Strategies for Development of Synthetic Heart Valve Tissue Engineering Scaffolds

The current clinical solutions, including mechanical and bioprosthetic valves for valvular heart diseases, are plagued by coagulation, calcification, nondurability, and the inability to grow with patients. The tissue engineering approach attempts to resolve these shortcomings by producing heart valve scaffolds that may deliver patients a life-long solution. Heart valve scaffolds serve as a three-dimensional support structure made of biocompatible materials that provide adequate porosity for cell infiltration, and nutrient and waste transport, sponsor cell adhesion, proliferation, and differentiation, and allow for extracellular matrix production that together contributes to the generation of functional neotissue. The foundation of successful heart valve tissue engineering is replicating native heart valve architecture, mechanics, and cellular attributes through appropriate biomaterials and scaffold designs. This article reviews biomaterials, the fabrication of heart valve scaffolds, and their in-vitro and in-vivo evaluations applied for heart valve tissue engineering.

Neutron-activated, plasmonically excitable Fe-Pt-Yb2O3 nanoparticles delivering anti-cancer radiation against human glioblastoma cells

Magnetic nanoparticles can be functionalized in many ways for biomedical applications. Here, we combine four advantageous features in a novel Fe-Pt-Yb2O3 core-shell nanoparticle. (a) The nanoparticles have a size of 10 nm allowing them to diffuse through neuronal tissue. (b) The particles are superparamagnetic after synthesis and ferromagnetic after annealing, enabling directional control by magnetic fields, enhance NMRI contrast, and hyperthermia treatment. (c) After neutron-activation of the shell, they carry low-energetic, short half-life β-radiation from 175Yb, 177Yb, and 177Lu. (d) Additionally, the particles can be optically visualized by plasmonic excitation and luminescence. To demonstrate the potential of the particles for cancer treatment, we exposed cultured human glioblastoma cells (LN-18) to non-activated and activated particles to confirm that the particles are internalized, and that the β-radiation of the radioisotopes incorporated in the neutron-activated shell of the nanoparticles kills more than 98% of the LN-18 cancer cells, promising for future anti-cancer applications.

Sub-Bandgap Sensitization of Perovskite Semiconductors via Colloidal Quantum Dots Incorporation

By taking advantage of the outstanding intrinsic optoelectronic properties of perovskite-based photovoltaic materials, together with the strong near-infrared (NIR) absorption and electronic confinement in PbS quantum dots (QDs), sub-bandgap photocurrent generation is possible, opening the way for solar cell efficiencies surpassing the classical limits. The present study shows an effective methodology for the inclusion of high densities of colloidal PbS QDs in a MAPbI3 (methylammonium lead iodide) perovskite matrix as a means to enhance the spectral window of photon absorption of the perovskite host film and allow photocurrent production below its bandgap. The QDs were introduced in the perovskite matrix in different sizes and concentrations to study the formation of quantum-confined levels within the host bandgap and the potential formation of a delocalized intermediate mini-band (IB). Pronounced sub-bandgap (in NIR) absorption was optically confirmed with the introduction of QDs in the perovskite. The consequent photocurrent generation was demonstrated via photoconductivity measurements, which indicated IB establishment in the films. Despite verifying the reduced crystallinity of the MAPbI3 matrix with a higher concentration and size of the embedded QDs, the nanostructured films showed pronounced enhancement (above 10-fold) in NIR absorption and consequent photocurrent generation at photon energies below the perovskite bandgap.

Elastomeric Trilayer Substrates with Native-like Mechanical Properties for Heart Valve Leaflet Tissue Engineering

Heart valve leaflets have a complex trilayered structure with layer-specific orientations, anisotropic tensile properties, and elastomeric characteristics that are difficult to mimic collectively. Previously, trilayer leaflet substrates intended for heart valve tissue engineering were developed with nonelastomeric biomaterials that cannot deliver native-like mechanical properties. In this study, by electrospinning polycaprolactone (PCL) polymer and poly(l-lactide-co-ε-caprolactone) (PLCL) copolymer, we created elastomeric trilayer PCL/PLCL leaflet substrates with native-like tensile, flexural, and anisotropic properties and compared them with trilayer PCL leaflet substrates (as control) to find their effectiveness in heart valve leaflet tissue engineering. These substrates were seeded with porcine valvular interstitial cells (PVICs) and cultured for 1 month in static conditions to produce cell-cultured constructs. The PCL/PLCL substrates had lower crystallinity and hydrophobicity but higher anisotropy and flexibility than PCL leaflet substrates. These attributes contributed to more significant cell proliferation, infiltration, extracellular matrix production, and superior gene expression in the PCL/PLCL cell-cultured constructs than in the PCL cell-cultured constructs. Further, the PCL/PLCL constructs showed better resistance to calcification than PCL constructs. Trilayer PCL/PLCL leaflet substrates with native-like mechanical and flexural properties could significantly improve heart valve tissue engineering.

Fibrin gel enhanced trilayer structure in cell-cultured constructs

Efficient cell seeding and subsequent support from a substrate ensure optimal cell growth and neotissue development during tissue engineering, including heart valve tissue engineering. Fibrin gel as a cell carrier may provide high cell seeding efficiency and adhesion property, improved cellular interaction, and structural support to enhance cellular growth in trilayer polycaprolactone (PCL) substrates that mimic the structure of native heart valve leaflets. This cell carrier gel coupled with a trilayer PCL substrate may enable the production of native-like cell-cultured leaflet constructs suitable for heart valve tissue engineering. In this study, we seeded valvular interstitial cells onto trilayer PCL substrates with fibrin gel as a cell carrier and cultured them for 1 month in vitro to determine if this gel can improve cell proliferation and production of extracellular matrix within the trilayer cell-cultured constructs. We observed that the fibrin gel enhanced cellular proliferation, their vimentin expression, and collagen and glycosaminoglycan production, leading to improved structure and mechanical properties of the developing PCL cell-cultured constructs. Fibrin gel as a cell carrier significantly improved the orientations of the cells and their produced tissue materials within trilayer PCL substrates that mimic the structure of native heart valve leaflets and, thus, may be highly beneficial for developing functional tissue-engineered leaflet constructs.

