Editorial

3 pages, 154 KiB

Open AccessEditorial

Experimental and Numerical Studies in Biomedical Engineering

by Spiros V. Paras and Athanasios G. Kanaris

Fluids 2019, 4(2), 106; https://doi.org/10.3390/fluids4020106 - 06 Jun 2019

Cited by 1 | Viewed by 2525

The term “biomedical engineering” refers to the application of the principles and problem-solving techniques of engineering to biology and medicine [...] Full article

(This article belongs to the Special Issue Experimental and Numerical Studies in Biomedical Engineering)

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15 pages, 2700 KiB

Open AccessArticle

Computational Study of the Interaction of a PEGylated Hyperbranched Polymer/Doxorubicin Complex with a Bilipid Membrane

by Prodromos Arsenidis and Kostas Karatasos

Fluids 2019, 4(1), 17; https://doi.org/10.3390/fluids4010017 - 24 Jan 2019

Cited by 2 | Viewed by 2266

Abstract

Fully atomistic molecular dynamics simulations are employed to study in detail the interactions between a complex comprised by a PEGylated hyperbranched polyester (HBP) and doxorubicin molecules, with a model dipalmitoylphosphatidylglycerol membrane in an aqueous environment. The effects of the presence of the lipid [...] Read more.

Fully atomistic molecular dynamics simulations are employed to study in detail the interactions between a complex comprised by a PEGylated hyperbranched polyester (HBP) and doxorubicin molecules, with a model dipalmitoylphosphatidylglycerol membrane in an aqueous environment. The effects of the presence of the lipid membrane in the drug molecules’ spatial arrangement were examined in detail and the nature of their interaction with the latter were discussed and quantified where possible. It was found that a partial migration of the drug molecules towards the membrane’s surface takes place, driven either by hydrogen-bonding (for the protonated drugs) or by hydrophobic interactions (for the neutral drug molecules). The clustering behavior of the drug molecules appeared to be enhanced in the presence of the membrane, while the development of a charge excess close to the surface of the hyperbranched polymer and of the lipid membrane was observed. The uneven charge distribution created an effective overcharging of the HBP/drug complex and the membrane/drug surface. The translational motion of the drug molecules was found to be strongly affected by the presence of the membrane. The extent of the observed changes depended on the charge of the drug molecule. The build-up of the observed charge excesses close to the surface of the polymeric host and the membrane, together with the changes in the diffusional behavior of the drug molecules are of particular interest. Both phenomena could be important at the latest stages of the liposomal disruption and the release of the drug cargo in formulations based on relevant liposomal carriers. Full article

(This article belongs to the Special Issue Experimental and Numerical Studies in Biomedical Engineering)

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17 pages, 7370 KiB

Open AccessArticle

Fluid-Structure Interaction in Abdominal Aortic Aneurysms: Effect of Haematocrit

by Yorgos G. Stergiou, Athanasios G. Kanaris, Aikaterini A. Mouza and Spiros V. Paras

Fluids 2019, 4(1), 11; https://doi.org/10.3390/fluids4010011 - 14 Jan 2019

Cited by 23 | Viewed by 5764

Abstract

The Abdominal Aortic Aneurysm (AAA) is a local dilation of the abdominal aorta and it is a cause for serious concern because of the high mortality associated with its rupture. Consequently, the understanding of the phenomena related to the creation and the progression [...] Read more.

The Abdominal Aortic Aneurysm (AAA) is a local dilation of the abdominal aorta and it is a cause for serious concern because of the high mortality associated with its rupture. Consequently, the understanding of the phenomena related to the creation and the progression of an AAA is of crucial importance. In this work, the complicated interaction between the blood flow and the AAA wall is numerically examined using a fully coupled Fluid-Structure Interaction (FSI) method. The study investigates the possible link between the dynamic behavior of an AAA and the blood viscosity variations attributed to the haematocrit value, while it also incorporates the pulsatile blood flow, the non-Newtonian behavior of blood and the hyperelasticity of the arterial wall. It was found that blood viscosity has no significant effect on von Mises stress magnitude and distribution, whereas there is a close relation between the haematocrit value and the Wall Shear Stress (WSS) magnitude in AAAs. This WSS variation can possibly alter the mechanical properties of the arterial wall and increase its growth rate or even its rupture possibility. The relationship between haematocrit and dynamic behavior of an AAA can be helpful in designing a patient specific treatment. Full article

