Calixarene-Assisted Pd Nanoparticles in Organic Transformations: Synthesis, Characterization, and Catalytic Applications in Water for C-C Coupling and for the Reduction of Nitroaromatics and Organic Dyes.

A new type of ternary hybrid, Pd@MCM-Calixox, based on mesoporous silica, calixarene conjugate, and Pd(0) nanoparticles (NPs) was synthesized by sacrificial oxidation of allylic calixarene conjugate eventually functionalized with mesoporous silica without using any external reducing agent. The role of the calix conjugate in the formation of Pd@MCM-Calixox has been established. The hybrid, Pd@MCM-Calixox, was characterized by different techniques to support the formation of well-dispersed Pd(0) NPs of 12 ± 2 nm size. The catalyst, Pd@MCM-Calixox, has been proven to be a resourceful one in water in three different types of reactions, namely, Suzuki C-C cross coupling, reduction of both hydrophilic and hydrophobic nitroaromatic compounds, and reduction and degradation of cationic, anionic, and neutral organic dyes. The catalyst exhibited higher turnover frequencies for all these transformations even when a very low concentration of Pd-based catalyst was used. The Pd@MCM-Calixox hybrid catalyst can be recycled several times without experiencing any significant loss in the activity. Also, the regenerated catalyst showed retention of well-spread Pd(0) species even after several catalytic cycles. The tetraallyl calixarene, allylCalix, conjugate acts as a reducing agent, also controls the size, and yields the well-dispersed Pd(0) NPs. The calix conjugate further provides a hydrophobic core in assisting the diffusion of hydrophobic substrates toward catalytic sites.

Silica-Calix Hybrid Composite of Allyl Calix[4]arene Covalently Linked to MCM-41 Nanoparticles for Sustained Release of Doxorubicin into Cancer Cells.

An inorganic-organic hybrid material, MCM-allylCalix, was synthesized by covalent modification of an MCM-41 surface with a tetra-allyl calixarene conjugate. The synthesized hybrid was characterized by 13C and 29Si MAS-NMR, Fourier transform infrared (FT-IR), Brunauer-Emmett-Teller surface area, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) analyses. The application of this MCM-allylCalix hybrid has been demonstrated for loading and in vitro release of doxorubicin (Dox) in phosphate-buffered saline (PBS) buffer as well as in the cancer cells, viz., MCF7, HeLa, and MDA-MB231. The Dox-loaded hybrid, MCM-allylCalix-Dox, was characterized by TEM, FT-IR, TGA, N2 sorption, diffuse refectance spectroscopy-UV, and fluorescence microscopy to confirm the presence of the drug. The release study of the drug from MCM-allylCalix-Dox was carried out in PBS buffer at pH 5 and 7.4. The results showed ∼140% increase in the release of Dox at pH 5 compared to that at pH 7.4 in 144 h, suggesting a pH-triggered release of the drug. MCM-allylCalix-Dox releases a greater amount of Dox compared to that released from unmodified MCM-Dox. Cytotoxicity studies suggested that MCM-allylCalix-Dox exhibits anticancer activity that is dependent on the nature of the cell. The Dox-loaded hybrid shows more cytotoxicity for MCF7 compared to that for the HeLa and MDA-MB231 cells. This was further supported by ∼120% more internalization of Dox into MCF7 cells compared to that in the other two cell lines. Both fluorescence microscopy and fluorescence-activated cell sorting studies suggested concentration-dependent internalization of Dox into the MCF7 and HeLa cells. The results suggested that the inorganic-organic hybrid can be useful in sustained drug delivery into cancer cells.

Mono lacunary phosphomolybdate supported on MCM-41: synthesis, characterization and solvent free aerobic oxidation of alkenes and alcohols.

A new catalyst comprising monolacunary phosphomolybdate and MCM-41 was synthesized and characterized by different physicochemical techniques. The catalytic activity was evaluated by carrying out solvent free aerobic oxidation of alkenes and alcohols. The catalyst showed 60% conversion of styrene and 28% conversion of benzyl alcohol. The superiority of the present catalytic system lies in obtaining better conversion under solvent free and aerobic conditions.

Flare up of choroiditis and choroidal neovasculazation associated with punctate inner choroidopathy during early pregnancy.

A 28-year-old, healthy female, who had a recent repeated history of miscarriage, presented with bilateral choroidal neovascular membranes (CNVM), for which she received photodynamic therapy with three doses of lucentis, at intervals of one month each, to which she responded. After five months, the patient again presented with complaints of diminution of vision since 15 days. She had a history of miscarriage two days before presenting to our clinic. CNVM was scarred at this time and the fundus picture showed multiple small punctate spots around the fovea at the level of the choroid, which showed early hyperfluroscence on fundus fluorescein angiography, suggestive of punctate inner choroidopathy. She was advised systemic steroids, to which she responded dramatically.