Tapas Sen

Superparamagnetic iron oxide nanoparticles (SPIONs): Development, surface modification and applications in chemotherapy

At present, nanoparticles are used for various biomedical applications where they facilitate laboratory diagnostics and therapeutics. More specifically for drug delivery purposes, the use of nanoparticles is attracting increasing attention due to their unique capabilities and their negligible side effects not only in cancer therapy but also in the treatment of other ailments. Among all types of nanoparticles, biocompatible superparamagnetic iron oxide nanoparticles (SPIONs) with proper surface architecture and conjugated targeting ligands/proteins have attracted a great deal of attention for drug delivery applications. This review covers recent advances in the development of SPIONs together with their possibilities and limitations from fabrication to application in drug delivery. In addition, the state-of-the-art synthetic routes and surface modification of desired SPIONs for drug delivery purposes are described.

Fe3O4@mesoporous SBA-15: a robust and magnetically recoverable catalyst for one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones via the Biginelli reaction

A magnetic nanoparticle conjugated mesoporous nanocatalyst (Fe(3)O(4)@mesoporous SBA-15) with a high surface area has been synthesized by chemical conjugation of magnetite (Fe(3)O(4)) nanoparticles with functionalized mesoporous SBA-15. Functionalized mesoporous SBA-15 containing surface carboxyl and amino groups was synthesized via the thiol-ene click reaction of cysteine hydrochloride and vinyl functionalized SBA-15. The catalytic activity of the robust, safe and magnetically recoverable Fe(3)O(4)@mesoporous SBA-15 nanocatalyst was evaluated in the Biginelli reaction under mild conditions for the synthesis of a diverse range of 3,4-dihydropyrimidin-2(1H)-ones. The separation and reuse of the Fe(3)O(4)@mesoporous SBA-15 nanocatalyst were simple, effective and economical.

Mesoporous alumina catalytic material prepared by grafting wide-pore MCM-41 with an alumina multilayer

Abstract An alumina multilayer grafted on the surface of MCM-41 produced a mesoporous material with the surface chemical functionality of alumina. The starting MCM-41 material (WPMCM) with a wide pore size distribution, a surface area of 858 m 2 /g, an average pore diameter of 8.2 nm and a pore volume of 1.75 cm 3 /g was synthesized by expanding the cetyltrimethylammonium chloride (CTAC) surfactant micelles with mesitylene at a high solubilizant/CTAC ratio of 10. Successive grafting consisting of aluminum butoxide anchoring followed by hydrolysis and calcination steps yielded a gradual increase of the aluminum content in WPMCM. Tetrahedral Al in the silica pore walls and clusters of a separate octahedral Al alumina phase were identified. Four grafting cycles produced a material with a surface area of 542 m 2 /g and a mean pore diameter of 4 nm containing 38 wt.% Al 2 O 3 that displayed chemical surface functionality of pure alumina. The activity of this material in the alkylation of phenol with methanol was 2.3 times higher than the activity of a reference alumina (460 m 2 /g). The highest activity of grafted alumina in cumene cracking and isopropanol dehydration was achieved at 21 wt.% Al 2 O 3 . Independent measurements of surface charging in aqueous solution, of [Mo 7 O 24 ] 6− anions adsorption and of surface acidity indicated that the material grafted with alumina and the reference alumina display similar chemical functionality.

Synthesis, Characterization and Catalytic properties of Zeolite PSH-3/MCM-22.

The synthesis, characterization and catalytic properties of PSH-3/MCM-22 are reported. Crystallization kinetics and detailed characterization using X-ray, TGA/DTA, MAS NMR are described. X-ray results show the zeolite to possess an orthorhombic unit cell. Adsorption and catalytic studies indicate that the zeolite has an internal void volume in between that of ZSM-12 and beta.

Extraction of DNA from soil using nanoparticles by magnetic bioseparation

Aims:  To develop a simple, rapid and inexpensive soil DNA extraction protocol.

Fabrication of novel hierarchically ordered porous magnetic nanocomposites for bio-catalysis

Novel hierarchically ordered porous magnetic nanocomposites with interconnecting macroporous windows and meso-microporous walls containing well dispersed magnetic nanoparticles have been fabricated and used as a support to immobilise lipase for the efficient hydrolysis of ester.

