Optimized triazine-mediated amidation for efficient and controlled functionalization of hyaluronic acid

Hyaluronic Acid Graft Copolymers with Cleavable Arms as Potential Intravitreal Drug Delivery Vehicles

“…The Fourier transform infrared spectroscopy (FT‐IR) spectra of HA‐propargyl esters exhibited the characteristic ester carbonyl stretch around 1740–1750 cm −1 (Figure S3, Supporting Information). Although this study was focused on HA‐ester derivatives, in some of the following experiments we also included a previously reported HA‐propargyl amide to get a qualitative idea of how both derivatives would compare during release tests …”

“…The standard aqueous click reaction protocol uses copper(II)sulfate and sodium ascorbate to create the catalytically active Cu + species in situ by reduction . At the same time hydroxyl radicals are formed that readily degrade HA .…”

“…Samples were incubated in either PBS or vitreous at 37 °C for 36 d to estimate the extent of nonenzymatic and enzymatic hydrolysis, respectively. Sodium hyaluronate, HA‐propargyl ester and HA‐propargyl amide, which was reported earlier, were used to determine whether polysaccharides with masked glucuronic acid groups were more stable toward enzymatic degradation. The incubated solutions were dialyzed (MWCO 25 kDa) to remove the buffer salts and ≈90% of the employed starting materials could be recovered.…”

“…* N ‐methylmorpholinium impurity originating from synthesis of the amide as detailed in ref. . ** Signal originating from the vitreous.…”

“…Although this study was focused on HA-ester derivatives, in some of the following experiments we also included a previously reported HA-propargyl amide to get a qualitative idea of how both derivatives would compare during release tests. [25]…”