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Gold-Speckled Multimodal Nanoparticles for Noninvasive Bioimaging.

Sharma P, Brown SC, Bengtsson N, Zhang Q, Walter GA, Grobmyer SR, Santra S, Jiang H, Scott EW, Moudgil BM - Chem Mater (2008)

Bottom Line: Multimodal Gold-speckled silica nanoparticles as contrast agents for noninvasive imaging with magnetic resonance imaging and photoacoustic tomography have been prepared in a simple one-pot synthesis using nonionic microemulsions.Magnetic resonance contrast is provided through gadolinium incorporated in the silica matrix, whereas the photoacoustic signal originates from nonuniform, discontinuous gold nanodomains speckled across the silica surface.

View Article: PubMed Central - PubMed

Affiliation: Materials Science and Engineering and Particle Engineering Research Center, Molecular Genetics and Microbiology, Biomedical Engineering, Physiology and Functional Genomics, and Department of Surgery, University of Florida, P.O. Box 116135 Gainesville, Florida 32611, and NanoScience Technology Center, Chemistry and Biomolecular Science Center, University of Central Florida, Orlando, Florida 32826.

ABSTRACT
Multimodal Gold-speckled silica nanoparticles as contrast agents for noninvasive imaging with magnetic resonance imaging and photoacoustic tomography have been prepared in a simple one-pot synthesis using nonionic microemulsions. Magnetic resonance contrast is provided through gadolinium incorporated in the silica matrix, whereas the photoacoustic signal originates from nonuniform, discontinuous gold nanodomains speckled across the silica surface.

No MeSH data available.


Magnetic resonance data and PAT contrast from Gd-doped GSS nanoparticle. (A) T1-weighted (repetition time (TR) = 11 000 ms, echo time (TE) = 4.2 ms) and (B) T2* TR = 500 ms, TE = 40 ms images of serial dilutions of Gd-doped GSS nanoparticle: (a) 0.24, (b) 0.12, (c) 0.06, (d) 0.03, and (e) 0.015 mM of Gd in 0.5% agarose and (f) 0.5% agarose (as control). Linear plots of Gd concentration vs (C) 1/T1, (D) 1/T2, and (E) 1/T2*, respectively, to obtain ionic relaxivities, R1, R2, and R2*, respectively, of Gd-doped GSS nanoparticle. (F) Comparison of PAT contrast from gold and GSS nanoparticles of similar size and concentration (8 μL of 10 mg/mL) in a tissue-like phantom with background: absorption coefficient μa = 0.007 mm−1 and reduced scattering coefficient, μs′ = 0.5 mm−1. A stronger photo-acoustic signal is obtained from GSS nanoparticles as compared to gold nanoparticles.
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fig4: Magnetic resonance data and PAT contrast from Gd-doped GSS nanoparticle. (A) T1-weighted (repetition time (TR) = 11 000 ms, echo time (TE) = 4.2 ms) and (B) T2* TR = 500 ms, TE = 40 ms images of serial dilutions of Gd-doped GSS nanoparticle: (a) 0.24, (b) 0.12, (c) 0.06, (d) 0.03, and (e) 0.015 mM of Gd in 0.5% agarose and (f) 0.5% agarose (as control). Linear plots of Gd concentration vs (C) 1/T1, (D) 1/T2, and (E) 1/T2*, respectively, to obtain ionic relaxivities, R1, R2, and R2*, respectively, of Gd-doped GSS nanoparticle. (F) Comparison of PAT contrast from gold and GSS nanoparticles of similar size and concentration (8 μL of 10 mg/mL) in a tissue-like phantom with background: absorption coefficient μa = 0.007 mm−1 and reduced scattering coefficient, μs′ = 0.5 mm−1. A stronger photo-acoustic signal is obtained from GSS nanoparticles as compared to gold nanoparticles.

