Incorporation Of Iron Oxide Nanoparticles Research Articles

Comparison of MAF-32 and a One-Pot Synthesized Superparamagnetic Iron Oxide/MAF-32 Composite for the Adsorption of Diclofenac.

The global presence of pharmaceutical pollutants in water sources represents a burgeoning public health concern. Recent studies underscore the urgency of addressing this class of emerging contaminants. In this context, our work focuses on synthesizing a composite material, FexOy/MAF-32, through a streamlined one-pot reaction process, as an adsorbent for diclofenac, an emerging environmental contaminant frequently found in freshwater environments and linked to potential toxicity towards several organisms such as fish and mussels. A thorough characterization was performed to elucidate the structural composition of the composite. The material presents magnetic properties attributed to its superparamagnetic behavior, which facilitates the recovery efficiency of the composite post-diclofenac adsorption. Our study further involves a comparative analysis between the FexOy/MAF-32 and a non-magnetic counterpart, comprised solely of 2-ethylimidazolate zinc polymer. This comparison aims to discern the relative advantages and disadvantages of incorporating magnetic iron oxide nanoparticles in the contaminant removal process facilitated by a coordination polymer. Our findings reveal that even a minimal incorporation of iron oxide nanoparticles substantially enhanced the composite's overall performance in pollutant adsorption.

Enhancing osteogenic bioactivities of coaxial electrospinning nano-scaffolds through incorporating iron oxide nanoparticles and icaritin for bone regeneration

Enhancing osteogenic bioactivities of coaxial electrospinning nano-scaffolds through incorporating iron oxide nanoparticles and icaritin for bone regeneration

Structural, thermal and optoelectrical study of PVA/iron oxide nanocomposite films

AbstractThe work reported here deals with fabricating iron oxide nanoparticles incorporated polyvinyl alcohol nanocomposite films via the solution‐casting green route, characterized using various characterization techniques. X‐ray diffraction analysis shows interaction of nanoparticles with the polyvinyl alcohol matrix, scanning electron microscopy shows surface morphology of crack‐free films, energy dispersive spectroscopy indicates elemental purity, tensiometer analysis shows changing behavior of hydrophilic to hydrophobic, thermogravimetric analysis shows improved thermal stability, ultraviolet‐visible spectroscopy shows tunable optical properties, and frequency response analysis shows improved electrical properties. A small incorporation (1 wt. %) of iron oxide nanoparticles has induced significant alternations in structural, wetting, thermal, optical, and electrical properties of the polyvinyl alcohol‐based nanocomposite films. Results showed notable changes in the structural phases, water contact angle (39.5° to 97.7°), optical absorption edge (5.12 eV to 4.84 eV), indirect band gap (4.99 eV to 4.68 eV), direct bandgap (5.41 eV to 5.21 eV), and band tail (0.57 eV to 0.89 eV) from native polyvinyl alcohol to polyvinyl alcohol/iron oxide nanocomposite films. Enhancements were observed in refractive indices, optical conductivity, optical dielectric loss, thermal stability, dielectric constant, and dielectric loss on incorporating iron oxide nanoparticles into the polyvinyl alcohol matrix. The fabricated nanocomposite films might be a potential material for optoelectronic and microelectronics applications.

Removal of Rhodamine B from Wastewater by Adsorption using Iron Oxide-Polymer Composite Material

The discharge of dye-containing wastewater from textile, paper and plastic industries poses serious environmental pollution hazards. This study investigates the potential application of an ion exchange material-iron oxide composite to remove rhodamine B dye from aqueous solutions. The composite was synthesized by incorporating iron oxide nanoparticles into a cationic ion exchange matrix containing amine groups with high affinity for rhodamine B dye. Batch adsorption experiments were conducted under controlled pH, temperature and initial rhodamine B dye concentrations. The results demonstrate that the composite material can effectively remove rhodamine B dye, with adsorption capacities reaching 23570.4 mg/g and removal efficiencies over 90% under the optimal conditions at pH 7 and 30 ºC. The adsorption followed pseudo-second order kinetics indicating chemisorption as the main mechanism. The findings suggested that this composite material can serve as an efficient and low-cost adsorbent for removing cationic dyes like rhodamine B dye from textile and other industrial wastewaters due to its high capacity, rapid adsorption rate and magnetic properties that enable easy separation.

