Microalgal biofouling formation on tubular cellulose-ester membranes during dewatering by forward osmosis.

This work assesses the biofouling formation of a microalgal consortium, cultivated in wastewater, on dialysis tubular membranes with no supporting layer, in both batch and continuous FO dewatering modes. The biological adhesion strength was compared with the predictions from the Baier and Vogler biocompatibility theories, employing critical surface tension (γc) and water adhesion tension (τ0), respectively, as measurable parameters of surface wettability. The results indicate that most of the tested membranes presented amphiphilic surface characteristics (τ0=22 to 45 mJ.m-2, θW ≈ 65˚) with a minimal biological adhesion tendency, which is compatible with the Vogler criteria. However, the membrane exposed the longest time to the microalgal culture presented more hydrophobic characteristics and poor wettability. The existing thermodynamic models succeeded in predicting cell-cell and cell-surface interactions as a competitive phenomenon. Nevertheless, the XDLVO model was used to determine changes in the cell-to-surface attraction dynamics. This assessment of microalgal foulant-membrane interfacial interactions helps to enhance understanding of the fouling mechanisms present on a novel FO membrane surface.

Durum wheat semolina-modified ceramic membranes as novel porous separators for enhanced power generation and wastewater remediation using microbial fuel cell.

This proof-of-concept study describes the enhanced performance efficiency of the dual-chambered microbial fuel cell equipped with the fabricated unmodified ceramic membranes and ceramic membranes modified with 5 % and 10 % (w/w) durum wheat semolina in comparison with the commercially available NafionTM 117 membranes. The chemical oxygen demand removal efficiencies were determined to be 85.6 ± 0.1, 72.1 ± 0.2 and 68.6 ± 0.1 % for microbial fuel cell equipped with 10 % (w/w) semolina-modified, 5 % (w/w) semolina-modified and unmodified ceramic membrane, respectively, which indicated the improved wastewater treatment efficiency with increasing content of semolina. Preliminary studies showed that the 10 % (w/w) semolina-modified ceramic was cost-effective (64 USD/m2) with improved water uptake, good proton mobility, low oxygen diffusion in addition to the enhanced power and current density output. The semolina-modified ceramic membranes have the potential to become a cost-effective alternative for the high-efficiency production of bioelectricity using microbial fuel cells.

Forward osmosis dewatering of seawater and pesticide contaminated effluents using the commercial fertilizers and zinc-nitrate blend draw solutions.

Fertilizer driven forward osmosis (FDFO) process would be feasible due to the possible prevention of the drainage of dewatered and concentrated pesticide effluent from agricultural pesticide industries to the environment. Instead, it would be possible to return the concentrated pesticide solution to the processing cycle, and on the other hand, employ directly the obtained diluted fertilizer draw solution for irrigation. This study investigated the performance of zinc-nitrate/amino-acids blends as fertilizer type draw solution, and distilled water, saline water (seawater), and synthetic wastewater containing pesticides as feed. The results indicated that the synergetic effect of blended type fertilizer presented significantly higher osmotic pressure and water flux than the sum of their individual ones, especially when the amount of amino acid increased. Conversely, an ignorable reverse flux of blended fertilizer draw solute was observed. The fertilizer blend with a molar ratio of 1:6 zinc-nitrate/amino-acid achieved the higher average fluxes of 34.7 and 23.92 L/m2h from distilled and saline waters compared to common draw solutions such as metal salts. Furthermore, the FDFO exhibited a high rejection (over 99%) of bentazon and imidacloprid in feed solutions compared to other agricultural pesticides due to their larger molecular weight and molecular size. The applied FDFO represented a significant reduction in specific energy consumption (from 0.17 to 0.049 kWh/m3) in a bench-scale setup as compared to the RO process almost at the same water permeation flux and the rejection of bentazon.

A mesoporous melamine/chitosan/activated carbon biocomposite: Preparation, characterization and its application for Ni (II) uptake via ion imprinting.