Mentions: The Gd-doped GSS nanoparticles were shown to generate MR contrast on both T1 and T2 proton relaxation time weighted sequences as depicted in Figure 4, parts A and B. Quantitatively, MR contrast is evaluated by estimating the relaxivity of the nanoparticle. The relaxivity (Ri, i = 1, 2) is defined as the gradient of the linear plot of relaxation rates (1/Ti, i = 1, 2) versus Gd concentration [Gd],(35) i.e., 1/Ti = 1/To + Ri[Gd], where Ti is the relaxation time for a contrast agent solution concentration [Gd] and To is the relaxation time in the absence of a contrast agent. From the data in Figure 4C−E, the relaxivities R1, R2, and R2* are determined to be 13, 110, and 173 mM−1 s−1, respectively. When compared with commercially available contrast agents, Gd−GSS exhibit much higher relaxivity values under the same magnetic strength of 4.7 T.(36) In MRI, it is well-established that the Gd-generated MR contrast relies on the relaxation process of the water molecules in association with the Gd ion and those exchanged in the surrounding environment.37,38 For an efficient relaxation process, rapid water exchange between bound (or inner coordination water) with the bulk water and slow tumbling play an important role.(37) The Gd-doped GSS nanoparticles address both these factors. First, the presence of the discontinuous GSS surface allows sufficient bulk water exchange with the Gd ions enabling MR tracking ability. It should be noted that a continuous gold shell over the silica core could limit the extent of water exchange inhibiting T1 contrast. Second, tumbling rate—another important factor for producing an effective MRI contrast—is also reduced in the Gd-doped GSS particles through the rigid binding of Gd to the nanoparticle surface. Because the tumbling rates are mass-dependent, nanoparticles are much slower than free Gd chelates and thus produce an enhanced relaxation. One of the major limitations of current molecular chelates used as MR contrast agent is their low sensitivity; this requires the use of higher dosages and results in poor targetability.(38) Both these concerns are also addressed in the present construct. Approximately, 34 000 ions of Gd are captured per nanoparticle with an average size of 100 nm, which is higher than the number of Gd ions previously reported in other nanoparticles such as synthetic polymers (6−70 ions) and in dendrimers (between 5 and 1331 ions, strongly dependent on particle size(39)) and comparable to perfluorocarbon nanoparticles (90 000 Gd ions in 250 nm diameter particle(40)).


Gold-Speckled Multimodal Nanoparticles for Noninvasive Bioimaging.

Sharma P, Brown SC, Bengtsson N, Zhang Q, Walter GA, Grobmyer SR, Santra S, Jiang H, Scott EW, Moudgil BM - Chem Mater (2008)

Magnetic resonance data and PAT contrast from Gd-doped GSS nanoparticle. (A) T1-weighted (repetition time (TR) = 11 000 ms, echo time (TE) = 4.2 ms) and (B) T2* TR = 500 ms, TE = 40 ms images of serial dilutions of Gd-doped GSS nanoparticle: (a) 0.24, (b) 0.12, (c) 0.06, (d) 0.03, and (e) 0.015 mM of Gd in 0.5% agarose and (f) 0.5% agarose (as control). Linear plots of Gd concentration vs (C) 1/T1, (D) 1/T2, and (E) 1/T2*, respectively, to obtain ionic relaxivities, R1, R2, and R2*, respectively, of Gd-doped GSS nanoparticle. (F) Comparison of PAT contrast from gold and GSS nanoparticles of similar size and concentration (8 μL of 10 mg/mL) in a tissue-like phantom with background: absorption coefficient μa = 0.007 mm−1 and reduced scattering coefficient, μs′ = 0.5 mm−1. A stronger photo-acoustic signal is obtained from GSS nanoparticles as compared to gold nanoparticles.
© Copyright Policy - open-access - ccc-price
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2664628&req=5

