Hydrogel Formulation for Biomimetic Fibroblast Cell Culture: Exploring Effects of External Stresses and Cellular Responses.

In the process of tissue engineering, several types of stresses can influence the outcome of tissue regeneration. This outcome can be understood by designing hydrogels that mimic this process and studying how such hydrogel scaffolds and cells behave under a set of stresses. Here, a hydrogel formulation is proposed to create biomimetic scaffolds suitable for fibroblast cell culture. Subsequently, we examine the impact of external stresses on fibroblast cells cultured on both solid and porous hydrogels. These stresses included mechanical tension and altered-gravity conditions experienced during the 83rd parabolic flight campaign conducted by the European Space Agency. This study shows distinct cellular responses characterized by cell aggregation and redistribution in regions of intensified stress concentration. This paper presents a new biomimetic hydrogel that fulfills tissue-engineering requirements in terms of biocompatibility and mechanical stability. Moreover, it contributes to our comprehension of cellular biomechanics under diverse gravitational conditions, shedding light on the dynamic cellular adaptations versus varying stress environments.

Influence of storage and buffer composition on the mechanical behavior of flowing red blood cells.

On-chip study of blood flow has emerged as a powerful tool to assess the contribution of each component of blood to its overall function. Blood has indeed many functions, from gas and nutrient transport to immune response and thermal regulation. Red blood cells play a central role therein, in particular through their specific mechanical properties, which directly influence pressure regulation, oxygen perfusion, or platelet and white cell segregation toward endothelial walls. As the bloom of in-vitro studies has led to the apparition of various storage and sample preparation protocols, we address the question of the robustness of the results involving cell mechanical behavior against this diversity. The effects of three conservation media (EDTA, citrate, and glucose-albumin-sodium-phosphate) and storage time on the red blood cell mechanical behavior are assessed under different flow conditions: cell deformability by ektacytometry, shape recovery of cells flowing out of a microfluidic constriction, and cell-flipping dynamics under shear flow. The impact of buffer solutions (phosphate-buffered saline and density-matched suspension using iodixanol/Optiprep) are also studied by investigating individual cell-flipping dynamics, relative viscosity of cell suspensions, and cell structuration under Poiseuille flow. Our results reveal that storing blood samples up to 7 days after withdrawal and suspending them in adequate density-matched buffer solutions has, in most experiments, a moderate effect on the overall mechanical response, with a possible rapid evolution in the first 3 days after sample collection.

Thermotropic Liquid Crystals for Temperature Mapping.

Wound management in Space is an important factor to be considered in future Human Space Exploration. It demands the development of reliable wound monitoring systems that will facilitate the assessment and proper care of wounds in isolated environments, such as Space. One possible system could be developed using liquid crystal films, which have been a promising solution for real-time in-situ temperature monitoring in healthcare, but they are not yet implemented in clinical practice. To progress in the latter, the goal of this study is twofold. First, it provides a full characterization of a sensing element composed of thermotropic liquid crystals arrays embedded between two elastomer layers, and second, it discusses how such a system compares against non-local infrared measurements. The sensing element evaluated here has an operating temperature range of 34-38°C, and a quick response time of approximately 0.25 s. The temperature distribution of surfaces obtained using this system was compared to the one obtained using the infrared thermography, a technique commonly used to measure temperature distributions at the wound site. This comparison was done on a mimicked wound, and results indicate that the proposed sensing element can reproduce the temperature distributions, similar to the ones obtained using infrared imaging. Although there is a long way to go before implementing the liquid crystal sensing element into clinical practice, the results of this work demonstrate that such sensors can be suitable for future wound monitoring systems.

High-frequency temperature pulse-response behavior through a porous nanocomposite scaffold for measuring the uptake of biological fluids.

The measurement of biological fluid uptake into a scaffold sensor has been modeled by measuring the response of induced high-frequency temperature pulses. For this, a heat transport equation is used, developed from Extended Thermodynamics, also equivalent to Cattaneo's equation, as well as an effective thermal conductivity. The effective thermal conductivity is experimentally validated against data measurements of a carbon nanotube porous nanocomposite, embedded with silica nanoparticles. This nanocomposite serves also as the case study for the scaffold sensor. The uptake of the biological fluid in this scaffold sensor is equivalent to a change in the effective thermal conductivity, monitored by an increase of the interstitial volume fraction. By imposing a high-frequency temperature oscillation, the temperature response at the other end of the porous medium is calculated. Depending on the ratio of the relaxation time and the thermal diffusion time, the temperature response can be of oscillatory nature or of an exponential growth to an asymptotic limit. It is observed that an observed phase lag in the temperature response indicates a change in the effective thermal conductivity and thus is a criterion denoting the amount of uptake.

