Synthesis of bi-metallic Au–Ag nanoparticles loaded on functionalized MCM-41 for immobilization of alkaline protease and study of its biocatalytic activity

In this work, Au–Ag nanoparticles (Au–Ag-bi-MNPs) have been prepared on amine functionalized Si-MCM-41 (NH₂–Si-MCM-41) particles through a reduction of AgNO₃ and HAuCl₄ by NaBH₄ at ambient conditions. Au–Ag-bi-MNPs loaded on the NH2–Si-MCM-41, provide a good biocompatible surface for immobilization of the enzyme alkaline protease. This immobilization, presumably due to bonding between core shell nanoparticles and OH in serine 183 in alkaline protease seems to be of an ionic exchange nature. We found that the alkaline protease immobilized on the Au–Ag-bi-MNPs/Si-MCM-41 is an active biocatalyst, stable at different pH and temperature. The bio catalytic activity of free alkaline protease in solution was 64 U/mg (Units per milligram), whereas that of the alkaline protease immobilized on Au–Ag-bi-MNPs/Si-MCM-41 was 75 U/mg. This improvement of the biocatalytic activity may be due to a really increased activity per molecule of immobilized enzyme or to a purification of the enzyme. The alkaline protease molecules immobilized on the (Au–Ag)/ NH₂-MCM-41 surface retained as much as 80% of the catalytic activity recorded at pH=8, and showed significant catalytic activity of alkaline protease in the bioconjugate material. The biocatalytic materials were easily separated from the reaction medium by mild centrifugation and exhibits excellent reuse and stability characteristics over four successive cycles. The optimum temperature ranged from 35 ^°C–55 ^°C and pH=8 for bioactivity of the alkaline protease in the assembly system was observed to be higher than that of the free enzyme in solution. The enzyme biocatalytic activity was monitored by UV-visible spectroscopy. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and dispersive analysis of X-RAY (EDAX) were used to characterize the size and morphology of the prepared materials.     

Surface functionalization of chitosan-coated magnetic nanoparticles for covalent immobilization of yeast alcohol dehydrogenase from Saccharomyces cerevisiae

A novel and efficient immobilization of yeast alcohol dehydrogenase (YADH, EC1.1.1.1) from Saccharomyces cerevisiae has been developed by using the surface functionalization of chitosan-coated magnetic nanoparticles (Fe₃O₄/KCTS) as support. The magnetic Fe₃O₄/KCTS nanoparticles were prepared by binding chitosan alpha-ketoglutaric acid (KCTS) onto the surface of magnetic Fe₃O₄ nanoparticles. Later, covalent immobilization of YADH was attempted onto the Fe₃O₄/KCTS nanoparticles. The effect of various preparation conditions on the immobilized YADH process such as immobilization time, enzyme concentration and pH was investigated. The influence of pH and temperature on the activity of the free and immobilized YADH using phenylglyoxylic acid as substrate has also been studied. The optimum reaction temperature and pH value for the enzymatic conversion catalyzed by the immobilized YADH were 30 °C and 7.4, respectively. Compared to the free enzyme, the immobilized YADH retained 65% of its original activity and exhibited significant thermal stability and good durability.     

Preparation of superparamagnetic sodium alginate nanoparticles for covalent immobilization of <Emphasis Type="Italic">Candida rugosa</Emphasis> lipase

Superparamagnetic sodium alginate nanoparticles with diameter around 25–30 nm were prepared with a water-in-oil emulsion method. The resulted magnetic SA nanoparticle was activated with glutaraldehyde and epichlorohydrin to form nanoscale support. Candida rugosa lipase (CRL), hereby chosen as a model enzyme, was covalently immobilized on the resulted magnetic support. The structure and magnetic behavior of the magnetic nanoparticles were confirmed by transmission electron microscopy, Fourier transform infrared spectroscopy, and vibrating sample magnetometer. Based on the structural character of enzyme (containing functional residues that are ideal reaction sites for the immobilization of enzyme repeatedly), the regeneration of support was investigated by reactivating the deactivated immobilized lipase with glutaraldehyde. And the results indicated that these regenerated supports remained to be efficient for lipase immobilization. Finally, all of the immobilized CRL prepared by different generations of supports displayed excellent reusability and applicability.     

