Curcumin has restrained clinical applications due to poor bioavailability. This study aimed to synthesize cockle shell-derived calcium carbonate (aragonite) nanoparticles (CSCaCO3NP) for delivery of curcumin and to evaluate its kinetic release in vitro. CSCaCO3NP was synthesized and conjugated with curcumin (Cur-CSCaCO3NP) using a simple top down approach and characterized for its physicochemical properties as a potential curcumin carrier. In vitro release profile was assessed using dialysis bag membrane method. The release data were fitted to Korsmeyer-Peppas, Zero order and Higuchi models to evaluate the mechanism of release pattern. A spherical shaped CSCaCO3NP with a surface area of 14.48±0.1 m2/g, average mean diameter size of 21.38±2.7 nm and a zeta potential of -18.7 mV was synthesized which has a high loading content and encapsulation efficiency. The FT-IR and XRD revealed less observable changes on the peaks after conjugation. In vitro kinetic release profile demonstrated sustained release and best fitted to the Higuchi equation model. The results of this study showed the capacity of the synthesized CSCaCO3NP to encapsulate curcumin efficiently with a stable release in vitro. This could give an insight and supportive ideas on the potentials of CSCaCO3NP for curcumin delivery. Therefore, CSCaCO3NP holds future prospects in preclinical framework to enhance curcumin efficacy for oral therapeutic applications.

In this work we aim to experimentally study the nucleation and growth of CaCO3 phases precipitated from supersaturated aqueous solutions in the presence of varying concentrations of sulphate oxyanion. The experiments were conducted under pH conditions close to neutral (7.6) and considering a wide range of initial (SO42-)/(CO32-) ratios (0 to ~ 68) in the aqueous solution. We paid special attention to the evolution of the precipitates during ageing within a time framework of 14 days. The mineralogy, morphology and composition of the precipitates were studied by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and EDX microanalysis. The concentration of sulphate ions in the reacted aqueous solution was study by ICPs. The experimental results show that the mineral composition of the precipitate recovered in each run varied with the (SO42-)/(CO32-) ratio in the parental solution, which influences the mineral evolution of the precipitates during ageing. We observe that high concentrations of sulphate in the aqueous solution stabilize the vaterite precipitates and inhibit calcite formation. Furthermore, aragonite never precipitates directly form the solution and it is only formed via a dissolution-precipitation process in solutions with high (SO42-)/(CO32-) ratio after long reaction times. Finally, gypsum only precipitates after long ageing in those aqueous solutions with the highest concentration of sulphate. The reaction pathways during ageing, the morphology of the calcite crystals and the composition of vaterite and calcite are discussed considering both, kinetic and thermodynamic factors. These results show a considerably more complex behavior of the system than that observed in experiments conducted under higher pHs and supersaturation levels and lower (SO42-)/(CO32-) ratios in the aqueous phase.

This work presents a new discussion about the vibrational properties of the carbonate ion displayed in several different environments, not only the microparameters introduced by cation substitution and different crystal lattices but also the crystal aggregation, showing how their active Raman modes are affected by these changes by using data obtained with four different laser excitation sources. New Raman spectra excited at 1064 nm are reported for calcite, aragonite, and dolomite groups, also including magnesite, witherite, rhodochrosite, siderite, malachite and azurite. These new data contribute to the discussion and understanding of these materials and their spectra, bringing new observations based on the Raman modes, focusing on the internal symmetrical and asymmetrical stretching and bending modes of the carbonate ion, highlighting the differences observed in the relative intensity and width of the bands. The results indicate some evidence of the influence of the crystal habit and/or the growth of the mineral itself in the Raman spectrum. In addition, the data show the influence of the cation substitution upon the Raman band width and that small cations contribute to less rigid crystalline structures and, consequently, larger Raman bandwidths.

Non-natural mineralization of CaCO3 with special structures or morphology is generated during the crude oil migration, which is the main scale of alkaline/surfactant/polymer (ASP) flooding in oilfields, adversely affecting the oil recovery and causing environmental pollution. Up to now, the mineralization of superstructural symbiotic aragonites and the role of heavy alkyl-benzene sulfonate (HABS) in directing mineralization are still unclear. In this work, rosette-like, bouquet-like and dumbbell-like aragonite-based superstructure of symbiotic CaCO3 crystals were obtained in a simulated O/W emulsion with HABS, which can help understanding the diversified growth of CaCO3 scaling in oilfield. As a result, HABS stabilized micelles acted as a framework for mineralization, and promoted the accumulation of Ca2+ and CO32-, generating pre-nucleation clusters and partial ion pairs by electrostatic attraction. Following, the sequential nucleation of amorphous CaCO3 interconnected with HABS molecules. Finally, these nanoparticles transformed into micro-meter crystals via dissolution-reprecipitation, forming the superstructures that controlled by a synergistic effect between HABS and kerosene phase. This work may enrich the understanding of CaCO3 mineralization in oilfield, provide theoretical support for the prevention of hard carbonate scaling, and also provide a novel strategy for organic-inorganic composites manufacturing.