2.B.96.  The Cobalt Bisdicarbollide Chaotropic Carrier (CBCC) Family 

Cobalt bisdicarbollides (COSANs) are inorganic boron-based anions that had been previously reported to permeate by themselves through lipid bilayer membranes, a propensity that is related to their superchaotropic character. Chen et al. 2023 introduced their use as selective and efficient molecular carriers of otherwise impermeable hydrophilic oligopeptides through both artificial and cellular membranes, without causing membrane lysis or poration at low micromolar carrier concentrations. COSANs transport arginine-rich and lysine-rich peptides, whereas low-molecular-weight analytes such as amino acids and neutral/anionic cargos (phalloidin and BSA) are not transported. In addition to the unsubstituted isomers (known as ortho- and meta-COSAN), four derivatives bearing organic substituents or halogen atoms have been evaluated, and all six of them surpass established carriers such as pyrenebutyrate in terms of activity. U-tube experiments and black lipid membrane conductance measurements established that transport across model membranes is mediated by a molecular carrier mechanism. Transport experiments in living cells showed that a fluorescent peptide cargo, FITC-Arg(8), is delivered into the cytosol.