[Show abstract][Hide abstract] ABSTRACT: The interactions of nanomaterials with plasma proteins have a significant impact on their in vivo transport and fate in biological fluids. This article discusses the binding of human serum albumin (HSA) to poly(amidoamine) [PAMAM] dendrimers. We use protein-coated silica particles to measure the HSA binding constants (K(b)) of a homologous series of 19 PAMAM dendrimers in aqueous solutions at physiological pH (7.4) as a function of dendrimer generation, terminal group, and core chemistry. To gain insight into the mechanisms of HSA binding to PAMAM dendrimers, we combined (1)H NMR, saturation transfer difference (STD) NMR, and NMR diffusion ordered spectroscopy (DOSY) of dendrimer-HSA complexes with atomistic molecular dynamics (MD) simulations of dendrimer conformation in aqueous solutions. The binding measurements show that the HSA binding constants (K(b)) of PAMAM dendrimers depend on dendrimer size and terminal group chemistry. The NMR (1)H and DOSY experiments indicate that the interactions between HSA and PAMAM dendrimers are relatively weak. The (1)H NMR STD experiments and MD simulations suggest that the inner shell protons of the dendrimers groups interact more strongly with HSA proteins. These interactions, which are consistently observed for different dendrimer generations (G0-NH(2)vs G4-NH(2)) and terminal groups (G4-NH(2)vs G4-OH with amidoethanol groups), suggest that PAMAM dendrimers adopt backfolded configurations as they form weak complexes with HSA proteins in aqueous solutions at physiological pH (7.4).
[Show abstract][Hide abstract] ABSTRACT: We investigate for the first time hydrophobic carbon nanotube-based electrochemical cells as an alternative solution to hydrogen sorting. We show that the electrically conducting surface of the nanotube arrays can be used as a cathode for hydrogen generation and absorption by electrolyzing water. We support our findings with Raman and gas chromatography measurements. These results suggest that carbon nanotube forests, presenting a unique combination of hydrophobicity and conductivity, are suitable for application in fuel cells and microelectromechanical devices.
[Show abstract][Hide abstract] ABSTRACT: We describe folate receptor targeted thermosensitive magnetic liposomes, which are designed to combine features of biological and physical (magnetic) drug targeting for use in magnetic hyperthermia-triggered drug release. The optimized liposome formulation DPPC:cholesterol:DSPE-PEG(2000):DSPE-PEG(2000)-Folate at 80:20:4.5:0.5 molar ratio showed calcein release of about 70% both in PBS and in 50% FBS (fetal bovine serum) at 43 degrees C and less than 5% release at 37 degrees C following 1h incubation. Folate-targeted doxorubicin-containing magnetic liposomes of the above lipid composition (MagFolDox) showed encapsulation efficiencies of about 85% and 24% for doxorubicin and magnetic nanoparticles (mean crystallite size 10nm), respectively. This magnetic formulation displayed the desired temperature sensitivity with 52% doxorubicin release in 50% fetal bovine serum (FBS) following 1h incubation at 43 degrees C. MagFolDox, when physically targeted to tumor cells in culture by a permanent magnetic field yielded a substantial increase in cellular uptake of doxorubicin as compared to Caelyx (a commercially available liposomal doxorubicin preparation), non-magnetic folate-targeted liposomes (FolDox) and free doxorubicin in folate receptor expressing tumor cell lines (KB and HeLa cells). This resulted in a parallel increase in cytotoxicity over Caelyx and FolDox. Magnetic hyperthermia at 42.5 degrees C and 43.5 degrees C synergistically increased the cytotoxicity of MagFolDox. The results suggest that an integrated concept of biological and physical drug targeting, triggered drug release and hyperthermia based on magnetic field influence can be used advantageously for thermo-chemotherapy of cancers.