(This article belongs to the Special Issue Experimental and Numerical Studies in Biomedical Engineering)

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15 pages, 5526 KiB

Open AccessArticle

Free-Flowing Shear-Thinning Liquid Film in Inclined μ-Channels

by Angeliki T. Koupa, Yorgos G. Stergiou and Aikaterini A. Mouza

Fluids 2019, 4(1), 8; https://doi.org/10.3390/fluids4010008 - 10 Jan 2019

Cited by 1 | Viewed by 4000

Abstract

Among the most important variables in the design of falling film microreactors (FFMRs) is the liquid film thickness as well as the gas/liquid interfacial area, which dictate the mass and heat transfer rates. In a previous work conducted in our lab the characteristics [...] Read more.

Among the most important variables in the design of falling film microreactors (FFMRs) is the liquid film thickness as well as the gas/liquid interfacial area, which dictate the mass and heat transfer rates. In a previous work conducted in our lab the characteristics of a free-falling Newtonian liquid film have been studied and appropriate correlations have been proposed. In this work the geometrical characteristics of a non-Newtonian shear thinning liquid, flowing in an inclined open microchannel, have been experimentally investigated and design correlations that can predict with reasonable accuracy the features of a FFMR have been proposed. The test section used was an open μ-channel with square cross section (W_O = 1200 μm) made of brass which can be set to various inclination angles. The liquid film characteristics were measured by a non-intrusive technique that is based on the features of a micro Particle Image Velocimetry (μ-PIV) system. Relevant computational fluid dynamics (CFD) simulations revealed that the volume average dynamic viscosity over the flow domain is practically the same as the corresponding asymptotic viscosity value, which can thus be used in the proposed design equations. Finally, a generalized algorithm for the design of FFMRs, containing non-Newtonian shear thinning liquids, is suggested. Full article

(This article belongs to the Special Issue Experimental and Numerical Studies in Biomedical Engineering)

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14 pages, 2856 KiB

Open AccessArticle

Advancing Chemical Risk Assessment through Human Physiology-Based Biochemical Process Modeling

by Dimosthenis Sarigiannis and Spyros Karakitsios

Fluids 2019, 4(1), 4; https://doi.org/10.3390/fluids4010004 - 04 Jan 2019

Cited by 4 | Viewed by 2853

Abstract

Physiology-Based BioKinetic (PBBK) models are of increasing interest in modern risk assessment, providing quantitative information regarding the absorption, metabolism, distribution, and excretion (ADME). They focus on the estimation of the effective dose at target sites, aiming at the identification of xenobiotic levels that [...] Read more.

Physiology-Based BioKinetic (PBBK) models are of increasing interest in modern risk assessment, providing quantitative information regarding the absorption, metabolism, distribution, and excretion (ADME). They focus on the estimation of the effective dose at target sites, aiming at the identification of xenobiotic levels that are able to result in perturbations to the biological pathway that are potentially associated with adverse outcomes. The current study aims at the development of a lifetime PBBK model that covers a large chemical space, coupled with a framework for human biomonitoring (HBM) data assimilation. The methodology developed herein was demonstrated in the case of bisphenol A (BPA), where exposure analysis was based on European HBM data. Based on our calculations, it was found that current exposure levels in Europe are below the temporary Tolerable Daily Intake (t-TDI) of 4 μg/kg_bw/day proposed by the European Food Safety Authority (EFSA). Taking into account age-dependent bioavailability differences, internal exposure was estimated and compared with the biologically effective dose (BED) resulting from translating the EFSA temporary total daily intake (t-TDI) into equivalent internal dose and an alternative internal exposure reference value, namely biological pathway altering dose (BPAD); the use of such a refined exposure metric, showed that environmentally relevant exposure levels are below the concentrations associated with the activation of biological pathways relevant to toxicity based on High Throughput Screening (HTS) in vitro studies. Full article

