Porous scaffolds were engineered from refibrillized collagen of the jellyfish Rhopilema esculentum for potential application in cartilage regeneration. The influence of collagen concentration, ...salinity and temperature on fibril formation was evaluated by turbidity measurements and quantification of fibrillized collagen. The formation of collagen fibrils with a typical banding pattern was confirmed by atomic force microscopy and transmission electron microscopy analysis. Porous scaffolds from jellyfish collagen, refibrillized under optimized conditions, were fabricated by freeze-drying and subsequent chemical cross-linking. Scaffolds possessed an open porosity of 98.2%. The samples were stable under cyclic compression and displayed an elastic behavior. Cytotoxicity tests with human mesenchymal stem cells (hMSCs) did not reveal any cytotoxic effects of the material. Chondrogenic markers SOX9, collagen II and aggrecan were upregulated in direct cultures of hMSCs upon chondrogenic stimulation. The formation of typical extracellular matrix components was further confirmed by quantification of sulfated glycosaminoglycans.
Unmanned aerial vehicles (UAVs) open new opportunities in precision agriculture and phenotyping because of their flexibility and low cost. In this study, the potential of UAV imagery was evaluated to ...quantify lodging percentage and lodging severity of barley using structure from motion (SfM) techniques. Traditionally, lodging quantification is based on time-consuming manual field observations. Our UAV-based approach makes use of a quantitative threshold to determine lodging percentage in a first step. The derived lodging estimates showed a very high correlation to reference data (R2 = 0.96, root mean square error (RMSE) = 7.66%) when applied to breeding trials, which could also be confirmed under realistic farming conditions. As a second step, an approach was developed that allows the assessment of lodging severity, information that is important to estimate yield impairment, which also takes the intensity of lodging events into account. Both parameters were tested on three ground sample distances. The lowest spatial resolution acquired from the highest flight altitude (100 m) still led to high accuracy, which increases the practicability of the method for large areas. Our new lodging assessment procedure can be used for insurance applications, precision farming, and selecting for genetic lines with greater lodging resistance in breeding research.
Two novel scaffold models made of chitosan fibers were designed, fabricated, and investigated. Raw chitosan fibers were either tightened between plastic rings or were processed into stand-alone ...scaffolds. Chitosan fiber scaffolds were further modified by coating with a thin layer of fibrillar collagen type I to biologize the surface. Cell culture experiments were carried out using murine osteoblast-like cells (7F2). Confocal laser scanning microscopy (cLSM) as well as scanning electron microscopy (SEM) revealed fast attachment and morphological adaptation of the cells on both the raw chitosan fibers and the collagen-coated scaffolds. Cells were cultivated for up to 4 weeks on the materials and proliferation as well as osteogenic differentiation was quantitatively analyzed in terms of lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) activity. We found a 14-16-fold increase of cell number and the typical pattern of ALP activity, whereas the collagen coating does not remarkably influence these parameters. The maintenance of osteogenic phenotype on the novel materials was furthermore confirmed by immunostaining of osteocalcin and study of matrix mineralization. The feature of the collagen-coated but also the raw chitosan fiber scaffolds to support the attachment, proliferation, and differentiation of osteoblast-like cells suggest a potential application of chitosan fibers and textile chitosan scaffolds for the tissue engineering of bone.
Land surface temperature (LST) is a fundamental parameter within the system of the Earth’s surface and atmosphere, which can be used to describe the inherent physical processes of energy and water ...exchange. The need for LST has been increasingly recognised in agriculture, as it affects the growth phases of crops and crop yields. However, challenges in overcoming the large discrepancies between the retrieved LST and ground truth data still exist. Precise LST measurement depends mainly on accurately deriving the surface emissivity, which is very dynamic due to changing states of land cover and plant development. In this study, we present an LST retrieval algorithm for the combined use of multispectral optical and thermal UAV images, which has been optimised for operational applications in agriculture to map the heterogeneous and diverse agricultural crop systems of a research campus in Germany (April 2018). We constrain the emissivity using certain NDVI thresholds to distinguish different land surface types. The algorithm includes atmospheric corrections and environmental thermal emissions to minimise the uncertainties. In the analysis, we emphasise that the omission of crucial meteorological parameters and inaccurately determined emissivities can lead to a considerably underestimated LST; however, if the emissivity is underestimated, the LST can be overestimated. The retrieved LST is validated by reference temperatures from nearby ponds and weather stations. The validation of the thermal measurements indicates a mean absolute error of about 0.5 K. The novelty of the dual sensor system is that it simultaneously captures highly spatially resolved optical and thermal images, in order to construct the precise LST ortho-mosaics required to monitor plant diseases and drought stress and validate airborne and satellite data.
► Complex ulvan/chitosan polyelectrolyte membranes were synthesised and characterised by ATR-FTIR and SEM. ► The ulvan/chitosan membranes possess a fibrous and nanofibrous morphology in a ...supramolecular self assembly. ► Cytocompatibility of ulvan and ulvan/chitosan membranes was proved by the attachment and proliferation of 7F2 osteoblasts.
