Immobilization of glucose oxidase onto cobalt based on silica core/shell nanoparticles as carrier

Co–B/SiO₂/NH₂ magnetic nanoparticles (NPs) were prepared from a silica shell-coated Co–B core using the Stöber method and amine-modification on the surface. Glucose oxidase (GOD) was covalently immobilized on the surface of Co–B/SiO₂/NH₂ NPs using N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDC) as an activating agent. The magnetic NPs characteristics, such as the synthesis of Co–B/SiO₂/NH₂ NPs, effect of pH, temperature, and concentration of buffer for enzyme immobilization, were investigated. The optimal reaction conditions for immobilization were determined to be 0.1 M of phosphate buffer solution, pH 7.0, and 5 °C. In the case of immobilized GOD without d-glucose and with 0.1 M of d-glucose for blocking, 22.98 U/g and 24.83 U/g of their original activity were retained after 7 reuses, respectively.     

Synthesis and characterization of a pH-sensitive conjugate of isoniazid with Fe3O4@SiO2 magnetic nanoparticles

The Letter describes the preparation and characterization of a conjugate of isoniazid (INH) with magnetic nanoparticles Fe₃O₄@SiO₂ 115 ± 60 nm in size. The INH molecules were attached to the surface of nanoparticles by a covalent pH-sensitive amidine bond. The conjugate was characterized by X-ray diffraction, SEM, dynamic light scattering, IR spectroscopy and microanalysis. The conjugate released isoniazid under in vitro conditions (pH = 4; 37 °C; t_1/2 ≈ 115 s). In addition, the cytotoxicity of the Fe₃O₄@SiO₂–INH conjugate was evaluated in SK-BR-3 cells using the xCELLigence system.     

Characterization of lactase-conjugated magnetic nanoparticles

Conjugation of lactase to magnetic nanoparticles is of interest in biosensor and ingredient processing applications that require high enzyme concentration and catalyst separation from the reaction stream. However, little is known about the effects of these materials on the physicochemical attributes of conjugated lactase. Lactase (Aspergillus oryzae) was covalently attached by carbodiimide chemistry to carboxylic-acid functionalized magnetic particles having a hydrodynamic radius of 18 nm. The resulting enzyme–nanoparticle conjugates were characterized with regard to particle size, zeta potential, enzyme kinetics, temperature and pH stability, catalyst recovery, and secondary structure changes. Following attachment, the materials retained colloidal stability and individual particle characteristics with a zeta potential of ?33 mV compared to ?46 mV for the native particle. The conjugated enzyme showed no changes in secondary structure and exhibited significant catalytic activity with a catalytic efficiency of 2.8 × 10³ M^?1 s^?1 compared to 2.5 × 10³ M^?1 s^?1 for the native enzyme. Relative to the free enzyme, the conjugated enzyme was recovered for repeated use with 78% activity retained after five cycles. This work demonstrates that carboxylic-acid functionalized magnetic nanoparticles can be utilized as a means of producing a simple and effective conjugated-lactase system that achieves both particle and enzyme stability.     

Magnetic nanocomposite of anti-human IgG/COOH-multiwalled carbon nanotubes/Fe₃O₄ as a platform for electrochemical immunoassay

An electrochemical immunosensing method was developed based on a magnetic nanocomposite. The multiwalled carbon nanotubes (MWCNTs) were treated with nitric acid to produce carboxyl groups at the open ends. Then, Fe₃O₄ nanoparticles were deposited on COOH–MWCNTs by chemical coprecipitation of Fe²⁺ and Fe³⁺ salts in an alkaline solution. Goat anti-human IgG (anti-hIgG) was covalently attached to magnetic nanocomposite through amide bond formation between the carboxylic groups of MWCNTs and the amine groups of anti-hIgG. The prepared bio-nanocomposite was used for electrochemical sensing of human tetanus IgG (hIgG) as a model antigen. The anti-hIgG magnetic nanocomposite was fixed on the surface of a gold plate electrode using a permanent magnet. The hIgG was detected using horseradish peroxidase (HRP)-conjugated anti-hIgG in a sandwich model. Electrochemical detection of hIgG was carried out in the presence of H₂O₂ and KI as substrates of HRP. Using this method, hIgG was detected in a concentration range from 30 to 1000 ng ml^?1 with a correlation coefficient of 0.998 and a detection limit of 25 ng ml^?1 (signal/noise = 3). The designed immunosensor was stable for 1 month.     

