We recently demonstrated that liposome-supported plasmon resonant gold nanoshells are degradable into
components of a size compatible with renal clearance, potentially enabling their use as multifunctional agents in
applications in nanomedicine, including imaging, diagnostics, therapy, and drug delivery (Troutman et al., Adv.
Mater. 2008, 20, 2604-2608). When illuminated with laser light at the wavelength matching their plasmon resonance
band, gold-coated liposomes rapidly release their encapsulated substances, which can include therapeutic and
diagnostic agents. The present research demonstrates that release of encapsulated agents from gold-coated liposomes
can be spectrally controlled by varying the location of the plasmon resonance band; this spectral tuning is
accomplished by varying the concentration of gold deposited on the surface of liposomes. Furthermore, the amount
of laser energy required for release is qualitatively explained using the concept of thermal confinement (Jacques,
Appl. Opt. 1993, 32(3), 2447-2454). Overlapping thermal confinement zones can be avoided by minimizing the laser
pulse width, resulting in lower energy requirements for liposomal content release and less global heating of the
sample. Control of heating is especially important in drug delivery applications, where it enables spatial and spectral
control of delivery and prevents thermal damage to tissue.