Sanjiv Prashar

Study of the cytotoxic activity of di and triphenyltin(IV) carboxylate complexes.

The reaction of 3-methoxyphenylacetic acid (3-MPAH), 4-methoxyphenylacetic acid (4-MPAH), 2,5-dimethyl-3-furoic acid (DMFUH) or 1,4-benzodioxane-6-carboxylic acid (BZDOH) with triphenyltin(IV) chloride (1:1) or diphenyltin(IV) dichloride (2:1) in the presence of triethylamine yielded the compounds [SnPh3(3-MPA)] (1), [SnPh3(4-MPA)] (2), [SnPh3(DMFU)] (3), [SnPh3(BZDO)] (4), [SnPh2(3-MPA)2] (5), [SnPh2(4-MPA)2] (6), [SnPh2(DMFU)2] (7) and [SnPh2(BZDO)2] (8), respectively. The tetranuclear complex [{Me2(DMFU)SnOSn(DMFU)Me2}2] (9) was prepared by the reaction of dimethyltin(IV) oxide and 2,5-dimethyl-3-furoic acid (DMFUH). The molecular structures of 3, 4 and 9, were determined by X-ray diffraction studies. The cytotoxic activity of the carboxylic acids (3-MPAH, 4-MPAH, BZDOH and DMFUH) and di (5-8) and triphenyltin(IV) complexes (2-4) was tested against tumor cell lines human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x and normal immunocompetent cells, peripheral blood mononuclear cells PBMC. Triphenyltin(IV) complexes show higher activities than the diphenyltin(IV) derivatives. The most active compound is [SnPh3(DMFU)] (3) with IC50 value of 0.15+/-0.01, 0.051+/-0.004, 0.074+/-0.004, 0.20+/-0.01, 0.15+/-0.02 on HeLa, K562, Fem-x, rested and stimulated PBMC, respectively, while the most selective are [SnPh2(3-MPA)2] (5), [SnPh(2)(DMFU)2] (7) and [SnPh((BZDO)2] (8). Compounds 3, 5, 7 and 8 present higher activities than cisplatin in all the tested cells and relative high selectivity especially on K562 cells.

Cytotoxic studies of substituted titanocene and ansa-titanocene anticancer drugs

A variety of substituted titanocene and ansa-titanocene complexes have been synthesized and characterized using traditional methods. The cytotoxic activity of the different titanocene complexes was tested against tumour cell lines human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x and normal immunocompetent cells, peripheral blood mononuclear cells PBMC. Alkenyl substitution, either on the cyclopentadienyl ring or on the silicon-atom ansa-bridge of the titanocene compounds [Ti{Me(2)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(3){CMe(2)CH(2)CH(2)CHCH(2)})}Cl(2)] (8), [Ti{Me(CH(2)CH)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)] (9) and [Ti(eta(5)-C(5)H(4){CMe(2)CH(2)CH(2)CHCH(2)})(2)Cl(2)] (12) showed higher cytotoxic activities (IC(50) values from 24+/-3 to 151+/-10 microM) relative to complexes bearing an additional alkenyl-substituted silyl substituent on the silicon bridge [Ti{Me{(CH(2)CH)Me(2)SiCH(2)CH(2)}Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)] (10) and [Ti{Me{(CH(2)CH)(3)SiCH(2)CH(2)}Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)] (11) which causes a dramatic decrease of the cytotoxicity (IC(50) values from 155+/-9 to >200 microM). In addition, the synthesis of the analogous niobocene complex [Nb(eta(5)-C(5)H(4){CMe(2)CH(2)CH(2)CH=CH(2)})(2)Cl(2)] (13), is described. Structural studies based on DFT calculations of the most active complexes 8, 9 and 12 and the X-ray crystal structure of 13 are reported.

A New Generation of Anticancer Drugs: Mesoporous Materials Modified with Titanocene Complexes