Formulation, Characterization, and Cytotoxic Effect of PVA Incorporated Iron Oxide Nanoparticles of Gramine Using HCT-116 Cell Line in vitro

Formulation, Characterization, and Cytotoxic Effect of PVA Incorporated Iron Oxide Nanoparticles of Gramine Using HCT-116 Cell Line in vitro

Tunning processes for organic matter removal from slaughterhouse wastewater treated by immediate one-step lime precipitation and atmospheric carbonation

Adsorption using unmodified/modified commercial activated carbons and constructed wetlands (CW) planted with Vetiveria zizanioides were evaluated as tuning processes for lowering chemical oxygen demand (COD) from slaughterhouse wastewater pretreated by the integrated process of immediate one-step lime precipitation and atmospheric carbonation. Powdered and granular activated carbons (PAC and GAC), and PAC and GAC incorporated with iron oxide nanoparticles (PACMAG and GACMAG) were used. COD removal using different adsorbent separation methods (i.e., sedimentation, filtration, or magnetic separation) was also evaluated. The adsorption results indicated that the best adsorbent doses and contact times of the studied adsorbents were 70 g L−1 and 5 min for PAC and PACMAG, and 60 g L−1 and 60 min for GAC and GACMAG. Under optimized conditions, GAC (75.7 ± 1.0%) and GACMAG (73.5 ± 2.1%) were more efficient than PAC (59.7 ± 1.0%) and PACMAG (59.0 ± 0.0%) in removing COD. The incorporation of iron oxide nanoparticles in GAC and PAC did not affect the adsorption of COD. The Temkin model was the best isotherm model found for PAC and PACMAG, while for GAC and GACMAG was the BET model. Pseudo-order n kinetic model was the best kinetic model found for all the adsorbents tested. There were no significant differences in the removal of COD between filtration and magnetic separations. Phytoremediation results indicated that increased COD removal efficiency occurred when the applied COD mass load decreased or when the bed depth was increased. Maximum COD removals of around 89.9–95.0% were achieved. Vetiveria zizanioides showed no signs of toxicity throughout the trials.

Complex dielectric-impedance spectroscopic studies of magnetite added chitin biopolymer

We have successfully synthesized magnetic chitin (MCH) by incorporating iron oxide nanoparticles into biodegradable and abundantly naturally available chitin by the coprecipitation method. X-ray diffraction (XRD) characterization revealed formation of cubic inverse spinel structure of Fe3O4 nanoparticles. In addition to this, other characterization studies like energy dispersive X-ray analysis (EDX) and vibrating sample magnetometry (VSM) were also performed to have an insight into the compositional and functional nature of the structure. A detailed spectroscopic study of complex impedance and dielectric constant for a wide frequency range of ~1 Hz to 10 MHz at discrete temperatures ~300–400 K has been performed by us for the first time on MCH in order to understand various relaxation processes. From permittivity, we have estimated the height of the potential barrier to be ~95.8 ± 0.3 meV. Impedance measurements yielded an activation energy of ~35.85 meV. Thermogravimetric analysis (TGA) of the sample showed exceptionally high thermal stability of the sample with percentage of residual mass at 800 ℃ being ~73% in MCH, which is quite high in comparison to the pristine chitin. An S shaped curve obtained through VSM measurement confirmed the superparamagnetic nature of the nanocomposite. The study assumes significance in the present scenario of rising awareness about the environment and demand to explore alternative green materials with numerous biomedical/environmental applications ranging from drug delivery vehicles in COVID-19 treatment to food packaging.

Heat Absorption Performance Enhancement of TES System Using Iron Oxide/Paraffin Wax Composite