Anisotropicity and flexibility in trilayered microfibrous substrates promote heart valve leaflet tissue engineering

Heart valve leaflet substrates with native trilayer and anisotropic structures are crucial for successful heart valve tissue engineering. In this study, we used the electrospinning technique to produce trilayer microfibrous leaflet substrates using two biocompatible and biodegradable polymers-poly (L-lactic acid) (PLLA) and polycaprolactone (PCL), separately. Different polymer concentrations for each layer were applied to bring a high degree of mechanical and structural anisotropy to the substrates. PCL leaflet substrates exhibited lower unidirectional tensile properties than PLLA leaflet substrates. However, the PLLA substrates exhibited a lower flexural modulus than the PCL substrates. These substrates were seeded with porcine valvular interstitial cells (PVICs) and cultured for one month in static conditions. Both substrates exhibited cellular adhesion and proliferation, resulting in the production of tissue-engineered constructs. The PLLA tissue-engineered constructs had more cellular growth than the PCL tissue-engineered constructs. The PLLA substrates showed higher hydrophilicity, lower crystallinity, and more significant anisotropy than PCL substrates, which may have enhanced their interactions with PVICs. Analysis of gene expression showed higherα-smooth muscle actin and collagen type 1 expression in PLLA tissue-engineered constructs than in PCL tissue-engineered constructs. The differences in anisotropic and flexural properties may have accounted for the different cellular behaviors in these two individual polymer substrates.

Volumetric quantification of choroid and Haller's sublayer using OCT scans: An accurate and unified approach based on stratified smoothing

BACKGROUND AND OBJECTIVE

The choroid, a dense vascular structure in the posterior segment of the eye, maintains the health of the retina by supplying oxygen and nutrients, and assumes clinical significance in screening ocular diseases including age-related macular degeneration (AMD) and central serous chorioretinopathy (CSCR). As a technological assist, algorithmic estimation of choroidal biomarkers has been suggested based on sectional (B-scan) optical coherence tomography (OCT) images. However, most such 2D estimation techniques are compute-intensive, yet enjoy limited accuracy and have only been validated on OCT image datasets of healthy eyes. Not surprisingly, fine-scale analyses, including those involving Haller's sublayer, remain relatively rare and unsophisticated. Against this backdrop, we propose an efficient algorithm to quantify desired biomarkers with improved accuracy based on volume OCT scans. Specifically, we attempted an accurate, computationally light volumetric segmentation method involving stratified smoothing to detect choroid and Haller's sublayer.

METHODS

For detecting the various boundaries of the choroid and the Haller's sublayer, we propose a common volumetric method that performs suitable exponential enhancement and maintains smooth spatial continuity across 2D B-scans. Further, we achieve suitable volumetric smoothing by primarily deploying light-duty linear regression, and sparingly using compute-intensive tensor voting, and hence significantly reduce overall complexity. The proposed methodology is tested on five health and five diseased OCT volumes considering various metrics including volumetric Dice coefficient and corresponding quotient measures to facilitate comparison vis-à-vis intra-observer repeatability.

RESULTS

On five healthy and five diseased OCT volumes, respectively, the proposed method for choroid segmentation recorded volumetric Dice coefficients of 93.53 % and 93.30 %, which closely approximate the respective reference observer repeatability values of 95.60 % and 95.49 %. In terms of related quotient measures, our method achieved more than 50 % improvement over a recently reported method. In detecting Haller's sublayer as well, our algorithm records statistical performance closely matching that of reference manual method.

CONCLUSION

Advancing the state-of-the-art, the proposed volumetric segmentation, tested on both healthy and diseased datasets, demonstrated close match with the manual reference. Our method assumes significance in accurate screening of chorioretinal diseases including AMD, CSCR and pachychoroid. Further, it enables generating accurate training data for developing deep learning models for improved detection of choroid and Haller's sublayer.

Leaflet Tissue Generation from Microfibrous Heart Valve Leaflet Scaffolds with Native Characteristics

Mechanical and bioprosthetic valves that are currently applied for replacing diseased heart valves are not fully efficient. Heart valve tissue engineering may solve the issues faced by the prosthetic valves in heart valve replacement. The leaflets of native heart valves have a trilayered structure with layer-specific orientations; thus, it is imperative to develop functional leaflet tissue constructs with a native trilayered, oriented structure. Its key solution is to develop leaflet scaffolds with a native morphology and structure. In this study, microfibrous leaflet scaffolds with a native trilayered and oriented structure were developed in an electrospinning system. The scaffolds were implanted for 3 months in rats subcutaneously to study the scaffold efficiencies in generating functional tissue-engineered leaflet constructs. These in vivo tissue-engineered leaflet constructs had a trilayered, oriented structure similar to native leaflets. The tensile properties of constructs indicated that they were able to endure the hydrodynamic load of the native heart valve. Collagen, glycosaminoglycans, and elastin─the predominant extracellular matrix components of native leaflets─were found sufficiently in the leaflet tissue constructs. The residing cells in the leaflet tissue constructs showed vimentin and α-smooth muscle actin expression, i.e., the constructs were in a growing state. Thus, the trilayered, oriented fibrous leaflet scaffolds produced in this study could be useful to develop heart valve scaffolds for successful heart valve replacements.

