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The effect of jet arrangement, jet Re number, jet exit angle (θ), the nozzle-to-surface distance (H/d), jet-to-jet spacing (S/d) on the heat transfer, and pressure force performance from multiple impinging round jets on a moving flat surface have been numerically evaluated. There is a minor difference between in-line and staggered arrangements on a moving flat surface. The averaged Nusselt number on a moving flat surface reduces with an increase in the relative velocity (VR). The surface motion effects become more pronounced on the local Nu distribution at low Re, small S/d, large H/d, and angled jets for a moving flat surface. The pressure force coefficient on a moving flat surface is highly dependent on the H/d and θ but relatively insensitive to the VR, Re, and S/d within the range examined. Two correlations are developed and validated for the average Nu and force coefficient and the agreement between the CFD and correlation is found to be reasonable.

Magnesium is a promising metal for resorbable cardiovascular implants due to its high biocompatibility, high corrosion tendency, and mechanical properties. However, adapting its corrosion rate to the physiological healing processes is required to ascertain a safe graft function. A protective polymeric layer is supposed to slow down the corrosion rate of magnesium. Additionally, coatings can improve the host’s tissue interaction with the implant by implementing the local delivery of antibiotic drugs and growth or cell adhesion factors. However, little is known about the interaction of polymer-based coatings, their degradation, and magnesium corrosion. This study examines the corrosion mechanism of magnesium protected by spin coatings and electrospun fiber coatings under physiological conditions. Pure magnesium specimens were coated with polycaprolactone (PCL). The corrosion of the coated magnesium was evaluated using an immersion test in simulated body fluid. Spin coatings provided efficient protection against corrosive attacks and a significantly lower corrosion rate by 75% compared to uncoated magnesium. In contrast, fiber coatings did not provide relevant corrosion protection. On the other hand, magnesium corrosion caused the accelerated degradation of the PCL layer. A reliable and safe implant function is vital, especially in cardiovascular applications. Magnesium coating, therefore, should be carried out with spin coatings.

Autologous plasma proteins can be used to fabricate patient specific cardiovascular implants but need to be cross-linked to increase their mechanical strength and reduce water solubility. Glutaraldehyde is the state-of-the-art solution but its reaction products have been shown to be cytotoxic and pro-inflammatory. In this work, it has been shown, that cross-linking of plasma proteins with biocompatible alternatives to glutaraldehyde is possible. This was achieved by identifying four candidate substances (thrombin, transglutaminase, genipin, EDC) from current literature and investigating their ability to cross-link porcine plasma proteins in vitro. The degree of crosslinking was examined using calorimetric (DSC) and spectroscopic (FTIR, Raman) methods, mapping the influence of cross-linking on the denaturation temperature and primary amino-group content of the proteins. It could be shown that thrombin, genipin and EDC are able to cross-link plasma proteins to a satisfactory degree and thus represent useful alternatives to glutaraldehyde. Transglutaminase, on the other hand, could not sufficiently cross-link the plasma proteins and was therefore ruled out as an alternative.

In order to improve the reliability of diagnosis of nasal breathing disorders, aerodynamic properties have to be analyzed through experiments based on 3D models. The surface properties of the prepared respective 3D models using fused deposition modeling (FDM) should match those of native nasal cavities, thus representing their normal state and typical pathologies. In this work, we validated the smoothing of dual extruded 3D printed samples of PLA (polylactide) and PVA (polyvinyl alcohol) using the solvent TFE (trifluoroethanol). The smoothing was conducted in vapour and liquid phases of TFE. Before and after treatment of the samples in liquid and vapour phases of TFE, mass and surface roughness analysis were performed. The results of this work will help to produce and process a representative model of the human paranasal sinuses, which can be created using CT data from a patient.

