Cytotoxicity of three carbon dioxide/butadiene-derived monomers

The utilization of carbon dioxide (CO2) as a raw material for synthesizing CO2-based polymers presents a promising large-scale strategy for its consumption and transformation. The recent successful syntheses of degradable and monomer-recyclable polyesters from CO2 and butadiene-derived monomers represent a series of significant advancements. These monomers include 1,2-ethylidene-6-vinyl-tetrahydro-2H-pyran-2-one (δ-L), 3,6-diethyl-tetrahydro-2H-pyran-2-one (HL), and 3-ethyl-6-vinyltetrahydro2H-pyran-2-one (δLH2). These developments are promising in meeting the urgent needs to achieve a circular economy in the current plastic industry. Herein, we reported the first study on the cytotoxicity of δ-L, HL, and δLH2. The effect concentration causing 50% inhibition of cell viability after 72 hr was determined to be < 0.25 mM for δ-L, 2.01 mM for HL, and 1.98 mM for δLH2. Mechanistic studies showed that the surprisingly high cytotoxicity of δ-L cannot be rationalized solely by the reactivity of its conjugated olefin as a Michael acceptor towards thiols. Based on these findings, δLH2 and HL are considered relatively suitable for potential large-scale applications, whereas δ-L requires additional protective measures.