In this work, data from two-dimensional (2D) images of the human retina were taken as a case study. First, the characteristic data points had been removed using the Douglas-Peucker (DP) method, and subsequently, more data points were added using random fractal interpolation approach, to reconstruct a three-dimensional (3D) model of the blood vessel. By visualizing the result, we can see that all the small blood vessels in the human retina are more visible and detailed. This algorithm of 3D reconstruction has the advantage of being fast with calculation time less than 40 s and also can reduce the 3D image storage level on a disk with a reduction ratio between 78% and 96.65%.
Ball milling (BM) offers a flexible process for nanomanufacturing of reactive bimetallic multiscale particulates (nanoheaters) for self-heated microjoining engineering materials and biomedical tooling. This paper introduces a mechanics-based process model relating the chaotic dynamics of BM with the random fractal structures of the produced particulates, emphasizing its fundamental concepts, underlying assumptions, and computation methods. To represent Apollonian globular and lamellar structures, the simulation employs warped ellipsoidal (WE) primitives of elasto-plastic strain-hardening materials, with Maxwell–Boltzmann distributions of ball kinetics and thermal transformation of hysteretic plastic, frictional, and residual stored energetics. Interparticle collisions are modeled via modified Hertzian contact impact mechanics, with local plastic deformation yielding welded microjoints and resulting in cluster assembly into particulates. The model tracks the size and diversity of such particulate populations as the process evolves via sequential collision and integration events. The simulation was shown to run in real-time computation speeds on modest hardware, and match successfully the fractal dimension and contour shape of experimental ball-milled Al–Ni particulate micrographs. Thus, the model serves as a base for the design of a feedback control system for continuous BM.
In this study, we report the bioprinting of a three-dimensional (3D) heterogeneous conduit structure encapsulating PC12 neural cells. A core–shell-based hybrid construct is fabricated by combining electrospinning, polymer extrusion, and cell-based bioprinting processes to create a multiscale and multimaterial conduit structure. PC12 nerve cells were shown to be printed with high cell viability (>95%) and to proliferate within the rolled construct at a rate consistent with traditional two-dimensional (2D) culture. Light microscopy and scanning electron microscopy (SEM) have also shown encapsulation of cells within the printed alginate gel and an even cell distribution throughout the heterogeneous cellular construct.
The rapid progress of embryonic stem cell (ESCs) research offers great promise for drug discovery, tissue engineering, and regenerative medicine. However, a major limitation in translation of ESCs technology to pharmaceutical and clinical applications is how to induce their differentiation into tailored lineage commitment with satisfactory efficiency. Many studies indicate that this lineage commitment is precisely controlled by the ESC microenvironment in vivo. Engineering and biomaterial-based approaches to recreate a biomimetic cellular microenvironment provide valuable strategies for directing ESCs differentiation to specific lineages in vitro. In this review, we summarize and examine the recent advances in application of engineering and biomaterial-based approaches to control ESC differentiation. We focus on physical strategies (e.g., geometrical constraint, mechanical stimulation, extracellular matrix (ECM) stiffness, and topography) and biochemical approaches (e.g., genetic engineering, soluble bioactive factors, coculture, and synthetic small molecules), and highlight the three-dimensional (3D) hydrogel-based microenvironment for directed ESC differentiation. Finally, future perspectives in ESCs engineering are provided for the subsequent advancement of this promising research direction.
In this paper, we present the synthesis of nanostructures of magnetite nanoparticles (NPs) with ciprofloxacin and kanamycin antibiotics, based on self-assembling principle. The nanostructures were prepared in crystallite size, ranging 8–16 nm, in one pot addition setup and further washing steps, using only iron precursors and above-mentioned antibiotics as stabilizers. Nanostructures were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis methods, Fourier transform infrared (FTIR) and ultraviolet (UV) spectroscopy methods. It was found that they have well-shaped spherical form and are homogeneous in size. The quantitative analysis of nanostructured antibiotics was performed by atom absorbance spectroscopy (AAS) as well as on the basis of Lambert–Beer law. Prepared nanostructures were tested on Staphylococcus aureus and Pseudomonas aeruginosa. Obtained results demonstrated that these nanostructures are able to improve antimicrobial properties and decrease the minimal inhibitory concentration (MIC) of pristine kanamycin and ciprofloxacin antibiotics.