[Show abstract][Hide abstract] ABSTRACT: Dendritic nanomaterials are emerging as key building blocks for a variety of nanoscale materials and technologies. Poly(amidoamine) (PAMAM) dendrimers were the first class of dendritic nanomaterials to be commercialized. Despite numerous investigations, the environmental fate, transport, and toxicity of PAMAM dendrimers is still not well understood. As a first step toward the characterization of the environmental behavior of dendrimers in aquatic systems, we measured the octanol-water partition coefficients (logK(ow)) of a homologous series of PAMAM dendrimers as a function of dendrimer generation (size), terminal group and core chemistry. We find that the logK(ow) of PAMAM dendrimers depend primarily on their size and terminal group chemistry. For G1-G5 PAMAM dendrimers with terminal NH2 groups, the negative values of their logK(ow) indicate that they prefer to remain in the water phase. Conversely, the formation of stable emulsions at the octanol-water (O/ W) interface in the presence of G6-NH2 and G8-NH2 PAMAM dendrimers suggest they prefer to partition at the O/W interface. In all cases, published studies of the cytotoxicity of Gx-NH2 PAMAM dendrimers show they strongly interact with the lipid bilayers of cells. These results suggest that the logK(ow) of a PAMAM dendrimer may not be a good predictor of its affinity with natural organic media such as the lipid bilayers of cell membranes.
[Show abstract][Hide abstract] ABSTRACT: Nanomagnetic particles have great potential in the biomedical applications like MRI contrast enhancement, magnetic separation, targeting delivery and hyperthermia. In this paper, we have explored the possibility of biomedical applications of [Fe1−xBxFe2O4, B=Mn, Co] ferrite. Superparamagnetic particles of substituted ferrites [Fe1−xBxFe2O4, B=Mn, Co (x=0–1)] and their fatty acid coated water base ferrofluids have been successfully prepared by co-precipitation technique using NH4OH/TMAH (Tetramethylammonium hydroxide) as base. In vitro cytocompatibility study of different magnetic fluids was done using HeLa (human cervical carcinoma) cell lines. Co2+-substituted ferrite systems (e.g. CoFe2O4) is more toxic than Mn2+-substituted ferrite systems (e.g. MnFe2O4, Fe0.6Mn0.4Fe2O4). The later is as cytocompatible as Fe3O4. Thus, Fe1−xMnxFe2O4 could be useful in biomedical applications like MRI contrast agent and hyperthermia treatment of cancer.
Journal of Magnetism and Magnetic Materials 03/2008; 320(5-320):724-730. DOI:10.1016/j.jmmm.2007.08.010 · 1.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this study, lauric acid-coated, superparamagnetic, nanoparticle-based magnetic fluids of different ferrites (Fe(3)O(4), MnFe(2)O(4), and CoFe(2)O(4)) were prepared and compared in terms of heating ability and biocompatibility to evaluate the feasibility of use in hyperthermia treatment of cancer. All the magnetic fluids prepared had particles of average sizes 9-11 nm. Heating ability of these magnetic fluids was evaluated by calorimetric measurement of specific absorption rate (SAR) at 300 kHz frequency and 15 kA/m field. Fe(3)O(4) and MnFe(2)O(4) showed higher SAR (120 and 97 W/g of ferrite, respectively) than CoFe(2)O(4) (37 W/g of ferrite). In vitro study on BHK 21 cell lines showed dose-dependent cell viability for all the magnetic fluids. Threshold-biocompatible ferrite concentration for all the magnetic fluids was 0.1 mg/mL. Above 0.2 mg/mL, CoFe(2)O(4) was more toxic than the other magnetic fluids. On intravenous injection of different doses (50, 200, and 400 mg/kg body weight) of magnetic fluids in mice, no significant changes in hematological and biochemical parameters were observed for Fe(3)O(4) and MnFe(2)O(4). With CoFe(2)O(4), an increase in SGPT levels at a dose rate of 400 mg/kg body weight was observed, indicating its mild hepatotoxic effect. However, histology of different vital organs showed no pathological changes for all the three magnetic fluids. Further, long term in vivo evaluation of biocompatibility of the lauric acid-coated ferrites is warranted. This study shows that lauric acid-coated, superparamagnetic Fe(3)O(4) and MnFe(2)O(4) may be used for hyperthermia treatment and are to be preferred over CoFe(2)O(4).