High activity and selectivity immobilized lipase on Fe3O4 nanoparticles for banana flavour synthesis

Lipase (E.C.3.1.1.3) from Thermomyces lanuginosus (TL) was directly bonded, through multiple physical interactions, on citric acid functionalized monodispersed Fe₃O₄ nanoparticles (NPs) in presence of a small amount of hydrophobic functionalities. A very promising scalable synthetic approach ensuring high control and reproducibility of the results, and an easy and green immobilization procedure was chosen for NPs synthesis and lipase anchoring. The size and structure of magnetic nanoparticles were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The samples at different degree of functionalization were analysed through thermogravimetric measurements. Lipase immobilization was further confirmed by enzymatic assay and Fourier transform infrared (FT-IR) spectra. Immobilized lipase showed a very high activity recovery up to 144% at pH = 7 and 323% at pH = 7.5 (activity of the immobilized enzyme compared to that of its free form). The enzyme, anchored to the Fe₃O₄ nanoparticles, to be easy recovered and reused, resulted more stable than the native counterpart and useful to produce banana flavour. The immobilized lipase results less sensitive to the temperature and pH, with the optimum temperature higher of 5 °C and optimum pH up shifted to 7.5 (free lipase optimum pH = 7.0). After 120 days, free and immobilized lipases retained 64% and 51% of their initial activity, respectively. Ester yield at 40 °C for immobilized lipase reached 88% and 100% selectivity.     

Immobilization of penicillin G acylase on paramagnetic aldehyde-functionalized mesostructured cellular foams

Paramagnetic aldehyde-functionalized mesostructured cellular foams (PAMCFs), synthesized by grafting 3-aminopropyltriethoxysilane modified Fe₃O₄ (NH₂-Fe₃O₄) nanoparticles with larger particle size than the window pore size of MCFs on the outer surface of aldehyde-functionalized mesostructured cellular foams (AMCFs), were investigated as efficient supports for immobilization of penicillin G acylase (PGA). The results show that NH₂-Fe₃O₄ nanoparticles were successfully grafted on the outer surface of AMCFs and PGA molecules were mainly immobilized covalently on the inner surface of PAMCFs, which was because amino groups of NH₂-Fe₃O₄ nanoparticles or PGA molecules reacted with aldehyde groups of AMCFs or PAMCFs to form imine bonds. PGA/PAMCFs-15 showed a rather high initial activity of 9563 U g⁻¹ and retained 89.1% of its initial activity after recycled for 10 times. PGA/PAMCFs are easily recycled by magnetic field in order to replace tedious separation of high-speed centrifugation for mesoporous materials.     

Hysteresis losses and specific absorption rate measurements in magnetic nanoparticles for hyperthermia applications

BackgroundMagnetic hysteresis loops areas and hyperthermia on magnetic nanoparticles have been studied with the aim of providing reliable and reproducible methods of measuring the specific absorption rate (SAR).MethodsThe SAR of Fe₃O₄ nanoparticles with two different mean sizes, and Ni_1 −xZn_xFe₂O₄ ferrites with 0 ≤ x ≤ 0.8 has been measured with three approaches: static hysteresis loops areas, dynamic hysteresis loops areas and hyperthermia of a water solution. For dynamic loops and thermometric measurements, specific experimental setups have been developed, that operate at comparable frequencies (≈ 69 kHz and ≈ 100 kHz respectively) and rf magnetic field peak values (up to 100 mT). The hyperthermia setup has been fully modelled to provide a direct measurement of the SAR of the magnetic nanoparticles by taking into account the heat exchange with the surrounding environment in non-adiabatic conditions and the parasitic heating of the water due to ionic currents.ResultsDynamic hysteresis loops are shown to provide an accurate determination of the SAR except for superparamagnetic samples, where the boundary with a blocked regime could be crossed in dynamic conditions. Static hysteresis loops consistently underestimate the specific absorption rate but can be used to select the most promising samples.ConclusionsA means of reliably measure SAR of magnetic nanoparticles by different approaches for hyperthermia applications is presented and its validity discussed by comparing different methods.General significanceThis work fits within the general subject of metrological traceability in medicine with a specific focus on magnetic hyperthermia. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editor: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader.     