(This article belongs to the Special Issue Experimental and Numerical Studies in Biomedical Engineering)

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11 pages, 1562 KiB

Open AccessArticle

A Computational Model for the Analysis of Spreading of Viscoelastic Droplets over Flat Surfaces

by Aleck H. Alexopoulos and Costas Kiparissides

Fluids 2018, 3(4), 78; https://doi.org/10.3390/fluids3040078 - 22 Oct 2018

Cited by 3 | Viewed by 2889

Abstract

The spreading of viscous and viscoelastic fluids on flat and curved surfaces is an important problem in many industrial and biomedical processes. In this work the spreading of a linear viscoelastic fluid with changing rheological properties over flat surfaces is investigated via a [...] Read more.

The spreading of viscous and viscoelastic fluids on flat and curved surfaces is an important problem in many industrial and biomedical processes. In this work the spreading of a linear viscoelastic fluid with changing rheological properties over flat surfaces is investigated via a macroscopic model. The computational model is based on a macroscopic mathematical description of the gravitational, capillary, viscous, and elastic forces. The dynamics of droplet spreading are determined in sessile and pendant configurations for different droplet extrusion or formation times for a hyaluronic acid solution undergoing gelation. The computational model is employed to describe the spreading of hydrogel droplets for different extrusion times, droplet volumes, and surface/droplet configurations. The effect of extrusion time is shown to be significant in the rate and extent of spreading. Full article

(This article belongs to the Special Issue Experimental and Numerical Studies in Biomedical Engineering)

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13 pages, 3730 KiB

Open AccessArticle

A Simplified Model for Predicting Friction Factors of Laminar Blood Flow in Small-Caliber Vessels

by Aikaterini A. Mouza, Olga D. Skordia, Ioannis D. Tzouganatos and Spiros V. Paras

Fluids 2018, 3(4), 75; https://doi.org/10.3390/fluids3040075 - 19 Oct 2018

Cited by 9 | Viewed by 5345 | Correction

Abstract

The aim of this study was to provide scientists with a straightforward correlation that can be applied to the prediction of the Fanning friction factor and consequently the pressure drop that arises during blood flow in small-caliber vessels. Due to the small diameter [...] Read more.

The aim of this study was to provide scientists with a straightforward correlation that can be applied to the prediction of the Fanning friction factor and consequently the pressure drop that arises during blood flow in small-caliber vessels. Due to the small diameter of the conduit, the Reynolds numbers are low and thus the flow is laminar. This study has been conducted using Computational Fluid Dynamics (CFD) simulations validated with relevant experimental data, acquired using an appropriate experimental setup. The experiments relate to the pressure drop measurement during the flow of a blood analogue that follows the Casson model, i.e., an aqueous Glycerol solution that contains a small amount of Xanthan gum and exhibits similar behavior to blood, in a smooth, stainless steel microtube (L = 50 mm and D = 400 μm). The interpretation of the resulting numerical data led to the proposal of a simplified model that incorporates the effect of the blood flow rate, the hematocrit value (35–55%) and the vessel diameter (300–1800 μm) and predicts, with better than ±10% accuracy, the Fanning friction factor and consequently the pressure drop during laminar blood flow in healthy small-caliber vessels. Full article

(This article belongs to the Special Issue Experimental and Numerical Studies in Biomedical Engineering)

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16 pages, 4141 KiB

Open AccessArticle

Pipette Petri Dish Single-Cell Trapping (PP-SCT) in Microfluidic Platforms: A Passive Hydrodynamic Technique

by Vigneswaran Narayanamurthy, Tze Pin Lee, Al’aina Yuhainis Firus Khan, Fahmi Samsuri, Khairudin Mohamed, Hairul Aini Hamzah and Madia Baizura Baharom

Fluids 2018, 3(3), 51; https://doi.org/10.3390/fluids3030051 - 24 Jul 2018

Cited by 5 | Viewed by 4163

Abstract

Microfluidics-based biochips play a vital role in single-cell research applications. Handling and positioning of single cells at the microscale level are an essential need for various applications, including genomics, proteomics, secretomics, and lysis-analysis. In this article, the pipette Petri dish single-cell trapping (PP-SCT) [...] Read more.