Journal of Biomedical Materials Research Part B Applied Biomaterials 04/2007; 81(1):12-22. DOI:10.1002/jbm.b.30630 · 2.76 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In vitro cytocompatibility and cellular interactions of lauric acid and dextran-coated magnetite nanoparticles were evaluated with two different cell lines (mouse fibroblast and human cervical carcinoma). Lauric acid-coated magnetite nanoparticles were less cytocompatible than dextran-coated magnetite nanoparticles and cellular uptake of lauric acid-coated magnetic nanoparticles was more than that of dextran-coated magnetite nanoparticles. Lesser cytocompatibility and higher uptake of lauric acid-coated magnetite nanoparticles as compared to dextran-coated magnetic nanoparticles may be due to different cellular interactions by coating material. Thus, coating plays an important role in modulation of biocompatibility and cellular interaction of magnetic nanoparticles.
Journal of Magnetism and Magnetic Materials 04/2007; 311(1):282–287. DOI:10.1016/j.jmmm.2006.10.1181 · 1.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Comparative evaluation of two different methods of magnetic liposomes preparation, namely thin film hydration (TFH) and double emulsion (DE) with different molar ratios of egg-phosphatidyl choline (egg-PC) and cholesterol using lauric acid coated manganese ferrite-based aqueous magnetic fluid, is reported. TFH was found to be a better method of encapsulation and TFH 2:1 (egg-PC: cholesterol) magnetic liposomes showed the highest encapsulation efficiency and comparable heating ability to that of magnetic fluids. Stealth TFH 2:1 magnetic liposomes containing DSPE-PEG2000 were three-fold more cytocompatible as compared to the magnetic fluid. Stealth TFH 2:1 manganese ferrite-based magnetic liposomes might be useful for hyperthermia treatment of cancer.
Journal of Magnetism and Magnetic Materials 04/2007; 311(1-311):208-215. DOI:10.1016/j.jmmm.2006.10.1179 · 1.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Magnetic nanoparticles have been prepared by various soft chemical methods including self-assembly. The bare or surface-modified
particles find applications in areas such as hyperthermia treatment of cancer and magnetic field-assisted radioactive chemical
separation. We present here some of the salient features of processing of nanostructured magnetic materials of different sizes
and shapes, their properties and some possible applications. The materials studied included metals, metal-ceramic composites,
[Show abstract][Hide abstract] ABSTRACT: Water-based ferrofluids of substituted ferrites Fe <sub>1-x</sub> Mn <sub>x</sub> Fe <sub>2</sub> O <sub>4</sub> (0≤x≤1) have been prepared by the co-precipitation method and characterized. Particles are superparamagnetic with an average particle size of about 10–12 nm . The specific absorption rate (SAR) was measured by calorimetric measurement at a frequency of 300 kHz and a field of 10–45 kA / m . The variation of SAR and magnetization of Fe <sub>1-x</sub> Mn <sub>x</sub> Fe <sub>2</sub> O <sub>4</sub> with Mn concentration shows similar dependence. Innocuousness studies of Mn Fe <sub>2</sub> O <sub>4</sub> ferrofluids to the living cells have been carried out with BHK-21 cells. In vitro studies showed that threshold biocompatible concentration is dependent on the nature of ferrites and coating.
[Show abstract][Hide abstract] ABSTRACT: Substituted ferrites [Mn1-xZnxFe2O4 (0 <= x <= 0.8)] of nanoscale dimensions have been prepared by a novel microwave refluxing method. The effect of different parameters [such as pH, reflux time, presence of PEG (MW-3350) molecules] on particle morphology and size has been studied. Characterization of the above capped particles was done by XRD, FTIR, TEM and SQUID magnetometry. The as-prepared particles were further used for magnetoliposome preparation. (c) 2005 Elsevier B.V. All rights reserved.
Journal of Magnetism and Magnetic Materials 05/2005; 293(1):55-61. DOI:10.1016/j.jmmm.2005.01.043 · 1.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The effects of phosphatidylcholine (PC) on the growth of magnetite superparamagnetic particles have been investigated. These coated particles give stable suspension in solvents like chloroform and were used for magnetoliposome preparation. The superparamagnetic particles and magnetoliposomes were characterized by X-ray diffraction (XRD), FTIR, Transmission electron microscopy (TEM) and SQUID measurements. The result shows that PC acts as capping agent to restrict the growth of the particles. (c) 2005 Elsevier B.V. All rights reserved.