Design of water-based ferrofluids as contrast agents for magnetic resonance imaging

We report the synthesis, characterization and relaxometric study of ferrofluids based on iron oxide, with potential for use as magnetic resonance imaging (MRI) contrast agents (CAs). The effect of different cost-effective, water-based surface modification approaches which can be easily scaled-up for the large scale synthesis of the ferrofluids has been investigated. Surface modification was achieved by silanization, and/or coating with non-toxic commercial dispersants (a lauric polysorbate and a block copolymer with pigment affinic groups, namely Tween 20 and Disperbyk 190) which were added after or during iron oxide nanoparticle synthesis. It was observed that all the materials synthesized functioned as negative contrast agents at physiological temperature and at frequencies covered by clinical imagers. The relaxometric properties of the magnetic nanoparticles were significantly improved after surface coating with stabilizers compared to the original iron oxide nanoparticles, with particular reference to the silica-coated magnetic nanoparticles. The results indicate that the optimization of the preparation of colloidal magnetic ferrofluids by surface modification is effective in the design of novel contrast agents for MRI by enabling better or more effective interaction between the coated iron oxide nanoparticles and protons present in their aqueous environment.

Carbon‐Dot‐Sensitized, Nitrogen‐Doped TiO2 in Mesoporous Silica for Water Decontamination through Nonhydrophobic Enrichment–Degradation Mode

Mesoporous silica synthesized from the cocondensation of tetraethoxysilane and silylated carbon dots containing an amide group has been adopted as the carrier for the in situ growth of TiO2 through an impregnation-hydrothermal crystallization process. Benefitting from initial complexation between the titania precursor and carbon dot, highly dispersed anatase TiO2 nanoparticles can be formed inside the mesoporous channel. The hybrid material possesses an ordered hexagonal mesostructure with p6mm symmetry, a high specific surface area (446.27 m(2)  g(-1) ), large pore volume (0.57 cm(3)  g(-1) ), uniform pore size (5.11 nm), and a wide absorption band between λ=300 and 550 nm. TiO2 nanocrystals are anchored to the carbon dot through TiON and TiOC bonds, as revealed by X-ray photoelectron spectroscopy. Moreover, the nitrogen doping of TiO2 is also verified by the formation of the TiN bond. This composite shows excellent adsorption capabilities for 2,4-dichlorophenol and acid orange 7, with an electron-deficient aromatic ring, through electron donor-acceptor interactions between the carbon dot and organic compounds instead of the hydrophobic effect, as analyzed by the contact angle analysis. The composite can be photocatalytically recycled through visible-light irradiation after adsorption. The narrowed band gap, as a result of nitrogen doping, and the photosensitization effect of carbon dots are revealed to be coresponsible for the visible-light activity of TiO2 . The adsorption capacity does not suffer any clear losses after being recycled three times.

Surface engineering of nanoparticles in suspension for particle based bio-sensing

Surface activation of nanoparticles in suspension using amino organosilane has been carried out via strict control of a particle surface ad-layer of water using a simple but efficient protocol ‘Tri-phasic Reverse Emulsion’ (TPRE). This approach produced thin and ordered layers of particle surface functional groups which allowed the efficient conjugation of biomolecules. When used in bio-sensing applications, the resultant conjugates were highly efficient in the hybrid capture of complementary oligonucleotides and the detection of food borne microorganism. TPRE overcomes a number of fundamental problems associated with the surface modification of particles in aqueous suspension viz. particle aggregation, density and organization of resultant surface functional groups by controlling surface condensation of the aminosilane. The approach has potential for application in areas as diverse as nanomedicine, to food technology and industrial catalysis.

Macro-cellular silica foams: synthesis during the natural creaming process of an oil-in-water emulsion

The room-temperature synthesis of a macro-mesoporous silica material during the natural creaming process of an oil-in-water emulsion is reported. The material has 3-dimensional interconnected macropores with a strut-like structure similar to meso-cellular silica foams with mesoporous walls of worm-hole structure. The material has very high surface area (approximately 800 m2 g(-1)) with narrow mesopore size distribution.