Hydrophobic starch esters have potential as tablet matrix formers in controlled drug delivery. The mechanical properties of native starch (SN), starch acetate (SA) and starch propionate (SP) were studied at particle and compact level. Particle microhardness and modulus of elasticity were evaluated by nanoindentation. Force-displacement data of compressed powder were analyzed using Heckel in conjunction with piecewise regression, Kuentz-Leuenberger, Kawakita and Adams models, and yield pressure parameters were derived. Starches were characterized for chemical structure by Raman spectroscopy, crystallinity from powder x-ray diffraction (PXRD) patterns and surface energy from apparent contact angle measurements. A-type starch reflections were absent in the PXRDs of esters indicating greater amorphicity. Consequently, the particle microhardness of starch esters decreased leading to greater deformation during compaction and lower values of yield pressure parameters. These parameters increased with microhardness and ranked the starches in the order: SP < SA < SN. Fitting the experimental data into Hiestand's bonding index equation, a linear correlation (R2 = 0.902) was established between experimental and calculated tablet strength describing results of all starches, when Adams (το') yield pressure was used as the 'effective compression pressure' in the above equation.

中文翻译：

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淀粉酯在颗粒和致密水平上的机械性能-Hiestand方程预测片剂强度的适用性的比较和探索。

疏水性淀粉酯在控制药物输送方面具有作为片剂基质形成剂的潜力。在颗粒和致密水平下研究了天然淀粉（SN），乙酸淀粉（SA）和丙酸淀粉（SP）的机械性能。通过纳米压痕评价颗粒的显微硬度和弹性模量。使用Heckel结合分段回归，Kuentz-Leuenberger，Kawakita和Adams模型分析了压缩粉末的力-位移数据，并得出了屈服压力参数。通过拉曼光谱对淀粉的化学结构，粉末X射线衍射（PXRD）图的结晶度以及表观接触角测量的表面能进行表征。酯的PXRD中没有A型淀粉反射，表明无定形性更高。所以，淀粉酯的颗粒显微硬度降低，导致压实过程中变形更大，屈服压力参数值降低。这些参数随显微硬度的增加而增加，并按以下顺序对淀粉进行排名：SP <SA <SN。将实验数据拟合到Hiestand的键合指数方程中，当描述所有淀粉的结果时，当将Adams（το）屈服压力用作“有效压缩压力”时，在实验和计算的片剂强度之间建立了线性相关性（R2 = 0.902）。以上等式。