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A new particle design method was proposed for the production of hydrophobic corn starch with high flowability by surface modification. The flowability and hydrophobicity of the native and modified corn starches were investigated by wettability (activation index) and flowability experiments (flow time), scanning electron microscopy (SEM), and X-ray diffraction (XRD). In corn starch modification, the optimal modifying agent is a mixture of tetraisopropyldi(dioctylphosphate)titanate (NDZ-401) and methyl hydrogen silicone oil (H202), and the optimal content is 1% (w/w). The optimal content of flow agent (R972 silica) is 1% (w/w). The results indicate that the modified corn starch is a free flowing powder, which is also remarkably water repellent. The crystalline structures of the native and modified corn starches are similar, and only the surface properties are changed from hydrophilic to hydrophobic.

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This work aimed to investigate the novel application of hydroxypropyl methylcellulose (HPMC) to improving the direct compaction properties of tablet fillers by co-spray drying. Commonly used three types of fillers were 10 investigated. Two representatives were chosen for each type, i.e., (i) water-soluble small molecules: lactose and mannitol; (ii) water-insoluble small molecules: calcium carbonate and anhydrous dibasic calcium phosphate; and (iii) macromolecules: corn starch (practically insoluble in cold water) and chitosan (sparingly soluble in water). Except for chitosan, improvements on both powder properties (e.g., flowability and hygroscopicity) and tableting properties (e.g., tableting ratio, yield pressure, tensile strength, and E sp ) were 15 achieved for the rest five fillers by co-spray drying with a small amount of HPMC. This is mainly attributed to the homogeneous distribution of plastic and nonhygroscopic HPMC macromolecules on the surface of the primary and composite particles. In addition, changes induced by spray drying, such as agglomeration, spheroidization, porosity increase, amorphous formation, and gelatinization, also contribute to some degree to the improvements. The above results, together with the data of lubrication sensitivity and tablet disintegration, 20 show that such a novel application of HPMC is effective and promising.

The publisher regrets not revising the caption for Fig. 1 as instructed by the author at the proof stage of the article. The revised caption for Fig. 1 appears below. The original article was corrected. Fig. 1. Three dimensional response surface plots of the developed models. a starch-HPMC powders. b calcium hydrogen phosphate dihydrate-HPMC powders. c mannitol-HPMC powders. % A HPMC concentration in products (w/w); % B concentration of solid content in feeds (w/v); ρb bulk density; ρta tap density; D(0.5) the median particle size; TS tensile strength; DTP disintegration time of tablets composed of 96.5% the coprocessed excipient and 3.5% PVPP; DT disintegration time of tablets containing the co-processed excipient only; Py yield pressure; Esp, unit effective compaction work.The online version of the original article can be found at http:// dx