Bioheat and mass transfer as viewed through a microscope

Cryoablation and Immunotherapy: An Enthralling Synergy for Cancer Treatment

As less invasive options for surgical tumor removal, minimally invasive ablative techniques have gained popularity. Several solid tumors are being treated with cryoablation, a non-heat-based ablation technique. Cryoablation data in comparison over time demonstrates better tumor response and faster recovery. Combining cryosurgery with other cancer therapies has been explored to improve the cancer-killing process. Cryoablation with the combination of immunotherapy, results in a robust and efficient attack on the cancer cells. This article focuses on investigating the ability of cryosurgery to create a strong antitumor response when combined with immunologic agents resulting in a synergetic effect. To achieve this objective, we combined cryosurgery with immunotherapy using Nivolumab and lpilimumab. Five clinical cases of lymph node, lung cancer, bone, and lung metastasis were followed and analyzed. In this series of patients, percutaneous cryoablation and addressing immunity agents were technically feasible. In the follow-ups, there appeared to be no radiological evidence of new tumor development.

In-situ cryo-immune engineering of tumor microenvironment with cold-responsive nanotechnology for cancer immunotherapy

Cancer immunotherapy that deploys the host's immune system to recognize and attack tumors, is a promising strategy for cancer treatment. However, its efficacy is greatly restricted by the immunosuppressive (i.e., immunologically cold) tumor microenvironment (TME). Here, we report an in-situ cryo-immune engineering (ICIE) strategy for turning the TME from immunologically "cold" into "hot". In particular, after the ICIE treatment, the ratio of the CD8+ cytotoxic T cells to the immunosuppressive regulatory T cells is increased by more than 100 times in not only the primary tumors with cryosurgery but also distant tumors without freezing. This is achieved by combining cryosurgery that causes "frostbite" of tumor with cold-responsive nanoparticles that not only target tumor but also rapidly release both anticancer drug and PD-L1 silencing siRNA specifically into the cytosol upon cryosurgery. This ICIE treatment leads to potent immunogenic cell death, which promotes maturation of dendritic cells and activation of CD8+ cytotoxic T cells as well as memory T cells to kill not only primary but also distant/metastatic breast tumors in female mice (i.e., the abscopal effect). Collectively, ICIE may enable an efficient and durable way to leverage the immune system for combating cancer and its metastasis.

Magnetic Nanoparticle-Mediated Heating for Biomedical Applications

Magnetic nanoparticles, especially superparamagnetic nanoparticles (SPIONs), have attracted tremendous attention for various biomedical applications. Facile synthesis and functionalization together with easy control of the size and shape of SPIONS to customize their unique properties, have made it possible to develop different types of SPIONs tailored for diverse functions/applications. More recently, considerable attention has been paid to the thermal effect of SPIONs for the treatment of diseases like cancer and for nanowarming of cryopreserved/banked cells, tissues, and organs. In this mini-review, recent advances on the magnetic heating effect of SPIONs for magnetothermal therapy and enhancement of cryopreservation of cells, tissues, and organs, are discussed, together with the non-magnetic heating effect (i.e., high Intensity focused ultrasound or HIFU-activated heating) of SPIONs for cancer therapy. Furthermore, challenges facing the use of magnetic nanoparticles in these biomedical applications are presented.

Lipid phase transitions in cat oocytes supplemented with deuterated fatty acids

Cryopreservation of oocytes has already been used to preserve genetic resources, but this technology faces limitations when applied to the species whose oocytes contain large amounts of cytoplasmic lipid droplets. Although cryoinjuries in such oocytes are usually associated with the lipid phase transition in lipid droplets, this phenomenon is still poorly understood. We applied Raman spectroscopy of deuterium-labeled lipids to investigate the freezing of lipid droplets inside cat oocytes. Lipid phase separation was detected in oocytes cryopreserved by slow-freezing protocol. For oocytes supplemented with stearic acid, we found that saturated lipids form the ordered phase being distributed at the periphery of lipid droplets. When an oocyte is warmed to physiological temperatures after cooling, a fraction of saturated lipids may remain in the ordered conformational state. The fractions of monounsaturated and polyunsaturated lipids redistribute to the core of lipid droplets. Monounsaturated lipids undergo the transition to the ordered conformational state below -10°C. Using deuterated fatty acids with a different number of double bonds, we reveal how different lipid fractions are involved in the lipid phase transition of a cytoplasmic lipid droplet and how they can affect cell survival. Raman spectroscopy of deuterated lipids has proven to be a promising tool for studying the lipid phase transitions and lipid redistributions inside single organelles within living cells.

