Plasmonic gold nanoparticles possess the ability to open potassium channels in rat thoracic aorta smooth muscles in a...

Colloidal gold nanoparticles (AuNPs) of ~5nm core size and Zeta-potential of -35mV, having absorption maximum and plasmon resonance in the range of 510-570nm, were studied as a potential K(+)-channel opener in vascular smooth muscle (SM) cells. Experimental design of the study comprised SM contractile recordings. When externally applied to the organ bath, AuNPs (10(-6)-3×10(-4)M) led to decrease in amplitude of norepinephrine-induced contractions in a concentration-dependent and endothelium-independent manner in SM thoracic aorta, with mean value of pD2 (-log EC50) 4.2±0.03, Emax=55±4%. Being added to the bath solution in concentration of 10(-4)M, AuNPs significantly increased whole cell peak outward current at +70mV from 32±2pA/pF to 59±5pA/pF (n=14, P<0.05). External irradiation using a 5mW/532nm green laser, to facilitate plasmon resonance, led to an increment in the AuNPs-induced macroscopic outward potassium current (IK) from 59±5pA/pF to 74±1pA/pF (n=10, P<0.05). Paxilline (500nM), when added to the external bathing solution, significantly decreased AuNPs-induced increment of IK in SM cells. Single channel recordings provided a direct confirmation of BKCa activation by AuNPs at the single-channel level. Application of AuNPs to the bath potentiated BKCa activity with a delay of 1-2min, as was seen initially by more frequent channel openings followed by the progressive appearance of additional open levels corresponding to multiple openings of channels with identical single-channel amplitudes. Eventually, after 10-15min in the presence of AuNPs and especially when combined with the green laser illumination, there was a massive increase in channel activity with >10 channels evident. When irradiated by laser, AuNPs significantly increased the amplitude of maximal AuNPs-induced relaxation from 55±5% to 85±5% (n=10, P<0.05) while the sensitivity of SM to AuNPs was without changes. In summary, plasmonic AuNPs possess the ability to activate BKCa channel opening in vascular SM. Laser irradiation facilitates this effect due to local plasmon resonance that, in turn, further increases BKCa channel activity causing SM relaxation.