Synthesis of Silica-Coated Magnetic Hydroxyapatite Composites for Drug Delivery Applications.

We have prepared a core-shell magnetic silica-coated hydroxyapatite, Fe3O4@SiO2@HAp composite materials for pH-responsive drug delivery applications. Captopril (Cap) and ibuprofen (Ibu) were chosen as model hydrophilic and hydrophobic drugs, respectively. The drugs were encapsulated into the Fe3O4@SiO2@HAp composite via electrostatic interactions with existing amine and carboxylic acid groups during calcium phosphate shell formation. The formation of calcium phosphate shell not only protects the encapsulated drugs from leaching but also controls the release rate of drugs from the composite system depending on various pH conditions. We have tested the release behavior of Cap and Ibu drugs under different pH conditions such as neutral pH (pH 7.4) and acidic pH (pH 5.0), respectively. The study result reveals that the synthesized Fe3O4@SiO2@HAp composite is suitable for release of both water soluble and water insoluble drugs based on a pH-responsive controlled manner.

Synthesis of surface capped mesoporous silica nanoparticles for pH-stimuli responsive drug delivery applications.

Mesoporous silica-based drug delivery carriers mostly require appropriate surface modifications to improve their drug delivery efficiency and to reduce their adverse side effects. In the present work, we have synthesised mesoporous silica nanoparticles and their surface was covered by using capping units such as tetrathio-maleimide (TTM) via a "host-guest" complexation mechanism for pH-responsive drug delivery applications. The surface-functionalised melamine (Mela) groups on the outer surface of the mesoporous silica nanoparticles act as "hosts" and the surface capped TTM units act as "guests" during the surface capping of the mesoporous silica nanoparticles via the "host-guest" complexation approach. After the encapsulation of cargoes into the mesopore channels, the melamine functional groups were covalently immobilised onto the outer surface of the cargo loaded MSNs and then the TTM units were introduced onto the outer surface of the silica nanoparticles as "gatekeepers" to obtain surface capped mesoporous silica (MSN@Mela@TTM/RhB) NPs to protect the loaded cargo molecules inside the mesopore channels and to prevent their premature leakage. The surface-capped TTM units controlled the drug release behavior with respect to the pH of the release medium. In this study, we used rhodamine B (RhB) as a model cargo to study the loading and pH-responsive release behavior of the MSN@Mela@TTM NPs. The encapsulated RhB molecules were retained inside the mesopore channels at physiological pH (pH 7.4) conditions while an enhanced release occurred at acidic pH (pH 5.0 and 4.0) conditions, respectively. Furthermore, the in vitro biocompatibility and the intracellular uptake efficiency of the synthesised MSNs@Mela@TTM NPs were examined by using the MDA-MB-231 cell line. The experimental results suggest that the MSNs@Mela@TTM nanoparticles are biocompatible and could be utilised for pH-stimuli responsive drug delivery applications.

Assessment of bacterial community composition in response to uranium levels in sediment samples of sacred Cauvery River.

Global industrialization is a major cause of effluent discharge from industries up to alarming concentrations. Especially, uranium concentrations in water bodies are of great concern, as its radioactivity significantly affects the persistent diversity of microbiota. Recently, continuous application of pesticides in the agricultural lands and accumulation of quartz that enter the Cauvery River has significantly increased the concentration of uranium (U) and other heavy metals. To perceive the impact of uranium on bacterial diversity in Cauvery River, sediment samples collected from polluted (UP) site with 32.4 Bq/K of U concentration and control (UNP) site were scrutinized for bacterial diversity through metagenomic analysis of the V3 region of 16S rDNA by Illumina sequencing. Taxonomic assignment revealed that the unpolluted sample was dominated by Bacteroidetes (27.7 %), and Firmicutes (25.9 %), while sediment sample from the highly polluted site revealed abundance of Proteobacteria (47.5 %) followed by Bacteroidetes (22.4 %) and Firmicutes (14.6 %). Among Proteobacteria, Gammaproteobacteria was the most prevalent group followed by alpha, delta, epsilon, and beta in the uranium-polluted sample. Rare and abundant species analysis revealed that species like Idiomarina loihiensis was abundant in the pollutant sample; however, it was rare (<0.1 %) in the sample from pristine environment. Similarly, the species distribution in both the samples varied, with the bacteria potentially active in redox activity and biosorption potential dominating in the polluted sample. Outcomes of the present study demonstrated the impact of uranium and metal accumulation on the bacterial communities and further confirmed the promising candidature of specific bacterial species as bioindicators of contamination.