Stabilization of d-amino acid oxidase from Rhodosporidium toruloides by encapsulation in polyallylamine-mediated biomimetic silica

d-Amino acid oxidase from Rhodosporidium toruloides (RtDAO) and Fe₃O₄ magnetic nanoparticles were encapsulated simultaneously within biomimetic silica, as mediated by polyallylamine. The capacity for this enzyme reached 193 mg/g of biomimetic silica when 15 mg/ml RtDAO was used during encapsulation; the average encapsulation efficiency was approximately 74%. The T_m value (the temperature at which 50% of the initial activity was retained after 1 h of incubation) was increased from 44.3 °C of the free RtDAO to 57.7 °C, clearly indicating the thermal stability was improved by encapsulation. In the presence of 50 mM hydrogen peroxide, encapsulated RtDAO had a half-life of 148 min, an approximately 2-fold increase in resistance to hydrogen peroxide as compared to 78-min half-life of the free form. The encapsulation process is simple and can be completed within minutes; besides, the resultant enzymes can be recovered easily under magnetic field. Such preparation of encapsulated d-amino acid oxidase could be exploited for many potential applications.     

Alkylation of a human telomere sequence by heterotrimeric chlorambucil PI polyamide conjugates

We designed and synthesized human telomere alkylating N-methylpyrrole-N-methylimidazole (PI) polyamide conjugates (1–6). The C-type conjugates 1–3 possessed a chlorambucil moiety at the C terminus, whereas the N-type conjugates 4–6 had one of these moieties at the N terminus. The DNA alkylating activity of these conjugates was evaluated by high-resolution denaturing polyacrylamide gel electrophoresis using a 220 bp DNA fragment containing the human telomere repeat sequence 5′-(GGGTTA)₄-3′/5′-(TAACCC)₄-3′. C-type conjugates are designed to alkylate the G-rich-strand-containing 5′-GGGTTA-3′ and N-type conjugates were designed to alkylate the complementary C-rich strand-containing 5′-TAACCC-3′ sequence. The difference between conjugates 1–3 and 4–6 lies in the linker region between the polyamide moiety and chlorambucil. Conjugates 1 and 4 efficiently alkylated the 5′-GGTTAGGGTTA-3′ and 5′-CCCTAACCCTAA-3′ sequences, respectively, by recognizing 11 bp in the presence of distamycin A (Dist), in a heterotrimeric manner: one long alkylating polyamide conjugate (1–6) and two short partners (Dist).     

Direct affinity immobilization of recombinant heparinase I fused to maltose binding protein on maltose-coated magnetic nanoparticles

Hybrid magnetic Fe₃O₄@SiO₂-poly(ethylene oxide)-maltose (Fe₃O₄@SiO₂-PEO-mal) nanoparticles synthesized by our group can be used as affinity adsorption carriers for direct separation of maltose binding protein-fused Hep I (MBP-Hep I) from a crude enzyme solution in a magnetic field. In this work, different PEO molecular weights for Fe₃O₄@SiO₂-PEO-mal nanoparticles were used for characterizing of MBP-Hep I immobilization. The results showed that all four kinds of Fe₃O₄@SiO₂-PEO-mal magnetic nanoparticles (6k, 20k, 35k and 100k for PEO) exhibited excellent adsorption capacities and the adsorption ratio increased as the PEO molecular weight increased from 6k to 100k. All four kinds of immobilized MBP-Hep I exhibited significantly improved stability at 30 °C compared with free MBP-Hep I and their half-lives were 20–50 times that of the free MBP-Hep I. Fe₃O₄@SiO₂-PEO-mal nanoparticles with a PEO molecular weight of 100k were best able to immobilize MBP-Hep I (Fe₃O₄@SiO₂-PEO_100k-mal-MBP-Hep I). The molecular weight distribution profiles and anticoagulant activities, obtained from heparin depolymerization by free Hep I, free MBP-Hep I and Fe₃O₄@SiO₂-PEO_100k-mal-MBP-Hep I were the same. Furthermore, Fe₃O₄@SiO₂-PEO_100k-mal-MBP-Hep I exhibited reasonable reusability during enzymatic production of low molecular weight heparins (LMWHs).     

