Biomedical Engineering Reference
In-Depth Information
doxorubicin [109-111], methylprednisolone succinate [110] and cisplatin
[112]. In the i eld of gene delivery, they have been used for the delivery of
DNA [113], RNA [114] and other oligonucleotides [115].
3.2.3.4 Hyperthermia-Triggered Liposomes
Hyperthermia has been used widely in nanocarrier research to increase
vascular permeability of the target tissue [116] and to trigger the drug
release from thermo-sensitive nanocarriers [117]. h is combination
strategy allows for the ei cient delivery of drugs [118] as well as to help
in image-guided therapies [119, 120]. h e use of magnetic liposomes to
induce cell death by magnetic l uid hyperthermia [121, 122] and combine
this with the delivery of cytotoxic molecules was demonstrated recently by
Clares
et al.
[123].
3.2.3.5
Other Triggered Release Liposomes
In another interesting approach, liposomes, which release their cargo in a
glucose-sensitive manner were prepared by incorporating a hydrophobi-
cally modii ed glucose oxidase into the membrane [124]. Another recent
advance in the i eld of triggered release is the use of photo-sensitive lipo-
somes that can degrade on irradiation with UV light [125] or where the
PEG coating can be removed by photoactivation thus allowing for the
improved uptake of the liposome [126]. Similarly, in another approach,
the permeability of the liposomal membrane was increased by irradiating
the membrane-bound photosensitizer with red light [127]. Wu
et al.
have
also demonstrated the use of near infrared-triggerable systems for the con-
trolled release of gold nanoparticles [128].
3.3
Actively Targeted Liposomes
Actively targeted liposomes reach the target site the same way as passively
targeted ones, i.e. by the EPR ef ect. h e role of the ligands comes into play
mainly when liposomes arrive at the target tissue, where they are able to bind
and subsequently internalize into the cell (See Figure 3.1 and Figure 3.2).
h erefore, it is imperative that they have longer blood circulation times
as well as enhanced binding ei ciencies. Most of the liposomal examples
discussed in this section include a combination of targeting and longev-
ity functionalities. h ough traditionally these have been thought of as
multi-functional, a study of the recent literature suggests that targeting