Immobilization of glucose oxidase using CoFe2O4/SiO2 nanoparticles as carrier

Aminated-CoFe₂O₄/SiO₂ magnetic nanoparticles (NPs) were prepared from primary silica particles using modified StÖber method. Glucose oxidase (GOD) was immobilized on CoFe₂O₄/SiO₂ NPs via cross-linking with glutaraldehyde (GA). The optimal immobilization condition was achieved with 1% (v/v) GA, cross-linking time of 3 h, solution pH of 7.0 and 0.4 mg GOD (in 3.0 mg carrier). The immobilized GOD showed maximal catalytic activity at pH 6.5 and 40 °C. After immobilization, the GOD exhibited improved thermal, storage and operation stability. The immobilized GOD still maintained 80% of its initial activity after the incubation at 50 °C for 25 min, whereas free enzyme had only 20% of initial activity after the same incubation. After kept at 4 °C for 28 days, the immobilized and free enzyme retained 87% and 40% of initial activity, respectively. The immobilized GOD maintained approximately 57% of initial activity after reused 7 times. The K_M (Michaelis-Menten constant) values for immobilized GOD and free GOD were 14.6 mM and 27.1 mM, respectively.     

Covalent immobilization of lipases on monodisperse magnetic microspheres modified with PAMAM-dendrimer

This paper reported an immobilization of Candida rugosa lipase (CRL) onto PAMAM-dendrimer-grafted magnetic nanoparticles synthesized by a modified solvothermal reduction method. The dendritic magnetic nanoparticles were amply characterized by several instrumental measurements, and the CRL was covalently anchored on the three generation supports with glutaraldehyde as coupling reagent. The amount of immobilized enzyme was up to 150 mg/g support and the factors related with the enzyme activity were investigated. The immobilization of lipase improved their performance in wider ranges of pH and temperature. The immobilized lipase exhibited excellent thermal stability and reusability in comparison with free enzyme and can be reused 10 cycles with the enzymatic activity remained above 90 %. The properties of lipase improved obviously after being immobilized on the dendritic supports. The inactive immobilized lipase could be regenerated with glutaraldehyde and Cu²⁺, respectively. This synthetic strategy was facile and eco-friendly for applications in lipase immobilization.     

Design of multifunctionalized γ-Fe2O3@SiO2 core–shell nanoparticles for enzymes immobilization

This article deals with the first covalent grafting of an enzyme on twice functionalized γ-Fe₂O₃@SiO₂ core–shell magnetic nanoparticles. First, amino-PEG functionalized nanoparticles were synthesized in order to comply with non-toxic platforms that would be stable in high concentration and would exhibit chemical groups to allow further coupling with biomolecules. This approach produces a colloidal suspension of covalently grafted enzymes that remains stable for months and mimics the enzyme–substrate interactions in solution. Secondly, nanoparticles synthesis and enzyme coupling process were reported and the catalytic properties of bound enzymes were measured and compared with that of the free one. These new materials appear to be useful tools for enzymatic catalysis research and may be extended to other biomolecules. Furthermore, magnetic properties of these materials open the way to separation, purification, and transport under magnetic field.     

Ultrasound-assisted dextranase entrapment onto Ca-alginate gel beads

In this research work, dextranase has immobilized onto calcium alginate beads using a novel ultrasound method. The process of immobilization of the enzyme was carried out in a one-step ultrasound process. Effects of ultrasound conditions on loading efficiency and immobilization yield of the enzyme onto calcium alginate beads were investigated. Furthermore, the activity of the free and immobilized enzymes prepared with and without ultrasound treatment, as a function of pH, temperature, recyclability and enzyme kinetic parameters, was compared. The maximum loading efficiency and the immobilization yield were observed when the immobilized dextranase was prepared with an ultrasonic irradiation at 25 kHz, 40 W for 15 min, under which the loading efficiency and the immobilization yield increased by 27.21% and 18.77%, respectively, compared with the immobilized enzymes prepared without ultrasonic irradiation. On the other hand, immobilized enzyme prepared with ultrasonic irradiation showed V_max and K_M value higher than that for the immobilized enzyme prepared without ultrasonic irradiation, likewise, both the catalytic and specificity constants of immobilized enzyme prepared with ultrasonic irradiation were higher than that for immobilized enzyme prepared without ultrasound, indicating that, this new ultrasonic method improved the catalytic kinetics activity of immobilized dextranase at all the reaction conditions studied. Compared with immobilized enzyme prepared without ultrasound treatment, the immobilized enzymes prepared with ultrasound irradiation exhibited: a higher pH optimum, optimal reaction temperature, activation energy, and thermal stability, as well as, a higher recyclability, which, illustrating the effectiveness of the sonochemical method. To the best of our knowledge, this is the first report on the effect of ultrasound treatments on the immobilization of dextranase.     