fig4: Magnetic resonance data and PAT contrast from Gd-doped GSS nanoparticle. (A) T1-weighted (repetition time (TR) = 11 000 ms, echo time (TE) = 4.2 ms) and (B) T2* TR = 500 ms, TE = 40 ms images of serial dilutions of Gd-doped GSS nanoparticle: (a) 0.24, (b) 0.12, (c) 0.06, (d) 0.03, and (e) 0.015 mM of Gd in 0.5% agarose and (f) 0.5% agarose (as control). Linear plots of Gd concentration vs (C) 1/T1, (D) 1/T2, and (E) 1/T2*, respectively, to obtain ionic relaxivities, R1, R2, and R2*, respectively, of Gd-doped GSS nanoparticle. (F) Comparison of PAT contrast from gold and GSS nanoparticles of similar size and concentration (8 μL of 10 mg/mL) in a tissue-like phantom with background: absorption coefficient μa = 0.007 mm−1 and reduced scattering coefficient, μs′ = 0.5 mm−1. A stronger photo-acoustic signal is obtained from GSS nanoparticles as compared to gold nanoparticles.
Mentions: The Gd-doped GSS nanoparticles were shown to generate MR contrast on both T1 and T2 proton relaxation time weighted sequences as depicted in Figure 4, parts A and B. Quantitatively, MR contrast is evaluated by estimating the relaxivity of the nanoparticle. The relaxivity (Ri, i = 1, 2) is defined as the gradient of the linear plot of relaxation rates (1/Ti, i = 1, 2) versus Gd concentration [Gd],(35) i.e., 1/Ti = 1/To + Ri[Gd], where Ti is the relaxation time for a contrast agent solution concentration [Gd] and To is the relaxation time in the absence of a contrast agent. From the data in Figure 4C−E, the relaxivities R1, R2, and R2* are determined to be 13, 110, and 173 mM−1 s−1, respectively. When compared with commercially available contrast agents, Gd−GSS exhibit much higher relaxivity values under the same magnetic strength of 4.7 T.(36) In MRI, it is well-established that the Gd-generated MR contrast relies on the relaxation process of the water molecules in association with the Gd ion and those exchanged in the surrounding environment.37,38 For an efficient relaxation process, rapid water exchange between bound (or inner coordination water) with the bulk water and slow tumbling play an important role.(37) The Gd-doped GSS nanoparticles address both these factors. First, the presence of the discontinuous GSS surface allows sufficient bulk water exchange with the Gd ions enabling MR tracking ability. It should be noted that a continuous gold shell over the silica core could limit the extent of water exchange inhibiting T1 contrast. Second, tumbling rate—another important factor for producing an effective MRI contrast—is also reduced in the Gd-doped GSS particles through the rigid binding of Gd to the nanoparticle surface. Because the tumbling rates are mass-dependent, nanoparticles are much slower than free Gd chelates and thus produce an enhanced relaxation. One of the major limitations of current molecular chelates used as MR contrast agent is their low sensitivity; this requires the use of higher dosages and results in poor targetability.(38) Both these concerns are also addressed in the present construct. Approximately, 34 000 ions of Gd are captured per nanoparticle with an average size of 100 nm, which is higher than the number of Gd ions previously reported in other nanoparticles such as synthetic polymers (6−70 ions) and in dendrimers (between 5 and 1331 ions, strongly dependent on particle size(39)) and comparable to perfluorocarbon nanoparticles (90 000 Gd ions in 250 nm diameter particle(40)).

Bottom Line: Multimodal Gold-speckled silica nanoparticles as contrast agents for noninvasive imaging with magnetic resonance imaging and photoacoustic tomography have been prepared in a simple one-pot synthesis using nonionic microemulsions.Magnetic resonance contrast is provided through gadolinium incorporated in the silica matrix, whereas the photoacoustic signal originates from nonuniform, discontinuous gold nanodomains speckled across the silica surface.

View Article: PubMed Central - PubMed

Affiliation: Materials Science and Engineering and Particle Engineering Research Center, Molecular Genetics and Microbiology, Biomedical Engineering, Physiology and Functional Genomics, and Department of Surgery, University of Florida, P.O. Box 116135 Gainesville, Florida 32611, and NanoScience Technology Center, Chemistry and Biomolecular Science Center, University of Central Florida, Orlando, Florida 32826.

ABSTRACT
Multimodal Gold-speckled silica nanoparticles as contrast agents for noninvasive imaging with magnetic resonance imaging and photoacoustic tomography have been prepared in a simple one-pot synthesis using nonionic microemulsions. Magnetic resonance contrast is provided through gadolinium incorporated in the silica matrix, whereas the photoacoustic signal originates from nonuniform, discontinuous gold nanodomains speckled across the silica surface.

No MeSH data available.