DNA binding and cytotoxicity studies of magnetic nanofluid containing antiviral drug oseltamivir

In this work, the possibility of preparing a nanoparticle with improved treatment properties was investigated. In this regard, synthesis, characterization, in vitro cytotoxicity and DNA binding of Fe₃O₄@oleate/oseltamivir magnetic nanoparticles (MNPs) were investigated. Fe₃O₄ nanoparticles were synthesized via chemical co-precipitation and coated by oleate bilayers. Then, Fe₃O₄@OA MNPs were functionalized with an antiviral drug (oseltamivir), for better biological applications. The MNPs were subsequently characterized by zeta sizer and Zeta potential measurements, Fourier transform infrared (FT-IR) spectroscopy, vibrating sample magnetometer (VSM) and transmission electron microscopy (TEM) analyses. The TEM image demonstrated that average sizes of Fe₃O₄@OA/oseltamivir MNPs were about 8?nm. The in vitro cytotoxicity of Fe₃O₄@OA/oseltamivir MNPs was studied against cancer cell lines (MCF-7 and MDA-MB-231) and compared with oseltamivir drug. The results illustrated that Fe₃O₄@OA/oseltamivir magnetic nanoparticles have better antiproliferative effects on the mentioned cell lines as compared with oseltamivir. Also, in vitro DNA binding studies were done by UV–Vis, circular dichroism, and Fluorescence spectroscopy. The results indicated that Fe₃O₄@OA/oseltamivir MNPs bound to DNA via groove binding. Moreover, this magnetic nanofluid has potential for magnetic hyperthermia therapy due to magnetic core of its nanoparticles.

Communicated by Ramaswamy H. Sarma     

Citrinin detection by intensified fluorescence signal of a FRET-based immunosensor using magnetic/silica core–shell

The specific immune-reaction between the anti-citrinin antibody immobilized on the surface of magnetic/silica core–shell (MSCS) and the citrinin–Rho123–BSA conjugate brings the Rho123 fluorophore as an acceptor and the QDs as a donor in close spatial proximity and causes FRET for occurring upon photo-excitation of the QDs. The novelties of this study include: (1) immobilization of the MSCS; (2) large amount of the immobilized QDs, and (3) immobilization of a large amount of Rho123 on the BSA macromolecule. Cd/Te QDs were synthesized by the simultaneous reduction of cadmium chloride and tellurium in the presence of sodium borohydride. Magnetic nanoparticles were synthesized using FeSO₄ and FeCl₃. The prepared magnetic nanoparticles shelled by silica using tetraethoxysilane in the presence of ammonia. Transmission electron microscopy (TEM) analysis was used for investigating shape and monodispersity of the nanoparticles. EDC/NHS was used as a cross linking agent for immobilization of the QDs, conjugation of citrinin to amino groups of BSA, labeling of BSA with Rho123 and also for immobilization of the amino-functionalized MSCS on the immobilized QDs. Immobilization of the anti-citrinin antibody on the surface of the amino-functionalized MSCS was performed by Schiff-base mechanism. By using these three effective strategies, sensitivity of the designed nanobiosensor was incredibly enhanced as a very low limit of detection (up to 0.1 pM). The feasibility of this technique was tested by the detection of citrinin in the spiked human serum. Results showed that there was a linear correlation between the decreased fluorescence intensity of the Rho123 and increased fluorescence intensity of the QDs with increasing concentration of citrinin in the spiked samples in the range of 1–6 pM. According to obtained results, we conclude that this highly sensitive detection scheme is a easy, quick and impressive method that can be used in optical-based nanosensors.     

