Porous Conduits Research Articles

Precursory crater contraction associated with the 2017 eruption of Shinmoe-dake volcano (Japan) detected by PALSAR-2 and Sentinel-1 InSAR

The time series of PALSAR-2 and Sentinel-1 images reveal inflation at the volcanic flank and contraction at the crater for approximately 5 months before the 2017 eruption of Shinmoe-dake volcano, Japan. While the observation of inflation at the volcano’s flank is ubiquitous, few studies have reported crater contraction preceding an eruption. The flank inflation stopped after the 2017 eruption, while the contraction at the crater continued until the 2018 eruption. We found that a pipe-shaped deformation source above sea level best fits the observation preceding the 2017 eruption. Suppose the flux of ejected materials constrains the conduit radius during the previous 2011 eruption. In that case, the amount of deformation of the pipe-shaped deformation source, whether open or closed at its top, is too large to be realistic. Although constraining the conduit radius from the eruption flux overestimates the pressure change of the pipe-shaped deformation source, water-saturated fractures along the volcanic conduit could extend the effective conduit radius of the pressure source. We propose one potential scenario for the mechanism of the crater contraction preceding volcanic eruptions based on the combination of compaction due to cooling by ambient groundwater and material withdrawal within the conduit. The groundwater inflows from the ambient aquifer through cracks in the porous conduit wall, which are generated by conduit expansion during the magma ascent. Decoupling from the conduit wall due to a decrease in volume of the material promotes material instability and crater contraction. The interaction between the groundwater and the magma triggers the 2017 eruption of Shinmoe-dake volcano, as previous studies have reported.Graphical

Investigation of convective peristaltic flow of non-Newtonian fluids through a non-uniform tapered porous conduit with Ohmic heating and viscous dissipation

ABSTRACT The study of convective magnetohydrodynamic (MHD) biofluid transport through a non-uniform duct is of interest due to its applications to biomedical devices and equipment. Because of this, a comparative study of free convective peristaltic flow of non-Newtonian (Casson and Jeffrey) fluids in a tapered porous symmetric duct with Hall current and viscous dissipation effects is carried out. The proposed dimensional governing equations are converted into a system of non-dimensional partial differential equations by invoking adequate non-dimensional parameters. Furthermore, a long-wavelength approximation is used to reduce the complexity of the system. Then the reduced system of partial differential equations is solved analytically using the regular perturbation method. The fascinating features of the influential parameters on the flow characteristics are demonstrated and analyzed in depth through graphs and tables. The results demonstrate that the velocity and temperature in the Jeffrey fluid flow are larger compared to those in the Casson fluid flow. The thermal Grashof number and the Hall current parameter enhanced the pressure rise profile. This research has significant implications in biomedical devices (MRI, vitamins A and D injections, heart-lung machines, etc.) and pharmaceutical fluid preparation in biomedical sciences.

Peristaltic flow of bioconvective Ree–Eyring nanofluid through an inclined elastic channel with partial slip effects

Pharmaceutical fluid processing is a procedure of medication manufacturing, utilizing a particular kind of heat transfer in a biofluid designed to maintain the desired temperature for extended periods. Choosing a suitable fluid can have a positive effect on the operating efficacy of the system and lengthen the fluid’s and system’s life spans. As an outcome of this development, we investigate the influence of the partial slip and gyrotactic microorganisms on the peristaltic transport of a magnetohydrodynamic Ree–Eyring nanofluid via an aligned porous conduit with thermal radiation, energy generation, along with cross and double diffusion effects. By invoking suitable nondimensional parameters, the proposed dimensional governing equations are transformed into a system of dimensionless partial differential equations. The analytical solutions for the system of partial differential equations are obtained by incorporating the homotopy perturbation method. Further, tabular and graphical presentations are used to examine the characteristics of the various sundry parameters on the temperature, concentration, motile microorganism density, axial velocity, trapping, and other relevant flow quantities. The observations of this study indicate that the Darcy number and thermal Grashof number have the capability to enhance the velocity distribution of the Ree–Eyring nanofluid in the presence of bioconvection. The trapped bolus size and the skin friction coefficient increase noticeably because of an enhancement in the Ree–Eyring fluid parameter. Also, the Darcy number and the Hall current parameter increase the skin friction coefficient. Furthermore, validation of the results is carried out to examine the consistency between the current and the previous findings for some special cases and excellent agreements are found.