Fibrous heart valve leaflet substrate with native-mimicked morphology

Tissue-engineered heart valves are a promising alternative solution to prosthetic valves. However, long-term functionalities of tissue-engineered heart valves depend on the ability to mimic the trilayered, oriented structure of native heart valve leaflets. In this study, using electrospinning, we developed trilayered microfibrous leaflet substrates with morphological characteristics similar to native leaflets. The substrates were implanted subcutaneously in rats to study the effect of their trilayered oriented structure on in vivo tissue engineering. The tissue constructs showed a well-defined structure, with a circumferentially oriented layer, a randomly oriented layer and a radially oriented layer. The extracellular matrix, produced during in vivo tissue engineering, consisted of collagen, glycosaminoglycans, and elastin, all major components of native leaflets. Moreover, the anisotropic tensile properties of the constructs were sufficient to bear the valvular physiological load. Finally, the expression of vimentin and α-smooth muscle actin, at the gene and protein level, was detected in the residing cells, revealing their growing state and their transdifferentiation to myofibroblasts. Our data support a critical role for the trilayered structure and anisotropic properties in functional leaflet tissue constructs, and indicate that the leaflet substrates have the potential for the development of valve scaffolds for heart valve replacements.

Trilayered tissue construct mimicking the orientations of three layers of a native heart valve leaflet

A tissue-engineered heart valve can be an alternative to a prosthetic valve in heart valve replacement; however, it is not fully efficient in terms of long-lasting functionality, as leaflets in engineered valves do not possess the trilayered native leaflet structure. Previously, we developed a flat, trilayered, oriented nanofibrous (TN) scaffold mimicking the trilayered structure and orientation of native heart valve leaflets. In vivo tissue engineering-a practical regenerative medicine technology-can be used to develop an autologous heart valve. Thus, in this study, we used our flat, trilayered, oriented nanofibrous scaffolds to develop trilayered tissue structures with native leaflet orientations through in vivo tissue engineering in a rat model. After 2 months of in vivo tissue engineering, infiltrated cells and their deposited collagen fibrils were found aligned in the circumferential and radial layers, and randomly oriented in the random layer of the scaffolds, i.e., trilayered tissue constructs (TTCs) were developed. Tensile properties of the TTCs were higher than that of the control tissue constructs (without any scaffolds) due to influence of fibers of the scaffolds in tissue engineering. Different extracellular matrix proteins-collagen, glycosaminoglycans, and elastin-that exist in native leaflets were observed in the TTCs. Gene expression of the TTCs indicated that the tissue constructs were in growing stage. There was no sign of calcification in the tissue constructs. The TTCs developed with the flat TN scaffolds indicate that an autologous leaflet-shaped, trilayered tissue construct that can function as a native leaflet can be developed.

In vivo tissue engineering of a trilayered leaflet-shaped tissue construct

Aim: We aimed to develop a leaflet-shaped trilayered tissue construct mimicking the morphology of native heart valve leaflets. Materials & methods: Electrospinning and in vivo tissue engineering methods were employed. Results: We developed leaflet-shaped microfibrous scaffolds, each with circumferentially, randomly and radially oriented three layers mimicking the trilayered, oriented structure of native leaflets. After 3 months in vivo tissue engineering with the scaffolds, the generated leaflet-shaped tissue constructs had a trilayered structure mimicking the orientations of native heart valve leaflets. Presence of collagen, glycosaminoglycans and elastin seen in native leaflets was observed in the engineered tissue constructs. Conclusion: Trilayered, oriented fibrous scaffolds brought the orientations of the infiltrated cells and their produced extracellular matrix proteins into the constructs.

Trilayered tissue structure with leaflet-like orientations developed through in vivo tissue engineering

A tissue-engineered heart valve can be an alternative to current mechanical or bioprosthetic valves that face limitations, especially in pediatric patients. However, it remains challenging to produce a functional tissue-engineered heart valve with three leaflets mimicking the trilayered, oriented structure of a native valve leaflet. In our previous study, a flat, trilayered nanofibrous substrate mimicking the orientations of three layers in a native leaflet-circumferential, random and radial orientations in fibrosa, spongiosa and ventricularis layers, respectively, was developed through electrospinning. In this study, we sought to develop a trilayered tissue structure mimicking the orientations of a native valve leaflet through in vivo tissue engineering, a practical regenerative medicine technology that can be used to develop an autologous heart valve. Thus, the nanofibrous substrate was placed inside the closed trileaflet-shaped cavity of a mold and implanted subcutaneously in a rat model for in vivo tissue engineering. After two months, the explanted tissue construct had a trilayered structure mimicking the orientations of a native valve leaflet. The infiltrated cells and their deposited collagen fibrils were oriented along the nanofibers in each layer of the substrate. Besides collagen, presence of glycosaminoglycans and elastin in the construct was observed.