Asymmetric ZnPc–rhodamine B conjugates for mitochondrial targeted photodynamic therapy

Design, synthesis, characterization, and photodynamic activity of mitochondria specific asymmetric ZnPc–Rh B conjugates are described. Conjugation of asymmetric ZnPc–OH chromophores 3a and 3b with rhodamine B via the corresponding DIC-activated ester gave the desired near IR-absorbing asymmetric ZnPc–Rh B conjugates 1a and 1b. Conjugates 1a and 1b were shown to produce singlet oxygen upon illumination in DMSO, MeOH and THF. Fluorescence aggregation studies of the dyes 1a, 1b, 3a and 3b in DMSO and phosphate buffered saline (PBS) solution showed that conjugates 1a and 1b were less aggregated compared to the corresponding non-conjugates 3a and 3b suggesting that incorporation of Rh B lowered aggregation of the conjugates in the PBS solution. The four dyes studied have log D_7.4 values between 2.31 and 2.48, with the sulfur-containing conjugate 1b being the most hydrophobic. All the dyes showed negligible dark toxicity when colon 26 cells were treated with 5 μM of the dyes while 10–15% cell death was observed for dye concentrations of 15 μM. Illumination (700 ± 40 nm, 45 J/cm², 15 min) of the cells ([dye] = 15 μM) gave 70% cell death for ZnPc–Rh B conjugates 1a and 1b while no killing for non-conjugates 3a and 3b suggesting that the incorporation of the Rh B in the photosensitizer lowered the aggregation and subsequently improved cellular uptake and phototoxicity.     

Glycation of lysozyme with galactose,galactooligosaccharides and potato galactan through the Maillard reaction and optimization of the production of prebiotic glycoproteins

The production of glycated lysozyme (LZM), with galactose, galactooligosaccharides (GOSs) and potato galactan through the Maillard reaction, was investigated. The percent blocked lysine, estimated from the furosine content, reached a maximum value of 11.2% for LZM:galactan conjugates after 1 day incubation at a a_w of 0.65. A maximum percent blocked lysine of 7.0 and 13.5% were obtained for LZM:galactose/GOS conjugates at a lower a_w of 0.45 after 3 and 7 days, respectively. However, the low percent blocked lysine and the high protein aggregation index of LZM:galactose/GOS conjugates at a_w 0.79 and 0.65 revealed the prevalence of the degradation of the Amadori compounds and the protein cross-linking. Mass spectrometry of LZM conjugates revealed the formation of different glycoforms. Glycated LZMs containing up to seven galactose moieties were formed; while only mono- and diglycated LZMs with GOSs were detected. 2–3 mol of galactan were conjugated to 1 mol of LZM. Response surface methodology, based on a 5-level and 3-factor central composite design, revealed that molar ratio and temperature were the most significant variables for the glycation of LZM with GOSs. The optimal conditions leading to a high percent blocked lysine (16.11%) with a low protein aggregation index (0.11) were identified: temperature of 49.5 °C, LZM:GOS molar ratio of 1:9 and a_w of 0.65. To the best of our knowledge, this is the first study on the optimization of LZM glycation with GOSs.     

Does conjugation of antioxidants improve their antioxidative/anti-inflammatory potential?