A novel imprinted biocomposite and its non-imprinted form were developed by melaminating and crosslinking of chitosan coated onto a bio-based activated carbon and characterized using FTIR, BET, FESEM-EDS and XRD. Nickel, 4-Toluenesulfonyl chloride, and glutaraldehyde were used as a template, converter of hydroxyl and amine groups to good leaving groups, and cross-linker, respectively. The factors affecting adsorptivity and imprinting factor were optimized by using the Taguchi method for the subsequent comparative adsorptivity, kinetics, isotherms, selectivity, and reusability studies of imprinted biocomposite with its non-imprinted one. The pseudo-first-order and Langmuir models were best fitted to the experimental kinetics and equilibrium isotherm data, respectively. The maximum Ni (II)) adsorptivity of 109.86 mg/g, the imprinting factor (I·F) of 5.45 and Ni (II) selectivity coefficients values of 3.13, 4.48, 3.72, 2.51 for Ni (II) toward Zn (II), Cd (II), Cu (II) and Pb (II), respectively, were obtained at optimum conditions. After five consecutive adsorption-desorption cycles, the biocomposites still presented a high adsorptivity (>83%), indicating their excellent reusability.

Fabrication and characterization of a novel compliant small-diameter PET/PU/PCL triad-hybrid vascular graft.

Nanomaterial structures are highly contributive in tissue engineering vascular scaffolds (TEVS) due to their ability to mimic the nanoscale dimension of the natural extracellular matrix (ECM) and the existing mechanical match between the native blood vessel and the scaffold as a vascular graft. The aim of this study was to develop and mechanically improve the nanofibrous triad-hybrid scaffolds with different composite ratios of polyethylene terephthalate (PET), polyurethane (PU), and polycaprolactone (PCL). The morphological, biological, mechanical, and biomechanical properties of the neat and hybrid structures were examined using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), tensile strength, compliance, burst pressure, MTT assay, and by implanting the specimens under rat skin to explore the immune system in vivo. The results showed that the fiber diameter and porosity changes in the triad-hybrid electrospun scaffold ranged within 388 ± 88 to 547 ± 89 nm and 56.60 ± 2.06% to 75.00 ± 1.94%, respectively. In addition, the changes in the tensile strength and force in the scaffolds were within the ranges 2.7 ± 0.44 to 5.27 ± 0.83 MPa and 2.68 ± 0.19 to 10.03 ± 0.75 MPa, respectively. Also, the compliance and burst pressure of the structures were reported as 4.05 ± 0.21 to 7.09 ± 0.49 and 1623 ± 329 to 2560 ± 121 mmHg, respectively. According to the MTT assay, high cell viability was observed on the triad-hybrid structures with a high percentage of PET when compared to that of PU. The findings of this research demonstrate that the PET/PU/PCL triad-hybrid vascular scaffold has enough potential to be used in vascular tissue engineering application.

Graphene oxide containing chitosan scaffolds for cartilage tissue engineering.

Enhancement of physical and mechanical properties of the scaffolds is achieved via various methods including cross-linking and incorporation of nano particles. In the present research chitosan-based scaffolds firstly were reinforced with the incorporation of the graphene oxide (GO) nanoparticles. The GO nanoparticles were synthesized from graphite successfully and were identified by TGA, XRD, SEM and FTIR analytical methods. Nanocomposite scaffolds based on chitosan with different percentages of the GO were prepared. The chitosan-GO nanocomposite scaffolds were then simultaneously sterilized and cross-linked in an autoclave and comprehensively characterized. In XRD measurements, the absence of the peak at 10° related to GO, is evidence that the GO layers are exfoliated. With increasing the GO concentration from 0 to 0.1, 0.2 and 0.3%, physical and mechanical properties were improved, considerably. Seeding of the human articular chondrocytes on the nanocomposite scaffolds showed an increased proliferation with augmentation of the GO percentage particularly in prolonged cultivation periods (14 days). Investigation of the human articular chondrocyte morphology revealed a more spherical morphology of the cells on the cross-linked scaffolds for 21 days of culture in vitro.

Numerical investigation of UF membrane to reduce energy consumption using double porosity approach.