Combined of ultrasound irradiation with high hydrostatic pressure (US/HHP) as a new method to improve immobilization of dextranase onto alginate gel

In this research work, dextranase was immobilized onto calcium alginate beads by the combination of ultrasonic irradiation and high hydrostatic pressure (US/HHP) treatments. Effects of US/HHP treatments on loading efficiency and immobilization yield of dextranase enzyme onto calcium alginate beads were investigated. Furthermore, the activities of immobilized enzymes prepared with and without US/HHP treatments and that prepared with ultrasonic irradiation (US) and high hydrostatic pressure (HHP), as a function of pH, temperature, recyclability and enzyme kinetic parameters, were compared with that for free enzyme. The maximum loading efficiency and the immobilization yield were observed when the immobilized dextranase was prepared with US (40 W at 25 kHz for 15 min) combined with HHP (400 MPa for 15 min), under which the loading efficiency and the immobilization yield increased by 88.92% and 80.86%, respectively, compared to immobilized enzymes prepared without US/HHP treatment. On the other hand, immobilized enzyme prepared with US/HHP treatment showed V_max, K_M, catalytic and specificity constants values higher than that for the immobilized enzyme prepared with HHP treatment, indicated that, this new US/HHP method improved the catalytic kinetics activity of immobilized dextranase at all the reaction conditions studied. Compared to immobilized enzyme prepared either with US or HHP, the immobilized enzymes prepared with US/HHP method exhibited a higher: pH optimum, optimal reaction temperature, thermal stability and recyclability, and lower activation energy, which, illustrating the effectiveness of the US/HHP method. These results indicated that, the combination of US and HHP treatments could be an effective method for improving the immobilization of enzymes in polymers.     

Surface functionalization of silica-coated magnetic nanoparticles for covalent attachment of cholesterol oxidase

A systematic approach towards the fabrication of highly functionalized silica shell magnetic nanoparticles, presently used for enzyme immobilization, is herein fully presented. The synthesis of bare maghemite (γ-Fe₂O₃) nanoparticles was accomplished by thermal co-precipitation of iron ions in ammonia alkaline solution at harsh reaction conditions, respectively. Primary surface engineering of maghemite nanoparticles was successfully performed by the proper deposition of silica onto nanoparticles surface under strictly regulated reaction conditions. Next, the secondary surface functionalization of the particles was achieved by coating the particles with organosilane followed by glutaraldehyde activation in order to enhance protein immobilization. Covalent immobilization of cholesterol oxidase was attempted afterwards. The structural and magnetic properties of magnetic silica nanocomposites were characterized by TEM and vibrating sample magnetometer (VSM) instruments. X-ray diffraction measurements confirmed the spinel structure and average size of uncoated maghemite nanoparticles to be around 20 nm in diameter. SEM-EDS spectra indicated a strong signal for Si, implying the coating procedure of silica onto the particles surface to be successfully accomplished. Fourier transform infrared (FT-IR) spectra analysis confirmed the binding of amino silane molecules onto the surface of the maghemite nanoparticles mediated Si-O-Si chemical bonds. Compared to the free enzyme, the covalently bound cholesterol oxidase retained 50% of its activity. Binding of enzyme onto chemically modified magnetic nanoparticles via glutaraldehyde activation is a promising method for developing biosensing components in biomedicine.     

