Synthesis and characterization of novel liquid crystalline cholesteryl-modified hydroxypropyl cellulose derivatives

Abstract

Two new series of cholesteryl-modified hydroxypropyl cellulose (HPC) derivatives were synthesized by performing reactions involving HPC, a cholesterol-based mesogenic dimer (HPC-G1-Chol), or cholesteryl chloroformate (HPC-Chol), all with different degrees of substitution (D Chol ). All of the compounds obtained were characterized by conventional spectroscopic methods. The D Chol values of the modified HPCs was obtained using 1 H NMR spectroscopy. Thermogravimetric analysis and differential scanning calorimetry (DSC) in combination with polarizing optical microscopy (POM) were used to investigate the thermal properties of the compounds obtained. The glass transitions of the modified HPCs occurred at lower temperatures than the glass transition temperature for HPC, but the glass transition temperatures increased with increasing D Chol . All of the synthesized polymers formed thermotropic liquid crystalline phases. Polymers with a mesogenic side chain (i.e., the HPC-G1-Chol series) had wider mesophases than HPC and polymers that were derived from HPCChol. These compounds were found to be soluble in a variety of organic solvents, so they formed lyotropic liquid crystal mesophases in acetone. The critical concentrations above which liquid crystalline order was observed were 20 and 25 wt% for a sample from each series (HPC-G1-Chol and HPC-Chol, respectively) in acetone. It can therefore be hypothesized that HPC-G1-Chol has a greater propensity to exhibit specific chain-chain association phenomena than HPC-Chol in acetone.

Thermosensitive biotinylated hydroxypropyl cellulose-based polymer micelles as a nano-carrier for cancer-targeted drug delivery

“…Methoxy polyethylene glycol (MPEG, MW=550) was purchased from Sigma-Aldrich (Milwaukee, WI, USA). The Cholesteryl derivative of propionic acid (Chol-COOH) was previously synthesized in our laboratory [25], and further details are given below. The purification or drying of compounds and solvents was carried out according to the common procedure.…”

“…Both of these suggest that the intermolecular and intramolecular hydrogen bonding in modified HPCs weakens with the loss of -OH groups. The peak at around 1,650 cm −1 in the modified HPCs' spectrum is probably the result of a more hygroscopic material, because water bound in cellulose fibers or molecules shows a bending absorption at this wave number [25]. 1 H-NMR spectra of both HPC [25] and modified HPCs are shown in Fig.…”

“…Synthesis of Chol-COOH was carried out according to the protocol reported in the literature [25]. Briefly, to the 2,2,2-trichloroethyl-2,2-bis (cholesteryloxycarbonyloxymethyl) propionate (synthesized according to the procedure described by Hult et al [28]) (3 g, 3.12 mmol) dissolved in THF (20 mL), glacial acetic acid (20 mL) was added, and the solution was stirred at room temperature under argon.…”

“…Well-defined cholesterol-based carboxylic acid, Chol-COOH, was prepared according to our previously reported procedures [25], and was characterized by FTIR and 1 H NMR spectroscopy. In this study, we first attempted to synthesize HPC-PEG-Chol through functionalization of the HPC-Chol, with PEG.…”

“…We have previously reported the potential of selfassembling micellar nanoparticles using amphiphilic cholesteryl-modified HPC derivatives (HPC-Chol) with different modification ratios [11,25]. Introduction of cholesterol as a hydrophobic group can enhance the association behavior of HPC-Chol, and the stable activity of the hydrophobic drug can be enhanced by forming a hydrophobic core.…”