A new generation of biomaterials composed of the natural polysaccharides, ulvans extracted from the green seaweed Ulva rigida and chitosan have been investigated. Ulvan, chitosan alone and ulvan/chitosan polyelectrolyte membranes have been synthesised and characterised. The structure of the membranes was altered by the weight ratio of the polyion components. Fibrous and nanofibrous morphology was created, in accordance with a supramolecular self assembly. ATR-FTIR measurements suggested the presence of both polycationic chitosan and polyanionic ulvan in the polyelectrolyte membranes. The cytocompatibility of these new materials was examined by fluorescence microscopy. The results show that ulvan as well as ulvan/chitosan membranes promoted the attachment and proliferation of 7F2 osteoblasts and maintained the cell morphology and viability. Thus, ulvan and chitosan which possess unique properties might have high impact in biomedical applications as potential scaffold materials.
Bone graft substitutes in orthopedic applications have to fulfill various demanding requirements. Most calcium phosphate (CaP) bone graft substitutes are highly porous to achieve bone regeneration, ...but typically lack mechanical stability. This study presents a novel approach, in which a scaffold structure with appropriate properties for bone regeneration emerges from the space between specifically shaped granules. The granule types were tetrapods (TEPO) and pyramids (PYRA), which were compared to porous CaP granules (CALC) and morselized bone chips (BC). Bulk materials of the granules were mechanically loaded with a peak pressure of 4 MP; i.e., comparable to the load occurring behind an acetabular cup. Mechanical loading reduced the volume of CALC and BC considerably (89% and 85%, respectively), indicating a collapse of the macroporous structure. Volumes of TEPO and PYRA remained almost constant (94% and 98%, respectively). After loading, the porosity was highest for BC (46%), lowest for CALC (25%) and comparable for TEPO and PYRA (37%). The pore spaces of TEPO and PYRA were highly interconnected in a way that a virtual object with a diameter of 150 µm could access 34% of the TEPO volume and 36% of the PYRA volume. This study shows that a bulk of dense CaP granules in form of tetrapods and pyramids can create a scaffold structure with load capacities suitable for the regeneration of an acetabular bone defect.
The use of autologous bone graft for oral rehabilitation of bone atrophy is considered the gold standard. However, the available grafts do not allow a fast loading of dental implants, as they require ...a long healing time before full functionality. Innovative bioactive materials provide an easy-to-use solution to this problem. The current study shows the feasibility of calcium phosphate cement paste (Paste-CPC) in the sinus. Long implants were placed simultaneously with the cement paste, and provisional prosthetics were also mounted in the same sessions. Final prosthetics and the full loading took place within the same week. Furthermore, the study shows for the first time the possibility to monitor not only healing progression using Cone Beam Computer tomography (CBCT) but also material retention, over two years, on a case study example. The segmented images showed a 30% reduction of the cement size and an increased mineralized tissue in the sinus. Mechanical testing was performed qualitatively using reverse torque after insertion and cement solidification to indicate clinical feasibility. Both functional and esthetic satisfaction remain unchanged after one year. This flowable paste encourages the augmentation procedure with less invasive measure through socket of removed implants. However, this limitation can be addressed in future studies.
The intention of this study was to establish a new critical size animal model that represents clinically relevant situations with osteoporotic bone status and internally fixated metaphyseal defect ...fractures in which biomaterials for the enhancement of fracture healing in osteoporotic fracture defects can be studied. Twenty-eight rats were ovariectomized (OVX) and treated with a calcium-, phosphorus-, vitamin D3-, soy- and phytoestrogen-free diet. After 3months Dual-energy X-ray absorptiometry measurements showed statistically significant reductions in bone mineral density of the spine of −25.9% and of the femur of −21.3% of the OVX rats compared with controls, confirming osteoporosis in the OVX rats. The OVX rats then underwent either 3 or 5mm wedge-shaped osteotomy of the distal metaphyseal area of the femur that was internally stabilized with a T-shaped mini-plate. After 42days biomechanical testing yielded completely unstable conditions in the 5mm defect femora (bending stiffness 0Nmm−2) and a bending stiffness of 12,500Nmm−2 in the 3mm defects, which showed the beginning of fracture consolidation. Micro-computed tomography showed statistically significant more new bone formation in the 3mm defects (4.83±0.37mm2), with bridging of the initial fracture defect area, compared with the 5mm defects (2.68±0.34mm2), in which no bridging of the initial defect was found. These results were confirmed by histology. In conclusion, the 5mm defect can be considered as a critical size defect model in which biomaterials can be tested.
A promising therapeutic option for the treatment of critical-size mandibular defects is the implantation of biodegradable, porous structures that are produced patient-specifically by using additive ...manufacturing techniques. In this work, degradable poly(DL-lactide) polymer (PDLLA) was blended with different mineral phases with the aim of buffering its acidic degradation products, which can cause inflammation and stimulate bone regeneration. Microparticles of CaCO
, SrCO
, tricalcium phosphates (α-TCP, β-TCP), or strontium-modified hydroxyapatite (SrHAp) were mixed with the polymer powder following processing the blends into scaffolds with the Arburg Plastic Freeforming 3D-printing method. An in vitro degradation study over 24 weeks revealed a buffer effect for all mineral phases, with the buffering capacity of CaCO
and SrCO
being the highest. Analysis of conductivity, swelling, microstructure, viscosity, and glass transition temperature evidenced that the mineral phases influence the degradation behavior of the scaffolds. Cytocompatibility of all polymer blends was proven in cell experiments with SaOS-2 cells. Patient-specific implants consisting of PDLLA + CaCO
, which were tested in a pilot in vivo study in a segmental mandibular defect in minipigs, exhibited strong swelling. Based on these results, an in vitro swelling prediction model was developed that simulates the conditions of anisotropic swelling after implantation.
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