Triggered and monitored drug release from bifunctional hybrid nanocomposites

Polymer-coated carbon dot-containing calcium carbonate nanoparticles are reported as unique nanocomposites capable of encapsulating a chemotherapeutic drug and displaying afterglow behaviour.

Dispersive and filter loss performance of calcium carbonate nanoparticles in water for drilling fluid applications

Adding nanoparticles in a drilling fluid can aid in the sealing of the nanopores in the borehole wall rock and the mud cake; in this way, the filtrate loss of the drilling fluid can be reduced and the borehole wall is stabilized. In this work, the spectrophotometric method was used to study the effect of dispersants on calcium carbonate nanoparticles. The best dispersion effect was achieved at cetyltrimethyl ammonium bromide (CTAB) concentration of 4 wt%, dispersing time of 45 min, pH value of 8 and stirring speed of 900 rpm. The structure analysis showed that the adsorption layer was formed on the surface of calcium carbonate nanoparticles after CTAB modification, and no new crystalline compounds appeared. Under these optimized dispersing conditions, aggregation was prevented as manifested by the dramatically decreased average particle size of calcium carbonate nanoparticles while the surface hydrophilicity and Zeta potential of calcium carbonate nanoparticles both increased. Furthermore, we showed that a drilling fluid incorporating such well dispersed calcium carbonate nanoparticles exhibit decreased filter loss and thus better performance in sealing compared to the calcium carbonate nanoparticles without dispersants.

Silanized Silica-Encapsulated Calcium Carbonate@Natural Rubber Composites Prepared by One-Pot Reaction

This article demonstrates the one-pot reaction, an efficient and environmentally friendly organic synthesis method, utilized to prepare the silanized silica-encapsulated calcium carbonate@natural rubber composites (SSC@NR), following first mixing the calcium carbonate (CaCO₃) solution, silica (SiO₂) sol solution and a small amount of Si-69 solution, to modify the surface of CaCO₃ particles, and then wet mixing with natural rubber latex. The obtained silanized silica-encapsulated calcium carbonate (SSC) particles were tested by TGA, FTIR and XRD, to substantiate the effect of surface modification. Moreover, the effects of the amount of SSC on the Mooney viscosity, curing characteristics, physical and mechanical properties and dynamic mechanical properties of the SSC@NR were investigated. The results show that the surface of modified CaCO₃ is effectively coated with SiO₂ particles by means of physical and chemical combination, to achieve the effect of surface coating. When the optimum amount of SSC filler is 40 phr, the SSC can form better physical adsorption and chemical combination with the NR molecular chains and can be evenly dispersed in the rubber matrix, resulting in the conspicuous improvement of physical and mechanical properties, such as the tensile strength, tear strength, elongation at break and abrasion resistance. Meanwhile, the compound with SSC has preferable processability and dynamic mechanical properties.

Adsorption of benzoxaboroles on hydroxyapatite phases

Benzoxaboroles are a family of molecules that are finding an increasing number of applications in the biomedical field, particularly as a "privileged scaffold" for the design of new drugs. Here, for the first time, we determine the interaction of these molecules with hydroxyapatites, in view of establishing (i) how benzoxaborole drugs may adsorb onto biological apatites, as this could impact on their bioavailability, and (ii) how apatite-based materials can be used for their formulation. Studies on the adsorption of the benzoxaborole motif (C7H7BO2, referred to as BBzx) on two different apatite phases were thus performed, using a ceramic hydroxyapatite (HAceram) and a nanocrystalline hydroxyapatite (HAnano), the latter having a structure and composition more similar to the one found in bone mineral. In both cases, the grafting kinetics and mechanism were studied, and demonstration of the surface attachment of the benzoxaborole under the form of a tetrahedral benzoxaborolate anion was established using (11)B solid state NMR (including (11)B-(31)P correlation experiments). Irrespective of the apatite used, the grafting density of the benzoxaborolates was found to be low, and more generally, these anions demonstrated a poor affinity for apatite surfaces, notably in comparison with other anions commonly found in biological media, such as carboxylates and (organo)phosphates. The study was then extended to the adsorption of a molecule with antimicrobial and antifungal properties (3-piperazine-bis(benzoxaborole)), showing, on a more general perspective, how hydroxyapatites can be used for the development of novel formulations of benzoxaborole drugs.

STATEMENT OF SIGNIFICANCE

Benzoxaboroles are an emerging family of molecules which have attracted much attention in the biomedical field, notably for the design of new drugs. However, the way in which these molecules, once introduced in the body, may interact with bone mineral is still unknown, and the possibility of associating benzoxaboroles to calcium phosphates for drug-formulation purposes has not been looked into. Here, we describe the first study of the adsorption of benzoxaboroles on hydroxyapatite, which is the main mineral phase present in bone. We describe the mode of grafting of benzoxaboroles on this material, and show that they only weakly bind to its surface, especially in comparison to other ionic species commonly found in physiological media, such as phosphates and carboxylates. This demonstrates that administered benzoxaborole drugs are unlikely to remain adsorbed on hydroxyapatite surfaces for long periods of time, which means that their biodistribution will not be affected by such phenomena. Moreover, this work shows that the formulation of benzoxaborole drugs by association to calcium phosphates like hydroxyapatite will lead to a rapid release of the molecules.

Recent NMR developments applied to organic-inorganic materials

In this contribution, the latest developments in solid state NMR are presented in the field of organic-inorganic (O/I) materials (or hybrid materials). Such materials involve mineral and organic (including polymeric and biological) components, and can exhibit complex O/I interfaces. Hybrids are currently a major topic of research in nanoscience, and solid state NMR is obviously a pertinent spectroscopic tool of investigation. Its versatility allows the detailed description of the structure and texture of such complex materials. The article is divided in two main parts: in the first one, recent NMR methodological/instrumental developments are presented in connection with hybrid materials. In the second part, an exhaustive overview of the major classes of O/I materials and their NMR characterization is presented.

Redox-responsive nanoreservoirs based on collagen end-capped mesoporous hydroxyapatite nanoparticles for targeted drug delivery

Schematic illustration of a redox-responsive system based on collagen-capped MHAp for cell-targeted drug delivery.

Monitoring bacterially induced calcite precipitation in porous media using magnetic resonance imaging and flow measurements

A range of nuclear magnetic resonance (NMR) techniques are employed to provide novel, non-invasive measurements of both the structure and transport properties of porous media following a biologically mediated calcite precipitation reaction. Both a model glass bead pack and a sandstone rock core were considered. Structure was probed using magnetic resonance imaging (MRI) via a combination of quantitative one-dimensional profiles and three-dimensional images, applied before and after the formation of calcite in order to characterise the spatial distribution of the precipitate. It was shown through modification and variations of the calcite precipitation treatment that differences in the calcite fill would occur but all methods were successful in partially blocking the different porous media. Precipitation was seen to occur predominantly at the inlet of the bead pack, whereas precipitation occurred almost uniformly along the sandstone core. Transport properties are quantified using pulse field gradient (PFG) NMR measurements which provide probability distributions of molecular displacement over a set observation time (propagators), supplementing conventional permeability measurements. Propagators quantify the local effect of calcite formation on system hydrodynamics and the extent of stagnant region formation. Collectively, the combination of NMR measurements utilised here provides a toolkit for determining the efficacy of a biological-precipitation reaction for partially blocking porous materials.