Thermal Energy Storage (TES) system has emerged as a promising solution of energy demand and supply management, which stores excess thermal energy and releases it when energy demand is high, making it an efficient and cost-effective energy storage solution when combined with renewable energy sources, such as solar and wind power. This study aimed to evaluate the thermal performance of TES units using Computational Fluid Dynamics (CFD) simulations in the ANSYS CFX software package. After comparing the heat storage capacity of conventional Phase Change Material (PCM) and iron oxide/paraffin wax composite ($2 \%$) using industrial residual water, temperature distribution plots and heat flux data were generated in simulations for both cases. Addition of iron oxide nanoparticles significantly improved the heat absorption performance of TES units. Both materials initially exhibited a higher heat absorption rate, which gradually decreased over time. CFD data analysis revealed that iron oxide/paraffin wax material enhanced heat absorption performance by up to $1.3 \%$, which demonstrated the potential of iron oxide nanoparticles in improving the efficiency of TES system and highlighted the advantages of TES system combined with renewable energy sources. By improving heat absorption properties, the incorporation of iron oxide nanoparticles had the potential to increase the lifespan of TES units and significantly reduced maintenance and replacement expenses. This breakthrough, along with the cost savings and energy efficiency offered by TES technology, may encourage its widespread application, thus reducing reliance on fossil fuels and promoting sustainable energy practices.

High Dielectric Constant Liquid Dielectrics Based on Magnetic Nanofluids

Magnetic nanofluids are increasingly finding new applications. They can be employed as liquid dielectrics. The advantage of having a liquid dielectric is that high dielectric constant can be achieved by a judicious choice of the base liquid. The dielectric constant can be tuned with the help of an external magnetic field too. Superparamagnetic iron oxide nanoparticles were dispersed in polar carriers, namely water, polyvinyl alcohol, ethylene glycol, and a nonpolar carrier like kerosene to obtain stable magnetic fluids after ensuring the crystallographic phase purity along with appropriate magnetic characteristics of the dispersant. The fluids were then subjected to dielectric studies using an automated homemade dielectric setup. The dielectric permittivity and dielectric loss at different frequencies with and without an external magnetic field were evaluated. The studies indicate that magnetic nanofluids based on polar carriers are excellent liquid dielectrics over a wide range of frequencies with the incorporation of iron oxide nanoparticles. The application of an external magnetic field enhances the dielectric constant considerably. These magnetic nanofluids can be employed as liquid dielectrics for applications. It has been found that kerosene based magneto fluids have a low dielectric constant while Polyvinyl alcohol based fluids exhibit the highest dielectric constant.

Targeted treatment of triple-negative-breast cancer through pH-triggered tumour associated macrophages using smart theranostic nanoformulations

Triple-negative breast cancer (TNBC) represents 15–25 % of the new breast cancer cases diagnosed worldwide every year. TNBC is among the most aggressive and worst prognosis breast cancer, mainly because targeted therapies are not available. Herein, we developed a magnetic theranostic hybrid nanovehicle for targeted treatment of TNBC through pH-triggered tumour associated macrophages (TAMs) targeting. The lipid core of the nanovehicle was composed of a Carnaúba wax matrix that simultaneously incorporated iron oxide nanoparticles and doxorubicin (DOX) - a chemotherapeutic drug. These drug-loaded wax nanovehicles were modified with a combination of two functional and complementary molecules: (i) a mannose ligand (macrophage targeting) and (ii) an acid-sensitive sheddable polyethylene glycol (PEG) moiety (specificity). The TAMs targeting strategy relied on the mannose − mannose receptor recognition exclusively after acid-sensitive “shedding” of the PEG in the relatively low tumour microenvironment pH. The pH-induced targeting capability towards TAMs was confirmed in vitro in a J774A.1 macrophage cell line at different pH (7.4 and 6.5). Biocompatibility and efficacy of the final targeted formulations were demonstrated in vitro in the TNBC MDA-MB-231 cell line and in vivo in an M-Wnt tumour-bearing (TNBC) mouse model. A preferential accumulation of the DOX-loaded lipid nanovehicles in the tumours of M-Wnt-tumour bearing mice was observed, which resulted both on an efficient tumour growth inhibition and a significantly reduced off-target toxicity compared to free DOX. Additionally, the developed magnetic hybrid nanovehicles showed outstanding performances as T2-contrast agents in magnetic resonance imaging (r2 ≈ 400–600 mM−1·s−1) and as heat generating sources in magnetic hyperthermia (specific absorption rate, SAR ≈ 178 W·g−1Fe). These targeted magnetic hybrid nanovehicles emerge as a suitable theranostic option that responds to the urgent demand for more precise and personalized treatments, not only because they are able to offer localized imaging and therapeutic potential, but also because they allow to efficiently control the balance between safety and efficacy.