Magnetic nanoparticles coated with polyaniline to stabilize immobilized trypsin

It is reported the synthesis of magnetic nanoparticles via the chemical co-precipitation of Fe ³⁺ ions and their preparation by coating them with polyaniline. The electronic micrograph analysis showed that the mean diameter for the nanoparticles is ～15 nm. FTIR, powder X-ray diffraction and Mössbauer spectroscopy were used to understand the chemical, crystallographic and ⁵⁷Fe hyperfine structures for the two samples. The nanoparticles, which exhibited magnetic behavior with relatively high spontaneous magnetization at room temperature, were identified as being mainly formed by maghemite (γFe₂O₃). The coated magnetic nanoparticles (sample labeled “mPANI”) presented a real ability to bind biological molecules such as trypsin, forming the magnetic enzyme derivative (sample “mPANIG-Trypsin”). The amount of protein and specific activity of the immobilized trypsin were found to be 13±5 μg of protein/mg of mPANI (49.3 % of immobilized protein) and 24.1±0.7 U/mg of immobilized protein, respectively. After 48 days of storage at 4 ^°C, the activity of the immobilized trypsin was found to be 89 % of its initial activity. This simple, fast and low-cost procedure was revealed to be a promising way to prepare mPANI nanoparticles if technological applications addressed to covalently link biomolecules are envisaged. This route yields chemically stable derivatives, which can be easily recovered from the reaction mixture with a magnetic field and recyclable reused.     

Towards Nanoscale Biomedical Devices in Medicine: Biofunctional and Spectroscopic Characterization of Superparamagnetic Nanoparticles

Medical interest in nanotechnology originates from a belief that nanoscale therapeutic devices can be constructed and directed towards its target inside the human body. Such nanodevices can be engineered by coupling superparamagnetic nanoparticle to biomedically active proteins. We hereby report the immobilization of a PhEst, a S-formylglutathione hydrolase from the psychrophilic P. haloplanktis TAC125 onto the gold coated surface of modified superparamagnetic core-shell nanoparticles (Fe₃O₄@Au). The synthesis of the nanoparticles is also reported. S-formylglutathione hydrolases constitute a family of ubiquitous enzymes which play a key role in formaldehyde detoxification both in prokaryotes and eukaryotes. PhEst was originally annotated as a putative feruloyl esterase, an enzyme that releases ferulic acid (an antioxidant reactive towards free radicals such as reactive oxygen species) from polysaccharides esters. Dynamic light scattering, scanning electron microscopy with energy dispersive X-ray spectroscopy, UV–visible absorption spectroscopy, fluorescence spectroscopy, magnetic separation technique and enzyme catalytic assay confirmed the chemical composition of the gold covered superparamagnetic nanoparticles, the binding and activity of the enzyme onto the nanoparticles. Activity data in U/ml confirmed that the immobilized enzyme is approximately 2 times more active than the free enzyme in solution. Such particles can be directed with external magnetic fields for bio-separation and focused towards a medical target for therapeutical as well as bio-sensor applications.     

Study on immobilization of lipase onto magnetic microspheres with epoxy groups

Magnetic microspheres were synthesized by the suspension polymerization of glycidyl methacrylate (GMA), methacrylic acid (MAA) and divinyl benzene (DVB) in the presence of oleic acid-coated Fe₃O₄ nanoparticles. Triacylglycerol lipase from porcine pancreas was covalently immobilized on the magnetic microspheres via the active epoxy groups with the activity yield up to 63% (±2.3%) and enzyme loading of 39 (±0.5) mg/g supports. The resulting immobilized lipase had higher optimum temperature compared with those of free lipase and exhibited better thermal, broader pH stability and excellent reusability. Furthermore, the catalyzed capability of immobilized lipase was also investigated by catalyzing synthesis of hexyl acetate and the esterification conversion rate reached to 83% (±2.5%) after 12 h in nonaqueous solvent.     

Superparamagnetic silica nanoparticles with immobilized metal affinity ligands for protein adsorption

Superparamagnetic silica-coated magnetite (Fe₃O₄) nanoparticles with immobilized metal affinity ligands were prepared for protein adsorption. First, magnetite nanoparticles were synthesized by co-precipitating Fe²⁺ and Fe³⁺ in an ammonia solution. Then silica was coated on the Fe₃O₄ nanoparticles using a sol–gel method to obtain magnetic silica nanoparticles. The condensation product of 3-Glycidoxypropyltrimethoxysilane (GLYMO) and iminodiacetic acid (IDA) was immobilized on them and after charged with Cu²⁺, the magnetic silica nanoparticles with immobilized Cu²⁺ were applied for the adsorption of bovine serum albumin (BSA). Scanning electron micrograph showed that the magnetic silica nanoparticles with an average size of 190 nm were well dispersed without aggregation. X-ray diffraction showed the spinel structure for the magnetite particles coated with silica. Magnetic measurement revealed the magnetic silica nanoparticles were superparamagnetic and the saturation magnetization was about 15.0 emu/g. Protein adsorption results showed that the nanoparticles had high adsorption capacity for BSA (73 mg/g) and low nonspecific adsorption. The regeneration of these nanoparticles was also studied.     