Digital holographic microscopy as a tool to study the thermal shape fluctuations of lipid vesicles.

The bending elasticity modulus of lipid membranes is obtained by applying for the first time, to the best of our knowledge, a novel experimental technique based on digital holographic microscopy. The fluctuations of the radius with time were extracted by tracking and measuring the optical thickness at the vesicle poles. The temporal autocorrelation function of the vesicle diameter computed for each of the studied vesicles was then fitted with the theoretical expression to deduce the membrane's tension and bending constant. For the bending elasticity modulus of SOPC bilayers, the value of (0.93 ± 0.03) × 10(-12) erg was obtained. This result is in accordance with values previously obtained by means of other conventional methods for the same type of lipid membrane in the presence of sugar molecules in aqueous medium. The obtained results encourage the future development of the digital holographic microscopy as a technique suitable for the measurement of the bending elasticity of lipid membranes.

Satisfaction and complications after lower body lift with autologous gluteal augmentation by island fat flap: 55 case series over 3 years.

BACKGROUND: Major weight loss causes body deformities. Lower circumferential dermolipectomy with autologous gluteal augmentation by a fat island flap can restore a part of the body contour, but this procedure is associated with a high incidence of complications. The aim of this study was to analyse the benefit/risk ratio and the patients' satisfaction. METHODS: All patients who underwent this procedure at the Nancy University Hospital over a 3-year period (between January 2010 and 2013) were reviewed; the complications were analysed and the patients' satisfaction rated. RESULTS: A total of 55 patients were included with a mean age of 41.0 years. The average body mass index of the patients was 28.2 kg/m² with a mean weight of 76.8 kg at the time of the procedure and a mean weight reduction of 49.6 kg. The mean operative time was 4.85 h. The average hospital stay was 6.1 days. The average haemoglobin loss was 3.0 g/dl, and 12 (21.8%) patients required a blood transfusion. Of the total number of patients, 22 (40%) developed at least one complication, including six (10.9%) major complications. Fifty-two patients answered the questionnaire; 49 (94.2%) patients would go through this procedure again. The overall satisfaction was rated as excellent by 29 (55.8%) patients and as pleasing by 22 (42.3%). The outcome was judged as excellent or pleasing for the abdomen by 29 (55.8%) and 20 (38.35%) patients, respectively, and for the buttocks by 17 (32.7%) and 29 (55.8%) patients, respectively. The quality of life was rated better after than before the intervention by 49 (94.2%) patients. CONCLUSION: Despite a high complication rate, the majority of patients confirmed that they would opt for this procedure again, showing an improvement in their quality of life with an aesthetic and functional benefit. LEVEL OF EVIDENCE: III.

Liposuction-assisted medial brachioplasty after massive weight loss: an efficient procedure with a high functional benefit.

BACKGROUND: Brachioplasty frequently offers functional benefits but results in poor aesthetic scars and a relatively high complication rate. The authors describe the complications and risk factors inherent in liposuction-assisted medial brachioplasty and assess patient satisfaction with the functional and aesthetic benefits. METHODS: A 5-year retrospective study was performed that included all patients who underwent liposuction-assisted medial brachioplasty. Complications were reviewed and analyzed by aesthetic and nonaesthetic categories, and patient satisfaction was rated. RESULTS: Sixty-six patients were included (mean age, 44.4 years). The average body mass index was 30.2 kg/m; mean weight reduction was 50.72 kg. Thirty-seven patients (56.1 percent) developed at least one complication, including six (9.1 percent) with a nonaesthetic complication versus 31 (47.0 percent) with an aesthetic complication. Complications were significantly associated with a longer operative time (p = 0.015), 233 minutes in the complication group versus 164 minutes in the no-complication group. Fifty-three patients answered the questionnaire. Forty-six (86.8 percent) stated that they would undergo this intervention again. Overall satisfaction was reported as excellent for 12 patients (22.6 percent) and pleasing for 24 (45.3 percent). All patients rated the functional outcome superior or equal to the aesthetic outcome. Quality of life was estimated to be better after than before the intervention for 41 patients (77.4 percent). CONCLUSIONS: Liposuction-assisted medial brachioplasty is a safe and efficient technique. It offers a functional benefit with a low nonaesthetic complication rate. Despite the inherent scars, the majority of patients would undergo this intervention again because of an important satisfaction rate and improvement in quality of life. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, III.

