Unconventional synthesis and characterization of novel abietic acid esters of hydroxypropylcellulose as potential macromolecular prodrugs

Thermoresponsive cellulosic hydrogels with cell-releasing behavior

Here we report the preparation and characterization of thermoresponsive cellulosic hydrogels with cell-releasing behavior. Hydroxypropyl cellulose (HPC) was modified with methacrylic anhydride (MA). The resultant macromonomer, HPC-MA, retains the characteristic thermoresponsive phase behavior of HPC, with an onset temperature of 36 °C and a lower critical solution temperature (LCST) of 37-38 °C, as determined by turbidity measurement. Homogenous HPC-MA hydrogels were prepared by UV-cross-linking the aqueous solutions of the macromonomer at room temperature, and characterized by water contact angle and swelling ratio measurements, and dynamic mechanical analysis. These hydrogels exhibit temperature-dependent surface hydrophilicity and hydrophobicity, equilibrium water content as well as mechanical properties. Cell-releasing characteristics were demonstrated using African green monkey kidney cell line (COS-7 cells) and murine-derived embryonic stem cell line (Oct4b2). By reducing temperature to 4 °C, the cultivated cells spontaneously detached from the hydrogels without the need of trypsin treatment. These unique properties make our HPC-MA hydrogels potential substrates for cell sheet engineering.

An efficient esterification of pullulan using carboxylic acid anhydrides activated with iodine

Acylation of alcohols (esterification) with anhydride is an important and routinely utilized transformation in organic synthesis. Iodine is a cheap and one of the most powerful anhydride activating agents for the esterification of alcohols. Therefore, an efficient and cost effective method was developed for the acylation of pullulan polysaccharide by using different acid anhydrides activated with iodine. A series of organo-soluble pullulan esters were successfully synthesized, purified and characterized. Under solvent free conditions, it was feasible to fabricate pullulan nonaacetate and pullulan stearate. Attachment (covalent) of the pendant groups onto polymer backbone was verified by spectroscopic techniques. All of the products were characterized by using thermal analysis, FTIR and 1H NMR spectroscopy.

An efficient acetylation of dextran using in situ activated acetic anhydride with iodine

A facile, efficient, cost-effective and solvent-free acetylation method has been developed for the acetylation of dextran. Dextran acetates were successfully synthesized using different molar ratios of acetic anhydride in the presence of iodine as a catalyst without the use of any solvent. The reactions were realized at 50?C for 3 h under stirring and nitrogen. This efficient method yielded highly pure and organosoluble dextran esters. The reaction appears highly effective for obtaining higher degrees of substitution (DS) with great efficiency. Under solvent-free conditions, dextran triacetates were efficiently synthesized. It was also observed that the molar ratio can easily control the DS of pendant groups onto the polymer backbone. Hence, a range of products with varying DS were successfully designed, purified and characterized. Covalent attachment of the pendant groups onto the polymer backbone was verified by spectroscopic techniques. Thermogravimetric analysis indicated that the obtained dextran esters were thermally as stable as dextran. The DS of the pendant groups onto the polymer backbone was calculated using standard acid base titration after saponification. Furthermore, all products were thoroughly characterized by thermal analysis (TG and DTG), and FTIR and 1H-NMR spectroscopic analysis.