DEVELOPMENTS TOWARDS BIOCOMPATIBLE DEGRADABLE MOLECULARLY IMPRINTED POLYMERS BASED ON POLY(ORGANO)PHOSPHAZENES

Despite several different approaches to obtain degradable and biodegradable molecularly imprinted polymers (MIPs), the extent of their application and further research into their properties remains scarce. In this contribution, we report the preparation of MIPs based on poly(organo)phosphazenes and the potential use as a modular construction kit for biocompatible, degradable MIPs.

Poly(organo)phosphazenes are a group of inorganic-organic hybrid polymers with a backbone of alternating phosphorus and nitrogen atoms which offer unique and highly tuneable characteristics due to the vast range of applicable organic substituents, enabling precise controlled degradability and degradation to benign small molecules.¹ This, as well as the use of various functional groups for imprinting, makes these polymers serve as first-class candidates as basis for biocompatible and degradable MIPs.

MIPs in general are to a great extent based on poly(meth)acrylates and derivatives, and furthermore, are synthesized in form of micro- or nanoparticles. However, they mostly lack of sufficient biodegradability, which significantly limits their applicability in medicine. To the best of our knowledge, only a few reports of (bio)degradable MIPs based on poly(3-hydroxybutyrate), poly(lactic acid)/poly(ethylene glycol) or degradable cross-linkers look specifically into these characteristics, despite their potential use in biomedical applications.^2-7

On the other hand, for medical applications, poly(organo)phosphazenes have been investigated, specifically for controlled drug release or tissue engineering.⁸ Although polyphosphazenes have been reported for molecular imprinting, the potential of degradable structure was not considered in that approach.⁹ Herein, we present the synthesis of polyphosphazenes with glycine ethyl ester substituents to render the polymers sensitive to hydrolytic degradation. The polymers were co-functionalized with thioglycolic acid operating as a functional monomer, to perform molecular imprinting with propranolol, a typical exemplary template allowing comparison with recent literature. The influence of different cross-linkers on the rigidity they provide to the polymer matrix, and hence, on the selectivity of the imprinted polymers over non-imprinted ones are shown.

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