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Selective Cell
Targeting With Light-Absorbing Particles and Short Laser Pulses
Pitsillides, Costas1,2
and Lin, Charles1
Wellman Laboratories of Photomedicine, Massachusetts General Hospital/Harvard
Medical School1
Department of Mechanical Engineering, Massachusetts Institute of Technology2
Abstract-
A novel method for selective cell targeting is introduced, based on
the use of light-absorbing microparticles or nanoparticles and short
laser pulses. The particles are delivered to cell surface receptors
through antibody conjugation. Upon exposure to short laser pulses, highly
localized heating and mechanical cell damage are created around the
particles. Experiments were carried out with human lymphocytes in vitro,
using either 0.83 micron iron oxide-doped latex microspheres or 30 nm
gold nanospheres. Selective killing of CD8+ T cells were demonstrated
for both types of particles after exposure to 20 nsec, 565 nm laser
pulses at a moderate fluence of 0.4-0.5 J/cm^2. Efficient cell killing
was achieved with an average of 5 microparticles or 500 nanoparticles
per cell The ability of nanoparticles and short laser pulses to inflict
localized damage to cells has been further exploited to selectively
modify the permeability of the cell plasma membrane rather than cause
cell death. Transiently altering the cell membrane permeability to foreign
molecules offers the possibility for light-activated delivery of proteins
and genes into living cells. Experiments were carried out with human
lymphocytes in vitro using 20-30 nm gold particles targeted against
the CD45 surface receptor and sublethal light doses. Gold-labeled cells
were irradiated with 20 nsec, 532 nm laser pulses at a fluence of 0.5
J/cm^2 in the presence of 10 kDa fluorescein (FITC)-dextran conjugate,
a membrane-impermeable probe. Uptake, by viable cells, of the permeability
probe was determined by flow cytometry (measured as the increase in
mean FITC fluorescence of the cells). The recovery time of the plasma
membrane was investigated and it was determined that the membrane recovers
and reseals within 2 minutes following laser-induced permeabilization.
The use of 30 nm gold particles leads to substantial cell death but
cell toxicity can be minimized by employing the smaller 20 nm particles.
Keywords: nanoparticles,
cavitation
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