A series of symmetric and asymmetric spermine (SPM) conjugates with all-trans-retinoic acid (ATRA), acitretin (ACI), (E)-3-(trioxsalen-4′-yl)acrylic acid (TRAA) and l-DOPA, amides of ACI, l-DOPA and TRAA with 1-aminobutane, benzylamine, dopamine and 1,12-diaminobutane as well as hybrid conjugates of O,O′-dimethylcaffeic acid (DMCA) with TRAA or N-fumaroyl-indole-3-carboxanilide (FICA) and 2-(2-aminoethoxy)ethanol were synthesized and their antioxidant properties were studied. The reducing activity (RA)% of the compounds were evaluated using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical-scavenging assay and found to be in the range 0–92(20 min)%/96(60 min)% at 100 μM, the most powerful being the conjugates l-DOPA-SPM-l-DOPA (8, RA = 89%/96%) and l-DOPA-dopamine (13, RA = 92%/92%). Conjugate DMCA-NH(CH₂CH₂O)₂-FICA (14) was the most powerful LOX inhibitor with IC₅₀ 33.5 μM, followed by the conjugates ACI-NHCH₂Ph (10, IC₅₀ 40.5 μM), ACI-SPM-TRAA (7, IC₅₀ 41.5 μM), DMCA-NH(CH₂CH₂O)₂-TRAA (15, IC₅₀ 65 μM), 13 (IC₅₀ 81.5 μM) and ACI-dopamine (11, IC₅₀ 87 μM). The most potent inhibitors of lipid peroxidation at 100 μM were the conjugates 15 (98%) and ACI-SPM-ACI (4, 97%) whereas all other compounds showed activities comparable or lower than trolox. The most interesting compounds, namely ATRA-SPM-ATRA (3), 4, 10, 11 and 15, as well as unconjugated compounds such as ATRA and dopamine, were studied for their anti-inflammatory activity in vivo on rat paw oedema induced by Carrageenan and found to exhibit, for doses of 0.01 mmol/mL of conjugates per Kg of rat body weight, weaker anti-inflammatory activities (3.6–40%) than indomethacin (47%) with conjugate 3 being the most potent (40%) in this series of compounds. The cytocompatibility of selected compounds was evaluated by the viability of RAMEC cells in the presence of different concentrations (0.5–50 μM) of the compounds. Conjugates 3 (IC₅₀ 2.6 μM) and 4 (IC₅₀ 4.7 μM) were more cytotoxic than the corresponding unconjugated retinoids ATRA (IC₅₀ 18.3 μM) and ACI (IC₅₀ 14.6 μM), whereas conjugate 15 (IC₅₀ 12.9 μM) was less cytotoxic than either DCSP (IC₅₀ 11.3 μM) or the tert-butyl ester of TRAA (IC₅₀ 2.9 μM).     

First proof of bismuth oxide nanoparticles as efficient radiosensitisers on highly radioresistant cancer cells

This study provides the first proof of the novel application of bismuth oxide as a radiosensitiser. It was shown that on the highly radioresistant 9L gliosarcoma cell line, bismuth oxide nanoparticles sensitise to both kilovoltage (kVp) or megavoltage (MV) X-rays radiation. 9L cells were exposed to a concentration of 50 μg.mL⁻¹ of nanoparticle before irradiation at 125 kVp and 10 MV. Sensitisation enhancement ratios of 1.48 and 1.25 for 125 kVp and 10 MV were obtained in vitro, respectively. The radiation enhancement of the nanoparticles is postulated to be a combination of the high Z nature of the bismuth (Z = 83), and the surface chemistry. Monte Carlo simulations were performed to elucidate the physical interactions between the incident radiation and the nanoparticle. The results of this work show that Bi₂O₃ nanoparticles increase the radiosensitivity of 9L gliosarcoma tumour cells for both kVp and MV energies. Monte Carlo simulations demonstrate the advantage of a platelet morphology.     

Immobilization of glycolate oxidase from Medicago falcata on magnetic nanoparticles for application in biosynthesis of glyoxylic acid

Glycolate oxidase was isolated from Medicago falcata Linn. after a screening from 13 kinds of C₃ plant leaves, with higher specific activity than the enzyme from spinach. The M. falcata glycolate oxidase (MFGO) was partially purified and then immobilized onto hydrothermally synthesized magnetic nanoparticles via physical adsorption. The magnetic nanoparticles were characterized with scanning electron microscope (SEM), transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectroscopy. The maximum load of MFGO was 56 mg/g support and the activity recovery was 45%. Immobilization of MFGO onto magnetic nanoparticles enhanced the enzyme stability, and the optimum temperature was significantly increased from 15 °C to 30 °C. The immobilized biocatalyst was successfully used in a batch reactor for repeated oxidization of glycolic acid to synthesize glyoxylic acid, retaining ca. 70% of its initial activity after 4 cycles of reaction at 30 °C for nearly 70 h, and its half-life was calculated to be 117 h.     

