In order to describe temperature-dependent cell osmotic behaviors in a more reliable method, a novel mathematical mass transfer model coupled with dynamic temperature change has been established based on the combination of a time domain to temperature domain transformation equation and a constant temperature mass transfer model. This novel model is numerically simulated under multiple temperature changing rates and extracellular osmolarities. A microfluidic system that can achieve single-cell osmotic behavior observation and provide dynamic and swift on-chip temperature control was built and tested in this paper. Utilizing the temperature control system, the on-chip heating processes are recorded and then described as polynomial time-temperature relationships. These dynamic temperature changing profiles were performed by obtaining cell membrane properties by parameter fitting only one set of testing experimental data to the mathematical model with a constant temperature changing rate. The numerical modeling results show that predicting the osmotic cell volume change using selected dynamic temperature profiles is more suitable for studies concerning cell membrane permeability determination and cryopreservation process than tests using constant temperature changing rates.

An integrated microfluidic device with active cooling and heating systems was developed in aiming a precise and rapid temperature control in the range between 2 degrees C and 37 degrees C. The platform, which consisted of a cooling chamber, a microheater, and a temperature sensor, achieved an active feedback control of on-chip local temperature. Multiphysics simulation was conducted in the coupled modeling of heat transfer, fluid flow, and Joule heating. These modeling and simulation validated the design parameters to achieve a precise and quick control of on-chip local temperature control. The main principle of the design is to enhance the external heat transfer by utilizing micro-channel array on the chip surface and increase the sample surface versus its volume by holding the sample inside the system as an ultra-thin film. Using the precooled saturated calcium chloride aqueous solution as the coolant, and the on-chip microheater as the heating unit, the temperature was able to be precisely adjusted, and meanwhile, the temperature was sensed by a thermal sensor at the region of interest. We demonstrated an actual temperature control and manipulation of the developed microfluidic cooling/heating system. The recorded temperature data showed that the developed integrated platform offered the capability of manipulating on-chip localized temperature ranging from 2 degrees C to 37 degrees C with active cooling/heating, especially for the temperature range from 2 degrees C to room temperature chosen due to typical cytotoxic issues with additive cryoprotective agents (CPAs). Additionally, this device provided valuable tools for studying temperature-dependent biological and chemical processes at microscale, for example, the determination of permeability of the cell membrane to water and CPAs in cryobiology study. (C) 2018 Published by Elsevier Ltd.

We develop a temperature controllable microfluidic device for the accurate measurement of temperature dependent interfacial tensions between two immiscible liquids. A localized temperature control system is integrated with the microfluidic platform to maintain an accurate temperature inside the device. The temperature uniformity and sensitivity are verified by both simulation and experimental results. Temperature dependent interfacial tensions are measured dynamically and rapidly, relying on quantitative analysis of the deformation and retraction dynamics of droplets under extensional flow. Our microfluidic tensiometry offers the capability of measuring temperature dependent interfacial tensions with precise and systematic temperature control in the range of room temperature to 70 °C, which is valuable for studying transient interfacial dynamics, interfacial reactions, and the surfactant adsorption process.

We developed an integrated microfluidic platform for instantaneous flow and localized temperature control. The platform consisted of a flow-focusing region for sample delivery and a cross-junction region embedded with a microheater for cell trapping and localized temperature control by using an active feedback control system. We further used it to measure the membrane transport properties of Jurkat cells, including the osmotically inactive cell volume (Vb) and cell membrane permeabilities to water (Lp) and to cryoprotective agent (CPA) solutions (dimethyl sulfoxide (DMSO) in this study) (PS) at various temperatures (room temperature, 30 °C, and 37 °C). Such characteristics of cells are of great importance in many applications, especially in optimal cryopreservation. With the results, the corresponding activation energy for water and CPA transport was calculated. The comparison of the results from the current study with reference data indicates that the developed platform is a reliable tool for temperature-dependent cell behavior study, which provides valuable tools for general cell manipulation applications with precise temperature control.