Endothelialization of cardiovascular devices

Blood-contacting surfaces of cardiovascular devices are not biocompatible for creating an endothelial layer on them. Numerous research studies have mainly sought to modify these surfaces through physical, chemical and biological means to ease early endothelial cell (EC) adhesion, migration and proliferation, and eventually to build an endothelial layer on the surfaces. The first priority for surface modification is inhibition of protein adsorption that leads to inhibition of platelet adhesion to the device surfaces, which may favor EC adhesion. Surface modification through surface texturing, if applicable, can bring some hopeful outcomes in this regard. Surface modifications through chemical and/or biological means may play a significant role in easy endothelialization of cardiovascular devices and inhibit smooth muscle cell proliferation. Cellular engineering of cells relevant to endothelialization can boost the positive outcomes obtained through surface engineering. This review briefly summarizes recent developments and research in early endothelialization of cardiovascular devices. STATEMENT OF SIGNIFICANCE: Endothelialization of cardiovascular implants, including heart valves, vascular stents and vascular grafts is crucial to solve many problems in our health care system. Numerous research efforts have been made to improve endothelialization on the surfaces of cardiovascular implants, mainly through surface modifications in three ways - physically, chemically and biologically. This review is intended to highlight comprehensive research studies to date on surface modifications aiming for early endothelialization on the blood-contacting surfaces of cardiovascular implants. It also discusses future perspectives to help guide endothelialization strategies and inspire further innovations.

Optimization of polycaprolactone fibrous scaffold for heart valve tissue engineering

Pore size is generally small in nanofibrous scaffolds prepared by electrospinning polymeric solutions. Increase of scaffold thickness leads to decrease in pore size, causing impediment to cell infiltration into the scaffolds during tissue engineering. In contrast, comparatively larger pore size can be realized in microfibrous scaffolds prepared from polymeric solutions at higher concentrations. Further, microfibrous scaffolds are conducive to infiltration of reparative M2 phenotype macrophages during in vivo/in situ tissue engineering. However, rise of mechanical properties of a fibrous scaffold with the increase of polymer concentration may limit the functionality of a scaffold-based, tissue-engineered heart valve. In this study, we developed microfibrous scaffolds from 14%, 16% and 18% (wt/v) polycaprolactone (PCL) polymer solutions prepared with chloroform solvent. Porcine valvular interstitial cells were cultured in the scaffolds for 14 d to investigate the effect of microfibers prepared with different PCL concentrations on the seeded cells. Further, fresh microfibrous scaffolds were implanted subcutaneously in a rat model for two months to investigate the effect of microfibers on infiltrated cells. Cell proliferation, and its morphologies, gene expression and deposition of different extracellular matrix proteins in the in vitro study were characterized. During the in vivo study, we characterized cell infiltration, and myofibroblast and M1/M2 phenotypes expression of the infiltrated cells. Among different PCL concentrations, microfibrous scaffolds from 14% solution were suitable for heart valve tissue engineering for their sufficient pore size and low but adequate tensile properties, which promoted cell adhesion to and proliferation in the scaffolds, and effective gene expression and extracellular matrix deposition by the cells in vitro. They also encouraged the cells in vivo for their infiltration and effective gene expression, including M2 phenotype expression.

The role of polymers in cross-kingdom bioadhesion

The secretion of extracellular polymeric substances provides an evolutionary advantage found in many organisms that can adhere to surfaces and cover themselves in a protective matrix. This ability is found in prokaryotes, archaea and eukaryotes, all of which use functionally similar polysaccharides, proteins and nucleic acids to form extracellular matrices, mucus and bioadhesive substances. These macromolecules have been investigated from the perspective of polymer biophysics, and theories to help understand adhesion, viscosity and gelling have been developed. These properties can be measured experimentally using straightforward methods such as cell counting as well as more advanced techniques such as atomic force microscopy and rheometry. An integrated understanding of the properties and uses of adhesive macromolecules across kingdoms is also important and can provide the basis for a range of biotechnological and medical applications. This article is part of the theme issue 'Transdisciplinary approaches to the study of adhesion and adhesives in biological systems'.

Infrared tunable, two colour-band photodetectors on flexible platforms using 0D/2D PbS-MoS2 hybrids

Two-dimensional (2D) MoS₂ nanosheets have been integrated with zero-dimensional (0D) PbS quantum dots to achieve a superior optical response extending to the short-wavelength infrared region along with a broadband visible response for multispectral photodetection. The 0D/2D hybrid nanostructures have been synthesized by a one pot, stabilizer-free solvothermal growth process. Microscopic and spectroscopic studies confirmed the formation of PbS QD decorated semiconducting 2H-MoS₂ layers. The size tunable absorption features with longer photo-generated carrier lifetime of synthesized hybrid nanostructures indicate that the integration of PbS QDs in MoS₂ could be a viable approach for fabricating two-colour band photodetectors, viz. visible broadband and wavelength selective short-wave IR photodetectors. Devices have also been demonstrated on polyethylene terephthalate substrates using a solution-based synthesis technique for flexible and ultrathin optoelectronic device applications. The photodetection performance of fabricated devices suggests that the synergic 0D/2D hybrid nanostructures are significantly superior to solution processed hybrid devices operating in the infrared region. The successful integration of 0D QDs in 2D materials may pave the way for novel, high performance, next-generation CMOS compatible flexible photonic devices.

Behavior of valvular interstitial cells on trilayered nanofibrous substrate mimicking morphologies of heart valve leaflet

Heart valve tissue engineering could be an alternative to the current bioprosthetic heart valve that faces limitations especially in pediatric patients. However, heart valve tissue engineering has remained challenging because leaflets - the primary component of a heart valve - have three layers with three diverse orientations - circumferential, random and radial, respectively. In order to mimic the orientations, we first designed three novel collectors to fabricate three nanofibrous layers with those orientations from a polymeric biomaterial in an electrospinning system. Then, we devised a novel direct electrospinning technique to develop a unified trilayered nanofibrous (TN) substrate comprising those oriented layers. The TN substrate supported the growth and orientations of seeded porcine valvular interstitial cells (PVICs) and their deposited collagen fibrils. After one month culture, the obtained trilayered tissue construct (TC) exhibited increased tensile properties over its TN substrate. Most importantly, the developed TC did not show any sign of shrinkage. Gene expression pattern of the PVICs indicated the developing stage of the TC. Their protein expression pattern was quite similar to that of leaflets. STATEMENT OF SIGNIFICANCE: This manuscript talks about development of a novel trilayered nanofibrous substrate mimicking the morphologies of a heart valve leaflet. It also describes culturing of valvular interstitial cells that reside in a leaflet, in the substrate and compares the behavior of the cultured cells with that in native leaflets in terms cell morphology, protein deposition and its orientation, and molecular signature. This study builds the groundwork for our future trilayered, tissue-engineered leaflet development. This research article would be of great interest to investigators and researchers in the field of cardiovascular tissue engineering especially in cardiac valve tissue engineering through biomaterial-based tissue engineering.

