Abstract
In this study, a simple method was used to synthesize novel thermosensitive hydroxybutyl chitosan oligosaccharide (HBCOS) by introducing hydroxybutyl groups to C6–OH of chitosan oligosaccharide (COS) chain. The variation in light scattering demonstrated that HBCOS had good thermosensitive properties and the particle size of HBCOS changed from 2.21–3.58 to 281.23–4,162.40 nm as the temperature increased to a critical temperature (LCST). The LCST of HBCOS (10 mg/ml) decreased from 56.25°C to 40.2°C as the degrees of substitution (DSs) increased from 2.96 to 4.66. The LCST of HBCOS with a DS of 4.66 decreased to 33.5°C and 30°C as the HBCOS and NaCl concentrations increased to 50 mg/ml and 4% (w/v), respectively. Variable-temperature FTIR spectroscopy confirmed that dehydration of hydrophobic chains and the transition of hydrogen bonds were the driving forces for the phase transition of HBCOS. Moreover, HBCOS was not cytotoxic at different concentrations. This work generated a novel thermosensitive HBCOS with tunable thermoresponsive properties and excellent biocompatibility, which may be a potential nanocarrier for the biomedical application.
Highlights
Over the past decades, environment-sensitive materials have gained extensive attention because of their controllable shrinkage or swelling behaviors in response to specific physicochemical stimuli including temperature, pH, light, and ionic strength (Chen et al, 2017; Ji et al, 2017; Yu et al, 2018; Theune et al, 2019)
Compared with the spectra of chitosan oligosaccharide (COS), additional peaks were observed in all hydroxybutyl chitosan oligosaccharide (HBCOS) at 2,964–2,878 and 1,460 cm−1, which were attributed to the stretching of C–H and bending of –CH3 groups in the hydroxybutyl groups (Jiang et al, 2019)
C6–OH in COS at 1,028 cm−1 was shifted to 1,063 cm−1 in HBCOSs after introducing the hydroxybutyl groups, indicating that hydroxybutyl substitution occurred at C6–OH (Jiang et al, 2019)
Summary
Environment-sensitive materials have gained extensive attention because of their controllable shrinkage or swelling behaviors in response to specific physicochemical stimuli including temperature, pH, light, and ionic strength (Chen et al, 2017; Ji et al, 2017; Yu et al, 2018; Theune et al, 2019). The stimuli-responsive properties of these materials make them ideal platforms for drug delivery as they can release the entrapped drug at the appropriate time and location. Numerous synthetic thermo-responsive materials including poly (N-isopropylacrylamide) (PNIPAAm), poly (N,N-diethylacrylamide) (PDEAAm), poly (ethylene oxide), and poly (N-vinlycaprolactam) (PVCL) have been developed over the years for biomedical applications (Ward and Georgiou, 2011; Zhang et al, 2016). The phase transition behavior of such synthetic polymers is controlled by the proportion, chain length, molecular weight, and architecture of copolymerizable hydrophilic or hydrophobic monomers (Ward and Georgiou, 2011).
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