@article {42631, title = {Crystal engineering of a zwitterionic drug to neutral cocrystals: a general solution for floxacins}, journal = {Chemical Communications}, volume = {52}, year = {2016}, month = {SEP}, pages = {12610-12613}, abstract = {

The transformation of zwitterionic Sparfloxacin (SPX) to the neutral form is achieved by cocrystallization. Neutral forms of drugs are important for higher membrane permeability, while zwitterions are more soluble in water. The twin advantages of higher solubility/dissolution rate and good stability of neutral SPX are achieved in a molecular cocrystal compared to its zwitterionic SPX hydrate. The amine-phenol supra-molecular synthon drives cocrystal formation, with the paraben ester acting as a "proton migrator{\textquoteright}{\textquoteright} for the ionic to neutral transformation.

}, doi = {10.1039/c6cc06627e}, author = {Gunnam, Anilkumar and Suresh, Kuthuru and Ganduri, Ramesh and Nangia, Ashwini} } @article {46118, title = {Crystalline acylhydrazone photoswitches with multiple mechanical responses}, journal = {Crystal Growth \& Design}, volume = {19}, year = {2019}, month = {MAY}, pages = {3039-3044}, type = {Article}, abstract = {

The advancement of our understanding of stimuli responsive molecular crystals has led to the realization that they hold great yet unexplored potential as adaptive materials. Although molecular crystals that exhibit a single mechanical response to a single input stimulus are now abundant, crystals that are capable of response to multiple stimuli are rather scarce. Here we report two photoswitchable acylhydrazone derivatives, Ac-1 and Ac-2, which respond to light as well as to mechanical force. Upon application of localized mechanical stress, the anhydrous (Ac-1a) and monohydrate (Ac-1h) crystals of Ac-1 undergo plastic shearing deformation and bending, whereas monohydrate crystals of Ac-2 undergo elastic deformation. When they are exposed to UV light, crystals of Ac-1h and Ac-2 undergo photoinduced bending; on the other hand, crystals of Ac-1a and thicker crystals of Ac-2 exhibit photosalient effect (light-induced leaping). It is demonstrated that the synergistic action of multiple stimuli (UV light and force) elicits enhanced mechanical response, and this strategy could be employed in the future to increase the efficacy of single crystal actuators.

}, issn = {1528-7483}, doi = {10.1021/acs.cgd.8b01860}, author = {Gupta, Poonam and Panda, Tamas and Allu, Suryanarayana and Borah, Silpisikha and Baishya, Anamika and Gunnam, Anilkumar and Nangia, Ashwini and Naumov, Pance and Nath, Naba K.} } @article {48812, title = {Cocrystallization of multi-kinase inhibitor pazopanib with fenamic acids: improving dissolution and inhibiting cell migration}, journal = {CrystEngComm}, volume = {25}, year = {2023}, month = {OCT }, pages = {5565-5574}, type = {Article}, abstract = {

A multi-kinase inhibitor, pazopanib (PAZ) is cocrystallized with cyclooxygenase (COX) inhibitor fenamic acids to investigate the dissolution rate and inhibition of cell migration in VEGF-triggered HUVEC cells to test the efficacy of stoichiometric drug-drug combinations. Crystallization experiments at the sub-milligram level in an acetonitrile-methanol mixture yielded two drug-drug salt forms of PAZ with flufenamic acid (FFA) and niflumic acid (NFA) as PAZ+center dot FFA-center dot ACN (an acetonitrile solvate named as form I) and PAZ+center dot NFA-. Structures of the crystal forms were characterized by single crystal X-ray diffraction (SC-XRD) method. Crystal structures revealed that the presence of a 2-aminopyrimidine group in PAZ is a strong partner for the carboxyl group in all solid forms, forming an acidMIDLINE HORIZONTAL ELLIPSISpyrimidine heterosynthon with COX inhibitor fenamic acids. To perform dissolution experiments and cell line analysis, the scale-up of both salt forms were done in the acetonitrile-methanol mixture through crystallization, which showed a polymorphic transformation in the case of PAZ+center dot FFA-center dot ACN (an acetonitrile solvate named form II). The thermodynamic stability of PAZ+center dot FFA-center dot ACN (form II) and PAZ+center dot NFA- were analysed using slurry experiment under ambient conditions in pH 1.2 (0.1 N HCl) buffer medium and the residual solid phase was characterized by powder XRD, which showed that PAZ+center dot FFA-center dot ACN (form II) was a metastable solid form while PAZ+center dot NFA- was a stable solid form. The dissolution experiments at gastric pH 1.2 showed that the rate of dissolution of PAZ+center dot FFA-center dot ACN was 10 times higher than PAZ+center dot NFA-. The cell migration assay suggested that PAZ+center dot FFA-center dot ACN inhibited similar to 25\% and PAZ+center dot NFA- inhibited similar to 20\% migration of HUVEC cells compared to PAZ alone. These investigations suggested that the drug-drug salts PAZ+center dot FFA- and PAZ+center dot NFA- would be potential combo drug candidates for clinical trials. Multi-drug crystalline salts of pazopanib with fenamic acids exhibit enhanced dissolution and 20\% higher inhibition in the migration of HUVEC cells compared to the reference drug.

}, doi = {10.1039/d3ce00773a}, author = {Rai, Sunil K. and Gunnam, Anilkumar and Roy, Debopriya and Rajput, Raveena and Kulkarni, Kiran and Nangia, Ashwini K.} }