Here, we report a threshold limit value (TLV) of on-chip cytotoxicity of Nepali Chiya, the Nepali traditional black tea. To demonstrate our proof-of-concept validation, we used the active sealing chip with serial dilution that can directly perform on-chip cytotoxicity testing onto the cells cultured in a petri dish. In our experiments, the TLV for mortality on HeLa cells was observed as 400 μg/ml for Nepali Chiya extract. We believe this approach would be a rapid and simple method for on-chip TLV screening of potability of tea extract at the laboratory level, and furthermore as a new potential drug supplement in pharmaceutical industries.
The aim of this study is to analyze the origin of multifractality of surface electromyography (sEMG) signals during dynamic contraction in nonfatigue and fatigue conditions. sEMG signals are recorded from triceps brachii muscles of 22 healthy subjects. The signals are divided into six equal segments on time scale for normalization. The first and sixth segments are considered as the nonfatigue and fatigue conditions, respectively. The source of multifractality can be due to correlation and probability distribution. The original sEMG series are transformed into shuffled and surrogate series. These three series namely, original, shuffled, and surrogate series in the nonfatigue and fatigue conditions are subjected to multifractal detrended fluctuation analysis (MFDFA) and features are extracted. The results indicate that sEMG signals exhibit multifractal behavior. Further investigation revealed that origin of multifractality is primarily due to correlation. The origin of multifractality due to correlation is quantified as 80% in nonfatigue and 86% in fatigue conditions. This method of multifractal analysis may be useful for analyzing the progressive changes in muscle contraction in varied neuromuscular studies.
Scaffolds play an important role in tissue engineering by providing structural framework and a surface for cells to attach, proliferate, and secrete extracellular matrix (ECM). In order to enable efficient tissue formation, delivering sufficient cells into the scaffold three-dimensional (3D) matrix using traditional static and dynamic seeding methods continues to be a critical challenge. In this study, we investigate a new cell delivery approach utilizing deposition of hydrogel-cell encapsulated microspheroids into polycaprolactone (PCL) scaffolds to improve the seeding efficiency. Three-dimensional-bioplotted PCL constructs (0 deg/90 deg lay down, 284 ± 6 μm strand width, and 555 ± 8 μm strand separation) inoculated with MG-63 model bone cells encapsulated within electrostatically generated calcium-alginate microspheroids (Ø 405 ± 13 μm) were evaluated over seven days in static culture. The microspheroids were observed to be uniformly distributed throughout the PCL scaffold cross section. Encapsulated cells remained viable within the constructs over the test interval with the highest proliferation noted at day 4. This study demonstrates the feasibility of the new approach and highlights the role and critical challenges to be addressed to successfully utilize 3D-bioprinting for microencapsulated cell delivery.