In order to achieve the high quality required in medical products, reliable characterization methods and quality management systems are necessary. In the field of musculoskeletal Tissue Engineering (mTE), electrospinning is utilized to manufacture fibre scaffolds as implant material. Depending on the application, in this case the regeneration of tendon-bone junctions, properties like the degree of fibre orientation, homogeneity of fibre throughout the scaffold and reaction to external mechanical load are of particular importance. Currently, destructive methods, like scanning electron microscopy (SEM), are widely used to determine these properties. In addition to the destruction of the samples, these methods often only allow the investigation of very small sections. In this study, we present two new methods for the fast, non-destructive and contactless characterization of electrospun fibre scaffolds for mTE. These methods are based on Transillumination Imaging (TI) and Mueller Matrix Polarimetry (MMP), utilizing low-power laser sources or LED light sources, respectively, to determine the relative homogeneity (TI) and the degree of fibre orientation (MMP) in electrospun fibre scaffolds.

Magnetic nanoparticles (MNPs) have been used in several medical applications, including targeted hyperthermia, resonance tomography, diagnostic sensors, and localized drug delivery. Further applications of magnetic field manipulation through MNPs in tissue engineering have been described. The current study aims to develop tissue-engineered polymeric scaffolds with incorporated MNPs for applications that require stimulation of the tissues such as nerves, muscles, or heart. Electrospun scaffolds were obtained using 14%w/v polycaprolactone (PCL) in 2,2,2-Trifluoroethanol (TFE) at concentrations of 5% & 7.5%w/v of dispersed MNPs (iron oxide, Fe3O4, or cobalt iron oxide, CoFe2O4). Scaffolds were analyzed using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy, uniaxial tensile testing, and cell seeding for biocompatibility. Human bone marrow mesenchymal stem cells (bmMSCs) were seeded on the scaffolds. Biocompatibility was assessed by metabolic activity with Resazurin reduction assay on day 1, 3, 7, 10. Cell-cell and cell-scaffold interactions were analyzed by SEM. Electrospun scaffolds containing MNPs showed a decrease in fiber diameter as compared to scaffolds of pure PCL. The maximum force increases with the inclusion of MNPs, with higher values revealed for iron oxide. The metabolic activity decreased with MNPs, especially for cobalt iron oxide at a higher concentration. On the other hand, the cells developed good cell-scaffold and cell-cell interactions, making the proposed scaffolds good prospects for potential use in tissue stimulation.

An optimal performance of bone implants with bioceramic coatings is closely related to the surface modification technology. For the first time, we have evaluated a gas detonation deposition (GDD) approach to obtain biocompatible ceramic coatings based on bioglass (BG) and calcium phosphates on Ti-based alloys as prospective materials towards their application for the development of bone implants. For the production of the coatings, hydroxyapatite (HA), HA metal-substituted (containing Ag+, Cu2+, or Zn2+) and tricalcium phosphate (TCP) were synthesized and characterized. Pure powders and their combination with BG were used to obtain coatings on a Ti–6Al–4V alloy using the developed automatized GDD setup. The microstructure, phase and chemical composition of the produced coatings were studied using XRD, SEM-EDS and Raman spectroscopy. The produced coated materials were evaluated in vivo in Wistar rats to analyze a reparative osteogenesis over a period of 12 weeks. The results regarding the optimization of the GDD method indicate its high productivity, as confirmed by high deposition rates. The highest deposition rate was observed for the coatings obtained from the HA metal-substituted powders. The results revealed a partial transformation of a HA phase to an α-TCP phase during the deposition, with a prevalence of the HA-phase in the coatings. According to the histological evaluation, the reparative osteogenesis occurs through the perimeter of the titanium implants, whereas the regeneration level increases from the 4th to the 12th week. The highest osteointegration level was detected for the implants coated with a biocomposite consisting of BG, HA and TCP. The results of the current study demonstrate an effectiveness of the GDD method to produce biocompatible coatings on Ti-based alloys. This provides excellent prerequisites towards the application and standardization of the GDD technology to manufacture bone implants for bone fixation and defect replacement, as well as the development of dental implants.