Chemically reactive MHD peristaltic flow of Jeffrey nanofluid via a vertical porous conduit with complaint walls under the effects of bioconvection and double diffusion

Inspired by significant physiological applications of peristaltic transport, a mathematical model for the peristaltic pumping of a Jeffrey nanofluid containing gyrotactic microorganisms through a flexible and vertical symmetric channel is investigated, along with the effects of thermal radiation, heat source/sink, chemical reaction, porous medium and Hall current. Swimming microorganisms in a model of non-Newtonian fluid has several biological and ecological benefits, including in the pharmaceutical industry, biofertilizers, biofuel technology, biosensors, etc. With these presumptions in mind, a conducting Jeffery fluid flow containing microorganisms via a porous vertical conduit is proposed. The expressions for the flow quantities are established by solving the governing equations of this study analytically using the homotopy perturbation method (HPM). A detailed examination is performed using the tables and graphical representations to comprehend the impact of significant components on this analysis. In addition, the results for Newtonian nanofluid are obtained as a special case and discovered that its velocity is lower than the Jeffrey nanofluid. It is observed that the best velocity distribution can be seen at larger thermal Grashof number and Darcy number. The size of the trapped bolus enhances with the increase of the Hall parameter. Furthermore, the density of the motile microorganism distribution declines for higher bioconvection Peclet number and bioconvection constant.

Second order slip flow of a conducting Jeffrey nanofluid in an inclined asymmetric porous conduit with heat and mass transfer

PurposeThe present work explores the influence of Hall and Ohmic heating effects on the convective peristaltic flow of a conducting Jeffrey nanofluid in an inclined porous asymmetric channel with slip. Also, the authors investigated the impact of viscous dissipation, thermal radiation, heat generation/absorption and cross diffusion effects on the flow. Peristaltic flow has many industrial and physiological applications and most of the biofluids show the non-Newtonian fluid behaviour. Further, in a living body, several biofluids flow through different kinds of systems that are not symmetric, horizontal or vertical. The purpose of this paper is to address these issues.Design/methodology/approachThe authors considered the flow of Jeffrey fluid which is generated by a sinusoidal wave propagating on the walls of an inclined asymmetric channel. The flow model is developed from the fixed frame to the wave frame. Finally, yield the nonlinear governing equations by applying the non-dimensional quantities with the assumptions of lengthy wave and negligible Reynolds number. The exact solution has been computed for the velocity and pressure gradient. The solutions for temperature and concentration are obtained by the regular perturbation technique.FindingsGraphical analysis is made for the present results for different values of emerging parameters and explained clearly. It is noticed that the magnetic field enriches the temperature where it drops the fluid velocity. This work describes that the temperature field is decreasing due to the radiation but it is a rising function of temperature slip parameter. The temperature profile declines for growing values of the Hall parameter. The flow velocity diminishes for boosting values of the Darcy parameter. Further, the authors perceived that the concentration field reduces for large values of the chemical reaction parameter.Originality/valueThe authors validated and compared the results with the existing literature. This investigation will help to study some physiological systems, and heat transfer in peristaltic transport plays key role in medical treatments, so we ensure that these results are applicable in medical treatments like cancer therapy, drug delivery, etc.

Natural proteins-derived asymmetric porous conduit for peripheral nerve regeneration

Artificial nerve guidance conduits (NGCs) have been developed by using various biomaterials for bridging relatively long nerve defects. Though integrating neurotrophic factors with these NGCs could improve the nerve repair effects, their uncontrolled degradation and roundly random administration still restrict complete nerve regeneration. Herein, a novel silk fibroin (SF)-derived NGC with internal-facing inverse opal structures is presented, achieving the local neurotrophic factor delivery and effective nerve regeneration. The resultant NGC is confirmed with excellent biocompatibility and suitable biodegradability, as well as satisfactory mechanical performance to bridge nerve defects. Significantly, benefiting from an asymmetric structure with inverse opal porous nanostructures inside walls and hybrid hydrogel outside walls, such NGC can spatially restrict the distribution of loading factors, thus enhancing the curative efficacy. By implanting in a sciatic nerve injury rat model with a long segment defect, it is demonstrated that the drug-loaded conduit presented a similar performance to autograft, which can facilitate axons growth and remyelination, thereby promoting nerve regeneration. These results indicate a great potential of such a novel design for peripheral nerve repair applications.