Immobilization of cholesterol oxidase to finely dispersed silica-coated maghemite nanoparticles based magnetic fluid

In the recent years, the potential applicability of magnetic nanoparticles (MNPs) has witnessed a significant increase in interest towards the medical field, in particular, towards the usage of novel nanoparticles in diagnostics and disease treatment, respectively. In a present study, cholesterol oxidase (ChOx) was covalently immobilized to magnetic nanoparticles of maghemite (γ-Fe₂O₃) and further functionalized by silica (SiO₂) and amino-silane molecules. The activity of the bound enzyme was retained up to 60%, respectively. The binding of cholesterol oxidase was confirmed using FT-IR spectrophotometer. SEM analysis showed uniformly dispersed functional magnetic nanoparticles, which ranged in size from 22.5 to 50.8 nm, surrounded by amorphous silica. In this paper, the potential applications of chemically modified magnetic nanoparticles as carriers for cholesterol oxidase and other enzymes are discussed.     

Covalent immobilization of invertase on PAMAM-dendrimer modified superparamagnetic iron oxide nanoparticles

In this study, polyamidoamine (PAMAM) dendrimer was synthesized on the surface of superparamagnetite nanoparticles to enhance invertase immobilization. The amount of immobilized enzyme on the surface-hyperbranched magnetite nanoparticle was up to 2.5 times (i.e., 250%) as much as that of magnetite nanoparticle modified with only amino silane. Maximum reaction rate (V _max) and Michaelis–Menten constant (K _m) were determined for the free and immobilized enzymes. Various characteristics of immobilized invertase such as; the temperature activity, thermal stability, operational stability, and storage stability were evaluated and results revealed that stability of the enzyme is improved upon immobilization.     

Preparation and characterization of magnetic levan particles as matrix for trypsin immobilization

Magnetic levan was synthesized by co-precipitating D-fructofuranosyl homopolysaccharide with a solution containing Fe²⁺ and Fe³⁺ in alkaline conditions at 100 °C. The magnetic levan particles were characterized by scanning electron microscopy (SEM), magnetization measurements, X-ray diffractometry (XRD) and infrared spectroscopy (IR). Afterwards, magnetic levan particles were functionalized by NaIO₄ oxidation and used as matrices for trypsin covalent immobilization. Magnetite and magnetic levan particles were both heterogeneous in shape and levan-magnetite presented bigger sizes compared to magnetite according to SEM images. Magnetic levan particles exhibited a magnetization 10 times lower as compared to magnetite ones, probably, due to the coating layer. XRD diffractogram showed that magnetite is the dominant phase in the magnetic levan. Infrared spectroscopy showed characteristics absorption bands of levan and magnetite (O-H, C-O-C and Fe-O bonds). The immobilized trypsin derivative was reused 10 times and lost 16% of its initial specific activity only. Therefore, these magnetic levan particles can be proposed as an alternative matrices for enzyme immobilization.     

Preparation and Characterization of Magnetic Microspheres with an Epoxy Group Coating and Their Applications for Lipase Immobilization

Magnetic microspheres coated with epoxy groups (Ep) were prepared by suspension polymerization of glycidyl methacrylate (GMA) and styrene (St) in the presence of oleic acid-coated Fe₃O₄ (OA-Fe₃O₄) nanoparticles, using ethylene glycol dimethacrylate (EGDMA) as a cross-link reagent. The resulting magnetic microspheres were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM). It was verified that the magnetic microspheres had small diameters of 10–30 μm, as well as having super paramagnetism with a saturation magnetization of 10.5 emu/g. Porcine pancreas lipase (PPL) was selected as a model enzyme to be covalently immobilized (IPPL) on the magnetic microspheres via the reactive Ep; they had an activity yield up to 58.6%, when the protein loading reached 55.4 mg/g supports. In addition, the resulting immobilized lipases exhibited a better thermal stability, temperature and pH endurance than that of the free ones. In particular, an excellent reusability of IPPL, which could meet industrial requirements, was achieved.     

