Abstract
Ice recrystallization is the main contributor to cell damage and death during the cryopreservation of cells and tissues. Over the past five years, many small carbohydrate-based molecules were identified as ice recrystallization inhibitors and several were shown to reduce cryoinjury during the cryopreservation of red blood cells (RBCs) and hematopoietic stems cells (HSCs). Unfortunately, clear structure-activity relationships have not been identified impeding the rational design of future compounds possessing ice recrystallization inhibition (IRI) activity. A set of 124 previously synthesized compounds with known IRI activities were used to calibrate 3D-QSAR classification models using GRid INdependent Descriptors (GRIND) derived from DFT level quantum mechanical calculations. Partial least squares (PLS) model was calibrated with 70% of the data set which successfully identified 80% of the IRI active compounds with a precision of 0.8. This model exhibited good performance in screening the remaining 30% of the data set with 70% of active additives successfully recovered with a precision of ~0.7 and specificity of 0.8. The model was further applied to screen a new library of aryl-alditol molecules which were then experimentally synthesized and tested with a success rate of 82%. Presented is the first computer-aided high-throughput experimental screening for novel IRI active compounds.
Highlights
Cryopreservation is an attractive strategy permitting the long-term storage of biological materials by using very low sub-zero temperatures (>−190 °C)
The Partial least squares (PLS) regression yielded an optimum 3D-quantitative structure activity relationship (QSAR) model of only 23 GRiND descriptors that successfully identified ice recrystallization inhibition (IRI) active compounds in the training set with accuracy of 95% given by the area-under the curve (AUC) of the receiver-operator-curve (ROC) plots of the model
The mechanism by which these molecules inhibit ice recrystallization is not known and this has hampered the rational design of new IRI active compounds resulting in an arduous trial-and-error discovery process
Summary
Cryopreservation is an attractive strategy permitting the long-term storage of biological materials by using very low sub-zero temperatures (>−190 °C). Subsequent to this, we have identified several structurally different classes of small molecules that are very effective inhibitors of ice recrystallization (Fig. 1)[17,18,19,20,21]. The IRI activity is measured as a percentage of the mean grain size of the ice crystals formed relative to those in a solution of phosphate buffered saline (PBS) in a splat cooling assay[22] While the exact mechanism by which these small molecules inhibit ice recrystallization is currently unknown, key structural attributes required for inhibition of this process are not known. This is unfortunate as this makes it very difficult to rationally design de novo inhibitors. QSAR modelling is an established tool in the pharmaceutical industry where it has been well documented to reduce drug discovery timelines[25]
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