DNA as a blueprint for synthetic polyphosphoesters
Inspired by DNA, a natural polyphosphodiester, my group has especially driven the development of phosphorus-containing polymers, i.e. polyphosphoesters (PPEs). With the natural phosphate building block, biodegradable and biomimetic PPEs can be synthesized by different strategies. We take the bridging element from DNA to materials science as the installation of the phosphate group into the polymer main chain allows installing diverse chemical functionalities, which eventually control the materials properties such as chemical reactivity, folding, self-assembly, or interactions (functionality, responsibility, degradation, blood interactions). Such PPEs can be used in diverse applications and have an industrial interest (e.g. as surfactants or flame retardants). By a living ring-opening polymerization of cyclic phosphoesters, we were able to prepare libraries of functional PPEs, which degrade on demand and carry functional groups to allow drug attachment, surface-immobilization (Polym. Chem. 2018), adhesive (Biomacromolecules 2017) or anti-fouling properties (Nat. Nano. 2016), or flame-retardant properties (Polym. Chem. 2014). The class of PPEs has emerged in the last decade to a powerful polymer class for various applications and due to the versatility of its chemistry, it certainly will find applications in diverse areas of research and industry. We further developed a reliable protocol for the preparation of hydrophobic polyphosphoesters allowing the large-scale preparation of phosphate-based flame-retardants by engineering the chemical structure, we control the degradation during a fire event (collaboration project with BAM (Prof. Schartel)) (Polym. Chem. 2014, Angew. Chem. 2018).
In addition, smart polymers (with LCST and UCST) are accessible from PPEs (Polym. Chem. 2017). For example, amphiphilic polyphosphonate block copolymers carrying hydrogen-bonding motifs allowed us to assemble stimuli-responsive polymersomes, which can be reversibly opened and closed by a temperature trigger (J. Am. Chem. Soc. 2017). Such vesicles are a first step towards the development of compartmentalized reactors on the nano- or microscale that can release reagents. The overall hydrophilicity controls the interactions with blood proteins (Angew. Chem. 2018). Such materials have led to the unraveling of the “stealth effect” of nanocarriers that is an underlying principle for drug delivery (in collaboration with Universitätsmedizin Mainz) (Nat. Nano. 2016, Biomaterials 2015 & 2017). Nanocarriers, coated with hydrophilic PPEs exhibit a “stealth” effect, similar to the well-known poly(ethylene glycol), rendering them as perfect biodegradable alternatives, especially for chronical diseases.