Nwosu et al. [1] presented a review and parametric investigation into nanofluid viscosity models. The purpose of the present discussion is to draw the attention of readers that Nwosu et al. [1] did not refer to some nanofluid viscosity equations, which are available in literature. Different examples for the missing nanofluid viscosity equations are given below.Nwosu et al. [1] mentioned the empirical model of Maïga et al. [2] for ethylene glycol (EG)–γAl2O3 nanofluid. It should be noted that Nwosu et al. [1] did not mention the empirical model of Maïga et al. [2] for water–γAl2O3 nanofluid. This empirical model for water–γAl2O3 nanofluid was(1)η=ηnfηbf=1+7.3ϕ+123ϕ2Nwosu et al. [1] mentioned the empirical models of Nguyen et al. [3] for Al2O3/H2O nanofluid with various particles sizes of 47 and 36 nm, respectively. It should be noted that Nwosu et al. [1] did not mention the empirical model of Nguyen et al. [3] for CuO/H2O nanofluid with 29 nm particle size. This empirical model for CuO/H2O nanofluid was(2)η=ηnfηbf=1.475−0.319ϕ+0.051ϕ2+0.009ϕ3Also, it should be noted that the correct form of Eq. (21) in the paper of Nwosu et al. [1] based on the study of Nguyen et al. [3] is(3)η=ηnfηbf=1.1250−0.0007TThat is, the second term on the right-hand side is −0.0007T and not −0.007T.In addition, the readers can notice that Nwosu et al. [1] mentioned that Eqs. (21) and (22), which are based on temperature, are for Al2O3/H2O nanofluid with nanoparticle sizes of 47 nm and 36 nm, respectively, which is not correct. It should be noted that Eqs. (21) and (22), which are based on temperature in the paper of Nwosu et al. [1] based on the study of Nguyen et al. [3], are for all three nanofluids tested (Al2O3/H2O nanofluid with various particles sizes of 47 and 36 nm, respectively, as well as CuO/H2O nanofluid with 29 nm particle size) and particle concentrations (ϕ) of 1% and 4%, respectively. This means that Eq. (21) is for ϕ = 1%, while Eq. (22) is for ϕ = 4% for all the three nanofluids tested.Chen et al. [4] formulated EG (>99.9%, Alfa Aesar, Ward Hill, MA) based titania (TiO2, spherical, 25 nm diameter, Degussa, Hanau, Germany) nanofluids and measured the rheological behavior of the nanofluids by means of a Bolin CVO rheometer (Malvern Instruments) over a range of shear rate (0.5–104 s−1), nanoparticle mass concentration (w = 0–8 wt. %), and temperature (293–333 K). The researchers found that the normalized shear viscosity with respect to the base liquid viscosity is found to be independent of temperature and could be given as a function of the volume fraction of nanoparticles (ϕ) as follows:(4)η=ηnfηbf=1+10.6 ϕ+(10.6ϕ)2Using water as the base fluid and alumina (Al2O3) and zirconia (ZrO2) as nanoparticles, Williams et al. [5] investigated experimentally the turbulent convective heat transfer and pressure loss in horizontal tubes at different flow rates (9000 < Re < 63,000), temperatures (21–76 °C), heat fluxes (up to ∼190 kW/m2), and particle concentrations (0.9–3.6 vol. % and 0.2–0.9 vol. % for Al2O3 and ZrO2, respectively). The researchers measured viscosity using a capillary viscometer submerged in a controlled-temperature bath. The viscometer was benchmarked with water at different temperatures and its accuracy was found to be within 0.5%. They found that alumina and zirconia nanofluid viscosities had no dependence on temperature and rapid increase with particle loading. They created curve fits for their viscosity experimental data to be used in the interpretation of the convective heat transfer data. For alumina nanofluids, their viscosity equation as a function of nanoparticle volumetric fraction (ϕ) was(5)η=ηnfηbf=exp[4.91ϕ/(0.2092−ϕ)]For zirconia nanofluids, their viscosity equation as a function of nanoparticle volumetric fraction (ϕ) was(6)η=ηnfηbf=exp[11.19ϕ/(0.1960−ϕ)]Using water as the base fluid, Azmi et al. [6] developed regression equation for nanofluid viscosity as a function of volume fraction (ϕ), nanofluid temperature (Tnf), and nanoparticle diameter (d) using the experimental data available in literature. Their equation was(7)η=ηnfηbf=0.9042+0.1245ϕ-0.08445[T72]+0.6436[d170]Equation (7) was applicable for 0.03 < ϕ < 4%, 15 < Tnf < 72 °C, and 20 < d < 170 nm. Equation (7) had average deviation of 4.2% and standard deviation of 5.6%.At the end, it is clear that current author presents in his discussion various examples for missing nanofluid viscosity equations in the paper of Nwosu et al. [1]. These equations include the empirical model of Maïga et al. [2] for water–γAl2O3 nanofluid, the empirical model of Nguyen et al. [3] for CuO/H2O nanofluid with 29 nm particle size, the equation of Chen et al. [4], the equations of Williams et al. [5] for Al2O3 and ZrO2, and the equation of Azmi et al. [6]. Moreover, corrections for Eqs. (21) and (22) in the paper of Nwosu et al. [1] based on the study of Nguyen et al. [3] are also presented.Based on this discussion, it is obvious that the important parameters affecting nanofluid viscosity are volume fraction (ϕ), nanofluid temperature (Tnf), and nanoparticle diameter (d). Regarding the composite of nanofluids that consist of various fluid bases and various nanoparticles, numerous nanofluid viscosity correlations were developed by numerous researchers.
