Dimethyl sulfoxide for cryopreservation of alginate encapsulated liver cell spheroids in bioartificial liver support; assessments of cryoprotectant toxicity tolerance and dilution strategies

The Bioartificial Liver (BAL) is an extra-corporeal liver support designed to support the function of the Liver in patients with impaired liver function. The BAL biomass consists of alginate encapsulated liver spheroids (AELS). To facilitate rapid delivery of a BAL to patients the AELS are cryopreserved using a DMSO-containing cryoprotectant solution. This study assesses toxicity of DMSO in AELS at concentrations and temperatures relevant to the cryopreservation and recovery process of a cellular biomass. Additionally, it develops a process to remove DMSO from AELS before delivery of cell product to patients. Exposure of AELS to DMSO, at a concentration of 12% (v/v) for 10 min did not have a negative effect on the viability of the AELS up to 24 h after exposure, irrespective of the exposure temperature between 37 C and 0 C. Evidence of toxicity was only seen with exposure to 40% (v/v) DMSO, which was more notable at warm temperatures. Post-Thaw removal of DMSO was measured by determining the DMSO concentration of the post-thaw washes using refractometry. Washing AELS 3 times in tapering concentrations of Glucose supplemented DMEM at an AELS:wash ratio of 1:2 was sufficient to reduce DMSO to undetectable levels (<1%). The study demonstrated that the thawing method minimised DMSO toxicity to the BAL biomass, and the post-thaw washing protocol successfully removed all the DMSO present in the cryopreserved BAL. Thereby enabling effective cryopreservation of the BAL for future clinical translation

Multifunctionalization of Poly(vinylidene fluoride)/Reactive Copolymer Blend Membranes for Broad Spectrum Applications

Simultaneous immobilization and cross-linking of antifouling/low toxic polymers, e.g., poly­(ethylenimine) (PEI), dextran (Dex), agarose (Agr), poly­(ethylene glycol) (PEG), PEI–Dex, and PEI–PEG conjugates, and stimuli-responsive copolymers on a porous membrane surface in mild reaction conditions is desirable for the enhancement of hydrophilicity, antifouling character, cytocompatibility, and inducing stimuli-responsive behavior. Grafting to technique is required since the precursors of most of these macromolecules are not amenable to surface-initiated polymerization. In this work, we report a versatile process for the simultaneous immobilization and cross-linking of a library of macromolecules on and into the blend membrane (PVDF-blend) of poly­(vinylidene fluoride) and poly­(methyl methacrylate)-<i>co</i>-poly­(chloromethyl­styrene). Sequential nucleophilic substitution reaction between activated halide moieties of the copolymer and amine groups of different macromolecules readily provided series of modified membranes. These membranes exhibited antifouling property superior to that of the unmodified membrane. The effectiveness of this technique has been demonstrated by the immobilization of pH or both pH- and temperature-responsive copolymer on PVDF-blend membrane for responsive separation of poly­(ethylene oxide) and bovine serum albumin. Silver nanoparticles were also anchored on the select modified membranes surfaces for the enhancement of antibiofouling property. Our approach is useful to obtain verities of functional membranes and selection of membrane for a particular application