Investigating the Solubility and Activity of a Novel Class of Ice Recrystallization Inhibitors

O-aryl-β-D-glucosides and N-alkyl-D-gluconamides are two classes of effective ice recrystallization inhibitors (IRIs), however their solubilities limit their use in cryopreservation applications. Herein, we have synthesized and assessed phosphonate analogues of small-molecule IRIs as a method to improve their chemical and physical properties. Four sodium phosphonate compounds 4–7 were synthesized and exhibited high solubilities greater than 200 mM. Their IRI activity was evaluated using the splat cooling assay and only the sodium phosphonate derivatives of α-methyl-D-glucoside (5-Na) and N-octyl-D-gluconamide (7-Na) exhibited an IC50 value less than 30 mM. It was found that the addition of a polar sodium phosphonate group to the alkyl gluconamide (1) and aryl glucoside (2) structure decreased its IRI activity, indicating the importance of a delicate hydrophobic/hydrophilic balance within these compounds. The evaluation of various cation-phosphonate pairs was studied and revealed the IRI activity of ammonium and its ability to modulate the IRI activity of its paired anion. A preliminary cytotoxicity study was also performed in a HepG2 cell line and phosphonate analogues were found to have relatively low cytotoxicity. As such, we present phosphonate small-molecule carbohydrates as a biocompatible novel class of IRIs with high solubilities and moderate-to-high IRI activities.

Methods in Biosynthesis and Characterization of the Antifreeze Protein (AFP) for Potential Blood Cryopreservation

The cryopreservation of red blood cells (RBCs) is very important to modern medicine. Cryoprotectants (CPAs) such as dimethyl sulfoxide (DMSO), proline, trehalose, and polyvinyl alcohol (PVA) have been used in the cryopreservation of RBCs, but the results are not satisfactory. Marinomonas primoryensis antifreeze protein (MpAFP) is a Ca2+-dependent AFP derived from Antarctic bacteria, which can prevent bacteria from freezing under extremely cold conditions and may be suitable for cryopreservation of RBCs. The active region of MpAFP is located in region IV and is called MPAFP_RIV. In this paper, the gene of region IV of MpAFP is introduced into BL21 (DE3) competent cells, and MpAFP_RIV is obtained after culture, separation, and purification. The improved splat assay is proposed, and this method first proves that MpAFP_RIV has strong ice recrystallization inhibition (IRI) activity without Ca2+. The improved splat assay is easier to operate and lower the cost compared to the traditional one, and the results are consistent with the classic sucrose sandwich assay, proving that this method can accurately detect IRI activity. The feasibility of MPAFP_RIV combined with classical CPA for cryopreservation of RBCs and the methods to increase the yield of MPAFP_RIV are proposed.