Mechanism study of dual-frequency ultrasound assisted enzymolysis on rapeseed protein by immobilized Alcalase

The mechanism of ultrasound field promoting enzymolysis efficiency is difficult to study, because the reaction system mixes with enzymes, proteins and hydrolysates. Immobilized enzyme is a good option that can be used to investigate the mechanism by separating enzymes out from the system after enzymolysis. The objective of this study was by using immobilized Alcalase to investigate the effects and mechanisms of the promotion of dual-frequency ultrasound (DFU) assisted-enzymolysis on rapeseed protein. Based on single factor experiments, response surface methodology model with three factors – hydrolysis time, power density and solid–liquid ratio at three levels was utilized to optimize the degree of hydrolysis (DH). Circular dichroism (CD) was used to analyze the secondary structure change of the protein, scanning electron microscopy (SEM) was used to analyze the surface microstructure change of the enzyme. The results showed that with DFU assisted-enzymolysis, the DH increased by 74.38% at the optimal levels for power density 57 W/L, solid–liquid ratio 5.3 g/L and enzymolysis time 76 min. After DFU assisted-enzymolysis, the yield of soluble solids content, including protein, peptides and total sugar in hydrolysate increased by 64.61%, 40.88% and 23.60%, respectively. CD analysis showed that after DFU assisted-enzymolysis, the number of α-helix and random coil decreased by 10.7% and 4.5%, β-chain increased by 2.4%. SEM showed that the degree of surface roughness of immobilized Alcalase increased. The above results indicated that the improvement of hydrolysis by DFU assisted-enzymolysis was achieved by enhancing the solid solubility, changing the molecular structure of protein and increased the surface area of immobilized enzyme.     

Magnetic composites from minerals: study of the iron phases in clay and diatomite using Mössbauer spectroscopy, magnetic measurements and XRD

Magnetic particles as matrix for enzyme immobilization have been used and due to the enzymatic derivative can be easily removed from the reaction mixture by a magnetic field. This work presents a study about the synthesis and characterization of iron phases into magnetic montmorillonite clay (mMMT) and magnetic diatomaceous earth (mDE) by ⁵⁷Fe Mössbauer spectroscopy (MS), magnetic measurements and X-ray diffraction (XRD). Also these magnetic materials were assessed as matrices for the immobilization of invertase via covalent binding. Mössbauer spectra of the magnetic composites performed at 4.2 K showed a mixture of magnetite and maghemite about equal proportion in the mMMT, and a pure magnetite phase in the sample mDE. These results were verified using XRD. The residual specific activity of the immobilized invertase on mMMT and mDE were 83 % and 92.5 %, respectively. Thus, both magnetic composites showed to be promising matrices for covalent immobilization of invertase.     

GoldMag nanoparticles with core/shell structure: characterization and application in MR molecular imaging

GoldMag is a kind of bi-functional nanoparticle, composed of a gold nanoshell and an iron oxide core. GoldMag combines the antibody immobilization property of gold nanoshell with the superparamagnetic feature of the iron oxide core. Rabbit anti-mouse IgG was immobilized on the surface of GoldMag to synthesize GoldMag-IgG in a single-step process. Transmission electron microscopy, UV/Vis spectrophotometry, zeta potential analysis, dynamic light scattering, enzyme-linked immunosorbent assay, and magnetic resonance imaging (MRI) were employed to characterize the nanostructures and the spectroscopic and magnetic properties of GoldMag and GoldMag-IgG. The antibody encapsulation efficiency of GoldMag was measured as 58.7%, and the antibody loading capacity was 88 μg IgG per milligram of GoldMag. The immunoactivity of GoldMag-IgG was estimated to be 43.3% of that of the original IgG. The cytotoxicity of GoldMag was assessed by MTT assay, which showed that it has only little influence on human dermal lymphatic endothelial cells. MR imaging of different concentrations of ultrasmall superparamagnetic iron oxide, GoldMag, and GoldMag-IgG showed that 3 μg/mL of nanoparticles could significantly affect the MRI signal intensity of GRE T2*WI. The results demonstrate that GoldMag nanoparticles can be effectively conjugated with biomacromolecules and possess great potential for MR molecular imaging.