Effect of iron oxide nanoparticles on the thermal characteristics of supramolecular, dendritic and macromolecular capping agents

The present study aimed at the enhancement of the thermal characteristics of different capping agents belonging to different macromolecular families, with the incorporation of iron oxide nanoparticles. Iron oxide nanocomposites were prepared following a simple reduction protocol using sodium borohydride (NaBH4) succeeded by air oxidation. Three iron oxide composites were prepared using different biocompatible capping agents. The capping agents used in the present study were supramolecular β-cyclodextrin, dendritic hyperbranched polyglycerol and macromolecular starch. The chemical nature of the composites was successfully confirmed by spectroscopy. The well-characterized composite systems were studied for their thermal characteristics using TG/DTG and DSC measurements. The primary focus of the study was to analyse any change in the thermal behaviour of the pure encapsulating systems on incorporation with the iron oxide species. The analysis was conducted by comparing the TG/DTG and DSC measurements of the pure capping agents- cyclodextrin, hyperbranched polyglycerol and starch with their respective nanoparticle incorporated composites. All the three capping agents were found to decompose in the temperature range 250–450 °C But these systems on incorporation of iron oxide nanoparticles have gained more thermal stability. Their decomposition shifted to a higher temperature with broadened curves suggestive of a slow and steady degradation pattern. DSC studies showed that the incorporation of IONPs could effectively prevent melting of the capping agents by which they could be propagated to a wide range of applications.

Rational synthesis of polymer coated inorganic nanoparticles-MWCNT hybrids via solvophobic effects

The efficient synthesis of inorganic nanoparticle-carbon nanotube hybrids requires the development of models and synthetic guidelines that can be used to maximise the interactions between both nanomaterials. Herein we report the application of the Hansen surface energy based solubility parameter theory as a model for the selection of solvents that can maximise the interactions between iron oxide nanoparticles and MWCNTs. To achieve this, we synthesized iron oxide nanoparticle-MWCNT hybrid materials in three different solvents and characterized their composition with TGA. The solvent was found to have a significant impact in the final amount of iron oxide composition of the hybrids. The Hansen surface energy based solubility parameters of MWCNTs were characterized via inverse gas chromatography and were used to evaluate the interactions between the MWCNTs and the solvent media. Under this model we expected that large differences between the Hansen surface energy based solubility parameters of solvents and MWCNTs would be correlated with larger incorporation of iron oxide nanoparticles in the hybrids. The amount of iron oxide nanoparticles found in the hybrids were indeed consistent with the predictions of the Hansen surface energy based solubility parameter theory making it a powerful tool for the design of nanoparticle-carbon nanotube hybrids.

Magnetically-stimulated transformations in the nanostructure of PEGylated phytantriol-based nanoparticles for on-demand drug release

Lipid-based liquid crystalline (LLC) systems are formed by the self-assembly of lipid materials in aqueous environments. The internal nanostructures of LLC systems can be manipulated using remote stimuli and have the potential to serve as ‘on-demand’ drug delivery systems. In this study, a magnetically-responsive system that displayed a transition in nanostructure from liposomes to cubosomes/hexasomes under external alternating magnetic field (AMF) was established by the incorporation of iron oxide nanoparticles (IONPs) into a PEGylated phytantriol (PHYT)-based LLC system. Small angle X-ray scattering (SAXS) was utilized to assess the equilibrium phase behaviour of the systems with different compositions of the lipids to find the optimized formulation. Time-resolved SAXS was then used to determine the dynamic transformation of nanostructures of the IONP-containing systems with the activation of AMF. The formulation containing PHYT and DSPE-PEG2000 at a 95 to 5 molar percent ratio produced a transition from lamellar phase to bicontinuous cubic phase, showing a slow-to-fast drug release profile. Inclusion of either 5 nm or 15 nm IONPs imparted magnetic-responsiveness to the system. The magnetically-responsive system produced an ‘on-demand’ drug delivery system from which the drug release was able to be triggered externally by AMF-stimulation.