Water-transport and intracellular ice formation of human adipose-derived stem cells during freezing

The key to optimizing the cryopreservation strategy of human adipose-derived stem cells (hADSCs) is to identify the biophysical characteristics during freezing. Systematic freezing experiments were conducted under a cryo-microscope system to investigate the cryoinjury mechanism for hADSCs at different cooling rates. By simultaneously fitting morphological change data to the water-transport equation at 5, 10 and 20 °C/min, the plasma membrane hydraulic conductivity, L_pg, and activation energy, E_Lp, were determined. Moreover, the optimal cooling rate was also predicted by using mathematical model methods. Additionally, the surface-catalyzed nucleation (SCN) parameters were calculated by fitting in numerical models, Ω₀^SCN and k₀^SCN were determined at cooling rates of 30, 45 and 60 °C/min. These results may provide potential application value for cryopreservation of hADSCs.

Alginate Hydrogel Microencapsulation Inhibits Devitrification and Enables Large-Volume Low-CPA Cell Vitrification

Cryopreservation of stem cells is important to meet their ever-increasing demand by the burgeoning cell-based medicine. The conventional slow freezing for stem cell cryopreservation suffers from inevitable cell injury associated with ice formation and the vitrification (i.e., no visible ice formation) approach is emerging as a new strategy for cell cryopreservation. A major challenge to cell vitrification is intracellular ice formation (IIF, a lethal event to cells) induced by devitrification (i.e., formation of visible ice in previously vitrified solution) during warming the vitrified cells at cryogenic temperature back to super-zero temperatures. Consequently, high and toxic concentrations of penetrating cryoprotectants (i.e., high CPAs, up to ~8 M) and/or limited sample volumes (up to ~2.5 μl) have been used to minimize IIF during vitrification. We reveal that alginate hydrogel microencapsulation can effectively inhibit devitrification during warming. Our data show that if ice formation were minimized during cooling, IIF is negligible in alginate hydrogel-microencapsulated cells during the entire cooling and warming procedure of vitrification. This enables vitrification of pluripotent and multipotent stem cells with up to ~4 times lower concentration of penetrating CPAs (up to 2 M, low CPA) in up to ~100 times larger sample volume (up to ~250 μl, large volume).

Improved low-CPA vitrification of mouse oocytes using quartz microcapillary

Cryopreservation by low-cryoprotectant (CPA) vitrification has the potential to combine all the advantages of the conventional high-CPA vitrification and slow-freezing approaches while avoiding their drawbacks. However, current low-CPA vitrification protocol for cryopreservation of oocytes requires a lengthy and multi-step procedure for unloading CPAs. In this study, we report a much-simplified procedure of using quartz microcapillary (QMC) for low-CPA vitrification of mouse oocytes with only one step for unloading CPAs. The immediate viability of oocytes after the improved low-CPA vitrification was determined to be more than 90%. Moreover, no significant difference was observed in terms of embryonic development from the two-cell to blastocyst stages between the fresh and vitrified oocytes after in vitro fertilization (IVF). This improved low-CPA vitrification technology has the potential for efficient cryopreservation of oocytes to preserve the fertility of mammals including humans for assisted reproductive medicine, maintenance of animal resource and endangered species, and livestock management.

Visualization of freezing process in situ upon cooling and warming of aqueous solutions

The freezing of aqueous solutions and reciprocal distribution of ice and a freeze-concentrated solution (FCS) are poorly understood in spite of their importance in fields ranging from biotechnology and life sciences to geophysics and climate change. Using an optical cryo-miscroscope and differential scanning calorimetry, we demonstrate that upon cooling of citric acid and sucrose solutions a fast freezing process results in a continuous ice framework (IF) and two freeze-concentrated solution regions of different concentrations, FCS₁ and FCS₂. The FCS₁ is maximally freeze-concentrated and interweaves with IF. The less concentrated FCS₂ envelops the entire IF/FCS₁. We find that upon further cooling, the FCS₁ transforms to glass, whereas the slow freezing of FCS₂ continues until it is terminated by a FCS₂-glass transition. We observe the resumed slow freezing of FCS₂ upon subsequent warming. The net thermal effect of the resumed freezing and a reverse glass-FCS₁ transition produces the T_tr2-transition which before has only been observed upon warming of frozen hydrocarbon solutions and which nature has remained misunderstood for decades.