Robust Heartbeat Detection From Multimodal Data via CNN-Based Generalizable Information Fusion

OBJECTIVE

Heartbeat detection remains central to cardiac disease diagnosis and management, and is traditionally performed based on electrocardiogram (ECG). To improve robustness and accuracy of detection, especially, in certain critical-care scenarios, the use of additional physiological signals such as arterial blood pressure (BP) has recently been suggested. Therefore, estimation of heartbeat location requires information fusion from multiple signals. However, reported efforts in this direction often obtain multimodal estimates somewhat indirectly, by voting among separately obtained signal-specific intermediate estimates. In contrast, we propose to directly fuse information from multiple signals without requiring intermediate estimates, and thence estimate heartbeat location in a robust manner.

METHOD

We propose as a heartbeat detector, a convolutional neural network (CNN) that learns fused features from multiple physiological signals. This method eliminates the need for hand-picked signal-specific features and ad hoc fusion schemes. Furthermore, being data-driven, the same algorithm learns suitable features from arbitrary set of signals.

RESULTS

Using ECG and BP signals of PhysioNet 2014 Challenge database, we obtained a score of 94%. Furthermore, using two ECG channels of MIT-BIH arrhythmia database, we scored 99.92%. Both those scores compare favorably with previously reported database-specific results. Also, our detector achieved high accuracy in a variety of clinical conditions.

CONCLUSION

The proposed CNN-based information fusion (CIF) algorithm is generalizable, robust and efficient in detecting heartbeat location from multiple signals.

SIGNIFICANCE

In medical signal monitoring systems, our technique would accurately estimate heartbeat locations even when only a subset of channels are reliable.

Biomaterial characterization of off-the-shelf decellularized porcine pericardial tissue for use in prosthetic valvular applications

Fixed pericardial tissue is commonly used for commercially available xenograft valve implants, and has proven durability, but lacks the capability to remodel and grow. Decellularized porcine pericardial tissue has the promise to outperform fixed tissue and remodel, but the decellularization process has been shown to damage the collagen structure and reduce mechanical integrity of the tissue. Therefore, a comparison of uniaxial tensile properties was performed on decellularized, decellularized-sterilized, fixed, and native porcine pericardial tissue versus native valve leaflet cusps. The results of non-parametric analysis showed statistically significant differences (p < .05) between the stiffness of decellularized versus native pericardium and native cusps as well as fixed tissue, respectively; however, decellularized tissue showed large increases in elastic properties. Porosity testing of the tissues showed no statistical difference between decellularized and decell-sterilized tissue compared with native cusps (p > .05). Scanning electron microscopy confirmed that valvular endothelial and interstitial cells colonized the decellularized pericardial surface when seeded and grown for 30 days in static culture. Collagen assays and transmission electron microscopy analysis showed limited reductions in collagen with processing; yet glycosaminoglycan assays showed great reductions in the processed pericardium relative to native cusps. Decellularized pericardium had comparatively low mechanical properties among the groups studied; yet the stiffness was comparatively similar to the native cusps and demonstrated a lack of cytotoxicity. Suture retention, accelerated wear, and hydrodynamic testing of prototype decellularized and decell-sterilized valves showed positive functionality. Sterilized tissue could mimic valvular mechanical environment in vitro, therefore making it a viable potential candidate for off-the-shelf tissue-engineered valvular applications.

A novel surgical technique for a rat subcutaneous implantation of a tissue engineered scaffold

Objectives

Subcutaneous implantations in small animal models are currently required for preclinical studies of acellular tissue to evaluate biocompatibility, including host recellularization and immunogenic reactivity.

Methods

Three rat subcutaneous implantation methods were evaluated in six Sprague Dawley rats. An acellular xenograft made from porcine pericardium was used as the tissue-scaffold. Three implantation methods were performed; 1) Suture method is where a tissue-scaffold was implanted by suturing its border to the external oblique muscle, 2) Control method is where a tissue-scaffold was implanted without any suturing or support, 3) Frame method is where a tissue-scaffold was attached to a circular frame composed of polycaprolactone (PCL) biomaterial and placed subcutaneously. After 1 and 4 weeks, tissue-scaffolds were explanted and evaluated by hematoxylin and eosin (H&E), Masson’s trichrome, Picrosirius Red, transmission electron microscopy (TEM), immunohistochemistry, and mechanical testing.

Results

Macroscopically, tissue-scaffold degradation with the suture method and tissue-scaffold folding with the control method were observed after 4 weeks. In comparison, the frame method demonstrated intact tissue scaffolds after 4 weeks. H&E staining showed progressive cell repopulation over the course of the experiment in all groups with acute and chronic inflammation observed in suture and control methods throughout the duration of the study. Immunohistochemistry quantification of CD3, CD 31, CD 34, CD 163, and αSMA showed a statistically significant differences between the suture, control and frame methods (P < 0.05) at both time points. The average tensile strength was 4.03 ± 0.49, 7.45 ± 0.49 and 5.72 ± 1.34 (MPa) after 1 week and 0.55 ± 0.26, 0.12 ± 0.03 and 0.41 ± 0.32 (MPa) after 4 weeks in the suture, control, and frame methods; respectively. TEM analysis showed an increase in inflammatory cells in both suture and control methods following implantation.