3D-ordered porous composite microparticles formed via substrate-free optical 3D lithography

This paper proposes a cutting-edge photolithography-based top-down approach to produce functional porous microparticles with three-dimensional (3D) periodic nanostructures. The developed fabrication process employs proximity-field nanopatterning (PnP), a representative optical 3D nanofabrication technique in which a new type of phase mask and exposure scheme have been introduced. In the modified PnP mode, where the photoresist is directly coated on the phase mask, a 3D nanostructured membrane detaches from the mask during the development process. The freestanding 3D nanostructured membrane is electromagnetically shredded through simple ultrasonication to produce a large amount of 3D-ordered porous microparticles. A Gaussian distribution of particle sizes with an average size of ∼37 µm can be obtained through an optimization of the sonication time. In addition, composite porous microparticles that exhibit exceptional magnetically responsive properties can be generated by incorporating iron oxide nanoparticles into the rinsing solution as nanofillers.

Iron oxide nanoparticle incorporated cement mortar composite: correlation between physico-chemical and physico-mechanical properties

Incorporation of iron oxide nanoparticles into cement mortar composites enhances the formation of hydration products and the physico-mechanical performances of the composite construct.

Remote Magnetic Nanoparticle Manipulation Enables the Dynamic Patterning of Cardiac Tissues.

The ability to manipulate cellular organization within soft materials has important potential in biomedicine and regenerative medicine; however, it often requires complex fabrication procedures. Here, a simple, cost-effective, and one-step approach that enables the control of cell orientation within 3D collagen hydrogels is developed to dynamically create various tailored microstructures of cardiac tissues. This is achieved by incorporating iron oxide nanoparticles into human cardiomyocytes and applying a short-term external magnetic field to orient the cells along the applied field to impart different shapes without any mechanical support. The patterned constructs are viable and functional, can be detected by T2*-weighted magnetic resonance imaging, and induce no alteration to normal cardiac function after grafting onto rat hearts. This strategy paves the way to creating customized, macroscale, 3D tissue constructs with various cell-types for therapeutic and bioengineering applications, as well as providing powerful models for investigating tissue behavior.

Synthesis of IONP's decorated graft copolymers and study of their magnetic force–induced wastewater treatment

Our work is focused on facile synthesis and modification of amylopectin‐grafted block copolymers by using reversible addition−fragmentation chain transfer (RAFT) polymerization technique. This technique yields polymers with controlled molecular weight and low polydispersity indexes and is feasible with a wide range of monomers. Five different grades of amylopectin‐grafted polymethacrylic acid and polyacrylamide block copolymers have been synthesized via RAFT, by varying the amount of acrylamide employing amylopectin‐based macro chain transfer agent. Graft copolymers have been upgraded as smart responsive graft copolymers, through the incorporation of iron oxide nanoparticles (IONPs) via condensation reaction. The polymeric materials have been extensively characterized by energy‐dispersive X‐ray analysis, Fourier transform infrared spectroscopy, proton magnetic resonance spectroscopy, scanning electron microscopy, ultraviolet‐visible spectroscopy, gel permeation chromatography, transmission electron microscopy, thermogravimetric analysis, and X‐ray diffraction analysis. Normal and responsive graft copolymers have been studied for removal of model contaminant (kaolin), and responsive graft copolymers have been used to remove methylene blue dye (without using any adsorbent) from water by applying external magnetic field. The upgraded block copolymers have shown best performance in wastewater treatment.

Fluorous-phase iron oxide nanoparticles as enhancers of acoustic droplet vaporization of perfluorocarbons with supra-physiologic boiling point

