A dilution-filtration system for removing cryoprotective agents.

In most cryopreservation applications, the final concentrations of cryoprotective agents (CPAs) must be reduced to biocompatible levels. However, traditional methods for removing CPAs usually have disadvantages of operation complexity, time consumption, and ease of contamination, especially for the applications involving large volumes of cell suspensions. A dilution-filtration system, which involves pure ultrafiltration for separation, was developed for continuous, automatic, and closed process of removing CPAs. To predict the optimal protocols under given experimental conditions, a theoretical model was established first. Cell-free experiments were then conducted to investigate the variation in CPA concentration during the process, and the experimental data were compared with the theoretical values for the validation of the model. Finally, ten units (212.9 ml/unit±9.5 ml/unit) of thawed human red blood cells (cryopreserved with 40% (w/v) glycerol) were deglycerolized using the theoretically optimal operation protocols to further validate the effectiveness and advantage of the system. In the cell-free experiments, glycerol was continuously removed and the concentration variations fitted the simulated results quite well. In the in-vitro experiments, glycerol concentration in RBC suspension was reduced to 5.57 g/l±2.81 g/l within an hour, and the cell count recovery rate was 91.19%±3.57%, (n=10), which proves that the system is not only safe for removing CPAs, but also particularly efficient for processing large-scale samples. However, the operation parameters must be carefully controlled and the optimal protocols should be specialized and various from case to case. The presented theoretical model provides an effective approach to find out the optimal operation protocols under given experimental conditions and constrains.

A rough set approach for determining weights of decision makers in group decision making.

This study aims to present a novel approach for determining the weights of decision makers (DMs) based on rough group decision in multiple attribute group decision-making (MAGDM) problems. First, we construct a rough group decision matrix from all DMs' decision matrixes on the basis of rough set theory. After that, we derive a positive ideal solution (PIS) founded on the average matrix of rough group decision, and negative ideal solutions (NISs) founded on the lower and upper limit matrixes of rough group decision. Then, we obtain the weight of each group member and priority order of alternatives by using relative closeness method, which depends on the distances from each individual group member' decision to the PIS and NISs. Through comparisons with existing methods and an on-line business manager selection example, the proposed method show that it can provide more insights into the subjectivity and vagueness of DMs' evaluations and selections.

Cryopreservation of Peripheral Blood Stem Cells Using a Box-in-Box Cooling Device.

The cooling process is critical for the cryopreservation of human hematopoietic stem cells (HSCs). Currently, programmed freezing methods and uncontrolled cooling methods are in use, both having obvious disadvantages. In this article, a novel device termed Box-in-Box (BIB) was developed and evaluated by in vitro cryopreservation tests in 2 different operation modes ("against-side" mode for Group I (n = 10), and "in-middle" mode for Group II (n = 10), respectively), and compared with an uncontrolled cooling method (Group III (n = 7), Styrofoam boxes) as well as a conventional programmed freezer method (Group IV (n = 10), CryoMed TM 1010, Cryogenic Tech., FL). Recorded temperature profiles of samples cryopreserved with BIB show that a consistent cooling procedure with a rate around -1°C to -3.5°C/min can be achieved during their transfer from room temperature to an -80°C freezer. Statistical analysis of the stem cell population recovery, survival, and colony generation recovery shows that there is no significant difference (P > 0.26) among the methods using the BIB or programmed freezer (Group I, Group II, and Group IV), and their related deviations are smaller than the uncontrolled cooling rate method (Group III). Methods using the BIB (Group I and Group II) generated significantly better cell survival rate (P < 0.01) than the uncontrolled cooling rate method (Group III). The results indicate that the controlled cooling rate methods (BIB or CryoMed PF) are more consistent and reliable for clinical use. Considering the advantages of low cost, durability, and no liquid nitrogen consumption for the cooling process, the BIB can be a good alternative to the programmed freezers for the cryopreservation of HSCs.