The results of numerical simulations of a single impinging round jet, using different numerical parameters are presented. To simulate the heat transfer in industrial drying with arrays of different jets the heat transfer for a single round jet (Re=23000 based on jet’s diameter and bulk velocity and the dimensionless jet’s outlet to target wall distance= 2) is used as a test case to validate the numerical model. The distribution of the Nusselt-number serves as a benchmark and the computational cost with regard to CPU-time and memory requirements should be minimal. To accurately predict the intensity and position of the secondary peak from an impinging flow, different approaches for turbulence modeling are considered and their results are compared with data from the literature. The influence of the grid size and the grid shape is analyzed and the grid-independent solution is determined. The results using different implementations of the SST k-omega model, as the best compromise between the computational cost and accuracy are compared. Low Re damping modification in the implementation of SST K-ω has an important role in the prediction of the secondary peak. Good results can be achieved with a coarse grid, as long as the boundary region is appropriately resolved. Polyhedral grids produce good quality results with lower memory requirements and cell numbers as well as shorter run times.

Due to the increasing energy cost, the efficiency of the industrial dryer as the energy-intensive processes should be improved. The designer should optimize the design parameters of industrial drying equipment to achieve the minimum drying energy consumption. SST k-ω turbulence model is used to simulate a real geometry for industrial drying applications. For the optimization of the impinging round jet, the specific drying energy consumption is set as the objective function to be minimized. The jet to surface distance, jet to jet spacing, jet inlet velocity, jet angle, and surface velocity are chosen as the design parameters. The SHERPA search algorithm is used to search for the optimal point from the weighted sum of all objectives method. One correlation is developed and validated for the specific drying energy consumption. It is found that the SST k-ω turbulence model succeeded with reasonable accuracy in reproducing the experimental results. The minimum specific energy consumption correlates with high values of the jet to jet spacing, jet angle, and surface velocity and low values of the nozzle to surface distance and jet inlet velocity. The agreement in the prediction of the specific drying energy consumption between the numerical simulation and correlation is found to be reasonable and all the data points deviate from the correlation by less than 7%.

This section describes a range of interventional therapies where cryopreservation plays an important role in delivery of cell therapies, and which are in wide use from a global perspective. The explosion in the development of advanced therapies and bioengineered constructs within medicine and biotechnology increasingly involves the in vitro manipulation of living cells and complex manufacturing processes. Successful cryopreservation is crucial to enable provision of reproducible starting cell stocks and cell-based products which can be thawed after quality and safety testing is completed and at the time they are needed by patients. Storage of large batch numbers of cells in a biologically stable state that can be recovered with consistent functional properties is crucial to delivering acceptable and effective cell-based medicines (Stacey et al. 2017a). While the technologies for isolation and manufacture of cell-based products have seen dramatic advances in recent years, biopreservation of these complex cell preparations remains an area for research and development and is a key road-block in the capability to deliver widespread access to the exciting potential benefits of these new medicines. In this chapter both nonfrozen live cell storage and cryopreserved storage methods are considered for a range of different cell-based medicines already in use and others that may form the basis of future medicines. While a detailed review of regulations applicable to storage and shipment of cells in different jurisdictions is beyond the scope of this chapter, we have considered the strategies to address regulatory considerations for the development of storage and shipment of cell-based products with reference to specific regulations in the European Union (EU) and the USA.

Jet impingements enhance the heat and mass transfer rate in industrial drying machines. The designer should optimize the design parameters of industrial drying equipment to achieve maximum heat transfer rate. The heat transfer between multiple jets and a moving curved surface is more difficult to study due to the changing boundaries and the effect of surface curvature but is also very relevant in industrial drying applications. SST k-ω turbulence model is used to simulate a real geometry for industrial drying applications. The SST k-ω turbulence model succeeded with reasonable accuracy in reproducing the experimental results. The jet to surface distance, jet to jet spacing, jet inlet velocity, jet angle, and surface velocity are chosen as the design parameters. For the optimization of the impinging round jet, the average Nu number on the moving curved surface is set as the objective functions to be maximized. The SHERPA search algorithm is used to search for the optimal point from the weighted sum of all objectives method. One correlation is developed and validated for the average Nu number. It is found that the maximum average Nu number correlates with high values of jet inlet velocity (Vj), jet angle (θ) and jet to jet spacing (S/d) and low values of the jet to surface distance (H/d) and relative surface velocity (VR). The agreement in the prediction of the average Nu number between the numerical simulation and correlation is found to be reasonable and all the data points deviate from the correlation by less than 4%.