Conclusion

Rat subcutaneous implantation with the frame method was performed with success and ease. The surgical approach used for the frame technique was found to be the best methodology for in vivo evaluation of tissue engineered acellular scaffolds, where the frame method did not compromise mechanical strength, but it reduced inflammation significantly.

A setup for element specific magnetization dynamics using the transverse magneto-optic Kerr effect in the energy range of 30-72 eV

In this paper, we present a spectrometer that is designed for element-specific and time-resolved transverse magneto-optic Kerr effect experiments at the high-harmonic generation pump-probe facility High Energy Laser Induced Overtone Source (HELIOS) laboratory. HELIOS delivers photons with energies between 30 eV and 72 eV with an overall time resolution of less than 40 fs. The spectrometer is based on a Rowland-circle geometry and allows for simultaneous measurements of all magnetic transition-metal elements. The setup also features easy sample transfer and alignment, and it combines high photon throughput, optimized data acquisition, and a fast switching of the magnetic field at the sample. The spectrometer performance is demonstrated by measuring the ultrafast demagnetization of permalloy. Our data are, for all practical purposes, identical to what have been reported in the earlier high-order harmonic generation work of a similar sample by Mathias et al. [Proc. Natl. Acad. Sci. U. S. A. 109, 4792-4797 (2012)], however, obtained within 15% of the acquisition time compared to their study. Furthermore, our data show a shift of the demagnetization curve of Ni relative to Fe, which has previously been interpreted as a delay of the Ni demagnetization to that of Fe [S. Mathias et al., Proc. Natl. Acad. Sci. U. S. A. 109, 4792-4797 (2012)].

Supercritical Carbon Dioxide–Based Sterilization of Decellularized Heart Valves

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Sterilization of a decellularized aortic valve was investigated.

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Various sterilization techniques including EOW, gamma radiation, ETPA, LHD, and scCO₂ were applied.

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Brown and Brenn staining, Periodic acid-Schiff staining, and aerobic broth culturing were used to characterize sterility.

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Differential scanning calorimetry was used to determine tissue matrix cross-linking.

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Scanning electron microscopy was used to characterize tissue matrix damage, at the structural level.

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EOW sterilization, which is done with electrolyzed water, could not sterilize efficiently.

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Gamma sterilization damaged the tissue matrix.

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Ethanol and peracetic acid–treated samples were cross-linked.

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Hydrogen peroxide sterilization damaged the tissue matrix.

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Supercritical carbon dioxide sterilization method was found efficient to provide 100% sterility of the sample. It neither damages nor cross-links the tissue.

Sterilization of grafts is essential. Supercritical carbon dioxide, electrolyzed water, gamma radiation, ethanol-peracetic acid, and hydrogen peroxide techniques were compared for impact on sterility and mechanical integrity of porcine decellularized aortic valves. Ethanol-peracetic acid– and supercritical carbon dioxide–treated valves were found to be sterile using histology, microbe culture, and electron microscopy assays. The cusp tensile properties of supercritical carbon dioxide–treated valves were higher compared with valves treated with other techniques. Superior sterility and integrity was found in the decellularized valves treated with supercritical carbon dioxide sterilization. This sterilization technique may hold promise for other decellularized soft tissues.

Anisotropic Materials for Skeletal-Muscle-Tissue Engineering

Repair of damaged skeletal-muscle tissue is limited by the regenerative capacity of the native tissue. Current clinical approaches are not optimal for the treatment of large volumetric skeletal-muscle loss. As an alternative, tissue engineering represents a promising approach for the functional restoration of damaged muscle tissue. A typical tissue-engineering process involves the design and fabrication of a scaffold that closely mimics the native skeletal-muscle extracellular matrix (ECM), allowing organization of cells into a physiologically relevant 3D architecture. In particular, anisotropic materials that mimic the morphology of the native skeletal-muscle ECM, can be fabricated using various biocompatible materials to guide cell alignment, elongation, proliferation, and differentiation into myotubes. Here, an overview of fundamental concepts associated with muscle-tissue engineering and the current status of muscle-tissue-engineering approaches is provided. Recent advances in the development of anisotropic scaffolds with micro- or nanoscale features are reviewed, and how scaffold topographical, mechanical, and biochemical cues correlate to observed cellular function and phenotype development is examined. Finally, some recent developments in both the design and utility of anisotropic materials in skeletal-muscle-tissue engineering are highlighted, along with their potential impact on future research and clinical applications.

Fabrication of Small Caliber Stent-grafts Using Electrospinning and Balloon Expandable Bare Metal Stents

Stent-grafts are widely used for the treatment of various conditions such as aortic lesions, aneurysms, emboli due to coronary intervention procedures and perforations in vasculature. Such stent-grafts are manufactured by covering a stent with a polymer membrane. An ideal stent-graft should have a biocompatible stent covered by a porous, thromboresistant, and biocompatible polymer membrane which mimics the extracellular matrix thereby promoting injury site healing. The goal of this protocol is to manufacture a small caliber stent-graft by encapsulating a balloon expandable stent within two layers of electrospun polyurethane nanofibers. Electrospinning of polyurethane has been shown to assist in healing by mimicking native extracellular matrix, thereby promoting endothelialization. Electrospinning polyurethane nanofibers on a slowly rotating mandrel enabled us to precisely control the thickness of the nanofibrous membrane, which is essential to achieve a small caliber balloon expandable stent-graft. Mechanical validation by crimping and expansion of the stent-graft has shown that the nanofibrous polyurethane membrane is sufficiently flexible to crimp and expand while staying patent without showing any signs of tearing or delamination. Furthermore, stent-grafts fabricated using the methods described here are capable of being implanted using a coronary intervention procedure using standard size guide catheters.