Background Understanding how leukocytes in the cervicovaginal and colorectal mucosae respond to pathogens, and how medical interventions affect these responses, is important for developing better tools to prevent HIV and other sexually transmitted infections. An effective cryopreservation protocol for these cells following their isolation will make studying them more feasible. Methods and findings To find an optimal cryopreservation protocol for mucosal mononuclear leukocytes, we compared cryopreservation media and procedures using human vaginal leukocytes and confirmed our results with endocervical and colorectal leukocytes. Specifically, we measured the recovery of viable vaginal T cells and macrophages after cryopreservation with different cryopreservation media and handling procedures. We found several cryopreservation media that led to recoveries above 75%. Limiting the number and volume of washes increased the fraction of cells recovered by 10-15%, possibly due to the small cell numbers in mucosal samples. We confirmed that our cryopreservation protocol also works well for both endocervical and colorectal leukocytes. Cryopreserved leukocytes had slightly increased cytokine responses to antigenic stimulation relative to the same cells tested fresh. Additionally, we tested whether it is better to cryopreserve endocervical cells on the cytobrush or in suspension. Conclusions Leukocytes from cervicovaginal and colorectal tissues can be cryopreserved with good recovery of functional, viable cells using several different cryopreservation media. The number and volume of washes has an experimentally meaningful effect on the percentage of cells recovered. We provide a detailed, step-by-step protocol with best practices for cryopreservation of mucosal leukocytes.

To study mucosal immunity and conduct HIV vaccine trials, it is important to be able to cryopreserve mucosal specimens and recover them in functional viable form. Obtaining a good recovery depends, in part, on cooling the cells at the appropriate rate, which is determined by the rate of water transport across the cell membrane during the cooling process. In this study, the cell membrane permeabilities to water at subzero temperatures of human vaginal mucosal T cells and macrophages were measured using the differential scanning calorimetry method proposed by Devireddy et al. in 1998. Thermal histograms were measured before and after cell lysis using a Slow-Fast-Fast-Slow cooling program. The difference between the thermal histograms of the live intact cells and the dead lysed cells was used to calculate the temperature-dependent cell membrane permeability at subzero temperatures, which was assumed to follow the Arrhenius relationship, [Formula: see text], where Lpg is the permeability to water at the reference temperature (273.15 K). The results showed that Lpg = 0.0209 ± 0.0108 μm/atm/min and Ea = 41.5 ± 11.4 kcal/mol for T cells and Lpg = 0.0198 ± 0.0102 μm/atm/min and Ea = 38.2 ± 10.4 kcal/mol for macrophages, respectively, in the range 0°C to -40°C (mean ± standard deviation). Theoretical simulations predicted that the optimal cooling rate for both T cells and macrophages was about -3°C/min, which was proven by preliminary immune cell cryopreservation experiments.

Cryopreservation of specimens taken from the genital tract of women is important for studying mucosa] immunity during HIV prevention trials. However, it is unclear whether the current, empirically developed cryopreservation procedures for peripheral blood cells are also ideal for genital specimens. The optimal cryopreservation protocol depends on the cryobiological features of the cells. Thus, we obtained tissue specimens from vaginal repair surgeries, isolated and flow cytometry-purified immune cells, and determined fundamental cryobiological characteristics of vaginal CD3(+) T cells and CD14(+) macrophages using a microfluidic device. The osmotically inactive volumes of the two cell types (V-b) were determined relative to the initial cell volume (V-0) by exposing the cells to hypotonic and hypertonic saline solutions, evaluating the equilibrium volume, and applying the Boyle van't Hoff relationship. The cell membrane permeability to water (L-p) and to four different cryoprotective agent (CPA) solutions (P-s) at room temperature were also measured. Results indicated V-b values of 0.516 V-0 and 0.457 V-0 for mucosa] T cells and macrophages, respectively. L-p values at room temperature were 0.196 and 0.295 pm/miniatm for T cells and macrophages, respectively. Both cell types had high P-s values for the three CPAs, dimethyl sulfoxide (DMSO), propylene glycol (PG) and ethylene glycol (EG) (minimum of 0.418 x 10(-3) cm/min), but transport of the fourth CPA, glycerol, occurred 50-150 times more slowly. Thus, DMSO, PG, and EG are better options than glycerol in avoiding severe cell volume excursion and osmotic injury during CPA addition and removal for cryopreservation of human vaginal immune cells. Published by Elsevier Inc. This is an open access article under the CC BY license.