In this paper extensive numerical investigation of the heat transfer characteristics and the pressure force of jet impingement from the single row and multiple rows on a fixed and moving flat surface are reported. The computations were carried out over a wide range of parameters: relative nozzle-to-surface distance (H/d) from 0.5 to 6, relative nozzle to nozzle distances (S/d) from 4 to 10, jet angle from 45° to 90°, relative velocity ratio (Vplate/Vj) i.e. ratio of surface velocity to jet velocity from 0 to 1. The jet Reynolds number (Re) of 2,500, 3,400, 10,000, 20,000, and 23,000 and the number of jet rows of 1, 2, 4, and 8 have been used. It was found that the numerical accuracy by SST k-ω model is reasonably high to allow for a discussion of the main flow and heat transfer characteristics. The jet impingement heat transfer performance is generally enhanced with the increase of jet Reynolds number and jet angle and with the decrease of surface distance (H/d), jet distance (S/d) and the relative velocity ratio (Vplate/Vj) within the range examined. The pressure force coefficients on the impingement surface are relatively insensitive to Re number and the velocity ratio within the range examined, while it has highly dependent on H/d, S/d and jet angle. For multiple rows of aligned jet holes, the flow pattern exhibited a different shape due to the different intensity of the interference between adjacent air jets. The effect of multiple rows with regards to the impact on average Nu and pressure force coefficient for different geometry variations such as Re, H/d, S/d, VR and ɵ is negligible compared to the single row by approximately 9 and 13% in average respectively. Based on the computed results, equations of dimensionless parameters are correlated.

For the optimization of the impinging round jet, the pressure force coefficient and drying energy consumption on the moving curved surface are set as the objective functions to be minimized simultaneously. SHERPA search algorithm is used to search for the optimal point from multiple objective tradeoff study (Pareto Front) method. It is found that the pressure force coefficient on the impingement surface is highly dependent on the jet to surface distance and jet angle, while the drying energy consumption is highly dependent on the jet to jet spacing. Generally, the best design study during the multi-objective optimization is found at the maximum jet to surface distance, jet to jet spacing and surface velocity, and also minimum inlet velocity and jet angle. © 2022, International Scientific Information, Inc.. All rights reserved.

Cryopreservation is the universal technology used to enable long-term storage and continuous availability of cell stocks and tissues for regenerative medicine demands. The main components of standard freezing media are dimethyl sulfoxide (hereinafter Me2SO) and fetal bovine serum (FBS). However, for manufacturing of cells and tissue-engineered products in accordance with the principles of Good Manufacturing Practice (GMP), current considerations in regenerative medicine suggest development of Me2SO- and serum-free biopreservation strategies due to safety concerns over Me2SO-induced side effects and immunogenicity of animal serum. In this work, the effect of electroporation-assisted pre-freeze delivery of sucrose, trehalose and raffinose into human umbilical cord mesenchymal stem cells (hUCMSCs) on their post-thaw survival was investigated. The optimal strength of electric field at 8 pulses with 100 μs duration and 1 Hz pulse repetition frequency was determined to be 1.5 kV/cm from permeabilization (propidium iodide uptake) vs. cell recovery data (resazurin reduction assay). Using sugars as sole cryoprotectants with electroporation, concentration-dependent increase in cell survival was observed. Irrespective of sugar type, the highest cell survival (up to 80%) was achieved at 400 mM extracellular concentration and electroporation. Cell freezing without electroporation yielded significantly lower survival rates. In the optimal scenario, cells were able to attach 24 h after thawing demonstrating characteristic shape and sugar-loaded vacuoles. Application of 10% Me2SO/90% FBS as a positive control provided cell survival exceeding 90%. Next, high glass transition temperatures determined for optimal concentrations of sugars by differential scanning calorimetry (DSC) suggest the possibility to store samples at −80 °C. In summary, using electroporation to incorporate cryoprotective sugars into cells is an effective strategy towards Me2SO- and serum-free cryopreservation and may pave the way for further progress in establishing clinically safe biopreservation strategies for efficient long-term biobanking of cells.

