Page 313 - Biodegradable Polyesters

11.3 Uniquely Encapsulated Drug/Biopolymer Nanofiber Systems for Drug Delivery 291

genetically engineered elastin-like polypeptides (ELPs), which exhibited a drug
release profile correlated with pH-dependent solubility of the parent ELPs.
Multifunctional core–shell capsules, one-step fabricated by coaxial electrospray
method, were triggered release by ultrasound stimulus. The shell suppressed the
initial burst release of paclitaxel. Fe O and graphene quantum dots inside the
3
4
oil core functioned successfully for magnetic targeting and fluorescence imaging,
respectively. Paclitaxel was trigger released when the dual layer of the TiO shell
2
cracked under ultrasound stimulation, with the releasing profile being controlled
by the length of applied ultrasound time (Figure 11.8) [89].
A coaxial electrospray process was also developed to encapsulate protein-based
drugs in biodegradable polymeric microparticles, eliminating the key problem
of protein denaturation and aggregation faced by other conventional methods of

(a) (b) (c)
40
60 Intact Intact
Shell cracked Shell cracked
50 Broken 30 Broken
Numbers 40 Numbers 20
30
20
10
10
0 0
Smaller than 1 1 to 3 Larger than 3 Smaller than 1 1 to 3 Larger than 3
(d) Capsule diameter (μm) (e) Capsule diameter (μm)
Ultrasound triggered releasing

Paclitaxel
(f) Graphene quantum dots
Figure 11.8 (a) SEM image of the capsules and capsules’ status of sample ultrasound
ultrasound for 5 min. (b) SEM image of the for 15 min. (f) Schematic illustration for pro-
capsules ultrasound for 15 min; the inset is a cedures of shell cracking until drug release
magnification of the capsules. (c) SEM image from the capsules with increasing ultrasound
of the capsules ultrasound for 30 min. (d) time. (Reproduced with permission from
Size distribution and capsules’ status of sam- Ref. [89]; Copyright 2011 American Chemical
ple ultrasound for 5 min. (e) Size distribution Society.)