We developed an integrated microfluidic platform for instantaneous flow and localized temperature control.

In cell/tissue cryopreservation, cryoprotective agents (CPAs) should be added before freezing and removed after thawing. Nowadays people mainly apply centrifugation for CPA removal, which may cause many problems. Meanwhile, a simple and cheap method for real-time monitoring of the residual CPA concentration during processing remains an unfilled need. In this work, a “dilution-filtration” system with hollow fiber dialyzer was implemented and approved to remove dimethyl sulfoxide (Me2SO) effectively. Compared to other methods (centrifugation and microfluidic approach), this one holds advantages of low time and labor consumption, low osmotic injury to the cells, high effectiveness, ease to control the final suspension volume and low risk of contamination. The “dilution-filtration” system can also be easily modified for CPA addition and cell suspension volume control (concentration or dilution of cell suspension). Meanwhile, a method of electrical conductivity (EC) measurement was applied to monitor the residual CPA concentration. The results showed EC measurements of waste solution can convey the CPA concentrations in cell suspension. This validates the feasibility of a safer and easier way to on-line and real-time monitoring of CPA concentration in cell suspension by measuring the EC of waste solution.

Neural repair and regeneration for tissue engineering is the most promising strategy for treating human brain neurological diseases. Main bottle neck of the clinical therapy is that no ideal scaffold biomaterials as vehicle of neural stem cells (NSCs) and growth factors have been developed yet, even for the clinical tests. To solve this problem, a lot of work has been done and numerous kinds of biomaterials have been studied. The interaction between NSCs and biomaterials, especially the regulation of NSCs by materials, plays an essential role during the scaffold biomaterial selection. The article gives an overview on the recent progresses on regulation of NSCs by biomaterial and shows some recent patents regarding the progress in the field. Keywords: Tissue engineering, neural repair, scaffold biomaterial, signal pathway, neural stem cells (NSCs), central nervous systems, cerebral ischemia, spinal cord injury (SCI), traumatic brain injury, neurodegenerative disorders, Alzheimer's disease, biocompatible, immunologically inert, conducting, biodegradable, infection-resistant, synthetic biomaterials, Natural biomaterials, inflammation-resistance, nylon, silica gel, polyurethane, biodegradable poly-hydroxyacetic acid, poly-lactic acid, Poly (DLlactide-co-glycolide acid, bioactive factors, Chitosan, poly (beta-(1, 4)-2-amino-2-deoxy-D-glucose, poly (beta-(1, 4)-D-glucosamine, neurotrophin-3 (NT-3), oligodendrocytes, Chitosan films (Chi-F), chitosan porous scaffolds (Chi-PS), chitosan multimicrotubule conduits (Chi-MC), methacrylamide chitosan (MAC), Young's elastic modulus (E-Y), Gelatin, Collagen Scaffolds, basic fibroblast growth factor (bFGF), synapses, Seeding human embryonic stem cell-derived NPC (hESC-NPC), CNTF (ciliary neurotrophic factor)-collagen gel-controlled delivery system, Extracellular Matrix (ECM), fibronectin, laminin, 3-D matrix adhesion, growth factor-reduced Matrigel (gfrMG), tyrosine hydroxylase (TH), dopaminergic neurons, Hyaluronic Acid (HA) Hydrogel, photoencapsulated, Self-assembling peptide, Self-assembling peptide nanofiber scaffold (SAPNS), glial cell adhesion, cytokines, regenerative medicine, mood disorders, manic depressive disorders, polyurethane (PU), polyhydroxyalkanoates (PHA) matrix, poly (ethylene) glycol (PEG), electrospinning, cell adhesion, proliferation, embryonic stem cell, chondrogenic cell, nanolithography technique, fibrin, ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) and, N-hydroxysuccinimide (NHS), biomimetic matrix, demyelinating disease, comprising leukemia inhibitory factor, Huntington disease, sonic hedgehog-GLI, (SHH-GLI) pathway, valproic acid (VPA), azacytidine (5AzaC), gene expressions, nanofabrication