In orthopaedic medicine, connective tissues are often affected by traumatic or degenerative injuries, and surgical intervention is required. Rotator cuff tears are a common cause of shoulder pain and disability among adults. The development of graft materials for bridging the gap between tendon and bone after chronic rotator cuff tears is essentially required. The limiting factor for the clinical success of a tissue engineering construct is a fast and complete vascularization of the construct. Otherwise, immigrating cells are not able to survive for a longer period of time, resulting in the failure of the graft material. The femur chamber allows the observation of microhaemodynamic parameters inside implants located in close vicinity to the femur in repeated measurements in vivo. We compared a porous polymer patch (a commercially available porous polyurethane-based scaffold from Biomerix™) with electrospun polycaprolactone (PCL) fibre mats and chitosan (CS)-graft-PCL modified electrospun PCL (CS-g-PCL) fibre mats in vivo. By means of intravital fluorescence microscopy, microhaemodynamic parameters were analysed repetitively over 20 days at intervals of 3 to 4 days. CS-g-PCL modified fibre mats showed a significantly increased vascularization at Day 10 compared with Day 6 and at Day 14 compared with the porous polymer patch and the unmodified PCL fibre mats at the same day. These results could be verified by histology. In conclusion, a clear improvement in terms of vascularization and biocompatibility is achieved by graft-copolymer modification compared with the unmodified material. © 2019 The Authors Journal of Tissue Engineering and Regenerative Medicine Published by John Wiley & Sons Ltd

Alginate as a versatile naturally occurring biomaterial has found widespread use in the biomedical field due to its unique features such as biocompatibility and biodegradability. The ability of its semipermeable hydrogels to provide a favourable microenvironment for clinically relevant cells made alginate encapsulation a leading technology for immunoisolation, 3D culture, cryopreservation as well as cell and drug delivery. The aim of this work is the evaluation of structural properties and swelling behaviour of the core-shell capsules for the encapsulation of multipotent stromal cells (MSCs), their 3D culture and cryopreservation using slow freezing. The cells were encapsulated in core-shell capsules using coaxial electrospraying, cultured for 35 days and cryopreserved. Cell viability, metabolic activity and cell–cell interactions were analysed. Cryopreservation of MSCs-laden core-shell capsules was performed according to parameters pre-selected on cell-free capsules. The results suggest that core-shell capsules produced from the low viscosity high-G alginate are superior to high-M ones in terms of stability during in vitro culture, as well as to solid beads in terms of promoting formation of viable self-assembled cellular structures and maintenance of MSCs functionality on a long-term basis. The application of 0.3 M sucrose demonstrated a beneficial effect on the integrity of capsules and viability of formed 3D cell assemblies, as compared to 10% dimethyl sulfoxide (DMSO) alone. The proposed workflow from the preparation of core-shell capsules with self-assembled cellular structures to the cryopreservation appears to be a promising strategy for their off-the-shelf availability.

Cryomicroscopy is one of the main techniques to visualize freezing and thawing events taking place during cryopreservation of cells, native and artificial tissues with the ultimate goal to provide cell- and tissue-specific cryogenic preservation. However, there is currently no unified software tool for the automated analysis of ice recrystallization kinetics for a variety of cryoprotective agents used in the cryobiological practice. In this regard, we focused on the particular aspect of image analysis in the course of ice recrystallization, i.e. the possibility of using a neural network for the segmentation of ice crystals during isothermal annealing. In the work, the U-Net deep neural network was used for segmentation of ice crystals on cryomicroscopic images. Using 100 images as training set, the resulting accuracy of ice crystal segmentation was about 74% on the test sample (30 images). The obtained results show the possibility of segmentation of ice crystals in cryomicroscopic images taking into account the overlapping of intensity levels of an object and background. Further improvement of the model through the use of an additional training data as well as augmentation techniques is required to more efficiently validate this approach.

