Clickable Poly(ionic liquids): A Materials Platform for Transfection.

The potential applications of cationic poly(ionic liquids) range from medicine to energy storage, and the development of efficient synthetic strategies to target innovative cationic building blocks is an important goal. A post-polymerization click reaction is reported that provides facile access to trisaminocyclopropenium (TAC) ion-functionalized macromolecules of various architectures, which are the first class of polyelectrolytes that bear a formal charge on carbon. Quantitative conversions of polymers comprising pendant or main-chain secondary amines were observed for an array of TAC derivatives in three hours using near equimolar quantities of cyclopropenium chlorides. The resulting TAC polymers are biocompatible and efficient transfection agents. This robust, efficient, and orthogonal click reaction of an ionic liquid, which we term ClickabIL, allows straightforward screening of polymeric TAC derivatives. This platform provides a modular route to synthesize and study various properties of novel TAC-based polymers.

Design, development, mechanistic elucidation, and rational optimization of a tandem Ireland Claisen/Cope rearrangement reaction for rapid access to the (iso)cyclocitrinol core.

An approach to the synthesis of the (iso)cyclocitrinol core structure is described. The key step is a tandem Ireland Claisen/Cope rearrangement sequence, wherein the Ireland Claisen rearrangement effects ring contraction to a strained 10-membered ring, and that strain in turn drives the Cope rearrangement under unusually mild thermal conditions. A major side product was identified as resulting from an unexpected and remarkably facile [1,3]-sigmatropic rearrangement, and a tactic to disfavor the [1,3] pathway and increase the efficiency of the tandem reaction was rationally devised.

Transferrin Receptor Is a Specific Ferroptosis Marker.

Ferroptosis is a type of regulated cell death driven by the iron-dependent accumulation of oxidized polyunsaturated fatty acid-containing phospholipids. There is no reliable way to selectively stain ferroptotic cells in tissue sections to characterize the extent of ferroptosis in animal models or patient samples. We address this gap by immunizing mice with membranes from lymphoma cells treated with the ferroptosis inducer piperazine erastin and screening ∼4,750 of the resulting monoclonal antibodies generated for their ability to selectively detect cells undergoing ferroptosis. We find that one antibody, 3F3 ferroptotic membrane antibody (3F3-FMA), is effective as a selective ferroptosis-staining reagent. The antigen of 3F3-FMA is identified as the human transferrin receptor 1 protein (TfR1). We validate this finding with several additional anti-TfR1 antibodies and compare them to other potential ferroptosis-detecting reagents. We find that anti-TfR1 and anti-malondialdehyde adduct antibodies are effective at staining ferroptotic tumor cells in multiple cell culture and tissue contexts.

Toward a Microparticle-Based System for Pooled Assays of Small Molecules in Cellular Contexts.

Experimental approaches to the discovery of small molecule probes and drug candidates often use biochemical or cell-based screening of large libraries (>105) of small molecules. Small molecules of interest are tested one at a time in individual wells of a microtiter plate, at a significant cost in time and resources. Furthermore, evaluation of large numbers of compounds in such assays requires robust cellular or biochemical screening formats that may not be relevant to the contexts found in human patients. We envision a solution to these issues that involves a pooled system of small molecule screening, which would require development of numerous new technologies, and solutions to several key challenges. We report here that a microparticle-based screening system can allow for screening of small molecules in such a pooled fashion, analogous to the pooled screens of genetic reagents that have been powerfully deployed in recent years. We developed a cleavable linker that can link small molecules of interest to silica microparticle beads, a DNA tag encoding the identity of the small molecule on each bead that was attached to the silica beads through a photocleavable linker to enable its amplification, and a bead-based fluorescent sensor that can report on the activity of small molecules in cells. We suggest that this pooled small molecule screening system could ultimately be useful for drug and probe discovery, allowing rapid and inexpensive screening of small molecules in assays of relevance to human diseases.