In Situ Prevascularization Strategy with Three-Dimensional Porous Conduits for Neural Tissue Engineering.

Neovascularization is crucial for peripheral nerve regeneration and long-term functional restoration. Previous studies have emphasized strategies that enhance axonal repair over vascularization. Here, we describe the development and application of an in situ prevascularization strategy that uses 3D porous nerve guidance conduits (NGCs) to achieve angiogenesis-mediated neural regeneration. The optimal porosity of the NGC is a critical feature for achieving neovascularization and nerve growth patency. Hollow silk fibroin/poly(l-lactic acid-co-ε-caprolactone) NGCs with 3D sponge-like walls were fabricated using electrospinning and freeze-drying. In vitro results showed that 3D porous NGC favored cell biocompatibility had neuroregeneration potential and, most importantly, had angiogenic activity. Results from our mechanistic studies suggest that activation of HIF-1α signaling might be associated with this process. We also tested in situ prevascularized 3D porous NGCs in vivo by transplanting them into a 10 mm rat sciatic nerve defect model with the aim of regenerating the severed nerve. The prevascularized 3D porous NGCs greatly enhanced intraneural angiogenesis, resulting in demonstrable neurogenesis. Eight weeks after transplantation, the performance of the prevascularized 3D NGCs was similar to that of traditional autografts in terms of improved anatomical structure, morphology, and neural function. In conclusion, combining a reasonably fabricated 3D-pore conduit structure with in situ prevascularization promoted functional nerve regeneration, suggesting an alternative strategy for achieving functional recovery after peripheral nerve trauma.

Effects of radiative heat flux and heat generation on magnetohydodynamics natural convection flow of nanofluid inside a porous triangular cavity with thermal boundary conditions

AbstractWhen the nanoparticles are incorporated into the base fluid, the resultant fluid is known as nanofluid. Nanofluids have higher thermal efficiency as compared to base fluid. Some fluids have poor thermal conductivity like, water, air and ethylene glycol and oil. Thus, the thermal efficiency of the work can be increased by inserting the nanoparticles into base fluid. Furthermore, the nanoparticles can be used to enhanced the cooling rate of the system due to higher thermal conductivity. In this investigation, the magnetohydodynamics convective flow phenomenon under the consideration of different nanofluids inside a triangular porous conduit will investigated. For the better understanding of heat transfer characteristics, the thermal radiation and heat generation (or absorption) will also incorporated. We will impose constant and variable temperature on the left inclined wall to analyze the heat transfer mechanism. Furthermore, the heat transfer rate will also be analyzed by considering different nanoparticles. The robust numerical scheme namely the finite element method has been selected to simulate the nonlinear complex flow equations based on iterative scheme. In this technique, at the first stage the penalty method is employed for the purpose of the elimination of pressure from the equations of motion. After that the developed the system in the absence of pressure term is solved. To simulate the problem the value of penalty parameter is chosen 10−7. The contours of stream function and temperature distribution are displayed for several values of physical parameters. Furthermore, the variations of important quantity known as an average heat transfer rate are displayed through bar charts. For constant heating case the aluminum nano particles are the best choice to enhance the heat transfer rate in the system. Moreover, the magnitude of the stream function rises against the radiation and Rayleigh number. Furthermore, the conduction mode of heat transfer is achieved via thermal radiation parameter. The applications of the given study can be found in various industrial processes like, cooling of electronic devices, cooling of house and commercial buildings, cooling of microelectronics, cancer therapy, vehicle thermal management, and heat exchangers.

