A ethylenediaminetetra-acetic acid (EDTA) cross-linked chitosan and N,N-methylenebis(acrylamide) (MBA) cross-linked polyacrylamide based double network hydrogel was successfully synthesized via a two-step method and then employed for heavy metal ion adsorption. Various adsorption conditions, such as pH, ionic strength, adsorbent dosage, and contact time were investigated. CTS/PAM gel have a theoretical maximum Cd(II), Cu(II), and Pb(II) sorption capacities of 86.00, 99.44, and 138.41 mg/g, respectively, at experimental conditions. The adsorption process of CTS/PAM gel on the heavy metal ion was identified to be endothermic and follows an ion-exchange reaction. The application of this gel adsorbent was demonstrated using practical industrial effluent. We found that it could effectively treat practical wastewater with all kinds of heavy metals. At an adsorbent dosage of 8 g/L, the total metal ions concentration declined from 448.5 to 5.0 mg/L. Simultaneously, the CTS/PAM gel exhibited remarkable mechanical strength and good recyclability. This study shows that CTS/PAM gel offers great potential for practical application in the removal of heavy metal ions from contaminated aquatic systems.

Recently, coamorphous systems, composed of a drug and a guest molecule, have gained increasing interest, due to their ability to overcome limitations associated with amorphous drug alone. In this study, a single-phase coamorphous form of lurasidone hydrochloride (LH) (a water-insoluble atypical antipsychotic agent with pH-dependent solubility) with saccharin (SAC) in a 1:1 molar ratio was obtained and characterized by differential scanning calorimetry and powder X-ray diffraction. Peak shifts in the Fourier transform infrared spectra indicated the formation of charge-assisted hydrogen bonds between the N + -H group of LH and the CO group of SAC. In comparison to crystalline LH, amorphous LH showed similar solubility and temporary improvement in the intrinsic dissolution rate and supersaturated dissolution, while coamorphous LH-SAC exhibited greatly improved solubility with pH-independent solubility behavior in a pH range of 2−5.5, as well as a persistent enhanced intrinsic dissolution rate and supersaturated dissolution. In addition, coamorphous LH-SAC showed superior physical stability compared to amorphous LH under the long-term storage condition. The coamorphization effect and charge-assisted hydrogen bond in coamorphous LH-SAC were speculated to be responsible for the above phenomena by prohibiting the recrystallization of LH.

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Pharmaceutical cocrystal has gained increasing interest due to its ability to modify various physicochemical properties of hydrophobic drugs, especially solubility and dissolution. The temporarily generated supersaturation during the dissolution of cocrystals, usually called “spring and parachute” effect, would favor the oral absorption of poorly soluble drugs. In this study, biopharmaceutics classification system II drug ibuprofen (IBU) was cocrystallized with nicotinamide (NIC) by slow solvent evaporation. An AP-type complexation between IBU and NIC was observed by phase solubility study, and complexation phenomenon was verified by fluorescence quenching method. Reduction of solvation barrier by inserting extremely soluble NIC in the crystal lattice of IBU makes the cocrystal gain a 70-fold higher aqueous solubility than that of original crystalline IBU. A novel mathematic model, considering both the ionization of IBU and the complexation between IBU and NIC, was developed and well-fitted to experimental pH solubility of cocrystal. Surprisingly, instead of common spring and parachute, the prepared IBU-NIC cocrystal demonstrated an initially rapid dissolution followed by a constant high concentration, like a helicopter hovering in the sky, during its nonsink dissolution. Such a result is interpreted with a spring and hover model, which should be ascribed to the enhanced IBU solubility by complexation with the coformer NIC.

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