Utilization of Directional Freezing for the Construction of Tissue Engineering Scaffolds

Preciado, Jessica; Skandakumaran, P.; Cohen, Smadar; Rubinsky, Boris

doi:10.1115/imece2003-42067

Cited by 12 publications

(9 citation statements)

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“…The SEM pictures show sheet-like arrangement of alginate resembling flaky pastry. Long parallel channels were also intentionally created in alginate scaffolds by directional freezing (Preciado et al, 2003) to facilitate cell in-growth and diffusion of nutrients. The presented SEM pictures again showed the typical flaky pastry appearance of freeze-dried aqueous alginate sols.…”

Section: Discussionmentioning

confidence: 99%

Proliferation and osteogenic differentiation of human bone marrow stromal cells on alginate-gelatine-hydroxyapatite scaffolds with anisotropic pore structure

Bernhardt

Despang

Lode

et al. 2009

J Tissue Eng Regen Med

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Porous mineralized scaffolds are required for various applications in bone engineering. In particular, tube-like pores with controlled orientation inside the scaffold may support homogeneous cell seeding as well as sufficient nutrient supply and may facilitate blood vessel ingrowth. Scaffolds with parallely orientated tube-like pores were generated by diffusion-controlled ionotropic gelation of alginate. Incorporation of hydroxyapatite (HA) during the gelation process yielded stable scaffolds with an average pore diameter of approximately 90 microm. To evaluate the potential use of alginate-gelatine-HA scaffolds for bone tissue engineering, in vitro tests with human bone marrow stromal cells (hBMSCs) were carried out. We analysed biocompatibility and cell penetration into the capillary pores by microscopic methods. hBMSCs were also cultivated on alginate-gelatine-HA scaffolds for 3 weeks in the presence and absence of osteogenic supplements. We studied proliferation and osteogenic differentiation in terms of total lactate dehydrogenase (LDH) activity, DNA content and alkaline phosphatase (ALP) activity and found a 10-14-fold increase of cell number after 2 weeks of cultivation, as well as an increase of specific ALP activity for osteogenic-induced hBMSCs. Furthermore, the expression of bone-related genes [ALP, bone sialoprotein II (BSPII)] was analysed. We found an increase of ALP as well as BSPII expression for osteogenic-induced hBMSCs on alginate-gelatin-HA scaffolds.

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Section: Discussionmentioning

confidence: 99%

Proliferation and osteogenic differentiation of human bone marrow stromal cells on alginate-gelatine-hydroxyapatite scaffolds with anisotropic pore structure

Bernhardt

Despang

Lode

et al. 2009

J Tissue Eng Regen Med

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“…High concentration salt solutions form along the ice crystals. This phenomenon occurs during freezing of any aqueous medium, in solutions (Ishiguro & Rubinsky, 1994), gels (Preciado et al, 2003) and tissues (Rubinsky & Pegg, 1988). While the electrical conductivity of ice is essentially zero, electrical currents can flow through these high concentration brine channels until the temperature reaches the eutectic −21.1 °C.…”

Section: Resultsmentioning

confidence: 99%

Cryoelectrolysis—electrolytic processes in a frozen physiological saline medium

Lugnani¹,

Macchioro²,

Rubinsky

2017

PeerJ

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BackgroundCryoelectrolysis is a new minimally invasive tissue ablation surgical technique that combines the ablation techniques of electrolytic ablation with cryosurgery. The goal of this study is to examine the hypothesis that electrolysis can take place in a frozen aqueous saline solution.MethodTo examine the hypothesis we performed a cryoelectrolytic ablation protocol in which electrolysis and cryosurgery are delivered simultaneously in a tissue simulant made of physiological saline gel with a pH dye. We measured current flow, voltage and extents of freezing and pH dye staining.ResultsUsing optical measurements and measurements of currents, we have shown that electrolysis can occur in frozen physiological saline, at high subzero freezing temperatures, above the eutectic temperature of the frozen salt solution. It was observed that electrolysis occurs when the tissue resides at high subzero temperatures during the freezing stage and essentially throughout the entire thawing stage. We also found that during thawing, the frozen lesion temperature raises rapidly to high subfreezing values and remains at those values throughout the thawing stage. Substantial electrolysis occurs during the thawing stage. Another interesting finding is that electro-osmotic flows affect the process of cryoelectrolysis at the anode and cathode, in different ways.DiscussionThe results showing that electrical current flow and electrolysis occur in frozen saline solutions imply a mechanism involving ionic movement in the fluid concentrated saline solution channels between ice crystals, at high subfreezing temperatures. Temperatures higher than the eutectic are required for the brine to be fluid. The particular pattern of temperature and electrical currents during the thawing stage of frozen tissue, can be explained by the large amounts of energy that must be removed at the outer edge of the frozen lesion because of the solid/liquid phase transformation on that interface.ConclusionElectrolysis can occur in a frozen domain at high subfreezing temperature, probably above the eutectic. It appears that the most effective period for delivering electrolytic currents in cryoelectrolysis is during the high subzero temperatures stage while freezing and immediately after cooling has stopped, throughout the thawing stage.

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“…Figure 6 in conjunction with Figure 3B provides an explanation for this observation. Figure 6 is a freeze-dried structure of a frozen agarose gel (from [22] with permission). The important observation is that the frozen agar structure is rugged with finger-like salt/agar structures that formed between the ice crystal during freezing.…”

Section: Resultsmentioning

confidence: 99%

An Electrochemistry Study of Cryoelectrolysis in Frozen Physiological Saline

Manuel

Munnangi

Rubinsky

2017

IEEE Trans. Biomed. Eng.

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Cryoelectrolysis is a new minimally invasive tissue ablation surgical technique that combines the processes of electrolysis and solid/liquid phase transformation (freezing). This study investigated this new technique by measuring the pH front propagation and the changes in resistance in a tissue simulant made of physiological saline gel with a pH dye as a function of the sample temperature in the high subzero range above the eutectic. Results demonstrated that effective electrolysis can occur in a high subzero freezing milieu and that the propagation of the pH front is only weakly dependent on temperature. These observations are consistent with a mechanism involving ionic movement through the concentrated saline solution channels between ice crystals at subfreezing temperatures above the eutectic. Moreover, results suggest that Joule heating in these microchannels may cause local microscopic melting, the observed weak dependence of pH front propagation on temperature, and the large changes in resistance with time. A final insight provided by the results is that the pH front propagation from the anode is more rapid than from the cathode, a feature indicative of the electro-osmotic flow from the cathode to the anode. The findings in this paper may be critical for designing future cryoelectrolytic ablation surgery protocols.

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Utilization of Directional Freezing for the Construction of Tissue Engineering Scaffolds

Cited by 12 publications

References 0 publications

Proliferation and osteogenic differentiation of human bone marrow stromal cells on alginate-gelatine-hydroxyapatite scaffolds with anisotropic pore structure

Proliferation and osteogenic differentiation of human bone marrow stromal cells on alginate-gelatine-hydroxyapatite scaffolds with anisotropic pore structure

Cryoelectrolysis—electrolytic processes in a frozen physiological saline medium

An Electrochemistry Study of Cryoelectrolysis in Frozen Physiological Saline

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