FINITE ELEMENT SIMULATIONS OF FREE CONVECTION FLOW INSIDE A POROUS INCLINED CAVITY FILLED WITH MICROPOLAR FLUID

The present study predicts the effects of inclined magnetic field and thermal boundary conditions on the natural convection flow inside a porous conduit filled with micropolar fluid. The lower wall is cold and the inclined walls of the conduit are constantly or sinusoidally heated. The nonlinear partial differential equations are solved by employing a robust Galerkin finite element scheme. The pressure term in this scheme is eliminated by using a penalty method. The value of penalty parameter ∏ is set at 107 to ensure consistent solutions. The results are presented in the form of streamlines, temperature contours, and local and average Nusselt numbers. The results show that the magnitude of the stream function decreases with increasing the inclination angle of the applied magnetic field, Hartmann number, and micropolar parameter while an opposite trend is noted against Darcy number, Prandtl number, and inclination angle of cavity. The average Nusselt number is substantially higher for the uniform heated case in comparison to the sinusoidal heated case regardless of the choice of other physical parameters. Further, the average Nusselt numbers decrease by increasing micropolar parameter (R0) and Hartmann number (Ha) while an opposite trend prevails with increasing rest of the parameters (ω, Da, Pr) for both cases. It is noted that when the cavity is inclined at 45° or 90° and magnetic field is applied either along the x-axis (φ = 0°) or inclined at 45° or 90°, only clockwise circulation exists inside the conduit. The presence of counterclockwise circulating roll in the top corner of the cavity is linked with the choice of heating mode adopted at the side walls. In fact, such circulations are more likely to appear for the case of nonuniform heated side walls. The solution is benchmarked with the previous available data. The analysis presented here has potential application in solar collectors and porous heat exchanges.

Mathematical Modelling Of Extraction Of The Underground Fluids: Application To Peristaltic Transportation Through A Vertical Conduit Occupied With Porous Material

This paper gives a theoretical idea for extracting the underground fluids through peristalsis. Due to the similarity in aforesaid problem, peristaltic transportation of a viscous Newtonian fluid over a vertical porous conduit is studied by considering the impact of heat transfer. Presuming the long-wavelength approximation, explicit solutions are found as asymptotic expansions with reference to free convection and porosity parameters. Mathematical expressions for coefficient of heat transfer, temperature and mean flux are derived. It is experiential that for few precise values of dissimilar parameters under contemplation, the coefficient of heat transfer increases significantly as Grashof number and Eckert number increases. This narrates to optimization of heat transfer in some processes. Further, it has been observed that mean flow enhances with amplitude ratio, porosity in addition to pressure drop. This authorizes auxiliary research on the impacts of peristalsis on the flow features in vertical channels.

Peristaltic flow of a Jeffery fluid over a porous conduit in the presence of variable liquid properties and convective boundary conditions

The present article addresses the peristaltic flow of a Jeffery fluid over an inclined axisymmetric porous tube with varying viscosity and thermal conductivity. Velocity slip and convective boundary conditions are considered. Resulting governing equations are solved using long wavelength and small Reynolds number approximations. The closed-form solutions are obtained for velocity, streamline, pressure gradient, temperature, pressure rise, and frictional force. The MATLAB numerical simulations are utilized to compute pressure rise and frictional force. The impacts of various physical parameters in the interims for time-averaged flow rate with pressure rise and is examined. The consequences of sinusoidal, multi-sinusoidal, triangular, trapezoidal, and square waveforms on physiological parameters are analyzed and discussed through graphs. The analysis reveals that the presence of variable viscosity helps in controlling the pumping performance of the fluid.

Concurrent Development of Thermal Energy with Magnetic Field on a Particle-Fluid Suspension Through a Porous Conduit

The impact of heat transfer on the magnetohydrodynamic peristaltically induced motion in a channel through porous medium has been investigated. The continuity, momentum, and energy equations have been utilized to represent the flow in a closed form. These non-linear governing equations are solved analytically by employing the perturbation method. The obtained expressions for streamlines, temperature, and heat transfer coefficient are presented through graphs for two dimensions with a small wave number. The variations of physical variables with the pertinent parameters have been presented and discussed. It has been found that the inclusion of fluid suspension brought about a decrease in the temperature distribution. The effect of magnetic field on the temperature of fluid has also been seen to depend upon the position and time.