Regeneration ability of valvular interstitial cells from diseased heart valve leaflets

Valvular interstitial cells from diseased aortic valve leaflets show their ability to regenerate–to proliferate and grow, to express appropriate genes and to deposit suitable proteins–in a non-degenerative nanofibrous substrate.

In Vitro Model of a Fibrosa Layer of a Heart Valve

The fibrosa layer of a cardiac aortic valve is composed mostly of a dense network of type I collagen fibers oriented in circumferential direction. This main layer bears the tensile load and responds to the high stress on a leaflet. The inner fibrosa layer is also the site of pathophysiologic changes that result in valvular dysfunction, including stenosis and regurgitation. In vitro studies of these changes are limited by the absence of a substrate that mimics the circumferentially oriented structure of the fibrosa layer. In heart valve tissue engineering, generation of this layer is challenging. This study aimed to develop an artificial fibrosa layer of a native aortic leaflet. A unique morphologically biomimicked, pliable, but standalone substrate with circumferentially oriented nanofibers was fabricated by electrospinning on a novel collector designed for this study. The substrate had low-bulk tensile stiffness and ultimate strength; thus, cultured valvular interstitial cells (VICs) showed a fibroblast phenotype that is generally observed in a healthy aortic leaflet. Furthermore, gene and protein expression and morphology of VICs in substrates were close to those in the fibrosa layer of a native aortic leaflet. This artificial fibrosa layer can be useful for in vitro studies of valvular dysfunctions.

Detection and characterization of zoonotic dermatophytes from dogs and cats in and around Kolkata

AIM

The ringworms of pet dogs, cats, and stray animals (dogs, cats, and other animals) could be a potential source of zoonotic infections causing a serious public health problem in the busy city Kolkata. The pet owners are more susceptible to get this infection from their pets, because of the close contact with them as dermatophytosis is very much prevalent in those pets. So, this study was aimed to check the prevalence of dermatophytosis in dogs, cats, and in pet owners.

MATERIALS AND METHODS

A total of 362 clinically suspected cases of dermatophytosis from dogs (123 in number), cats (202 in number), and human beings (37 in number) were collected and studied from in and around Kolkata to detect the presence of significant dermatophytes. Direct microscopy and cultural examination of the isolates were performed following standard methodology. Identification and characterization of the isolates were done by different biochemical tests.

RESULTS

Samples (n=285) having significant dermatophytic fungal infections were found to be of highest number in cats (158, 55.5%) than in dogs (108, 37.8%) and humans (19, 6.7%), respectively. The incidence of Microsporum canis (60.0%) was the highest from affecting dogs, cats, and human beings in comparison to Microsporum gypseum (22.5%), Trichophyton mentagrophytes (15.8%) and Trichophyton rubrum (1.7%). Detection of T. rubrum was only from human cases in this study, whereas the presence of rest three were slightly higher in cats than that of the dogs and humans in this present study. The incidences were higher in young animals and in humans of the age group of 21-30 years, during the rainy season (from April to August) and also in in-contact human beings.

CONCLUSION

M. canis was the most commonly pathogen among all causing dermatophytosis in animals and also in the pet owners. M. gypseum and T. mentagrophytes were other pathogens associated with these infections. These infections were more prevalent in the rainy seasons and in in-contact human patients or pet owners.

Lupus cystitis: An unusual presentation of systemic lupus erythematosus

Lupus cystitis is a rare complication of systemic lupus erythematosus (SLE) and occurs in association with gastrointestinal symptoms. This rare disorder has been reported mainly from Japan. We report a 20 year old female who diagnosed as having SLE associated with paralytic ileus and chronic interstitial cystitis. Treatment with intravenous methylprednisolone, cyclophosphamide pulse therapy followed by oral prednisolone and azathioprine led to amelioration of manifestations. Later she developed lupus nephritis which was treated with mycophenolate mofetil.

Scaffolds for tissue engineering of cardiac valves

Tissue engineered heart valves offer a promising alternative for the replacement of diseased heart valves avoiding the limitations faced with currently available bioprosthetic and mechanical heart valves. In the paradigm of tissue engineering, a three-dimensional platform - the so-called scaffold - is essential for cell proliferation, growth and differentiation, as well as the ultimate generation of a functional tissue. A foundation for success in heart valve tissue engineering is a recapitulation of the complex design and diverse mechanical properties of a native valve. This article reviews technological details of the scaffolds that have been applied to date in heart valve tissue engineering research.

