Mohammad E. Khosroshahi

Simultaneous dual-wavelength photoacoustic radar imaging using waveform engineering with mismatched frequency modulated excitation

The spectroscopic imaging capability of photoacoustics (PA) without the depth limitations of optical methods offers a major advantage in preclinical and clinical applications. Consecutive PA measurements with properly chosen wavelengths allow composition related information about blood or tissue. In this work, we propose and experimentally introduce modulation waveform engineering through the use of mismatched (uncorrelated or weakly correlated) linear frequency modulated signals for PA characterization and imaging. The feasibility of the method was tested on oxygen saturated hemoglobin and deoxygenated hemoglobin in vitro in a blood circulating rig. The method was also employed for in vivo imaging of a neck carcinoma tumor grown in a mouse thigh. The proposed method can increase the accuracy and speed of functional imaging by simultaneous PA probing with two wavelengths using portable laser-diode based PA imaging systems.

Characterisation of binary (Fe3O4/SiO2) biocompatible nanocomposites as magnetic fluid

This article describes coating of magnetite nanoparticles (NPs) with amorphous silica shells. Controlled co-precipitation technique under N2 gas was used to prevent undesirable critical oxidation of Fe2+. The synthesised Fe3O4 NPs were first coated with trisodium citrate to achieve solution stability and then covered by SiO2 layer using Stober method. For uncoated Fe3O4 NPs, the results showed an octahedral geometry with saturation magnetisation range of 82–96 emu/g and coercivity of 85–120 Oe for particles between 35 and 96 nm, respectively. The best value of specific surface area (41 m2/g) for Fe3O4 alone was obtained at 0.9 M NaOH at 750 rpm and it increased to about 81 m2/g for Fe3O4/SiO2 combination. The total thickness and the structure of core–shell was measured and studied by transmission electron microscopy. The average particles size was about 50 nm, indicating the presence of about 15 nm SiO2 layer. Finally, the stable magnetic fluid contained well-dispersed magnetite-silica nanocomposites which showed monodispersity and fast magnetic response.

Effect of Alkaline Media Concentration and Modification of Temperature on Magnetite Synthesis Method Using FeSO4/NH4OH

Superparamagnetic particles find a great situation in a large number of science. Despite high number of research in the field of magnetic nanoparticle production, there are some drawbacks regarding this kind of materials. In this study in order to overcome some of these drawbacks, nano-sized magnetite fine powder was produced via coprecipitation method under N2 atmosphere by modification of two significant parameters, alkaline media concentration and temperature. Effect of named parameters on the particle size, size distribution was analyzed by transmission electron microscopy (TEM), and in order to evaluate magnetic behaviour of particles, vibrating sample magnetometry (VSM) was used. Crystalline phase of synthesized material were determined by means of X-ray diffraction spectroscopy (XRD). As authors know, there is not any evidence of evaluation of sample synthesized at room temperature for a short period of time and then post modification at higher temperature on particle size and its magnetic properties. Results show the particles synthesized at elevated temperature (70°C) and lower alkaline concentration (0.9 M) have highest saturation magnetization, about 68 emu/gr at 70°C, compared with 63 emu/gr at 25°C and smallest particle size. On the base of our experimental data we can introduce a modification way for copercipitation method which improves the magnetic properties with reduction of particle size at the same time.

Effect of Nd:Yttrium-aluminum-garnet laser radiation on Ti6Al4V alloy properties for biomedical applications