Thermostability of biological systems: fundamentals, challenges, and quantification

This review examines the fundamentals and challenges in engineering/understanding the thermostability of biological systems over a wide temperature range (from the cryogenic to hyperthermic regimen). Applications of the bio-thermostability engineering to either destroy unwanted or stabilize useful biologicals for the treatment of diseases in modern medicine are first introduced. Studies on the biological responses to cryogenic and hyperthermic temperatures for the various applications are reviewed to understand the mechanism of thermal (both cryo and hyperthermic) injury and its quantification at the molecular, cellular and tissue/organ levels. Methods for quantifying the thermophysical processes of the various applications are then summarized accounting for the effect of blood perfusion, metabolism, water transport across cell plasma membrane, and phase transition (both equilibrium and non-equilibrium such as ice formation and glass transition) of water. The review concludes with a summary of the status quo and future perspectives in engineering the thermostability of biological systems.

Preferential vitrification of water in small alginate microcapsules significantly augments cell cryopreservation by vitrification

The morphological changes of small (approximately 100 microm) alginate microcapsules and the biophysical alterations of water in the microcapsules during cryopreservation were studied using cryomicroscopy and scanning calorimetry. It was found that water in the small microcapsules can be preferentially vitrified over water in the bulk solution in the presence of 10% (v/v) or more dimethylsulfoxide (DMSO, a cryoprotectant), which resulted in an intact morphology of the microcapsules post cryopreservation with a cooling rate of 100 degrees Celsius/min. A small amount of Ca(2+) (up to 0.15 M) was also found to help maintain the microcapsule integrity during cryopreservation, which is attributed to the enhancement of the alginate matrix strength by Ca(2+) rather than promoting vitrification of water in the microcapsules. The preferential vitrification of water in small microcapsules was further found to significantly augment cell cryopreservation by vitrification at a low concentration of cryoprotectants (i.e., 10% (v/v)) using a small quartz microcapillary (400 microm in diameter). Therefore, the small alginate microcapsule could be a great system for protecting living cells that are highly sensitive to stresses due to freezing (i.e., ice formation) and high concentration of cryoprotectants from injury during cryopreservation.

Visualization of intracellular ice formation using high-speed video cryomicroscopy

A high-speed video cryomicroscopy system was developed, and used to observe the process of intracellular ice formation (IIF) during rapid freezing (130 degrees C/min) of bovine pulmonary artery endothelial cells adherent to glass substrates, or in suspension. Adherent cells were micropatterned, constraining cell attachment to reproducible circular or rectangular domains. Employing frame rates of 8000 frames/s and 16,000 frames/s to record IIF in micropatterned and suspended cells, respectively, intracellular crystal growth manifested as a single advancing front that initiated from a point source within the cell, and traveled at velocities of 0.0006-0.023 m/s. Whereas this primary crystallization process resulted in minimal change in cell opacity, the well-known flashing phenomenon (i.e., cell darkening) was shown to be a secondary event that does not occur until after the ice front has traversed the cell. In cells that were attached and spread on a substrate, IIF initiation sites were preferentially localized to the peripheral zone of the adherent cells. This non-uniformity in the spatial distribution of crystal centers contradicts predictions based on common theories of IIF, and provides evidence for a novel mechanism of IIF in adherent cells. A second IIF mechanism was evident in approximately 20% of attached cells. In these cases, IIF was preceded by paracellular ice penetration; the initiation site of the subsequent IIF event was correlated with the location of the paracellular ice dendrite, indicating an association (and possibly a causal relationship) between the two. Together, the peripheral-zone and dendrite-associated initiation mechanisms accounted for 97% of IIF events in micropatterned cells.