Macro-anatomical variation of the olfactory apparatus in some Indian teleosts with special reference to their ecological habitat

The anatomy of the peripheral olfactory apparatus (i.e. olfactory lamellae, olfactorychambers, accessory nasal sacs, olfactory nerve tracts, olfactory bulbs and brain) of some teleosts, viz. Pseudapocryptes lanceolatus (Bloch and Schneider, 1801) - an air breathing mudskipper, Lepidocephalichthys guntea (Hamilton, 1822) - a freshwater scavenger fish and Mastacembelus armatus (Lacepède, 1800) - a freshwater potamodromous fish, has been studied in relation to their specific ecological habitat. Live, adult, sex-independent fish species were collected from the local markets of West Bengal, India, and acclimatised with the laboratory conditions (for 72 h at 32°C). The specimens were anaesthetised by MS-222 (dose: 100-200 mg/L). Olfactory apparatuses were dissected out and fixed inaqueous Bouin's solution. The macro- and microstructures (using haematoxylin and eosin) of the olfactory apparatuses were examined under binocular light microscope (LM) and trinocular LM (Primo Star; Carl Zeiss Microscpy, GmbH, Germany) respectively. P. lanceolatus possesses unilamellar olfactory apparatus at therounded snout, whereas L. guntea shows small rosette with 18 to 24 lamellae oneither side of the elliptical snout. Elongated olfactory rosette (number of lamellae ranges from 60 to 76) is present at the pointed snout of M. armatus. Morpho-anatomical variation in snout structure of the respective species is an indicative of divergence in ecological habitat, but variation in olfactory apparatus is significant for species-specific differentiation. Pseudostratified olfactory neuroepithelial components (i.e. sensory receptor cell, supporting cell and basal cell) show striking similarities amongst these species. Therefore comparative anatomical changes of the snout and olfactory apparatus are not only representing ecological habitat based on interspecific variation, but may also indicate the phylogenetic relation amongst said species.

Automated detection of choroid boundary and vessels in optical coherence tomography images

Structural changes in the choroid, a layer located between the retina and sclera, could indicate various vision impairments. Consequently, ophthalmologists inspect optical coherence tomography (OCT) scans of the posterior section of the eye towards making diagnosis. With a view to assist diagnosis, we propose an automated technique for segmentation of the choroid layer. Specifically, we detect the upper and lower boundaries of the choroid using structural similarity and adaptive Hessian analysis. Subsequently, we detect choroid vessels within those boundaries using a level set method. Experimental results are presented using spectral domain (SD) OCT images.

Aligned chitosan-polycaprolactone polyblend nanofibers promote the migration of glioblastoma cells

In vitro models that accurately mimic the microenvironment of invading glioblastoma multiform (GBM) cells will provide a high-throughput system for testing potential anti-invasion therapies. Here, the ability of chitosan-polycaprolactone polyblend nanofibers to promote a migratory phenotype in human GBM cells by altering the nanotopography of the nanofiber membranes is investigated. Fibers are prepared with diameters of 200 nm, 400 nm, and 1.1 μm, and are either randomly oriented or aligned to produce six distinct nanotopographies. Human U-87 MG GBM cells, a model cell line commonly used for invasion assays, are cultured on the various nanofibrous substrates. Cells show elongation and alignment along the orientation of aligned fibers as early as 24 h and up to 120 h of culture. After 24 h of culture, human GBM cells cultured on aligned 200 nm and 400 nm fibers show marked upregulation of invasion-related genes including β-catenin, Snail, STAT3, TGF-β, and Twist, suggesting a mesenchymal change in these migrating cells. Additionally, cells cultured on 400 nm aligned fibers show similar migration profiles as those reported in vivo, and thus these nanofibers should provide a unique high-throughput in vitro culture substrate for developing anti-migration therapies for the treatment of GBM.

Uniaxially-aligned PVDF nanofibers as a sensor and transmitter for biotelemetry

Biotelemetry has become an important part of medical research for patient care by remotely monitoring continuing biological processes and physiological functions. However, current biotelemetry systems are complex requiring multiple electronic components to function: a battery, a sensor, and a transmitter, and a receiver. Another paramount concern of biotelemetry is the coupling of its in vivo portion to external supporting equipment. Here we report a novel biotelemetry device made primarily of a coiled bundle of uniaxially-aligned biocompatible polyvinylidene fluoride (PVDF) nanofibers of ∼200 nm in diameter and with piezoelectric properties that can serve concurrently as a power source, sensor, and transmitter. We tested this device on a cantilever beam that was periodically deflected at its free end. Without a power supply the coil of a nanofiber bundle is shown to generate and transmit an electrical signal wirelessly in response to the beam deflection which was received by an external receiver. The coil of a nanofiber bundle was encapsulated in a thin biocompatible polymer shell for device integrity and moisture isolation. Our results suggest that the device can potentially serve as a mechanical sensor and biotelemeter for various in vitro and in vivo biomedical applications.

Immunodiagnosis as an aid for early detection of Fasciola gigantica by glutathione S-transferase (GST)

In the present study, effort to isolate purified GST from Fasciola gigantica homogenate and its early detection for confirmation of infection has been successful. In this study, immunoprotection studies with GST and antibody titer post-infection has revealed GST to be an immunogenic protein with high sensitivity to detect anti-Fasciola antibody as early as two weeks post-infection in large ruminants.

Wetting and surface energy of vertically aligned silicon nanowires

The vertically aligned silicon nanowires (SiNWs) have been synthesized by metal assisted chemical etching process on commercially available p type silicon wafer. The aspect ratios of the SiNWs have been modified by simply varying the etching time. The microstructures of the as prepared samples have been investigated with the field emission scanning electron microscope as well as with a high resolution transmission electron microscope. The bonding information has been obtained by Fourier transformed infrared spectroscopy and X-ray photoelectron spectroscopy. The contact angles for water with the as-prepared SiNWs films were measured and found to be highly dependent upon the aspect ratio of the as synthesized wires. For obtaining a deep insight regarding the reasons behind this dependence the surface energies of the as prepared SiNWs films have been calculated by Owens method using two liquids, water and glycerol. The porosity of the films has been calculated indirectly from the equilibrium equations. It has been found that the etching time has a profound effect on the aspect ratio and thus on the surface energy of SiNWs that governs the wetting behaviour of the as prepared samples.