Peristaltic slip flow of a Bingham fluid in an inclined porous conduit with Joule heating

Abstract The present study deals with simultaneous effects of Joule heating and slip on peristaltic flow of a Bingham fluid in an inclined tapered porous channel with elastic walls. The closed form solutions for the stream function, the velocity and the temperature fields are obtained. The effects of the physical parameters on the flow characteristics are presented through graphs for both slip and no-slip cases. In addition, the performance of the temperature is studied with and without Joule heating effects. Moreover, the trapping phenomenon is analysed. The size of the trapped bolus increases with increasing values of the slip parameter and decreasing values of the magnetic, the permeability and the yield stress parameters. The present results are compared with the available results in the literature and our results agree well with the available results for some special cases.

Оценка проходимости синтетических кондуитов из пористого политетрафторэтилена при реконструкции магистральных вен (экспериментальное исследование)

Цель - изучение проходимости синтетических кондуитов из пористого политетрафторэтилена при реконструкции магистральных вен и обоснование их применения в клинической практике. Методика. Исследование выполнено на 70 кроликах половозрелого возраста мужского пола породы «Белый новозеландский» массой 3,0-3,5 кг. 40 кроликам выполнено линейное протезирование инфраренального отдела задней полой вены. 30 кроликам выполнено линейное протезирование инфраренального отдела брюшной аорты (группа сравнения). Оперативные вмешательства были выполнены в асептических условиях под внутримышечным наркозом. Для протезирования брюшной аорты и задней полой вены использовали политетрафторэтиленовые протезы (7 поколение, 2010) производства ЗАО «НПК «Экофлон» (Россия) с внутренним диаметром 4,0 мм и длиной 20,0 мм. Все анастомозы формировали атравматическим шовным материалом 7/0 или 8/0 с использованием микроинструментов. На протяжении всего срока эксперимента антикоагулянтной и антиагрегантной терапии не проводилось. В течение всего срока наблюдения контроль проходимости протезов осуществляли ультразвуковой допплерографией скоростных показателей кровотока дистальнее и проксимальнее протеза на сроках 3, 10, 30, 90, 180, 270 сут. На контрольных сроках наблюдения проходимость протеза оценивали прямым инвазивным измерением давления крови, а также интраоперационной ультразвуковой допплерографией линейной скорости кровотока дистальнее и проксимальнее протеза. После вывода животного из эксперимента протез иссекали с окружающими тканями для дальнейшего изучения. При сравнении показателей давления крови и линейной скорости кровотока дистальнее и проксимальнее протеза на разных сроках использовали критерий Манна-Уитни. Критический уровень значимости при проверке статистических гипотез принимался <0,05. Результаты. Статистически значимой разницы линейных скоростей кровотоков и давления крови проксимальнее и дистальнее протеза на всех сроках наблюдения не выявлено. Проходимость протезов из политетрафторэтилена в венозной позиции не отличается от таковой в артериальной позиции. Тромбозов и гемодинамически значимых стенозов синтетических кондуитов из пористого политетрафторэтилена, как в венозной, так и в артериальной позиции не отмечено на всех сроках. Заключение. Проходимость синтетических кондуитов из пористого политетрафторэтилена в венозной позиции сравнима и не отличается от таковой в артериальной позиции. Полученные данные позволяют получить экспериментальное обоснование возможности использования синтетических кондуитов из пористого политетрафторэтилена при реконструкции магистральных вен в клинической практике. Aim. To study patency of synthetic, porous polytetrafluoroethylene (PTFE) conduits in reconstruction of great veins and to justify their use in clinical practice. Methods. The study was conducted on 70 New Zealand male rabbits weighing 3.0-3.5 kg. Infrarenal linear prosthetic reconstruction of posterior vena cava was performed in 40 rabbits. Infrarenal linear prosthetic reconstruction of abdominal aorta was performed in 30 rabbits (control group). All surgical procedures were conducted in aseptic conditions under intramuscular anesthesia. Porous PTFE conduits with 4 mm internal diameter and 20 mm length (7th generation, 2010; ZAO NPK Ecoflon, Russia) were used for prostheses of aorta and posterior vena cava. All anastomoses were made of atraumatic 7/0-8/0 ligature using microsurgical instruments. No anticoagulant therapy was used throughout the experimental period. During the study, conduit patency was controlled by ultrasound Doppler monitoring of blood flow velocity distal and proximal to the conduit and direct, invasive BP measurements during the surgery and at 3, 10, 30, 90, 180, and 270 days of surgery. At the end of experiment, the conduit was removed from the animal together with adjacent structures. The Mann-Whitney U-test was used for comparison of BP and blood flow velocity distal and proximal to the conduit. Differences were considered significant at p ?0.05. Results. Significant differences between values of linear blood flow velocity and BP distal and proximal to the conduit were absent in the entire follow up period. The patency of porous PTFE conduits was similar in both arterial and venous positions. No conduit thrombosis or hemodynamically significant stenosis were observed in arterial or venous positions in the entire follow up period. Conclusion. The patency of PTFE conduits in the venous position is similar to and not different from the arterial position. The obtained experimental data support the use of synthetic PTFE conduits for reconstruction of great veins in clinical practice. Conclusion. The polytetrafluoroethylene conduits patency of in venous position is similar and does not differ from arterial position. Obtained experimental data gives the opportunity for synthetic polytetrafluoroethylene conduits appliance for main vein reconstruction in clinical practice.