Subzero water transport characteristics and optimal rates of freezing rhesus monkey (Macaca mulatta) ovarian tissue

The purpose of the present study was to examine the effect of two different suprazero (room temperature +25 degrees C to +4 degrees C) cooling conditions on the measured water transport response of primate (Macaca mulatta) ovarian tissue in the presence and absence of cryoprotective agents (CPAs). Freshly collected Macaca mulatta (rhesus monkey) ovarian tissue sections were cooled at either 0.5 degrees C/min or 40 degrees C/min from 25 to 4 degrees C. A shape independent differential scanning calorimeter (DSC) technique was then used to measure the volumetric shrinkage during freezing of ovarian tissue sections at a freezing rate of 5 degrees C/min in the presence and absence of three different CPAs (0.85 M glycerol, 0.85 M dimethylsulfoxide, and 0.85 M ethylene glycol). Thus, water transport during freezing of primate ovarian tissue was obtained at eight different conditions (i.e., at four different freezing media with two different suprazero cooling conditions). The water transport response of ovarian tissue cooled rapidly from 25 to 4 degrees C was significantly different (P < 0.01) than that of slow cooled tissue, in the freezing media without CPAs and with dimethylsulfoxide. However, the differences in the measured water transport response due to the imposed suprazero cooling conditions were reduced with the addition of glycerol and ethylene glycol (statistically different with P < 0.05). By fitting a model of water transport to the experimentally obtained volumetric shrinkage data the best-fit membrane permeability parameters (L(pg) and E(Lp)) were determined. The best-fit parameters of water transport in primate ovarian tissue sections ranged from: L(pg) = 0.7 to 0.15 microm/min-atm and E(Lp) = 22.1 to 32.1 kcal/mol (the goodness of fit parameter, R(2) > 0.96). These parameters suggest that the "optimal rates of cryopreservation" for ovarian tissue are significantly dependent upon suprazero cooling conditions and the choice of CPA.

Freezing response and optimal cooling rates for cryopreserving sperm cells of striped bass, Morone saxatilis

This study explored the optimization of techniques for sperm cryopreservation of an economically important fish species, the striped bass Morone saxatilis. The volumetric shrinkage or the water transport response during freezing of sperm cells was obtained using a differential scanning calorimeter (DSC) technique. Water transport was obtained in the presence of extracellular ice at a cooling rate of 20 degrees C/min in two different media: (1) without cryoprotective agents (CPAs), and (2) with 5% (v/v) dimethyl sulfoxide (DMSO). The sperm cell was modeled as a cylinder of length of 22.8 microm and diameter 0.288 microm and was assumed to have an osmotically inactive cell volume (V(b)) of 0.6 V(0), where V(0) is the isotonic or initial cell volume. By fitting a model of water transport to the experimentally determined water transport data, the best fit membrane permeability parameters (reference membrane permeability to water, L(pg) or L(pg)[cpa] and the activation energy, E(Lp) or E(Lp)[cpa]) were determined and ranged from L(pg)=0.011-0.001 microm/min-atm, and E(Lp)=40.2-9.2 kcal/mol). The parameters obtained in this study suggested that the optimal rate of cooling for striped bass sperm cells in the presence and absence of DMSO range from 14 to 20 degrees C/min. These theoretically predicted rates of optimally freezing M. saxatilis sperm compared quite closely with independent and experimentally determined optimal rates of cooling striped bass sperm.

Transport phenomena during freezing of adipose tissue derived adult stem cells

In the present study a well-established differential scanning calorimeter (DSC) technique is used to measure the water transport phenomena during freezing of stromal vascular fraction (SVF) and adipose tissue derived adult stem (ADAS) cells at different passages (Passages 0 and 2). Volumetric shrinkage during freezing of adipose derived cells was obtained at a cooling rate of 20 degrees C/min in the presence of extracellular ice and two different, commonly used, cryoprotective agents, CPAs (10% DMSO and 10% Glycerol). The adipose derived cells were modeled as spheres of 50 microm diameter with an osmotically inactive volume (Vb) of 0.6Vo, where Vo is the isotonic cell volume. By fitting a model of water transport to the experimentally obtained volumetric shrinkage data, the "best-fit" membrane permeability parameters (reference membrane permeability to water, Lpg or Lpg[cpa] and the activation energy, ELp or ELp[cpa]) were determined. The "best-fit" membrane permeability parameters for adipose derived cells in the absence and presence of CPAs ranged from: Lpg=23.1-111.5x10(-15) m3/Ns (0.135-0.652 microm/min-atm) and ELp=43.1-168.8 kJ/mol (9.7-40.4 kcal/mol). Numerical simulations of water transport were then performed under a variety of cooling rates (5-100 degrees C/min) using the experimentally determined membrane permeability parameters. And finally, the simulation results were analyzed to predict the optimal rates of freezing adipose derived cells in the presence and absence of CPAs.