Hollow fiber (HF) membranes with circular geometry, are used in many separation processes such as water and wastewater treatment. Since optimization of energy efficiency is important for wastewater treatment, the aim of this study was to investigate the effect of non-circular geometry of the inner surface of the HF on the separation performance. To this purpose, the HF bundle has been assumed as a double porous media having two porosities and permeabilities. Since these two parameters are defined by the geometry of the porous medium, any change in the geometry affects their values and the media performance. Therefore, in this study a mathematical modeling has been divided into five categories, including circular, oval, square, rectangular and triangular geometries, and their geometric properties have been calculated based on three different strategies. The results have been compared with the data obtained from literature and showed that the membrane inner surface to cross-section area ratio (a), axial permeability, and porosity in the inner region for the non-circular HF are larger than that of the circular HF and a increased 16%, 27%, 35% and 65% in ellipse, square, rectangle and triangle geometry, respectively, in comparison with the circle. Axial permeability increased 98%, 68%, 63%, and 26% for a triangle, rectangle, ellipse, and square respectively in the third strategy when compared to the circle. Due to 50% feed flow rate reduction, maximum transmembrane pressure (TMP) reduction was 85% related to the rectangular geometry in the first strategy and minimum was 55% corresponding to the triangle in the third strategy. As a increased up to 65%, TMP reduced by up to 200% and consequently energy consumption and operating costs of the system are decreased.

Small-diameter vascular graft using co-electrospun composite PCL/PU nanofibers.

Small-diameter vascular scaffolds have been developed by a co-electrospinning method using polyethylene terephthalate (PCL) and elastic polytetrafluoroethylene (PU) as biopolymers with long degradation time. Although they possess favorable properties, individually these two polymers do not meet the requirements for the production of synthetic vascular scaffolds. The co-electrospinning method was adopted to develop and mechanically improve the composite PCL/PU vascular scaffolds. The morphological, mechanical and biological properties of these vascular scaffolds were evaluated through scanning electron microscopy, differential scanning calorimetry, Fourier transform infrared spectroscopy, compliance, tensile testing and MTT assay. The in vivo study of the vascular scaffolds was performed by implanting them on rat and sheep models. The compliance of the composite vascular scaffolds improved by up to 43% through an increased percentage of PU from 10%-90%. The obtained UTS of the scaffolds at 10%, 25%, 50%, 75% and 90% of PU were 4.7 ± 0.34, 3.4 ± 0.6, 4.8 ± 0.62, 2.2 ± 0.34 and 4.4 ± 1.9 MPa, respectively. The results of MTT assays indicated that the cell growth on the scaffolds was augmented when compared to the control, from day one to day seven. Mild edema, mild foreign-body granulomatous reaction and mild fibrosis were observed by pathology test as the side effects in the composite scaffold with 50% PCL. Doppler ultrasound and angiography images confirm that no aneurysm, thrombogenesis, neointimal hyperplasia or occlusion exist, and there is complete patency at the end of an eight month investigation. The fabricated composite vascular scaffolds provide appropriate mechanical and biological properties and clinical requirements, indicating their required potential to be applied as a small-diameter vascular graft.

Engineering of oriented carbon nanotubes in composite materials.

The orientation and arrangement engineering of carbon nanotubes (CNTs) in composite structures is considered a challenging issue. In this regard, two groups of in situ and ex situ techniques have been developed. In the first, the arrangement is achieved during CNT growth, while in the latter, the CNTs are initially grown in random orientation and the arrangement is then achieved during the device integration process. As the ex situ techniques are free from growth restrictions and more flexible in terms of controlling the alignment and sorting of the CNTs, they are considered by some as the preferred technique for engineering of oriented CNTs. This review focuses on recent progress in the improvement of the orientation and alignment of CNTs in composite materials. Moreover, the advantages and disadvantages of the processes are discussed as well as their future outlook.

Synthesis, Characterization, and in Vitro Biological Evaluation of Copper-Containing Magnetic Bioactive Glasses for Hyperthermia in Bone Defect Treatment.

