collagen-glycosaminoglycan (CG) matrices preloaded with adenoviral vectors containing various marker genes into lesions surgically generated in rabbit femoral condyles. Analysis of the recovered implants showed transgenic expression up to 21 days; however, a considerable portion was found in the synovial lining, indicating leakage of the vector and/or transduced cells from the matrix. As an alternative medium for gene delivery, we investigated the feasibility of using coagulated bone marrow aspirates. Mixture of an adenoviral suspension with the fluid phase of freshly aspirated bone marrow resulted in uniform dispersion of the vector throughout, and levels of transgenic expression in direct proportion to the density of nucleated cells in the ensuing clot. Furthermore, cultures of mesenchymal progenitor cells, previously transduced ex vivo with recombinant adenovirus, were readily incorporated into the coagulate when mixed with fresh aspirate. These vector-seeded and cell-seeded bone marrow clots were found to maintain their structural integrity following extensive culture and maintained transgenic expression in this manner for several weeks. When used in place of the CG matrix as a gene delivery vehicle in vivo, genetically modified bone marrow clots were able to generate similarly high levels of transgenic expression in osteochondral defects with better containment of the vector within the defect. Our results suggest that coagulates formed from aspirated bone marrow may be useful as a means of gene delivery to cartilage and perhaps other musculoskeletal tissues. Cells within the fluid can be readily modified with an adenoviral vector, and the matrix formed from the clot is completely natural, native to the host and is the fundamental platform on which healing and repair of mesenchymal tissues is based.

In vivo investigations on composites made of resorbable ceramics and poly(lactide) used as bone graft substitutes.

Porous composites made of poly(L, DL-lactide) (PLA) and alpha-tricalcium phosphate (alpha-TCP) or the glass ceramic, GB14N, respectively, were investigated in a loaded implant model in sheep. Six, 12 and 24 months after implantation histological and biomechanical evaluation were performed and compared to autogenous bone transplants. No significant differences were observed between the composites. After 6 months, the interconnecting pores of the alpha-TCP-composite and the GB14N-composite were filled with newly formed bone (14 +/- 5% or 29 +/-15% of the implant, respectively) and soft tissue (30 +/-9% or 21 +/-12% of the implant, respectively). Only a mild inflammatory response was observed. The reaction was similar after 12 months. However, after 24 months a strong inflammatory reaction was seen. The newly formed bone was partly osteolytic. The adverse reaction occurred simultaneously to a significant reduction of the PLA component. The histological results were reflected by the biomechanical outcomes. Both composites showed compression strengths in the range of the autologous bone graft until 12 months of implantation. After 2 years, however, the strengths were significantly decreased. It is concluded that the new composites cannot yet be used for clinical application. An improvement in biocompatibility might be reached by a better coordination of the degradation times of the polymer and the ceramic component.

Gene therapy for rheumatoid arthritis.

Advances in understanding the biology of rheumatoid arthritis (RA) have opened new therapeutic avenues. One of these, gene therapy, involves the delivery to patients of genes encoding anti-arthritic proteins. This approach has shown efficacy in animal models of RA, and the first human, phase I trial has just been successfully completed. Hand surgery featured prominently in this pioneering study, as a potentially anti-arthritic gene encoding the interleukin-1 receptor antagonist was transferred to the metacarpophalangeal joints of subjects with RA one week before total joint arthroplasty. This study has confirmed that it is possible to transfer genes safely to human joints. It should pave the way for additional application of gene therapy to arthritis and other orthopaedic conditions.

The predatory legs of Philonthus marginatus (Coleoptera, Staphylinidae): functional morphology and tarsal ultrastructure.

Representatives of the staphylinid beetle Philonthus marginatus are characterized by highly modified raptorial forelegs which are used to strike prey in a particularly fast manner. Beetles ready to capture prey remain in a characteristic precapture ambush posture characterized by lifted and folded forelegs. Triggered by sensory input from the antenna or other parts of the fore body, the actual strike is released, essentially taking the form of a rapid (about 9 ms) depression of the unfolding forelegs towards the prey. This movement is based on the presence of a coxo-trochanteral catch mechanism and a particularly wide angle of rotation in the coxo-trochanteral joint. It is made possible by the specific mechanics of this joint which probably also involves a co-contraction of the antagonistic trochantero-femoral flexor and extensor muscles suggesting a spring-loaded system. This phase of the strike is immediately followed by fixation of the prey by the ventral adhesive tarsal setae supported by a grasp of the flexing last tarsomere and the claws. After withdrawal of the forelegs together with the prey, the sequence eventually results in the formation of a capture-basket formed frontally by the perpendicularly flexing head and laterally by the spiny inner sides of the coxae.