Yuan Youling, Chesnutt Betsy M, Haggard Warren O, Bumgardner Joel D
Department of Biomedical Engineering, University of Memphis, Memphis, TN 38152, USA.
Materials (Basel). 2011 Aug 12;4(8):1399-1416. doi: 10.3390/ma4081399.
Degree of deacetylation (DDA) and molecular weight (MW) of chitosans are important to their physical and biological properties. In this study, two chitosans, HS (DDA = 73.3%) and AT (DDA = 76.8%), were deacetylated with 45% sodium hydroxide under nitrogen atmosphere at 80 °C or 90 °C for up to 120 min, to obtain two series of chitosans. The polymers produced were characterized for MW by gel permeation chromatography, DDA by titration and UV-vis methods, and crystallinity, hydrophilicity and thermal stability by X-ray diffraction, water contact angle and differential scanning calorimetry respectively. Films, made by solution casting in dilute acetic acid at ambient conditions, were evaluated for biological activity by albumin adsorption and the attachment and growth of a pre-osteoblast cell line. Chitosans with between 80-93% DDA's (based on titration) were reproducibly obtained. Even though deacetylation under nitrogen was supposed to limit chain degradation during decetylation, MW decreased (by maximum of 37.4% of HS and 63.0% for AT) with increasing deacetylation reaction time and temperature. Crystallinity and decomposition temperature increased and water contact angles decreased with processing to increase DDA. Significantly less albumin was absorbed on films made with 93% DDA chitosans as compared with the original materials and the AT chitosans absorbed less than the HS chitosans. The cells on higher DDA chitosan films grew faster than those on lower DDA films. In conclusion, processing conditions increased DDA and influenced physicochemical and biological properties. However, additional studies are needed to unambiguously determine the influence of DDA or MW on in vitro and in vivo performance of chitosan materials for bone/implant applications.
壳聚糖的脱乙酰度（DDA）和分子量（MW）对其物理和生物学性质至关重要。在本研究中，两种壳聚糖，HS（DDA = 73.3%）和AT（DDA = 76.8%），在氮气氛围下于80℃或90℃用45%的氢氧化钠脱乙酰长达120分钟，以获得两个系列的壳聚糖。通过凝胶渗透色谱法表征所制备聚合物的MW，通过滴定法和紫外 - 可见光谱法表征DDA，分别通过X射线衍射、水接触角和差示扫描量热法表征结晶度、亲水性和热稳定性。在环境条件下于稀醋酸中通过溶液浇铸制成的薄膜，通过白蛋白吸附以及前成骨细胞系的附着和生长来评估其生物活性。可重复获得DDA在80 - 93%之间（基于滴定）的壳聚糖。尽管在氮气下脱乙酰被认为可限制脱乙酰过程中的链降解，但随着脱乙酰反应时间和温度的增加，MW降低（HS最多降低37.4%，AT降低63.0%）。随着脱乙酰度增加，结晶度和分解温度升高，水接触角降低。与原始材料相比，用93% DDA壳聚糖制成的薄膜上吸附的白蛋白明显更少，且AT壳聚糖吸附的白蛋白比HS壳聚糖少。较高DDA壳聚糖薄膜上的细胞比较低DDA薄膜上的细胞生长得更快。总之，加工条件提高了DDA并影响了物理化学和生物学性质。然而，需要进一步研究以明确确定DDA或MW对用于骨/植入应用的壳聚糖材料的体外和体内性能的影响。