Hyperthermia treatment induced by magnetic mesoporous glasses has been applied as a potential therapeutic approach for bone defects due to malignant tumors. The objective of this study was to synthesize and characterize the structural and biological properties of magnetic bioactive glasses (BGs) for producing multifunctional materials. The effect of the addition of copper (Cu) to the bioactive glass composition was also evaluated. Fe BG and FeCu BG as magnetic mesoporous BGs, and Cu BG as mesoporous BG were synthesized and dried by template sol-gel method. Then the synthesized bioglasses were characterized and analyzed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive electron disperse spectroscopy (EDS), Brunauer-Emmett-Teller (BET), and vibrating sample magnetometer (VSM). In addition, the antibacterial behavior, cytotoxicity assay (MTT test), proliferation assay of HUVEC cell assay, and bioactivity (ALP activity test) of the synthesized BGs were evaluated. The characterization results exhibited that the synthesized powders formed mesoporous glasses with nanoparticle morphology, good surface area, and magnetic properties. The synthesized BGs also demonstrated suitable biological behavior. The magnetic saturation of bioactive glasses was increased by the addition of copper oxide. A two-phase structure was observed for the magnetic glasses compared to the copper-containing glasses, thus making them suitable for drug delivery systems. The antibacterial behavior was found to be better for the Cu BG and Fe BG compared to the FeCu BG. However, the least amount of cytotoxicity was observed for the Fe BG and FeCu BG, compared to the Cu BG. In addition, the Fe-containing BGs compared with the control group showed a lack of HUVEC cell proliferation and angiogenesis motivation. From the ALP assay, higher bioactivity for the magnetic bioglasses in the presence of mesenchymal cells was found. From the results of this in vitro study, the Cu-containing magnetic bioglass (FeCu BG) could be considered as a new generation of magnetic glasses for inducing hyperthermia in treatment of bone defects due to malignant tumors. However, further in vitro and in vivo studies are required to confirm their applications in healing of bone defects and tissue engineering.

Fabrication and Characterization of Electrospun Bi-Hybrid PU/PET Scaffolds for Small-Diameter Vascular Grafts Applications.

In spite of advances have been made during the past decades, the problems associated with small-diameter vascular grafts, including low patency and compliance mismatch and in consequence of that thrombosis, aneurysm and intimal hyperplasia are still challenges. To address these problems, net polyurethane (PU) and poly (ethylene terephthalate) (PET) polymers and hybrid PU/PET were electrospun to create three different types of small-diameter vascular scaffolds due to their unique physicochemical characteristics: PU, PET, and novel hybrid PU/PET scaffolds. The results show that the PU and PET composite can improve the mechanical properties of the tissue-engineered vascular scaffolds in the range of the native vessels where the non-cytotoxicity characteristic of these well-known polymers is still immutable. The compliance and stiffness factor of the fabricated hybrid scaffolds were 4.468 ± 0.177 and 22.718 ± 0.896%/0.01 mmHg, respectively, which were significantly different with that of the net PU and PET electrospun scaffolds. Other properties such as ultimate tensile stress (UTS) (3.56 ± 1.21 MPa) were also in good accordance with the native vessels. Furthermore, FT-IR analysis testified the presence of both PU and PET in the hybrid scaffolds. Overall, we were able to fabricate a hybrid scaffold as a small-diameter vascular graft that mechanically matched the gold standard of blood vessel substitution.

Fabrication and characterization of hydrothermal cross-linked chitosan porous scaffolds for cartilage tissue engineering applications.

The use of various chemical cross-linking agents for the improvement of scaffolds physical and mechanical properties is a common practical method, which is limited by cytotoxicity effects. Due to exerting contract type forces, chondrocytes are known to implement shrinkage on the tissue engineered constructs, which can be avoided by the scaffold cross-linking. In the this research, chitosan scaffolds are cross-linked with hydrothermal treatment with autoclave sterilization time of 0, 10, 20 and 30min, to avoid the application of the traditional chemical toxic materials. The optimization studies with gel content and crosslink density measurements indicate that for 20min sterilization time, the gel content approaches to ~80%. The scaffolds are fully characterized by the conventional techniques such as SEM, porosity and permeability, XRD, compression, thermal analysis and dynamic mechanical thermal analysis (DMTA). FT-IR studies shows that autoclave inter-chain cross-linking reduces the amine group absorption at 1560cm-1 and increase the absorption of N-acetylated groups at 1629cm-1. It is anticipated, that this observation evidenced by chitosan scaffold browning upon autoclave cross-linking is an indication of the familiar maillard reaction between amine moieties and carbonyl groups. The biodegradation rate analysis shows that chitosan scaffolds with lower concentrations, possess suitable degradation rate for cartilage tissue engineering applications. In addition, cytotoxicity analysis shows that fabricated scaffolds are biocompatible. The human articular chondrocytes seeding into 3D cross-linked scaffolds shows a higher viability and proliferation in comparison with the uncross-linked samples and 2D controls. Investigation of cell morphology on the scaffolds by SEM, shows a more spherical morphology of chondrocytes on the cross-linked scaffolds for 21days of in vitro culture.

Engineered electrospun polycaprolactone (PCL)/octacalcium phosphate (OCP) scaffold for bone tissue engineering.