Microfluidics-based biochips play a vital role in single-cell research applications. Handling and positioning of single cells at the microscale level are an essential need for various applications, including genomics, proteomics, secretomics, and lysis-analysis. In this article, the pipette Petri dish single-cell trapping (PP-SCT) technique is demonstrated. PP-SCT is a simple and cost-effective technique with ease of implementation for single cell analysis applications. In this paper a wide operation at different fluid flow rates of the novel PP-SCT technique is demonstrated. The effects of the microfluidic channel shape (straight, branched, and serpent) on the efficiency of single-cell trapping are studied. This article exhibited passive microfluidic-based biochips capable of vertical cell trapping with the hexagonally-positioned array of microwells. Microwells were 35 μm in diameter, a size sufficient to allow the attachment of captured cells for short-term study. Single-cell capture (SCC) capabilities of the microfluidic-biochips were found to be improving from the straight channel, branched channel, and serpent channel, accordingly. Multiple cell capture (MCC) was on the order of decreasing from the straight channel, branch channel, and serpent channel. Among the three designs investigated, the serpent channel biochip offers high SCC percentage with reduced MCC and NC (no capture) percentage. SCC was around 52%, 42%, and 35% for the serpent, branched, and straight channel biochips, respectively, for the tilt angle, θ values were between 10–15°. Human lung cancer cells (A549) were used for characterization. Using the PP-SCT technique, flow rate variations can be precisely achieved with a flow velocity range of 0.25–4 m/s (fluid channel of 2 mm width and 100 µm height). The upper dish (UD) can be used for low flow rate applications and the lower dish (LD) for high flow rate applications. Passive single-cell analysis applications will be facilitated using this method. Full article

(This article belongs to the Special Issue Experimental and Numerical Studies in Biomedical Engineering)

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16 pages, 2374 KiB

Open AccessArticle

Comparative Study of PEGylated and Conventional Liposomes as Carriers for Shikonin

by Stella K. Tsermentseli, Konstantinos N. Kontogiannopoulos, Vassilios P. Papageorgiou and Andreana N. Assimopoulou

Fluids 2018, 3(2), 36; https://doi.org/10.3390/fluids3020036 - 26 May 2018

Cited by 39 | Viewed by 4987

Abstract

Liposomes are considered to be one of the most successful drug delivery systems. They apply nanotechnology to potentiate the therapeutic efficacy and reduce the toxicity of conventional medicines. Shikonin and alkannin, a pair of chiral natural naphthoquinone compounds, derived from Alkanna and Lithospermum [...] Read more.

Liposomes are considered to be one of the most successful drug delivery systems. They apply nanotechnology to potentiate the therapeutic efficacy and reduce the toxicity of conventional medicines. Shikonin and alkannin, a pair of chiral natural naphthoquinone compounds, derived from Alkanna and Lithospermum species, are widely used due to their various pharmacological activities, mainly wound healing, antioxidant, anti-inflammatory and their recently established antitumor activity. The purpose of this study was to prepare conventional and PEGylated shikonin-loaded liposomal formulations and measure the effects of different lipids and polyethylene glycol (PEG) on parameters related to particle size distribution, the polydispersity index, the zeta potential, drug-loading efficiency and the stability of the prepared formulations. Three types of lipids were assessed (1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC), 1,2-Distearoyl-sn-glycero-3-phosphocholine (DSPC) and 1,2-distearoyl-sn-glycero-3-phospho-rac-(1-glycerol) (DSPG)), separately and in mixtures, forming anionic liposomes with good physicochemical characteristics, high entrapment efficiencies (varying from 56.5 to 89.4%), satisfactory in vitro release profiles and good physical stability. The addition of the negatively charged DSPG lipids to DOPC, led to an increment in the drug’s incorporation efficiency and reduced the particle size distribution. Furthermore, the shikonin–loaded PEGylated sample with DOPC/DSPG, demonstrated the most satisfactory characteristics. These findings are considered promising and could be used for further design and improvement of such formulations. Full article

(This article belongs to the Special Issue Experimental and Numerical Studies in Biomedical Engineering)

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