Low-density lipoprotein (LDL) is the main carrier of blood cholesterol, with elevated levels of LDL increasing the risk of atherosclerosis.

We describe a versatile approach to synthesize glycosylated polyphosphazenes with controllable density of glycosyl groups. These glycopolymers have been synthesized by the nucleophilic substitution of poly(dichlorophosphazene) with propargylamine and subsequent “thiol–yne” click reaction between poly[di(propargylamine)phosphazene] and 2,3,4,6‐tetra‐O‐acetyl‐1‐thio‐β‐D‐glucopyranose (SH‐GlcAc4). The polymers were characterized with FTIR and 1H NMR. We found that the high steric hindrance of SH‐GlcAc4 plays a key role in the overall reaction process, and ∼55% of the alkyne groups participate in the “thiol–yne” click reaction. About 8% of the alkyne groups convert to alkene groups at the end of click reaction. The substitution of alkyne/alkane mixture was conducted to reduce the alkyne density in the side groups of polyphosphazenes and minimize the influences of this steric effect. Mixed‐substituent polyphosphazene was synthesized with 2:3 ratio of alkyne and alkane. In this case, almost no alkyne group remains after the “thiol–yne” click reaction, and thus the glycosylated polyphosphazene is able to form into micelles through self‐assembly process. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

The thiol–ene radical addition reaction has been successfully used to synthesize polyphosphazene derivatives. Poly[bis(allylamino)phosphazene] with pendant allyl groups was reacted with different thiol reagents under UV irradiation. These thiol reagents include 1‐pentanethiol, 3‐mercaptopropionic acid, 3‐mercapto‐1,2‐propane‐diol, and 2,3,4,6‐tetra‐O‐acetyl‐1‐thio‐β‐D‐glucopyranose. 1H NMR analyses confirm that the allyl polyphosphazene can be quantitatively modified by the mercaptans. In total, 100% conversion of the allyl groups was reached in <60 min toward the first three mercaptans, whereas about 80% conversion of the allyl groups was reached after 120‐min reaction toward the thioglucose. This method is a facile route for the synthesis of functional polyphosphazenes without the needs for protection/deprotection procedures. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Abstract:We report on the synthesis and application of a new hydrogel based on a methacrylate substituted polyphosphazene. Through ring-opening polymerization and nucleophilic substitution, poly[bis(methacrylate)phosphazene] (PBMAP) was successfully synthesized from hexachlorocyclotriphosphazene. By adding PBMAP to methacrylic acid solution and then treating with UV light, we could obtain a cross-linked polyphosphazene network, which showed an ultra-high absorbency for distilled water. Lipase from Candida rugosa was used as the model lipase for entrapment immobilization in the hydrogel. The influence of methacrylic acid concentration on immobilization efficiency was studied. Results showed that enzyme loading reached a maximum of 24.02 mg/g with an activity retention of 67.25% when the methacrylic acid concentration was 20% (w/w).

In this study, a chemically crosslinkable cationic polyphosphazene was synthesized and fabricated into ionic strength-responsive hydrogels for enzyme binding. This novel polyphosphazene was synthesized via the macromolecular substitution reaction of poly(dichlorophosphazene) with 2-dimethylaminoethylamine, followed by the quaternization to yield the allyl groups. Hydrogels were easily prepared via the thiol-ene click reaction between polyphosphazene and poly(ethylene glycol) dithiol (dithiol PEG) under UV radiation. The inner three-dimensional structure of the hydrogels was investigated by swelling experiments, mechanical property tests, and field emission-scanning electron microscopy. The resulting hydrogels exhibited sensitivity to the ionic strength of the surrounding environment. Lipase from Candida rugosa was selected as the model enzyme for the entrapment in these hydrogels, resulting in a maximum enzyme loading of 16.6 mg g À1 and activity retention as high as 61.6%. Furthermore, the cationic hydrogels were effectively used for reversible enzyme binding owing to the electrostatic interaction, regulated by the ionic strength.

A novel core/sheath glycosylated polyphosphazene nanofi brous membrane for use in protein recognition is fabricated via coaxial electrospinning process with alkyl polyphosphazene as the sheath and polyacrylonitrile (PAN) as the core, followed by introduction of saccharide residues to the surface of the polyphosphazene nanofi brous membrane using alkyne-azide "click" chemistry. A glucose/protein binding assay effectively demonstrates that this nanofi brous membrane can selectively recognize Con A while showing almost no binding with bovine serum albumin (BSA). Furthermore, the affi nity capability of proteins (BSA and Con A) for the glycosylated polyphosphazene surface is investigated quantitatively using a surface plasmon resonance (SPR) technique.

A green route is reported for functionalizing polyphosphazene via the thiol-ene click reaction in an aqueous medium. Poly[bis(allylamino)phosphazene] is used as the precursor polymer, which is easily dissolved in water containing 5% (v/v) phosphoric acid, but barely dissolved in other acidic aqueous solutions with the same pH value. Three thiol reagents, namely, 3-mercapto-1,2-propanediol, 2-mercaptoethoxy ethanol, and L -cysteine, are then reacted with the precursor in the phosphoric acid aqueous solutions. 1 H and 31 P NMR analyses confi rm that the allyl polyphosphazene can be quantitatively modifi ed by the mercaptans without hydrolysis degradation during the synthesis and purifi cation processes. Moreover, these polyphosphazenes exhibit higher regioselectivity than those functionalized in organic solvents. This method provides a facile route for the green synthesis of functional polyphosphazenes without organic solvents.

Strong carbohydrate–lectin binding interactions in biological systems can be mimicked through the synthesis of glucose containing macromolecules, particularly glycosylated polymers.