The main challenge in bone tissue engineering is to find suitable biological substitutes which act as scaffolds. Hence, in this work, a novel scaffold composed of octacalcium phosphate (OCP) particles fabricated by co-precipitation method and polycaprolactone (PCL) using electrospinning technique was introduced. The electrospun scaffolds were characterized by SEM, FTIR, XRD, DSC and TGA analysis. The mechanical properties of the composite scaffolds including maximum tensile stress, strain at break and Young modulus were measured. The bioactivity of the scaffolds was determined by soaking in simulated body fluid (SBF). The osteoblast human G-292 cells were seeded on the scaffold's surface for in vitro studies including cell culture and MTT assay. The FTIR and XRD results showed that OCP component has an appropriate incorporation into the polymeric PCL matrix. The SEM analysis exhibited a significant reduction in the fiber size thanks to the OCP. The results of tensile test confirmed that the PCL/OCP composite introduced suitable mechanical properties. Furthermore, the OCP particles led to form hydroxyapatite layer on the scaffold's surface in the vicinity of SBF solution. The obtained results from the MTT assay described that OCP particles have a positive impact on the growth of the osteoblast human G-292 cells on the scaffolds. Overall, aforesaid features of the PCL/OCP composite scaffold make it a great candidate for the bone tissue engineering application.

An experimental-numerical investigation on the effects of macroporous scaffold geometry on cell culture parameters.

INTRODUCTION: Perfused bioreactors have been demonstrated to be effective in the delivery of nutrients and in the removal of waste products to and from the interior of cell-populated three-dimensional scaffolds. In this paper, a perfused bioreactor hosting a macroporous scaffold provided with a channel is used to investigate transport phenomena and culture parameters on cell growth. METHODS: MG63 human osteosarcoma cells were seeded on macroporous poly​(ε-caprolactone) scaffolds provided with a channel. The scaffolds were cultured in a perfused bioreactor and in static conditions for 5 days. Cell viability and growth were assessed while the concentration of oxygen, glucose and lactate were measured. An in silico, multiphysics, numerical model was set up to study the fluid dynamics and the mass transport of the nutrients in the perfused bioreactor hosting different scaffold geometries. RESULTS: The experimental and numerical results indicated that the specific cell metabolic activity in scaffolds cultured under perfusion was 30% greater than scaffolds cultured under static conditions. In addition, the scaffold provided with a channel enabled the shear stress to be controlled, the initial seeding density to be retained, and adequate mass transport and waste removal. CONCLUSIONS: We show that the macroporous scaffold provided with a channel cultured in a macroscale bioreactor can be a robust reference experimental model system to systematically investigate and assess crucial culture parameters. We also show that such an experimental model system can be employed as a simplified "representative unit" to improve the performance of both perfused culture systems and hollow, fiber-integrated scaffolds for large-scale tissue engineering.

Hollow fiber bioreactor technology for tissue engineering applications.

Hollow fiber bioreactors are the focus of scientific research aiming to mimic physiological vascular networks and engineer organs and tissues in vitro. The reason for this lies in the interesting features of this bioreactor type, including excellent mass transport properties. Indeed, hollow fiber bioreactors allow limitations to be overcome in nutrient transport by diffusion, which is often an obstacle to engineer sizable constructs in vitro. This work reviews the existing literature relevant to hollow fiber bioreactors in organ and tissue engineering applications. To this purpose, we first classify the hollow fiber bioreactors into 2 categories: cylindrical and rectangular. For each category, we summarize their main applications both at the tissue and at the organ level, focusing on experimental models and computational studies as predictive tools for designing innovative, dynamic culture systems. Finally, we discuss future perspectives on hollow fiber bioreactors as in vitro models for tissue and organ engineering applications.

Computational study of culture conditions and nutrient supply in a hollow membrane sheet bioreactor for large-scale bone tissue engineering.