Journal of Magnetism and Magnetic Materials 05/2005; 293(1-293):62-68. DOI:10.1016/j.jmmm.2005.01.044 · 1.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An optimization study of different parameters for the synthesis of well dispersed nanoparticles (5-30 nm) of the system Co1-xZnxFe2O4, (0 less than or equal to x less than or equal to 0.8) has been carried out using a novel microwave refluxing method. Ethylene glycol has been used as the medium which serves as the solvent as well as a complexing and capping agent. The parameters chosen were the zinc content (x), pH of the solution, reflux time and the metal:ethylene glycol ratio. The influence of the above parameters is discussed in terms of the chemistry of the reactions and the role of ethylene glycol. The method appears much superior to other chemical/hydrothermal methods in terms of size distribution and dispersity of the nanoparticles.
[Show abstract][Hide abstract] ABSTRACT: Ferrite particles coated with biocompatible phases can be used for hyperthermia treatment of cancer. We have synthesized substituted
calcium hexaferrite, which is not stable on its own but is stabilized with small substitution of La. Hexaferrite of chemical
composition (CaO)0.75(La203)0.20(Fe2O3)6 was prepared using citrate gel method. Hydroxyapatite was prepared by precipitating it from aqueous solution of Ca(NO3)2 and (NH4)2HPO4 maintaining pH above 11. Four different methods were used for coating of hydroxyapatite on ferrite particles. SEM with EDX
and X-ray diffraction analysis shows clear evidence of coating of hydroxyapatite on ferrite particles. These coated ferrite
particles exhibited coercive field up to 2 kOe, which could be made useful for hysteresis heating in hyperthermia. Studies
by culturing BHK-21 cells and WBC over the samples show evidence of biocompatibility. SEM micrographs and cell counts give
clear indication of cell growth on the surface of the sample. Finally coated ferrite particle was implanted in Kasaulli mouse
to test its biocompatibility. The magnetic properties and biocompatibility studies show that these hydroxyapatite coated ferrites
could be useful for hyperthermia.
[Show abstract][Hide abstract] ABSTRACT: Magnetism plays an important role in different applications of health care. Magnetite (Fe3O4) is biocompatible and therefore is one of the most extensively used biomaterials for different applications ranging from
cell separation and drug delivery to hyperthermia. Other than this, a large number of magnetic materials in bulk as well as
in the form of nano particles have been exploited for a variety of medical applications. In this review, we summarize the
salient features of clinical applications, where magnetic biomaterials are used. Magnetic intracellular hyperthermia for cancer
therapy is discussed in detail.
[Show abstract][Hide abstract] ABSTRACT: Superparamagnetic as well as fine ferrimagnetic particles such as Fe3O4, have been extensively used in magnetic field induced localized hyperthermia for the treatment of cancer. The magnetic materials with Curie temperature (Tc) between 42 and 50 degrees C, with sufficient biocompatibility are the best candidates for effective treatment such that during therapy it acts as in vivo temperature control switch and thus over heating could be avoided. Ultrafine particles of substituted ferrite Co(1-a)Zn(a)Fe2O4 and substituted yttrium-iron garnet Y3Fe(5-x)Al(x)O12 have been prepared through microwave refluxing and citrate-gel route respectively. Single-phase compounds were obtained with particle size below 100 nm. In order to make these magnetic nano particles biocompatible, we have attempted to coat these above said composition by alumina. The coating of alumina was done by hydrolysis method. The coating of hydrous aluminium oxide has been done over the magnetic particles by aging the preformed solid particles in the solution of aluminium sulfate and formamide at elevated temperatures. In vitro study is carried out to verify the innocuousness of coated materials towards cells. In vitro biocompatibility study has been carried out by cell culture method for a period of three days using human WBC cell lines. Study of cell counts and SEM images indicates the cells viability/growth. The in vitro experiments show that the coated materials are biocompatible.
Bio-medical materials and engineering 02/2003; 13(4):387-99. · 1.09 Impact Factor