Abstract
A synthetic route to prepare a poly(ethylene glycol) with a single cinnamaldehyde acetal unit in the polymer chain, was successfully established using a newly synthesized cinnamaldehyde acetal diethylene glycol (CADEG) as initiator. This HO-PEG(ca)-OH is non-toxic and would be degraded into a cinnamaldehyde and two PEG diols in acid environment. A whole polyethylene glycol based hydrogel was easily fabricated by thiol-ene “click” reaction in alkalescence aqueous solution using acrylate-PEG(ca)-acrylate and 4-arm PEG-SH as raw materials at room temperature. The gel time was dependent on the pH of the solution and its alkalinity can promote gel. The hydrogel can be degradable in acidic conditions and the stronger the acidity, the faster the degradation. This HO-PEG(ca)-OH also can be used in synthesis of cinnamaldehyde containing PEG derivatives, block copolymers or other acid degradable materials.
Highlights
Poly(ethylene glycol) (PEG), a prominent synthetic polymer approved by the Food and Drug Administration (FDA) of the United States has been wildly used in material science, biology, cosmetics, drug excipient, typically in PEGylation of protein, drug, or gene owing to its peculiar properties, including non-toxic, chemically inert, extremely low immunogenicity, non-antigenicity, and well soluble in many organic solvents and water (Harris and Chess, 2003; Pasut and Veronese, 2012; Herzberger et al, 2016; Cabral et al, 2018)
A whole polyethylene glycol based hydrogel was fabricated by thiol-ene “click” reaction in alkalescence aqueous solution using acrylate-PEG(ca)-acrylate and 4-arm PEG-SH as raw materials at room temperature
Acetal or ketal containing initiator or monomer was broadly used in anionic polymerization of epoxides for synthesis of acid-labile linear or hyperbranched polymers owing to the stability and tolerating the harsh conditions of the anionic polymerization of acetal or ketal moieties (Feng et al, 2011; Shenoi et al, 2012; Tonhauser et al, 2012; Dingels et al, 2013; Pohlit et al, 2017). These polymers can generate acetaldehyde or acetone from polyacetal or polyketal, respectively, when they were hydrolyzed in acid niches, for example, in solid tumor (Chen et al, 2010; Binauld and Stenzel, 2013)
Summary
Poly(ethylene glycol) (PEG), a prominent synthetic polymer approved by the Food and Drug Administration (FDA) of the United States has been wildly used in material science, biology, cosmetics, drug excipient, typically in PEGylation of protein, drug, or gene owing to its peculiar properties, including non-toxic, chemically inert, extremely low immunogenicity, non-antigenicity, and well soluble in many organic solvents and water (Harris and Chess, 2003; Pasut and Veronese, 2012; Herzberger et al, 2016; Cabral et al, 2018). To improve the circulation time of PEGylated proteins or to implement enhanced permeability and retention (EPR) effect of PEGylated drugs or nanoparticles, higher average molecular weight of PEG is needed. While with the increasing of the average molecular weight (Mn), in particular when the Mn is higher than 40 kDa, the PEG will accumulate in the liver and result in organ damage due to its non-biodegradable property (Maeda et al, 2013). Biodegradable PEGs with cleavable moieties in the backbone are in need and attract great interests. Many multiblock PEGs carrying cleavable moieties such as acetal (Tomlinson et al, 2003; Rickerby et al, 2005; Wang et al, 2011), imine or oxime (Collins et al, 2017), maleamic
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