Fully automated digital holographic processing for monitoring the dynamics of a vesicle suspension under shear flow.

We investigate the dynamics of a vesicle suspension under shear flow between plates using DHM with a spatially reduced coherent source. Holograms are grabbed at a frequency of 24 frames/sec. The distribution of the vesicle suspension is obtained after numerical processing of the digital holograms sequence resulting in a 4D distribution. Obtaining this distribution is not straightforward and requires special processing to automate the analysis. We present an original method that fully automates the analysis and provides distributions that are further analyzed to extract physical properties of the fluid. Details of the numerical implementation, as well as sample experimental results are presented.

Three-dimensional Marangoni cell in self-induced evaporating cooling unveiled by digital holographic microscopy.

A digital holographic microscope has been used to trace the trajectory of a tracer particle inside the liquid phase of an evaporating meniscus formed at the mouth of a 1-mm2 borosilicate tube filled with ethanol. The Marangoni flow cells are generated by the self-induced differential evaporating cooling along the meniscus interface that creates gradients of surface tension which drive the convection. The competition between surface tension and gravity forces along the curved meniscus interface disrupts the symmetry due to surface tension alone. This distorts the shape of the toroidal Marangoni vortex. Thermocapillary instabilities of the evaporating meniscus are reported by analyzing the trajectories of the tracer particle. It is found that the trajectory of the tracer particle makes different three-dimensional loops and every four loops it returns to the first loop. By analyzing several loops it was found that the characteristic frequency of the periodic oscillatory motion is around 0.125 Hz.

FVIIIra, CD15, and tryptase performance in the diagnosis of skin stab wound vitality in forensic pathology.

The timing of skin wounds is one of the most challenging problems in forensic pathology. In the first minutes or hours after infliction, histological examination fails to determine whether a wound was sustained before or after death. The aim of this study was to evaluate the use of three immunohistochemical markers (FVIIIra, CD15, and tryptase) for the interpretation of the timing of cutaneous stab wounds. We evaluated these markers in intravital wounds from autopsy cases (n = 12) and surgical specimens (n = 58). As controls, we used normal skin samples from autopsies (n = 8) and an original ex vivo surgical human model of recent postmortem wounds (n = 24). We found overexpression of FVIIIra in 100 % of vital wounds, but also in 53 % of the controls. The number of CD15-positive cells was higher in wound margins than in internal controls (p < 0.0001) and was significantly correlated with the time interval between incision and devascularization (p = 0.0005; minimal time for positivity, 9 min). Using the anti-tryptase antibody, we found that the mast cell degranulation rate was higher in wound margins (p < 0.0001) and correlated with the time interval (minimal time, 1 min). The sensitivity and specificity for the diagnosis of vitality were respectively 100 and 47 % for FVIIIra, 47 and 100 % for CD15, and 60 and 100 % for tryptase. The inter-observer agreement coefficients were 0.68 for FVIIIra, 0.90 for CD15, and 0.46 for tryptase. Finally, we demonstrated that these markers were not reliable in putrefied or desiccated specimens. In conclusion, CD15 and tryptase, but not FVIIIra, may be useful markers for differentiating recent antemortem from postmortem injuries.

Lift and down-gradient shear-induced diffusion in red blood cell suspensions.

The distribution of red blood cells (RBCs) in a confined channel flow is inhomogeneous and shows a marked depletion near the walls due to a competition between migration away from the walls and shear-induced diffusion resulting from interactions between particles. We investigated the lift of RBCs in a shear flow near a wall and measured a significant lift velocity despite the tumbling motion of cells. We also provide values for the collective and anisotropic shear-induced diffusion of a cloud of RBCs, both in the direction of shear and in the direction of vorticity. A generic down-gradient subdiffusion characterized by an exponent 1/3 is highlighted.