The effect of Nd:yttrium-aluminum-garnet laser on the microtopography and physicochemical properties of Ti6Al4V alloy are investigated in the view of biomedical applications. The surface roughness and hardness for laser treated samples (LTS) at 140 J cm−2 were measured 7±0.02 and 825 vickers hardness number, respectively. This superior microhardness value is attributed to grain refinement associated with laser melting and rapid solidification. The electrochemical property, mainly pitting corrosion resistance, has been carried out in Hanks salt balanced physiological solution using standard potentiodynamic polarization testing. A higher corrosion potential of −0.21 V was achieved for LTS. At the optimium treating value of laser fluence (140 J cm−2), the energy dispersive x-ray analysis showed about a 30% decrease of vanadium. The contact angle measurements also indicated an improved surface wettability (i.e., hydrophilicity) characteristic at 35°. Finally, the cell culture studies provided a useful tool to investigate the morphology and cell cytotoxicity.The effect of Nd:yttrium-aluminum-garnet laser on the microtopography and physicochemical properties of Ti6Al4V alloy are investigated in the view of biomedical applications. The surface roughness and hardness for laser treated samples (LTS) at 140 J cm−2 were measured 7±0.02 and 825 vickers hardness number, respectively. This superior microhardness value is attributed to grain refinement associated with laser melting and rapid solidification. The electrochemical property, mainly pitting corrosion resistance, has been carried out in Hanks salt balanced physiological solution using standard potentiodynamic polarization testing. A higher corrosion potential of −0.21 V was achieved for LTS. At the optimium treating value of laser fluence (140 J cm−2), the energy dispersive x-ray analysis showed about a 30% decrease of vanadium. The contact angle measurements also indicated an improved surface wettability (i.e., hydrophilicity) characteristic at 35°. Finally, the cell culture studies provided a useful tool to...

Enhanced laser tissue soldering using indocyanine green chromophore and gold nanoshells combination

Gold nanoshells (GNs) are new materials that have an optical response dictated by the plasmon resonance. The wavelength at which the resonance occurs depends on the core and shell sizes. The purposes of this study were to use the combination of indocyanine green (ICG) and different concentration of gold nanoshells for skin tissue soldering and also to examine the effect of laser soldering parameters on the properties of repaired skin. Two mixtures of albumin solder and different combinations of ICG and gold nanoshells were prepared. A full thickness incision of 2 × 20 mm(2) was made on the surface and after addition of mixtures it was irradiated by an 810 nm diode laser at different power densities. The changes of tensile strength (σ(t)) due to temperature rise, number of scan (Ns), and scan velocity (Vs) were investigated. The results showed at constant laser power density (I), σ(t) of repaired incisions increases by increasing the concentration of gold nanoshells in solder, Ns, and decreasing Vs. It was demonstrated that laser soldering using combination of ICG + GNs could be practical provided the optothermal properties of the tissue are carefully optimized. Also, the tensile strength of soldered skin is higher than skins that soldered with only ICG or GNs. In our case, this corresponds to σ(t) = 1800 g cm(-2) at I ∼ 47 Wcm(-2), T ∼ 85 [ordinal indicator, masculine]C, Ns = 10, and Vs = 0.3 mms(-1).

Amino surface modification of Fe3O4/SiO2 nanoparticles for bioengineering applications

Abstract The purpose of this research was to synthesise Fe3O4/SiO2 nanoparticles (NPs) modified by amine groups for bioengineering applications. Magnetic iron oxide NPs were prepared via coprecipitation. The NPs were then modified with a thin layer of amorphous silica, as described by Stober. The particle surface was then terminated with amine groups. The results showed that smaller particles can be synthesised by decreasing the NaOH concentration, which, in the present case, corresponded to 35 nm using 0·9M NaOH at 750 rev min−1 with a specific surface area of 41 m2 g−1. For uncoated Fe3O4 NPs, the results showed an octahedral geometry with saturation magnetisation range of 80–100 emu g−1 and coercivity of 80–120 Oe for particles between 35 and 96 nm respectively. The Fe3O4/SiO2 NPs with 50 nm particle size demonstrated a magnetisation value of 30 emu g−1. The stable magnetic fluid contained well dispersed Fe3O4/SiO2/3-aminopropyltriethoxysilane NPs, which indicated fast magnetic response.

Evaluation of mechanical and electrochemical properties of laser surface modified Ti–6Al–4V for biomedical applications: in vitro study

Abstract The effect of Nd:YAG laser surface modification on the microtopography and physicochemical properties of Ti–6Al–4V alloy has been investigated with a view of biomedical applications. The surface roughness and hardness of laser treated samples at 140 J cm−2 were found to be 7±0·02 and 825 VHN respectively. The superior microhardness value can be attributed to grain refinement associated with laser melting and rapid solidification. The electrochemical property, mainly pitting corrosion resistance, has been carried out in Hank’s salt balanced physiological solution using standard potentiodynamic polarisation testing. A higher corrosion potential of −0·21 V was achieved for laser treated samples. At the optimum of laser fluence (140 J cm−2), energy dispersive X-ray analysis showed about a 30% decrease in vanadium content. Contact angle measurements also indicated improved surface wettability (i.e. hydrophilicity) characteristics at 35°. Finally, cell culture studies provided a useful tool to investigate the morphology and cell cytotoxicity of the laser treated surfaces.