Microfluidic platforms offer revolutionary and practical solutions to challenging problems in biology and medicine. Even though traditional micro/nanofabrication technologies expedited the emergence of the microfluidics field, recent advances in advanced additive manufacturing hold significant potential for single-step, stand-alone microfluidic device fabrication. One such technology, which holds a significant promise for next generation microsystem fabrication is three-dimensional (3D) printing. Presently, building 3D printed stand-alone microfluidic devices with fully embedded microchannels for applications in biology and medicine has the following challenges: (i) limitations in achievable design complexity, (ii) need for a wider variety of transparent materials, (iii) limited z-resolution, (iv) absence of extremely smooth surface finish, and (v) limitations in precision fabrication of hollow and void sections with extremely high surface area to volume ratio. We developed a new way to fabricate stand-alone microfluidic devices with integrated manifolds and embedded microchannels by utilizing a 3D printing and laser micromachined lamination based hybrid manufacturing approach. In this new fabrication method, we exploit the minimized fabrication steps enabled by 3D printing, and reduced assembly complexities facilitated by laser micromachined lamination method. The new hybrid fabrication method enables key features for advanced microfluidic system architecture: (i) increased design complexity in 3D, (ii) improved control over microflow behavior in all three directions and in multiple layers, (iii) transverse multilayer flow and precisely integrated flow distribution, and (iv) enhanced transparency for high resolution imaging and analysis. Hybrid manufacturing approaches hold great potential in advancing microfluidic device fabrication in terms of standardization, fast production, and user-independent manufacturing.
Three-dimensional (3D) printing offers versatile possibilities for adapting the structural parameters of tissue engineering scaffolds. However, it is also essential to develop procedures allowing efficient cell seeding independent of scaffold geometry and pore size. The aim of this study was to establish a method for seeding the scaffolds using photopolymerizable cell-laden hydrogels. The latter facilitates convenient preparation, and handling of cell suspension, while distributing the hydrogel precursor throughout the pores, before it is cross-linked with light. In addition, encapsulation of living cells within hydrogels can produce constructs with high initial cell loading and intimate cell-matrix contact, similar to that of the natural extra-cellular matrix (ECM). Three dimensional scaffolds were produced from poly(lactic) acid (PLA) by means of fused deposition modeling. A solution of methacrylamide-modified gelatin (Gel-MOD) in cell culture medium containing photoinitiator Li-TPO-L was used as a hydrogel precursor. Being an enzymatically degradable derivative of natural collagen, gelatin-based matrices are biomimetic and potentially support the process of cell-induced remodeling. Preosteoblast cells MC3T3-E1 at a density of 10 × 106 cells per 1 mL were used for testing the seeding procedure and cell proliferation studies. Obtained results indicate that produced constructs support cell survival and proliferation over extended duration of our experiment. The established two-step approach for scaffold seeding with the cells is simple, rapid, and is shown to be highly reproducible. Furthermore, it enables precise control of the initial cell density, while yielding their uniform distribution throughout the scaffold. Such hybrid tissue engineering constructs merge the advantages of rigid 3D printed constructs with the soft hydrogel matrix, potentially mimicking the process of ECM remodeling.