Dehydroxylated MCM-41 and SBA-15 surfaces were modified by the grafting of two different titanocene complexes ([Ti(eta(5)-C(5)H(4)Me)(2)Cl(2)] and [Ti{Me(2)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)]) to give new materials, which have been characterized by powder X-ray diffraction, X-ray fluorescence, nitrogen gas sorption, MAS-NMR spectroscopy, thermogravimetry, SEM, and TEM. The toxicity of the resulting materials toward human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x, and normal immunocompetent cells, such as peripheral blood mononuclear cells PBMC has been studied. Estimation of the number of particles per gram of material led to the calculation of Q(50) values for these samples, which is the number of particles required to inhibit normal cell growth by 50%. In addition, M(50) values (quantity of material needed to inhibit normal cell growth by 50%) of the studied surfaces is also reported. Nonfunctionalized MCM-41 and SBA-15 did not show notable antiproliferative activity, whereas functionalization of these materials with different titanocene based anticancer drugs led to very promising antitumoral activity. The best Q(50) values correspond to titanocene functionalized MCM-41 surfaces (MCM-41/[Ti(eta(5)-C(5)H(4)Me)(2)Cl(2)] (1) and MCM-41/[Ti{Me(2)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)] (2)) with Q(50) values between 3.8+/-0.6x10(8) and 24.5+/-3.0x10(8) particles. Titanocene functionalized SBA-15 surfaces (SBA-15/[Ti(eta(5)-C(5)H(4)Me)(2)Cl(2)] (3) and SBA-15/[Ti{Me(2)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)] (4)) gave higher Q(50) values, showing lower activity from 73.2+/-9.9x10(8) to 362+/-7x10(8) particles. The best response of the studied materials in terms of M(50) values was observed against Fem-x (309+/-42 microg for 4) and K562 (338+/-18 microg for 2), whereas moderate activities were observed in HeLa cells (from 508+/-63 microg of 2 to 912+/-10 microg of 1). In addition, the analyzed surfaces presented only marginal activity against unstimulated and stimulated PBMC, showing a slight selectivity on human cancer cells. Comparison of the in vitro cytotoxicity in solution of the titanocene complexes [Ti(eta(5)-C(5)H(4)Me)(2)Cl(2)] and [Ti{Me(2)Si(eta(5)-C(5)Me(4))(eta(5)-C(5)H(4))}Cl(2)] and the corresponding titanocene functionalized materials is also described.

Study of the influence of the metal complex on the cytotoxic activity of titanocene-functionalized mesoporous materials

Four different titanocene complexes, [Ti(η5-C5H5)2Cl2] (1), [Ti(η5-C5H5)(η5-C5H4Pri)Cl2] (2), [Ti(η5-C5H5)(η5-C5H4But)Cl2] (3) and [Ti(η5-C5H5){η5-C5H3(SiMe3)2}Cl2] (4), have been grafted onto dehydroxylated MCM-41 to give the novel materials MCM-41/[Ti(η5-C5H5)2Cl2] (S1), MCM-41/[Ti(η5-C5H5)(η5-C5H4Pri)Cl2] (S2), MCM-41/[Ti(η5-C5H5)(η5-C5H4But)Cl2] (S3) and MCM-41/[Ti(η5-C5H5){η5-C5H3(SiMe3)2}Cl2] (S4), which have been characterized by powder X-ray diffraction, X-ray fluorescence, nitrogen gas sorption, multinuclear MAS NMR spectroscopy, thermogravimetry, UV spectroscopy, SEM and TEM. The cytotoxicity of the non-functionalized MCM-41 and S1–S4 toward human cancer cell lines, such as adenocarcinoma HeLa, human myelogenous leukemia K562 and human malignant melanoma Fem-x, has been studied. Additional studies of the toxicity of these materials on stimulated and non-stimulated peripheral blood mononuclear cells (PBMC + PHA and PBMC − PHA; i.e. normal immunocompetent cells) have been also carried out. M50 values (quantity of material needed to inhibit normal cell growth by 50%) of the studied surfaces are reported observing that non-functionalized MCM-41 did not show notable antiproliferative activity, while the functionalized surfaces S1–S4 were active against all of the studied human cancer cells. The cytotoxic activities of surfaces S1–S3 were very similar on all the studied cancer cells, however, S4 showed M50 values that indicate the highest activity of all the analyzed materials on all the studied cells, being two to three times more cytotoxic than S1–S3. The same tendency in the cytotoxic activity of the metal complexes 1–3 compared with 4 was observed. Taking into account that all the studied surfaces had a very similar titanium content, the activity of these surfaces strongly depends on the grafted titanocene complex (1–4). This phenomenon indicates that, in contrast with that observed by other authors, the cytotoxicity of the studied materials may be due to action of the released metal complex and is probably not due to the particle action.