Perfluorocarbon emulsion nanodroplets containing iron oxide nanoparticles (IONPs) within their inner perfluorohexane (PFH) core were prepared to investigate potential use as an acoustically activatable ultrasound contrast agent, with the hypothesis that incorporation of IONPs into the fluorous phase of a liquid perfluorocarbon emulsion would potentiate acoustic vaporization. IONPs with an oleic acid (OA) hydrophobic coating were synthesized through chemical co-precipitation. To suspend IONP in PFH, OA was exchanged with perfluorononanoic acid (PFNA) via ligand exchange to yield fluorophilic PFNA-coated IONPs (PFNA-IONPs). Suspensions with various amounts of PFNA-IONPs (0–15% w/v) in PFH were emulsified in saline by sonication, using 5% (w/v) egg yolk phospholipid as an emulsifier. PFNA-IONPs were characterized with transmission electron microscopy (TEM), transmission electron cryomicroscopy (cryoTEM), and thermogravimetric analysis (TGA) with Fourier transform infrared spectroscopy (FTIR). IONP were between 5 and 10 nm in diameter as measured by electron microscopy, and hydrodynamic size of the PFH nanodroplets were 150 to 230 nm as measured by dynamic light scattering (DLS). Acoustic droplet vaporization of PFH nanodroplets (PFH-NDs) was induced using conversion pulses (100 cycle at 1.1 MHz and 50% duty cycle) provided by a focused ultrasound transducer, and formed microbubbles were imaged using a clinical ultrasound scanner. The acoustic pressure threshold needed for PFH-NDs vaporization decreased with increasing temperature and IONP content. PFH-NDs containing 5% w/v IONP converted to microbubbles at 42 °C at 2.18 MI, which is just above the exposure limits of 1.9 MI allowed by the FDA for clinical ultrasound scanners, whereas 10 and 15% emulsion vaporized at 1.87 and 1.24 MI, respectively. Furthermore, 5% IONP-loaded PFH-NDs injected intravenously into melanoma-bearing mice at a dose of 120 mg PFH/kg, converted into detectable microbubbles in vivo 5 h, but not shortly after injection, indicating that this technique detects NDs accumulated in tumors.

Electrochemical paper based cancer biosensor using iron oxide nanoparticles decorated PEDOT:PSS

We report results of the studies relating to the fabrication of a label-free, flexible, light weight and disposable conducting paper based immunosensing platform comprising of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and nanostructured iron oxide (nFe2O3@PEDOT:PSS) nanocomposite for detection of carcinoembryonic antigen (CEA), a cancer biomarker. The effect of various solvents such as sorbitol, ethanol, propanol, n-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO) on the electrical conductivity of Whatman filter paper (WP) modified with nFe2O3@PEDOT:PSS/WP was investigated. The electrical conductivity of the PEDOT:PSS/WP electrode was found to be enhanced by two orders of magnitude (from 6.8× 10−4 to 1.92 × 10−2 Scm−1) after its treatment with DMSO. Further, nFe2O3 doped PEDOT:PSS/WP electrode exhibited the electrical conductivity as 2.4 × 10−2 Scm−1. Besides this, the incorporation of iron oxide nanoparticles (nFe2O3) into PEDOT:PSS/WP resulted in improved electrochemical performance and signal stability. This nFe2O3@PEDOT:PSS/WP based platform was used for immobilization of the anti-carcinoembronic antigen (anti-CEA) protein for quantitative estimation of cancer biomarker (CEA). The results of electrochemical response studies revealed that this conducting paper based immunoelectrode had a sensitivity of 10.2 μAng−1mLcm−2 in the physiological range (4–25 ngmL−1) and shelf life of 34 days. Further, the proposed immunoelectrode was validated with conventional ELISA for the detection of CEA in serum samples of cancer patients.

Assessment of iron oxide nanoparticle ecotoxicity on regeneration and homeostasis in the replacement model system Schmidtea mediterranea_suppl

Iron oxide nanoparticles (IONs) are used in a number of applications from food to cosmetics and from medical applications to magnetic storage. In spite of the 550 tons produced each year in Europe alone, no effective dose limit recommendations are established and the overall risks connected to IONs are still debated. The incorporation of IONs in daily life raises a concern about their effects on the environment, on living organisms, and on human health. In this study, we used freshwater planarians to assess the nanoecotoxicity of IONs. Planarians are free-living invertebrates known for their astonishing regenerative ability. Because of their sensitivity to toxicants, they are often used to determine the effects of toxic, genotoxic, and carcinogenic environmental compounds with an approach in line with the 3Rs (Reduce, Refine, Replace) principle. Planarians were exposed to IONs at concentrations up to 1 mg/ml and their effects were evaluated at the behavioral, morphofunctional, and molecular levels, with a special emphasis on the regeneration process. Our results indicate that IONs did not affect the stem cell population dynamics, nor did they induce substantial changes in either homeostatic or regenerating planarians. As positive controls, gold nanoparticles coated with the pro-apoptotic anti-cancer drug hexadecylmethylammonium bromide and highly concentrated polystyrene nanoparticles were used; these all elicited toxic effects. Therefore, we conclude that IONs at environmental concen­trations are safe for planarians, and that the planarian is a powerful model system that can replace vertebrate animal models in nanoecotoxicology research and for nanoecotoxicology studies.