We have recently reported on the high practical utility of using electroporation of clinically relevant cells with sugars for their xeno-free cryopreservation in suspension. This paper extends our earlier approach to in situ electroporating attached cells for their robust cryopreservation on artificial scaffolds. Using CAD modelling, a two-electrode setup has been designed and in-house constructed allowing for simultaneous electroporation in multi-well cell culture plates. Blend electrospinning process has been optimized in order to manufacture porous fibrous mats made of polycaprolactone (PCL, 100 mg/ml) and polylactide (PLA, 50 mg/ml) with an average thickness of 100 µm. Chinese hamster ovary (CHO) cells were grown and directly electroporated in nanofibrous blend electrospun fiber mats. An electric pulse was applied in the presence of propidium iodide and CellTracker Green to determine viable permeabilized cell counts using fluorescence microscopy. Cell recovery was evaluated using metabolic MTS assay 24 h post-electroporation. Electric field intensity and distribution within a 3D reconstructed fiber mat was simulated and visualized using COMSOL software. The results demonstrate that with developed setup it is feasible to electroporate around 80% of attached cells with 80% viability after electroporation when electric field strength was ≥1.7 kV/cm. COMSOL simulations showed local increases of electric field at intersection points of numerous fibers which may in part contribute to the observed drop in cell viability post-electroporation. Future studies anticipate implementation of the developed approach in effective biopreservation of stem cells on electrospun fiber mats as a model of tissue-engineered constructs.

Surgical medicine is one of the most radical approaches for the treatment of numerous types of diseases. Recently broad application has taken the direction of computational surgery that aims to improve the quality of treatment through the use of computer tools. The use of computational surgery in rhinoplasty is important due to the fact that the results of the intervention directly affect the geometry of the nasal cavity and, as a consequence, the aerodynamic parameters of the nose. In turn, these parameters determine the functional characteristics of the patient’s nasal cavity. In this paper, we have focused on modeling the deformation of anatomical structures using SOFA framework software library considering tetrahedron finite element modeling (FEM), hexahedron FEM, triangle FEM and mesh spring force fields. The simulation results indicate the high functionality of the SOFA framework for modeling the deformation of the airway in rhinosurgical interventions. These results could further be applied for modeling the deformation of the anatomical structure taking into account the change in the topology of a 3D model to simulate such surgical procedures as a cut.

As novel tissue engineered constructs (TECs) are developed, current tissue banking practices need better control over ice formation and growth to prevent cryodamage to cells and a scaffold. Directional solidification demonstrates benefits in adhered cells and native tissues cryopreservation through controlled heat transfer. Therefore, this study aims to investigate the feasibility of using this technique for cryopreservation of cell-seeded electrospun fiber mats as model TECs. Fiber mats were produced using blend electrospinning of polycaprolactone (PCL, 200 mg/ml) and poly-L-lactic acid (PLA, 100 mg/ml) dissolved in 2,2,2-Trifluoroethanol. The fiber size and morphology was characterized using scanning electron microscopy. Specific heat measurements were conducted using differential scanning calorimetry. The square-shaped fiber mats were seeded under static conditions with HeLa cells and cultivated for 24 h. Samples were directionally frozen in a sandwich format either in 10% DMSO or culture medium with the sample movement at 30 μm/s through the predetermined temperature gradients along a 2.6 mm slit. After directional solidification, samples were gradually frozen at 1 K/min down to −80 ℃. Crystal shape was visualized using cryomicroscopic system. Before freezing and 24 h after thawing, cell viability was assessed using live-dead assay. Within randomly orientated PCL-PLA fibers, HeLa cells exhibited typical shape and attachment with higher than 90% viability prior to freezing. While up to 80% of HeLa cells were alive on fiber mats after freezing using DMSO with or without directional solidification step. The demonstrated controlled freezing may assist optimizing the freezing of more sensitive cells. The results suggest that directional freezing becomes a viable option for cryopreservation in tissue engineering applications.

