BackgroundWith the increased use of nanoparticles in biomedical applications there is a growing need to understand the effects that nanoparticles may have on cell function. Identifying these effects and understanding the mechanism through which nanoparticles interfere with the normal functioning of a cell is necessary for any therapeutic or diagnostic application. The aim of this study is to evaluate if gold nanoparticles can affect the normal function of neurons, namely their activity and coding properties.ResultsWe synthesized star shaped gold nanoparticles of 180 nm average size. We applied the nanoparticles to acute mouse hippocampal slices while recording the action potentials from single neurons in the CA3 region. Our results show that CA3 hippocampal neurons increase their firing rate by 17% after the application of gold nanostars. The increase in excitability lasted for as much as 50 minutes after a transient 5 min application of the nanoparticles. Further analyses of the action potential shape and computational modeling suggest that nanoparticles block potassium channels responsible for the repolarization of the action potentials, thus allowing the cell to increase its firing rate.ConclusionsOur results show that gold nanoparticles can affect the coding properties of neurons by modifying their excitability.
The physical, chemical and optical properties of nano-scale colloids depend on their material composition, size and shape. There is a great interest in using nano-colloids for photo-thermal ablation, drug delivery and many other biomedical applications. Gold is particularly used because of its low toxicity. A property of metal nano-colloids is that they can have a strong surface plasmon resonance. The peak of the surface plasmon resonance mode depends on the structure and composition of the metal nano-colloids. Since the surface plasmon resonance mode is stimulated with light there is a need to have the peak absorbance in the near infrared where biological tissue transmissivity is maximal. We present a method to synthesize star shaped colloidal gold, also known as star shaped nanoparticles or nanostars. This method is based on a solution containing silver seeds that are used as the nucleating agent for anisotropic growth of gold colloids. Scanning electron microscopy (SEM) analysis of the resulting gold colloid showed that 70 % of the nanostructures were nanostars. The other 30 % of the particles were amorphous clusters of decahedra and rhomboids. The absorbance peak of the nanostars was detected to be in the near infrared (840 nm). Thus, our method produces gold nanostars suitable for biomedical applications, particularly for photo-thermal ablation.
Background: With the increased use of nanoparticles in biomedical applications there is a growing need to understand the effects that nanoparticles may have on cell function. Identifying these effects and understanding the mechanism through which nanoparticles interfere with the normal functioning of a cell is necessary for any therapeutic or diagnostic application. The aim of this study is to evaluate if gold nanoparticles can affect the normal function of neurons, namely their activity and coding properties. Results: We synthesized star shaped gold nanoparticles of 180 nm average size. We applied the nanoparticles to acute mouse hippocampal slices while recording the action potentials from single neurons in the CA3 region. Our results show that CA3 hippocampal neurons increase their firing rate by 17% after the application of gold nanostars. The increase in excitability lasted for as much as 50 minutes after a transient 5 min application of the nanoparticles. Further analyses of the action potential shape and computational modeling suggest that nanoparticles block potassium channels responsible for the repolarization of the action potentials, thus allowing the cell to increase its firing rate.
The physical, chemical and optical properties of nano-scale colloids depend on their material composition, size and shape [1][2][3][4][5] . There is a great interest in using nano-colloids for photo-thermal ablation, drug delivery and many other biomedical applications 6 . Gold is particularly used because of its low toxicity [7][8][9] . A property of metal nano-colloids is that they can have a strong surface plasmon resonance 10 . The peak of the surface plasmon resonance mode depends on the structure and composition of the metal nano-colloids. Since the surface plasmon resonance mode is stimulated with light there is a need to have the peak absorbance in the near infrared where biological tissue transmissivity is maximal 11,12 .We present a method to synthesize star shaped colloidal gold, also known as star shaped nanoparticles [13][14][15] or nanostars 16 . This method is based on a solution containing silver seeds that are used as the nucleating agent for anisotropic growth of gold colloids [17][18][19][20][21][22] . Scanning electron microscopy (SEM) analysis of the resulting gold colloid showed that 70 % of the nanostructures were nanostars. The other 30 % of the particles were amorphous clusters of decahedra and rhomboids. The absorbance peak of the nanostars was detected to be in the near infrared (840 nm). Thus, our method produces gold nanostars suitable for biomedical applications, particularly for photo-thermal ablation.
Stimulation of the localized surface plasmon of metallic nanoparticles has been shown to be an effective mechanism to induce photothermal damage in biological tissues. However, few studies have focused on single cell or subcellular ablation. Our results show that, upon incubation, gold nanostars are internalized by neurons of acute mouse cerebellar brain slices, clustering inside or close to the nucleus. By stimulating the nanostars' surface plasmon using a femtosecond laser, we show deformation of single nuclei and single cells. Given its precision and extremely localized effect, this is a promising technique for photothermal therapy in areas sensitive to collateral thermal damage such as the nervous system. 409-453 (2000). 30. S. Link, C. Burda, B. Nikoobakht, and M. A. El-Sayed, "Laser-induced shape changes of colloidal gold nanorods using femtosecond and nanosecond laser pulses," J.
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