Page 147 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

6.4 NIR-triggered anticancer drug delivery 145

6.4 NIR-triggered anticancer drug delivery

Conventional cancer therapies have suffered from lack of specificity and toxicity.
To solve the issue, nanotechnology-based drug delivery systems have been intro-
duced to improve ERP effect, reduce toxicity and increase half-life during blood
circulation. However, insufficient drug release in the tumorogenic side is the main
drawback of using these systems. Stimuli-drug delivery systems have been provided
the opportunity to tackle the limitation of typical drug delivery systems releasing
the cargo under a specific stimulus which can be both internal or external. Although
internal stimuli—such as pH, hypoxia, temperature, and so on—improved drug
accumulation in tumor tissue, they have some limitations regarding poor control on
drug release and difficulty in synthesis [60]. Compared to internal stimuli, external
stimuli—such as light, magnetic field, ultrasound, and so on—release their cargo
in a controllable manner during excitation [139]. Among these, NIR-light stimuli-
responsive systems (NIRSRS) have absorbed great attention due to the ease of syn-
thesis as compared to other stimuli-sensitive systems and deep penetration depth
compared to other light-stimuli sensitive systems. There are three different mecha-
nisms in NIRSRS for drug release included: (1) photothermal effect, (2) two-photon
conversion, and (3) upconverting nanoparticles (UCNPs) [61]. These mechanisms
are shown in Fig. 6.4.

6.4.1 Photothermal-guided drug release (PT-NIRSRS)

To prepare NIRSRS, thermo-sensitive materials are employed. These materials
convert irradiated NIR light to heat which leads to an increase in the temperature
and subsequently increases cargo release from the carrier either by phase transition
mechanism or disrupting whole or part of the carrier. In addition, as already men-
tioned, heat has a cytotoxic effect on cancer cells, so these systems are considered for
chemo-photothermal therapy.

FIGURE 6.4 Three suggested mechanisms for laser-assisted drug delivery.