Multi-tubule conduit-filler constructs loaded with gradient-distributed growth factors for neural tissue engineering applications.

Chitosan/silk fibroin/glycerophosphate gels were loaded with nerve growth factor (NGF) and further processed into multi-tubule fillers. NGF was loaded into the fillers in such a way so that a NGF gradient was established longitudinally along the filler length. A type of poly(lactide-co-glycolide)(PLGA)/chitosan(CH) porous conduit was fabricated using a pre-crosslinking method. The filler was fully filled into the lumen of conduits to build multi-tubule conduit-filler constructs that are intended for long-gap peripheral nerve repair. In vitro degradation in a lysozyme-contained medium revealed that constructs had degradation-tolerant features and the optimized multi-tubule filler was capable of maintaining its multi-tubules unblocked for around 10-week. After being degraded for various periods up to 8 weeks, the optimal conduit-filler constructs showed confirmative ability to retain their compressive load, deformation recovery and tensile strength at about 80N/m, 75% and 15N/cm2 in wet state, respectively. The constructs were able to administer NGF release and to maintain persistent NGF gradients longitudinally distributed inside the PLGA/CH conduit for about 6 weeks or even longer. The PC12 cell neurite extension assay confirmed that the presently developed multi-tubule conduit-filler constructs were reliable for effectively preserving the bioactivity of released NGF.

Modeling of Fluid Flow and Heat Transfer inside a Saturated Porous Conduit at Constant Surface Heat Flux

Modeling of Fluid Flow and Heat Transfer inside a Saturated Porous Conduit at Constant Surface Heat Flux

A 3D-engineered porous conduit for peripheral nerve repair

End-to-end neurorrhaphy is the most commonly used method for treating peripheral nerve injury. However, only 50% of patients can regain useful function after treating with neurorrhaphy. Here, we constructed a 3D-engineered porous conduit to promote the function recovery of the transected peripheral nerve after neurorrhaphy. The conduit that consisted of a gelatin cryogel was prepared by molding with 3D-printed moulds. Due to its porous structure and excellent mechanical properties, this conduit could be collapsed by the mechanical force and resumed its original shape after absorption of normal saline. This shape-memory property allowed a simply surgery process for installing the conduits. Moreover, the biodegradable conduit could prevent the infiltration of fibroblasts and reduce the risk of scar tissue, which could provide an advantageous environment for nerve regeneration. The efficiency of the conduits in assisting peripheral nerve regeneration after neurorrhaphy was evaluated in a rat sciatic nerve transected model. Results indicated that conduits significantly benefitted the recovery of the transected peripheral nerve after end-to-end neurorrhaphy on the static sciatic index (SSI), electrophysiological results and the re-innervation of the gastrocnemius muscle. This work demonstrates a biodegradable nerve conduit that has potentially clinical application in promoting the neurorrhaphy.