Fabrication and Characterization of Magnetoplasmonic Liposome Carriers

Phospholipid liposome encapsulating gold-coated superparamagnetic iron oxide nanostructures is developed. Gold nanoshells were fabricated by a multistep procedure through electroless plating of Au on the surface of the gold decorated superparamagnetic iron oxide nanoparticles (SPIONs). They were then stabilized using polyvinyl pyrolidone (PVP) with the molecular weight of 25 kDa, followed by their encapsulation within hydrophilic core of liposomes, composed of egg yolk phosphatidylcholine (EPC) : cholesterol (CHOL) with a molar ratio of 2:1and an efficiency of 94%. Surface chemistry, hydrodynamic size and electrokinetic potential, morphology and optical properties of magnetoplasmonic liposomes (MPLs) were studied by FT-IR, DLS, TEM and UV-Vis spectroscopy, respectively. FT-IR results showed the presence of amine functional groups on the surface of SPIONs as well as coordination of the nitrogen and oxygen atoms of PVP to the Au atoms at the surface of gold nanoshells. The effect of surface coating on the stability of nanostructures was discussed. The obtained results show that the fabricated hybrid nanostructures are potentially useful for delivery of plasmonic nanoparticles to cells and can be used as exogenous absorber in laser thermal therapy.

Simulation and experimental results of optical and thermal modeling of gold nanoshells

This paper proposes a generalized method for optical and thermal modeling of synthesized magneto-optical nanoshells (MNSs) for biomedical applications. Superparamagnetic magnetite nanoparticles with diameter of 9.5 ± 1.4 nm are fabricated using co-precipitation method and subsequently covered by a thin layer of gold to obtain 15.8 ± 3.5 nm MNSs. In this paper, simulations and detailed analysis are carried out for different nanoshell geometry to achieve a maximum heat power. Structural, magnetic and optical properties of MNSs are assessed using vibrating sample magnetometer (VSM), X-ray diffraction (XRD), UV-VIS spectrophotometer, dynamic light scattering (DLS), and transmission electron microscope (TEM). Magnetic saturation of synthesized magnetite nanoparticles are reduced from 46.94 to 11.98 emu/g after coating with gold. The performance of the proposed optical-thermal modeling technique is verified by simulation and experimental results.

In-vitro Application of Doxorubicin Loaded Magnetoplasmonic Thermosensitive Liposomes for Laser Hyperthermia and Chemotherapy of Breast Cancer

We describe doxorubicin loaded magnetoplasmonic thermosensitive liposomes (MPTL-DOX), which are designed to combine features of magnetic drug targeting and laser hyperthermia-triggered drug release. The synthesized magnetite/gold nanoshells are stabilized using polyvinyl pyrolidone (PVP) with mean crystallite size of 15.8 ± 3.5 nm. The liposome formulation DPPC:cholesterol:DSPE-PEG2000 at 80:20:5 molar ratio shows DOX release of less than 5% at 37°C following 24 h incubation. MPTL-DOX shows encapsulation efficiencies of about 95% and 74% for DOX and magnetoplasmonic nanoshells (MPNS), respectively. The MPTL-DOX formulation displays a desired temperature sensitivity with 65% and 100% DOX release following laser irradiation and then 24 h incubation at 37°C, respectively. The rate of DOX release from liposome using this formulation is 0.09 which was obtained by heating to 43°C, and agrees well with the first kinetic model. A temperature rise between 4-12°C was achieved for MNS using 25 μg/ml and 300 μg/ml after 400 s respectively. For cytotoxicity measurement, one untreated (control) and two treatment groups are studied. The first treatment groups are: with MPNS only, with MPTL only, and laser irradiation only. The second treatment groups are: laser hyperthermia using MPTL, MPTL with magnetic field (MF), MPTL-DOX, and MPTL-DOX with MF. MPTL-DOX is targeted to breast cancer cell lines (MCF-7 cells) under a permanent magnetic field and exhibits a substantial increase in cytotoxicity and apoptotic effects. The results suggest that externally guided drug targeting can trigger drug release using an exogenous absorber in laser hyperthermia which can be used advantageously for thermo-chemotherapy of cancers.