Co-polymer polyvinylidene fluoride-co-trifluoroethylene (PVDF-TrFE) is a promising piezoelectric material for a range of medical and industrial applications such as tissue engineering, sensors and membrane technics. In this regard, blend electrospinning is an ideal method to produce suitable polymeric nano- and micro-fiber scaffolds or membranes from polymer solutions. Stable electrospinning process is strongly dependent on PVDF-TrFE solution properties. Thus, this study aimed at evaluating the effect of different suitable solvents on physical properties PVDF-TrFE polymer solutions and produced films with different solvent combinations and mixing ratios. The results indicate that solution viscosities range between 5.47 and 37.17 Pa.s. Furthermore, piezoelectric phase fraction and crystallinity of PVDF-TrFE films were characterized using Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry, respectively. All films exhibited a piezoelectric polar beta-phase formation. The crystalline beta-phase fraction of the most of the films was higher than the value of the initial material (77%). Results demonstrate the influence of solvent combinations and mixing ratios on melting temperature and crystallinity.

Electrospinning is a versatile fibre fabrication method with applications from textile to tissue engineering. Despite the appearance that the influencing parameters of electrospinning are fully understood, the effect of setup orientation has not been thoroughly investigated. With current burgeoning interest in modified and specialised electrospinning apparatus, it is timely to review the impact of this seldom-considered parameter. Apparatus configuration plays a major role in the morphology of the final product. The primary difference between spinning setups is the degree to which the electrical force and gravitational force contribute. Since gravity is much lower in magnitude when compared with the electrostatic force, it is thought to have no significant effect on the spinning process. But the shape of the Taylor cone, jet trajectory, fibre diameter, fibre diameter distribution, and overall spinning efficiency are all influenced by it. In this review paper, we discuss all these developments and more. Furthermore, because many research groups build their own electrospinning apparatus, it would be prudent to consider this aspect as particular orientations are more suitable for certain applications.

Mesenchymal stem/stromal cells (MSCs) exert beneficial effects during wound healing, and cell-seeded scaffolds are a promising method of application. Here, we compared the suitability of a clinically used collagen/elastin scaffold (Matriderm) with an electrospun Poly(ε-caprolactone)/poly(l-lactide) (PCL/PLA) scaffold as carriers for human amnion-derived MSCs (hAMSCs). We created an epidermal-like PCL/PLA scaffold and evaluated its microstructural, mechanical, and functional properties. Sequential spinning of different PCL/PLA concentrations resulted in a wide-meshed layer designed for cell-seeding and a dense-meshed layer for apical protection. The Matriderm and PCL/PLA scaffolds then were seeded with hAMSCs, with or without Matrigel coating. The quantity and quality of the adherent cells were evaluated in vitro. The results showed that hAMSCs adhered to and infiltrated both scaffold types but on day 3, more cells were observed on PCL/PLA than on Matriderm. Apoptosis and proliferation rates were similar for all carriers except the coated Matriderm, where apoptotic cells were significantly enhanced. On day 8, the number of cells decreased on all carrier types except the coated Matriderm, which had consistently low cell numbers. Uncoated Matriderm had the highest percentage of proliferative cells and lowest apoptosis rate of all carrier types. Each carrier also was topically applied to skin wound sites in a mouse model and analyzed in vivo over 14 days via optical imaging and histological methods, which showed detectable hAMSCs on all carrier types on day 8. On day 14, all wounds exhibited newly formed epidermis, and all carriers were well-integrated into the underlying dermis and showing signs of degradation. However, only wounds treated with uncoated PCL/PLA maintained a round appearance with minimal contraction. Overall, the results support a 3-day in vitro culture of scaffolds with hAMSCs before wound application. The PCL/PLA scaffold showed higher cell adherence than Matriderm, and the effect of the Matrigel coating was negligible, as all carrier types maintained sufficient numbers of transplanted cells in the wound area. The anti-contractive effects of the PCL/PLA scaffold offer potential new therapeutic approaches to wound care.