Fibrin glue as a stabilization strategy in peripheral nerve repair when using porous nerve guidance conduits

Porous conduits provide a protected pathway for nerve regeneration, while still allowing exchange of nutrients and wastes. However, pore sizes >30 µm may permit fibrous tissue infiltration into the conduit, which may impede axonal regeneration. Coating the conduit with Fibrin Glue (FG) is one option for controlling the conduit’s porosity. FG is extensively used in clinical peripheral nerve repair, as a tissue sealant, filler and drug-delivery matrix. Here, we compared the performance of FG to an alternative, hyaluronic acid (HA) as a coating for porous conduits, using uncoated porous conduits and reverse autografts as control groups. The uncoated conduit walls had pores with a diameter of 60 to 70 µm that were uniformly covered by either FG or HA coatings. In vitro, FG coatings degraded twice as fast as HA coatings. In vivo studies in a 1 cm rat sciatic nerve model showed FG coating resulted in poor axonal density (993 ± 854 #/mm2), negligible fascicular area (0.03 ± 0.04 mm2), minimal percent wet muscle mass recovery (16 ± 1 in gastrocnemius and 15 ± 5 in tibialis anterior) and G-ratio (0.73 ± 0.01). Histology of FG-coated conduits showed excessive fibrous tissue infiltration inside the lumen, and fibrin capsule formation around the conduit. Although FG has been shown to promote nerve regeneration in non-porous conduits, we found that as a coating for porous conduits in vivo, FG encourages scar tissue infiltration that impedes nerve regeneration. This is a significant finding considering the widespread use of FG in peripheral nerve repair.Graphical

Design and optimization of a biodegradable porous zein conduit using microtubes as a guide for rat sciatic nerve defect repair.

Various degradable biomaterials have been used to bridge injured peripheral nerve defect; however, drawbacks such as poor mechanical properties, inappropriate degradation rate, and toxic degradation products continue to limit the application of them in nerve repair. Considering the unique properties of zein, such as its biocompatibility, biodegradability and ease of fabrication, we report the use of zein conduits to repair injured rat sciatic nerves with a 10-mm defect. Three-dimensional zein conduits were designed with/without pores, and with/without microtubes including in the lumen of conduits. Zein conduit with microtubes yielded satisfactory results in sciatic function index (SFI), proximal compound muscle action potentials, density of myelinated nerve fibres and myelin thickness, which were not inferior to autograft but slightly superior to the hollow conduit at the 4th month post-implantation. The conduits degraded almost completely within two months, which was shorter than the suggested period of four months. Thus, the use of a porous conduit with microtubes inside as the guidance may play important roles in successful repair. Notably, the regulatory body will more likely approve designs employing a single component, such as the natural polymer zein.

Injectable polymeric biomaterials: a brief review

This review summarizes some recent work done by the corresponding author and his co-workers on photo-crosslinkable and injectable polymeric systems developed for biomedical applications. First, we discuss the synthesis, chemical structures, and physical properties of different injectable polymeric systems, including poly(propylene fumarate)-based, poly(ε-caprolactone)-based, and poly(ethylene glycol)-based homo-polymers, their copolymers and blends, and their nanocomposites containing hydroxyapatite (HA) nanoparticles or polyhedral oligomeric silsesquioxane nanocages. Then we present different fabrication methods of two-dimensional (2D) surface features, for example, honey-comb pores and microgrooves, and three-dimensional (3D) porous scaffolds and nerve conduits using these injectable polymeric systems. At last, we elaborate on the applications of these injectable polymeric systems, including regulation of in vitro cellular behavior on 2D substrates and 3D structures, and in vivo animal implantation of porous scaffolds and nerve conduits aiming for assisting bone regeneration and peripheral nerve regeneration, respectively.