Successful bone tissue culture in a large implant is still a challenge. We have previously developed a porous hollow membrane sheet (HMSh) for tissue engineering applications (Afra Hadjizadeh and Davod Mohebbi-Kalhori, J Biomed. Mater. Res. Part A [2]). This study aims to investigate culture conditions and nutrient supply in a bioreactor made of HMSh. For this purpose, hydrodynamic and mass transport behavior in the newly proposed hollow membrane sheet bioreactor including a lumen region and porous membrane (scaffold) for supporting and feeding cells with a grooved section for accommodating gel-cell matrix was numerically studied. A finite element method was used for solving the governing equations in both homogenous and porous media. Furthermore, the cell resistance and waste production have been included in a 3D mathematical model. The influences of different bioreactor design parameters and the scaffold properties which determine the HMSh bioreactor performance and various operating conditions were discussed in detail. The obtained results illustrated that the novel scaffold can be employed in the large-scale applications in bone tissue engineering.

Computational modeling of adherent cell growth in a hollow-fiber membrane bioreactor for large-scale 3-D bone tissue engineering.

The use of hollow-fiber membrane bioreactors (HFMBs) has been proposed for three-dimensional bone tissue growth at the clinical scale. However, to achieve an efficient HFMB design, the relationship between cell growth and environmental conditions must be determined. Therefore, in this work, a dynamic double-porous media model was developed to determine nutrient-dependent cell growth for bone tissue formation in a HFMB. The whole hollow-fiber scaffold within the bioreactor was treated as a porous domain in this model. The domain consisted of two interpenetrating porous regions, including a porous lumen region available for fluid flow and a porous extracapillary space filled with a collagen gel that contained adherent cells for promoting long-term growth into tissue-like mass. The governing equations were solved numerically and the model was validated using previously published experimental results. The contributions of several bioreactor design and process parameters to the performance of the bioreactor were studied. The results demonstrated that the process and design parameters of the HFMB significantly affect nutrient transport and thus cell behavior over a long period of culture. The approach presented here can be applied to any cell type and used to develop tissue engineering hollow-fiber scaffolds.

A novel automated cell-seeding device for tissue engineering of tubular scaffolds: design and functional validation.

Obtaining an efficient, uniform and reproducible cell seeding of porous tubular scaffolds constitutes a major challenge for the successful development of tissue-engineered vascular grafts. In this study, a novel automated cell-seeding device utilizing direct cell deposition, patterning techniques and scaffold rotation was designed to improve the cell viability, uniformity and seeding efficiency of tubular constructs. Quantification methods and imaging techniques were used to evaluate these parameters on the luminal and abluminal sides of fibrous polymer scaffolds. With the automated seeding method, a high cell-seeding efficiency (~89%), viability (~85%) and uniformity (~85-92%) were achieved for both aortic smooth muscle cells (AoSMCs) and aortic endothelial cells (AoECs). The duration of the seeding process was < 8 min. Initial cell density, cell suspension in matrix-containing media, duration of seeding process and scaffold rotation were found to affect the seeding efficiency. After few days of culture, a uniform longitudinal and circumferential cell distribution was achieved without affecting cell viability. Both cell types were viable and spread along the fibres after 28 h and 6 days of static incubation. This new automated cell-seeding method for tubular scaffolds is efficient, reliable and meets all the requirements for clinical applicability.

A positron emission tomography approach to visualize flow perfusion in hollow-fiber membrane bioreactors.

Despite the success of hollow-fiber membrane bioreactors in tissue engineering, few evaluations of steady- and pulsatile-flow perfusion through these bioreactors have been made. Such evaluations are vital to the optimization of bioreactor culture conditions. In this study, positron emission tomography (PET) was proposed and used to visualize steady- and pulsatile-flow perfusion in hollow-fiber membrane bioreactors for tissue-engineering applications. PET is a noninvasive method that allows measuring the spatial distribution of a radioactive tracer by detecting its activity within porous scaffolds. A radioactive tracer, 18-fluoro-deoxy-glucose ((18)FDG), was injected into a fluid circuit having a hollow-fiber membrane bioreactor with gel-devoid or gel-filled extracapillary space. Dynamic PET scans of the inlet section were acquired and followed by volumetric PET scans of the whole bioreactor. Results were used to reconstruct dynamic and volumetric two- and three-dimensional images. Pulsatile inlet flow improved the uniformity of perfusion flow within the bioreactor in comparison to the steady inlet flow. Pulsatile flow also reduced the accumulation of radioactive tracer for both gel-devoid and gel-filled bioreactors compared to the steady flow. The stability of the radioactive tracer for both conditions was evaluated. The potential of the PET approach was demonstrated by the quantification of the imaging results for steady- and pulsatile-flow perfusions that can be used for the development of bioreactors for tissue-engineering applications.