Hollow Nanocapsules in Biomedical Imaging Applications - Nanotechnology for Biomedical Imaging and Diagnostics - page 98

(a) (c)

ii

iii

i

Swelling

Deswelling

4 dispersed in MeOH 4 dispersed in MeOH/H 2 O mixture

(b) (d) (e)

20 20

15 15

10 10

HCl

5 5

0

0

500 520 540

Wavelength (nm)

560 580 600 0 5 10 15

Time (days)

20 25 30

Figure 4.19 (a) Examples of triggers to release encapsulants from polymer carriers: (i) light (NIR light-absorbing
nanoparticles), (ii) redox potential (cleavage of disulfide bonds), and (iii) enzymes (enzymatic cleavage). (b) Triggered
release of entrapped molecules from NCs. The complex between DA18C6 and metal cations is dissociated upon lowering
pH of the solution. The cation and DA18C6 are now free to leave the NC. (c) Reversible swelling and deswelling of
polymer NC. (d) Changes in the emission spectra of carboxyfluorescein (CF) upon release from the interior of polymer
NC by swelling in 10% methanol-water ( l ex = 458 nm, l em = 512 nm). (e) Release profile of the encapsulated CF from the
interior of the polymer NC in 10% methanol-water as a function of time. (Reprinted with permission from Ref. [83]. ©
Wiley.)