We have developed a three-dimensional (3D) bioprinting system capable of multimaterial and multiscale deposition to enable the next generation of “bottom-up” tissue engineering. This area of research resides at the interface of engineering and life sciences. As such, it entails the design and implementation of diverse elements: a novel hydrogel-based bioink, a 3D bioprinter, automation software, and mammalian cell culture. Our bioprinter has three components uniquely combined into a comprehensive tool: syringe pumps connected to a selector valve that allow precise application of up to five different materials with varying viscosities and chemistries, a high velocity/high-precision x–y–z stage to accommodate the most rapid speeds allowable by the printed materials, and temperature control of the bioink reservoirs, lines, and printing environment. Our custom-designed bioprinter is able to print multiple materials (or multiple cell types in the same material) concurrently with various feature sizes (100 μm–1 mm wide; 100 μm–1 cm high). One of these materials is a biocompatible, printable bioink that has been used to test for cell survival within the hydrogel following printing. Hand-printed (HP) controls show that our bioprinter does not adversely affect the viability of the printed cells. Here, we report the design and build of the 3D bioprinter, the optimization of the bioink, and the stability and viability of our printed constructs.
A transport model of magnetic drug carrier particles (MDCPs) in permeable microvessel based on statistical mechanics has been developed to investigate capture efficiency (CE) of MDCPs at the tumor position. Casson-Newton two-fluid model is used to describe the flow of blood in permeable microvessel and the Darcy model is used to characterize the permeable nature of the microvessel. Coupling effect between the interstitial fluid flow and blood flow is considered by using the Starling assumptions in the model. The Boltzmann equation is used to depict the transport of MDCPs in microvessel. The elastic collision effect between MDCPs and red blood cell is incorporated. The distribution of blood flow velocity, blood pressure, interstitial fluid pressure, and MDCPs has been obtained through the coupling solutions of the model. Based on these, the CE of the MDCPs is obtained. Present results show that the CE of the MDCPs will increase with the enhancement of the size of the MDCPs and the external magnetic field intensity. In addition, when the permeability of the inner wall is better and the inlet blood flow velocity is slow, the CE of the MDCPs will increase as well. Close agreements between the predictions and experimental results demonstrate the capability of the model in modeling transport of MDCPs in permeable microvessel.
Magnetic drug targeting (MDT) involves the localization of drug loaded iron oxide nanoparticles (IONPs) around the malignant tissue using external magnetic field for therapeutic purposes. The present in vitro study reports the visualization and motion of curcumin loaded IONPs (CU-IONPs) around the target site inside a microcapillary (500 × 500 μm2 square cross section), in the presence of an externally applied magnetic field. Application of magnetic field leads to transportation and aggregation of CU-IONPs toward the target site inside the capillary adjacent to the magnet. The localization/aggregation of CU-IONPs at the target site shows strong dependence on the strength of the applied magnetic field and flow rate of ferrofluid through the capillary. Such an in vitro study offers a viable for optimization and design of MDT systems for in vivo applications.
Nanocomposite materials filled with multiwall carbon nanotubes (MWCNTs) having three types of structures, i.e., longer (200 μm), shorter (20–50 μm), and aminated (20–50 μm), are manufactured for microwave absorption (MA) in 11–17 GHz frequency range. Microstructure, dielectric permittivity, direct current (DC) electrical conductivity, and MA properties of the MWCNTs–epoxy nanocomposite were investigated. A correlation has been developed between the structure (aspect ratio and surface functionality) of MWCNTs, electrical conductivity of the composite, and MA (return loss (RL)). E-glass/epoxy composite filled with longer carbon nanotubes (CNTs) has shown higher RL as compared to that of other two nanocomposites. The measurements have shown that the magnitude of RL of microwaves depends strongly on the structure of MWCNTs used in the composite. Furthermore, the effect of synthesis route followed for the manufacturing of nanocomposite on its electrical conductivity and microwave absorbing properties is also investigated; three different approaches were followed to manufacture CNT/epoxy nanocomposites from longer CNTs (200 μm).