Automated three-dimensional detection and classification of living organisms using digital holographic microscopy with partial spatial coherent source: application to the monitoring of drinking water resources.

In this paper, we investigate the use of a digital holographic microscope working with partially coherent spatial illumination for an automated detection and classification of living organisms. A robust automatic method based on the computation of propagating matrices is proposed to detect the 3D position of organisms. We apply this procedure to the evaluation of drinking water resources by developing a classification process to identify parasitic protozoan Giardia lamblia cysts among two other similar organisms. By selecting textural features from the quantitative optical phase instead of morphological ones, a robust classifier is built to propose a new method for the unambiguous detection of Giardia lamblia cyst that present a critical contamination risk.

Shape diagram of vesicles in Poiseuille flow.

Soft bodies flowing in a channel often exhibit parachutelike shapes usually attributed to an increase of hydrodynamic constraint (viscous stress and/or confinement). We show that the presence of a fluid membrane leads to the reverse phenomenon and build a phase diagram of shapes-which are classified as bullet, croissant, and parachute-in channels of varying aspect ratio. Unexpectedly, shapes are relatively wider in the narrowest direction of the channel. We highlight the role of flow patterns on the membrane in this response to the asymmetry of stress distribution.

Fast measurements of concentration profiles inside deformable objects in microflows with reduced spatial coherence digital holography.

We investigate the use of a digital holographic microscope working with partially coherent spatial illumination to study concentration profiles inside confined deformable bodies flowing in microchannels. The studied phenomenon is rapidly changing in time and requires the recording of the complete holographic information for every frame. For this purpose, we implemented one of the classical methods of off-axis digital holography: the Fourier method. Digital holography allows one to numerically investigate a volume by refocusing the different planes of depth, allowing one to locate the objects under investigation in three dimensions. Furthermore, the phase is directly related to the refractive index, thus to the concentration inside the body. Based on simple symmetry assumptions, we present an original method for determining the concentration profiles inside deformable objects in microconfined flows. Details of the optical and numerical implementation, as well as exemplative experimental results are presented.

Surgical options for beating-heart aortic valve replacement in patients with patent coronary artery bypass.

BACKGROUND AND AIM OF THE STUDY: The study aim was to assess the surgical options and advantages of beating-heart aortic valve replacement (AVR) in patients with patent coronary artery bypasses. METHODS: In this prospective study, conducted between January and August 2006, four consecutive patients (mean age 77.5 +/- 6.6 years) each with patent coronary artery bypasses, underwent beating-heart AVR using two specific methods of myocardial perfusion based on the origin and status of the grafts, as assessed by preoperative angiography. Pre-operatively, all patients were in NYHA functional class III, and each received an aortic valve bioprosthesis. RESULTS: There were no hospital deaths. The mean duration of ICU stay was 3.2 +/- 1.3 days. One patient presented with transitory atrial fibrillation. At discharge, echocardiography confirmed normally functioning bioprostheses, with no significant transprosthetic gradient. CONCLUSION: Beating-heart AVR with patent coronary artery bypasses using continuous myocardial perfusion is a reliable, simple and effective technique to reduce the risks of graft and myocardial injuries, and to achieve optimal preservation of the hypertrophic myocardium with coronary artery disease.

Partial spatial coherence effects in digital holographic microscopy with a laser source.

We investigate a digital holographic microscope that permits us to modify the spatial coherence state of the sample illumination by changing the spot size of a laser beam on a rotating ground glass. Out-of-focus planes are refocused by digital holographic reconstruction with numerical implementation of the Kirchhoff-Fresnel integral. The partial coherence nature of the illumination reduces the coherent artifact noise with respect to fully coherent illumination. The investigated configuration allows the spatial coherence state to be changed without modifying the illumination level of the sample. The effect of the coherence state on the digital holographic reconstruction is theoretically and experimentally evaluated. We also show how multiple reflection interferences are limited by the use of reduced spatial coherent illumination.

Reduction of the correlation sensitivity to the changes of the input illumination by a post processing based on the correlation statistics.

Linear-correlation amplitude changes when the intensity level of the input image is modified. As recognition is often based on the correlation-peak level, a change of the input illumination may result in a false recognition. We propose an illumination-change compensation by a post processing of the correlation distribution that is based on statistical measures of the correlation histograms. The theoretical background and simulation results are provided in the frame of an actual application in biology.