Exposure of rainbow trout (Oncorhynchus mykiss) to magnetite (Fe3O4) nanoparticles in simplified food chain: Study on ultrastructural characterization

The widespread exposure of metallic nanoparticles to the aquatic ecosystem and its adverse impact on human life is the colossal concern worldwide. In view of this, this context was investigated to analyze microscopically the bioaccumulation and localization of magnetite (Fe₃O₄) nanoparticles in the cellular organelles of rainbow trout (Oncorhynchus mykiss, Walbaum, 1792) in aquatic conditions. Initially, Fe₃O₄ nanoparticles were absorbed on to Elodea (Elodea canadensis) and fed to molluscs (Melanopsis praemorsa). Fish were fed with the same molluscs, and then the intestines and liver were examined using light and transmission electron microscopy. Results showed that nanoparticles were present in the cytoplasm and other organelles of cells (mitochondrion and lysosome) by absorbing through microvilli of the epithelial cells of the tunica mucosa in the intestine. Further, nanoparticles passed through the vessels of the lamina propria of the tunica mucosa and reached to the sinusoids of the liver via blood circulation. It was then accumulated from the endothelium of the sinusoid to the cytoplasm of liver hepatocytes and to mitochondria and lysosome. The accumulation of nanoparticles in the epithelial cells, cytoplasm, mitochondria, and lysosome revealed the degree of transparency of the pattern with slight hesitation. In summary, this investigation contributed towards the understanding of the physiological effects of Fe₃O₄ nanoparticles on O. mykiss, which ascertains essentiality for sustainable development of nanobiotechnology in the aquatic ecosystem.     

Nanostructured materials for magnetic biosensing

BackgroundMagnetic nanoparticles (MNPs) are at the leading edge of the field of biomedical applications and magnetic biosensing.MethodsMNPs were fabricated by electrophysical methods of the laser target evaporation (LTE) and spark discharge with electrodynamic acceleration of plasma jumpers (SD). Synthesis of polyacrylamide hydrogel was done in the presence of Fe₂O₃ MNPs in different concentrations obtained by LTE. [FeNi/Ti]₃/Cu/[Ti/FeNi]₃/Ti multilayers for giant magnetoimpedance (GMI) based sensitive elements were prepared by rf-sputtering for testing a biosensor prototype.ResultsIron oxide MNPs, ferrofluids, ferrofluids contacting with biological systems, synthetic ferrogels mimicking natural tissues – are the steps of the discussed in this work development of bionanomaterials. Thorough the structural and magnetic studies of a multilayered sensitive element, MNPs and ferrogels insure the complete characterization of biosensor prototype. The GMI responses were carefully evaluated in initial state and in the presence of ferrogel with known concentration of MNPs. SD MNPs had the smallest 5–8 nm size. This nanomaterial was characterized by large internal strains of the order of 25 × 10^− 3, which can play an important role for the interaction with different biosystems.ConclusionsIron oxide MNPs were fabricated by LTE and SD methods. SD MNPs had the smallest 5–8 nm size and large internal strains of the order of 25 × 10^− 3. Designed GMI biosensor prototype allowed precise evaluation of the stray field of the MNPs present in the ferrogel by evaluating the systematic changes of the GMI in a 20–400 MHz frequency range.General significanceThis work summarizes recent developments in the field of nanomaterials potentially applicable in magnetic biosensing.     

Magnetic behaviour of negatively charged nickel(II) hexacyanoferrate(III) coordination nanoparticles

Negatively charged 4 nm bimetallic Ni^II–Fe^III cyanide-bridged nanoparticles were obtained and isolated by different coating agents. The magnetic properties of the particles were studied in the powder form and in diluted samples. A spin-glass like behaviour occurs in the concentrated sample, while the magnetic behaviour of the diluted ones strongly depends on the method used to isolate the nanoparticles. Only high dilution in a polymer matrix leads to a single-domain superparamagnetic behaviour, with a blocking temperature of 3.5 K.