Thin glass-fiber/epoxy-composite sheets filled with multiwalled carbon nanotubes (MWCNTs) are manufactured to make lightweight honeycomb sandwich microwave absorbers. A multilayered sandwich structure of thin nanocomposite sheets and honeycomb spacers have been also proposed and developed to work in a wide frequency range. The nanocomposite sheets are prepared from 0.5, 1.0, 1.5, 2.0, and 2.5 wt. % of MWCNTs. A commercially available simulation software computer simulation technology (CST) microwave studio was used for the designing and development of radar absorbing structure (RAS) composed of MWCNTs/glass-fiber/epoxy-composite sheets and honeycomb cores. The measurements of return loss (RL) from sandwich structures with 5 mm and 20 mm honeycomb cores in the Ku band (11–17 GHz) show that maximum RL is achieved at 11 GHz and 16 GHz, respectively. The stacking of three nanocomposite sheets and three 5 mm-thick honeycomb spacers produced a wide band microwave absorber with −10 dB RL over 9 GHz bandwidth.
We report a facile fabrication of a high-performance supercapacitor (SC) using a flexible cellulose-based composite film of polyaniline (PANI), reduced graphene oxide (RGO), and silver nanowires (AgNWs). The flexibility, high capacitive behavior, cyclic stability, and enhanced rate capability of the entire device make it a good candidate for flexible and wearable SCs. Our results demonstrate that a capacitance as high as 73.4 F/g (1.6 F/cm2) at a discharge rate of 1.1 A/g is achieved. In addition, the SC shows a power density up to 468.8 W/kg and an energy density up to 5.1 Wh/kg. The flexibility of the composite film is owing to the binding effect of cellulose fibers as well as AgNWs. The superb electrochemical performance of the device is found to be mainly attributed to the synergistic effect between PANI/RGO/AgNWs ternary in a cushiony cellulose scaffold and porous structure of the composite.
Fabrication of cellular spheroids is critical for creating functional tissue units and investigating the mechanism of tumorigenesis, development, and intercellular and cell–matrix interactions in vitro. Herein, we developed a novel, simple, and facile method for cell spheroid fabrication by using polyacrylamide/gelatin methacrylate (PA/GelMA) hydrogel composites. Arrays of Michigan Cancer Foundation-7 (MCF-7) breast cancer cell spheroids can be easily formed by tuning the GelMA composition. The shape and size of cell spheroids can be also well controlled by regulating cell seeding density and culturing time. All these results suggested that this simple and facile platform can serve as a useful tool to generate three-dimensional (3D) cell spheroids and can be integrated within high-throughput drug screening platforms, which will be of great help in engineering functional tissue models and regenerative medicines.
Bioprinting is a technology that allows making complex tissues from the bottom-up. The need to control accurately both the resolution of the printed droplet and the precision of its positioning was reported. Using a bioink with 1 × 108 cells/mL, we present evidence that the laser-assisted bioprinter (LAB) can deposit droplets of functional mesenchymal stem cells with a resolution of 138 ± 28 μm and a precision of 16 ± 13 μm. We demonstrate that this high printing definition is maintained in three dimensions.
Porous silicon (PS) has become the focus of attention in upgrading silicon for optoelectronics. In this work, various structures were produced depending on the formation parameters by photo-electrochemical etching (PECE) process of n- and p-type silicon wafer at different time durations (5–90 mins) and different current densities (5, 15, and 20 mA/cm2) for each set of time durations. Diode lasers of 405 nm, 473 nm, and 532 nm wavelengths, each 50 mW power, were used to illuminate the surface of the samples during the etching process. The results showed that controlled porous layers were achieved by using blue laser, giving uniform structure which can make it possible to dispense with expensive methods of patterning the silicon.
