Gold Nanoshell-Assisted Wireless Activation of Myotube Contraction

INTRODUCTION Different approaches have been developed in the recent years for muscle cell stimulation and for myotube contraction, aiming at various applications in tissue engineering, regenerative medicine, and bionics. Mild... [ view full abstract ]

INTRODUCTION
Different approaches have been developed in the recent years for muscle cell stimulation and for myotube contraction, aiming at various applications in tissue engineering, regenerative medicine, and bionics. Mild heat stimulation of muscle cells within physiological range represents an intriguing strategy for the modulation of cell functions. In this context, plasmonic properties of gold nanostructures can be exploited upon near-infrared (NIR) excitation in order to remotely heat cells, also into deep tissues, owing to the low absorption in the NIR (λ ~ 800 nm) [1].
Although the effects of nanoparticle-assisted photo-thermal stimulation have been widely investigated in neurons and nerves, no significant studies on muscle cells can be found in the literature. In this work, for the first time, photo-thermal conversion was exploited to remotely stimulate muscle cells by using gold nanoshells (NS) in combination with NIR radiation.
MATERIALS AND METHODS
Au@SiO2 NS in water suspension (50 μg/ml, Nano-Composix) were centrifuged and re-dispersed in the cell medium (50 μg/ml). NS were characterized with scanning electron microscopy and UV-Vis absorbance was also investigated (Hitachi F-2700).
Intracellular temperature dynamics in response to a NIR stimulation (0.25 W/cm2) were assessed both in presence and in absence of the NS (Nano-Composix, 50 μg/ml) treatment, after 5 days of differentiation, by using a temperature-sensitive fluorescent thermometer targeting endoplasmic/sarcoplasmic reticulum (ER thermo yellow).[2] Calcium imaging was performed by using Fluo-4 AM fluorescent indicator.
RESULTS AND DISCUSSIONS
Intracellular temperature increments of about 5°C were induced by the NIR stimulation in the presence of NS. The increments of temperature were demonstrated able to efficiently induce a myotube contraction. Fluorescence Ca2+ imaging analysis demonstrated as no intracellular Ca2+ transients can be detected during the NIR + NS stimulation, so indicating that Ca2+ fluxes are not involved in the described phenomena.
Our results report, for the first time, a "wireless" activation of muscle cells mediated by light and nanoparticles, envisaging applications in tissue engineering as well as in bionics.
REFERENCES
[1] J. Yong et al. Adv. Healthc. Mater. 2014, 3, 1862–186.
[2] S. Arai et al. Sci. Rep. 2014, 4.