Aim To introduce a methodology designed to simultaneously visualize dental ultrastructures, including cellular and soft tissue components, by utilizing phosphotungstic acid (PTA) as a contrast-enhancement agent. Methodology Sound third molars were collected from healthy human adults and fixed in 4% buffered paraformaldehyde. To evaluate the impact of PTA in concentrations of 0.3%, 0.7% and 1% on dental soft and hard tissues for CT imaging, cementum and dentine-pulp sections were cut, dehydrated and stained with immersion periods of 12, 24 h, 2 days or 5 days. The samples were scanned in a high-resolution nano-CT device using pixel sizes down to 0.5 µm to examine both the cementum and pulpal regions. Results Dental cementum and periodontium as well as odontoblasts and predentine were made visible through PTA staining in high-resolution three-dimensional nano-CT scans. Different segments of the tooth required different staining protocols. The thickness of the cementum could be computed over the length of the tooth once it was made visible by the PTA-enhanced contrast, and the attached soft tissue components of the interior of the tooth could be shown on the dentine-pulp interface in greater detail. Three-dimensional illustrations allowed a histology-like visualization of the sections in all orientations with a single scan and easy sample preparation. The segmentation of the sigmoidal dentinal tubules and the surrounding dentine allowed a three-dimensional investigation and quantitative of the dentine composition, such as the tubular lumen or the ratio of the tubular lumen area to the dentinal surface. Conclusion The staining protocol made it possible to visualize hard tissues along with cellular layers and soft tissues in teeth using a laboratory-based nano-CT technique. The protocol depended on both tissue type and size. This methodology offers enhanced possibilities for the concomitant visualization of soft and hard dental tissues.

Electrospun polycaprolactone:gelatin (PCL:GT) fibre scaffolds are widely employed in the field of tissue implants. Here, the orientation of fibres plays an important role in regard to implantation due to the impact on the mechanical properties. Likewise, the orientation of collagen fibres in skin tissue is relevant for dermatology. State-of-the-art fibre orientation measurement methods like electron microscopy are time consuming and destructive. In this work, we demonstrate polarimetry as a non-invasive approach and evaluate its potential by measuring the Mueller matrix (MM) of gelatin and collagen containing samples as simple skin tissue phantoms. We demonstrate that it is possible to determine the orientation of PCL:GT fibre scaffolds within one MM measurement. Furthermore, we determine the structural orientation in collagen film samples. Currently, the diagnosis of skin diseases is often performed by image analysis or histopathology respectively, which are either subjective or invasive. The method presented, here, provides an interesting alternative approach for such investigations. Our findings indicate that the orientation of collagen fibres within skin lesions might be detectable by MM measurements in the future, which is of interest for skin diagnostics, and will be further investigated during the next step.

The most important factor that determines the normal functional state of the nasal mucosa is that which passes through it during inhalation and exhalation air flow, which, entering the nasal cavity, due to the active expansion of the chest feels resistance from the surrounding structures. This factor is influenced by an indicator such as air flow resistance, with 54% of the total resistance of the respiratory system to the upper respiratory tract, including 46% of the resistance of the nasal cavity. In addition, it is necessary to study the aerodynamic laws that play an important role in the regulation of the degree of nasal resistance. Nasal resistance can be affected by a variety of external factors and pathological processes in the nasal mucosa: cold air inhalation, hyperventilation, allergy and inflammation, alcohol abuse. Thus, the blood supply in the cavernous venous plexuses promotes swelling of the nasal membranes, an increase in their size, and narrowing of the lumen of the nasal valve to completely block the nasal cavity, causing changes in normal function. Such air flow supports clearly require an objective study to overcome it. Given that the objective assessment of nasal resistance is extremely difficult, it is necessary to create additional diagnostic methods, tools and criteria based on data from a complex of diagnostic measures, such as computed tomography, endoscopy, rhinomanometry.