@article { ISI:000297470800009, title = {pH Sensitive graft copolymers for zero order drug release: a mechanistic analysis}, journal = {Drug Development and Industrial Pharmacy}, volume = {38}, number = {1}, year = {2012}, month = {JAN}, pages = {73-83}, publisher = {INFORMA HEALTHCARE}, address = {TELEPHONE HOUSE, 69-77 PAUL STREET, LONDON EC2A 4LQ, ENGLAND}, abstract = {

Aliphatic polyesters containing pendent unsaturation were synthesized by the polycondensation of a diol, dicarboxylic acid and glycidyl methacrylate. Grafting methacrylic acid (MAA) resulted in graft copolymers containing polyester backbone and MAA grafts. Depending on composition, the polymers swelled extensively and eroded or dissolved at near neutral pH but remained in collapsed state at acidic pH. Three representative drugs differing in solubility, viz., Diltiazem hydrochloride (DH), Indomethacin (IM) and Verapamil hydrochloride (VH) were released at constant rate from tablets made by compressing spray-dried microparticles. The release of DH at constant rate has been attributed to increase in diffusion coefficient of the drug from the swollen layer of matrix. The release of IM and VH at constant rate was governed by erosion and was enhanced in matrices which undergo dissolution. The release rate was enhanced with increasing MAA content and the frequency of grafts along the polyester backbone. Once a day dosage forms for drugs differing in solubility have been developed using a single polymer matrix which is easy to manufacture.

}, keywords = {Diffusion, erosion, Graft copolymer, matrix tablets, microparticles, spray drying, sustained release}, issn = {0363-9045}, doi = {10.3109/03639045.2011.590991}, author = {Muthusamy, Ramesh and Kulkarni, Mohan Gopalkrishna} } @article {46003, title = {Antisolvent based precipitation: batch, capillary flow reactor and impinging jet reactor}, journal = {Chemical Engineering Journal}, volume = {369}, year = {2019}, month = {AUG }, pages = {1161-1171}, type = {Article}, abstract = {

A method for continuous antisolvent precipitation of ammonium perchlorate (AP) using a confined impinging jet reactor (CIJR) is studied. The geometry of the CIJR was optimized to achieve excellent mixing with a significant reduction in the particle deposition on walls. Initially, the experimental conditions were optimized in a batch system and then in a continuous capillary reactor. Later those conditions extended for antisolvent precipitation of AP in an impinging jet reactor using water and n-butyl alcohol as a solvent and antisolvent, respectively for optimum performance. The performance was compared with the experiments in batch mode as well as and in a continuous capillary reactor. Over a range of inlet jet velocity that corresponded to 1792 \< Re \< 7193 for the saturated aqueous solution of AP and 1135 \< Re \< 4553 for the antisolvent butanol phase, 8.98-16.98 mu m Ammonium perchlorate particles were attained.

}, keywords = {Ammonium perchlorate, Antisolvent precipitation, CFD, continuous flow, Impinging jet reactor, microparticles}, issn = {1385-8947}, doi = {10.1016/j.cej.2019.03.107}, author = {Pal, Sayan and Madane, Ketan and Kulkarni, Amol A.} } @article {48742, title = {i-Indigo-based self-assembled microparticles and their conversion to nanoparticles}, journal = {ChemistrySelect}, volume = {8}, year = {2023}, month = {AUG }, pages = {e202300859}, type = {Article}, abstract = {

Microscopic particles (MPs) are used to scatter and reflect UV light. It is well established that inorganic MPs such as TiO2 and ZnO produce carcinogens. Therefore, organic MPs are explored for UV absorption. Conjugated chromophores with differing lipophilicity usually self-assemble into nanoscopic structures. In our previous experiments, unsymmetrical i-Indigo was found to self-assemble into 500 nm particles. We hypothesized that the size of the self-assembled particles can be increased by increasing the lipophilicity difference between the side chains. Toward this objective, we have chosen the i-Indigo core with TEG and alkyl chains as side chains. As a result, the i-Indigo molecules were found to self-assemble into 3 \& mu; spheres in solution. By substituting side chains with different lipophilicity, i-Indigo microparticles with the size of 5 \& mu; are prepared. A careful analysis showed that the spheres are similar to a soccer ball, and they deflate upon drying on the substrate surface. The judiciously chosen side chain binds with a metal-ion (Cs+) and forms nanoscopic assemblies. After Cs+ binding, the size of the particles is decreased drastically to 100 nm. The simple addition of ions converts microscopic assemblies into nanoscopic assemblies.

}, keywords = {Isoindigo, microparticles, Nanoparticles, Self-assembly, UV absorber}, issn = {2365-6549}, doi = {10.1002/slct.202300859}, author = {Singh, Anup Kumar and Swain, Gitanjali} }