Study of the cytotoxicity and particle action in human cancer cells of titanocene-functionalized materials with potential application against tumors

Titanocene dichloride [Ti(η(5)-C(5)H(5))(2)Cl(2)] (1), has been grafted onto dehydrated hydroxyapatite (HAP), Al(2)O(3) and two mesoporous silicas MSU-2 (Michigan State University Silica type 2) and HMS (Hexagonal Mesoporous Silica), to give the novel materials HAP/[Ti(η(5)-C(5)H(5))(2)Cl(2)] (S1) (1.01 wt.% Ti), Al(2)O(3)/[Ti(η(5)-C(5)H(5))(2)Cl(2)] (S2) (2.36 wt.% Ti), HMS/[Ti(η(5)-C(5)H(5))(2)Cl(2)] (S3) (0.75 wt.% Ti) and MSU-2/[Ti(η(5)-C(5)H(5))(2)Cl(2)] (S4) (0.74 wt.% Ti), which have been characterized by powder X-ray diffraction, X-ray fluorescence, nitrogen gas sorption, multinuclear magic angle spinning NMR spectroscopy, IR spectroscopy, thermogravimetry analysis, UV spectroscopy, scanning electronic microscopy and transmission electronic microscopy. The cytotoxicity of the titanocene-functionalized materials toward human cancer cell lines from five different histogenic origins: 8505C (anaplastic thyroid cancer), A253 (head and neck cancer), A549 (lung carcinoma), A2780 (ovarian cancer) and DLD-1 (colon cancer) has been determined. M(50) values (quantity of material needed to inhibit normal cell growth by 50%) and Ti-M(50) values (quantity of anchored titanium needed to inhibit normal cell growth by 50%) indicate that the activity of S1-S4 against studied human cancer cells depended on the surface type as well as on the cell line. In addition, studies on the titanocene release and the interaction of the materials S1-S4 with DNA show that the cytotoxic activity may be due to particle action, because no release of titanium complexes has been observed in physiological conditions, while electrostatic interactions of titanocene-functionalized particles with DNA have been observed.

Study of the Anticancer Properties of Tin(IV) Carboxylate Complexes on a Panel of Human Tumor Cell Lines

A group of organotin(IV) complexes were prepared: [SnCy3(DMNI)] (1), [SnCy3(BZDO)] (2), [SnCy3(DMFU)] (3), and [SnPh2(BZDO)2] (4), for which DMNIH=2,6‐dimethoxynicotinic acid, BZDOH=1,4‐benzodioxane‐6‐carboxylic acid, and DMFUH=2,5‐dimethyl‐3‐furoic acid. The cytotoxic activities of compounds 1–4 were tested against pancreatic carcinoma (PANC‐1), erythroleukemia (K562), and two glioblastoma multiform (U87 and LN‐229) human cell lines; they show very high antiproliferative activity, with IC50 values in the 150–700 nM range after incubation for 72 h. Distribution of cellular DNA upon treatment with 1–4 revealed that whereas compounds 1–3 induce apoptosis in most of the cell lines, compound 4 does not affect cell viability in any cell line tested, indicating a possible difference in cytotoxic mechanism. Studies with the daunomycin‐resistant K562/R cell line expressing P‐glycoprotein (Pgp) showed that compounds 1–4 are not substrates of this protein efflux pump, indicating that these compounds do not induce acquisition of multidrug resistance, which is associated with the overexpression of Pgp.

Niobium, titanium, zirconium and hafnium complexes incorporating germanium bridged ansa ligands. X-ray crystal structures of [Zr{Me2Ge(η5-C5Me4)2}Cl2] and [M{Me2Ge(η5-C5Me4)(η5-C5H4)}Cl2] (M = Zr, Hf)

Abstract Both the symmetric and asymmetric ansa-ligand precursors Me2Ge(C5Me4H)2 (1) and Me2Ge(C5Me4H)(C5H4R) (R=H (3), Me (4)) and their lithium derivatives Li2{Me2Ge(C5Me4)2} (5) and Li2{Me2Ge(C5Me4)(C5H3R)} (R=H (6), Me (7)) have been prepared. The ansa-niobocene imido complex [Nb(NBut){Me2Ge(η5-C5Me4)(η5-C5H4)}Cl] (8) was synthesized by the reaction of [Nb(NBut)Cl3(py)2] with the appropriate lithiated ansa-precursor. The Group 4 metal complexes containing germanium bridged ansa-ligands [M{Me2Ge(η5-C5Me4)2}Cl2] (M=Ti (9), Zr (10), Hf (11)), [M{Me2Ge(η5-C5Me4)(η5-C5H4)}Cl2] (M=Ti (12), Zr (13), Hf (14)), and [M{Me2Ge(η5-C5Me4)(η5-C5H3Me)}Cl2] (M=Ti (15), Zr (16), Hf (17)) were prepared by the reaction of MCl4 and the corresponding lithiated ansa-derivative. The molecular structures of 10, 13 and 14 were determined by single-crystal X-ray diffraction studies. Preliminary results for the catalytic activity of the Group 4 ansa-metallocene complexes in the polymerization of ethylene and propylene are reported.

Curcumin-loaded silica-based mesoporous materials: Synthesis, characterization and cytotoxic properties against cancer cells

Two different silica based (MSU-2 and MCM-41) curcumin loaded mesoporous materials V3 and V6 were synthesized and characterized by several physico-chemical techniques. Release kinetic study revealed the slow and sustained release of curcumin from those materials in blood simulated fluid (pH: 7.4). The materials V3 and V6 were found to be biocompatible in non-cancerous CHO cell line while exhibiting significant cytotoxicity in different cancer cells (human lung carcinoma cells: A549, human breast cancer cells: MCF-7, mouse melanoma cells: B16F10) compared to pristine curcumin indicating the efficacy of the mesoporous silica materials based drug delivery systems (DDSs). The generation of intracellular reactive oxygen species (ROS) and down regulation of anti-apoptotic protein leading to the induction of apoptosis were found to be the plausible mechanisms behind the anti-cancer activity of these DDSs. These results suggest that curcumin-loaded drug delivery system may be successfully employed as an alternative treatment strategy for cancer therapeutics through a nanomedicine approach in near future.

Dual application of Pd nanoparticles supported on mesoporous silica SBA-15 and MSU-2: supported catalysts for C–C coupling reactions and cytotoxic agents against human cancer cell lines

Two different mesoporous silica-based materials (SBA-15 and MSU-2) have been treated under mild conditions with different quantities of [PdCl2(cod)] (cod = 1,5-cyclooctadiene) to promote the formation of supported palladium nanoparticles (materials of the type SBA-15–Pd and MSU-2–Pd). The synthesized materials have been characterized by different techniques observing that the palladium nanoparticles remain impregnated in the silica. The catalytic activity of the hybrid Pd–silica materials has been tested in Suzuki–Miyaura C–C coupling reactions observing moderate conversion rates in the reactions of 3-bromoanisole with 4-carboxyphenylboronic acid and 2-bromopyridine with 4-carboxyphenylboronic acid. In addition, the synthesized materials showed a good degree of recyclability, being catalytically active in five consecutive catalytic tests. Finally, in order to evaluate the cytotoxicity of the synthesized materials, in vitro tests against five different human cancer cell lines have been carried out, observing high cytotoxic activities of the hybrid systems comparable if not somewhat higher to other systems based on metal complexes supported on mesoporous silicas described previously in the literature. To the best of our knowledge the cytotoxic study reported here represents the first evaluation of the anticancer action of supported palladium nanoparticles in human cancer cells.

Photodegradation of organic pollutants in water and green hydrogen production via methanol photoreforming of doped titanium oxide nanoparticles

Novel nanomaterials based on doped TiO2 nanoparticles with different morphological, textural and band-gap properties have been synthesized using scalable methods. The influence of synthetic parameters such as titanium source (titanium(IV) isopropoxide and titanium(IV) butoxide), doping quantity (0%, 2% or 5% Zn), acidic solution for the hydrolysis reaction (ascorbic acid, nitric acid) and calcination temperatures (500°C and 600°C) was simultaneously investigated. The obtained nanomaterials were characterized by different methods and photocatalytic tests of methylene blue (MB) degradation under UV-light were conducted to determine their activity. The results revealed that the synthesized nanomaterials are porous aggregates with very high crystallinity and are mainly composed of the anatase phase; although their physical properties vary depending on the different synthetic parameters employed. These changes are able to modify the apparent rate constant of the degradation of MB up to one order of magnitude, indicating, substantial changes in their photoactivity. Hybrid materials TiO2-Pd nanoparticles have also been prepared, characterized and tested for hydrogen production using photocatalytic methanol reforming where supported palladium nanoparticles acted as co-catalyst. Furthermore, the hybrid materials TiO2-Pd nanoparticles were studied in photocatalytic tests of methylene blue degradation under visible LED-light. The results obtained in the production of hydrogen from the photocatalytic reforming of methanol by hybrid materials suggest that the reported hybrid systems could be suitable photocatalysts for future sustainable hydrogen production upon tuning of the morphological, textural and band gap energy properties to allow processes to be carried out under visible light.