4 Aptamer-Based Drug Delivery Systems
89
4.4.1.4 Metal-Organic Framework (MOF)
Metal-organic framework (MOF) is a hybrid porous material composed of metal ions
and organic connectors, which is also a commonly used carrier in DDSs, especially
for stimuli-responsive drug delivery, and the detailed mechanisms involved have
been systematically illustrated by Liu group [64]. In a study, Chen et al. [65] fabricated pH-responsive nanosized MOFs (NMOFs) for the transportation of anticancer
drug to inhibit the breast cancer cells’ proliferation. The DOX-loaded NMOFs were
modified with cytosine (C)-rich i-motif sequences for hybridizing with guanine (G)rich AS1411 aptamers. The NMOFs exhibited pH-induced DOX release because the
release efficiency at pH 5.0 was higher than at pH 7.4 and showed higher cytotoxicity to cancer cells than bare NMOFs. Afterward, Chen’s group realized controllable
release of antiblood clotting drugs (Apixaban) through lock-key system of NMOFs,
in which the lock and the key were thrombin aptamer and thrombin, respectively
[66]. Drugs were loaded on MOFs by physical adsorption, and the helices formed by
aptamers and complementary strands were anchored on the surface of MOF to trap
drugs. In the presence of thrombin, the helices were dissociated due to the leaving
of aptamers, resulting in the release of drugs (Fig. 4.5e).
4.4.1.5 Carbon Nanomaterials
Graphene has large surface area, possesses characteristics of high carrier transport
mobility, mechanical flexibility, excellent chemical and thermal stability. Besides,
graphene oxide (GO) is an excellent fluorescence quencher. Liu group modified
GO with fluorescence-labeled aptamers, such as ATP aptamer, achieved intracellular detection of ATP with increased specificity and ability to resistance nonspecific probe displacement (Fig. 4.5f) [67]. Besides, the supramolecular π–π stacking
enabled the adsorption of DOX on GO surface, thus making GO a potential material in theranostic [68]. In another study, Liu group [69] prepared a drug delivery
system, namely, AS1411-GO/B3 for tumor targeting, in which nanographene oxide
(NGO) sheets were employed as the drug carrier, and the aptamer AS1411 was
conjugated onto GO for tumor targeting. GO also had photothermal effect, which
promoted the release of B3 from GO as well as the generation of thermal cytotoxicity to cells. This AS1411-GO/B3 platform with chemo-photothermal synergetic
therapy provided a promising treatment platform for tumors (Fig. 4.5g). In a study,
Hu et al. [70] reported a SiNP/CNT-DNA nanocomposite for traceable and targeted
drug delivery. This nanocomposite was synthesized in a highly modular fashion from
DNA-functionalized carbon nanotubes (CNT) and silica nanoparticles (SiNP) via
enzymatic rolling circle amplification. GC/CG-rich stem loops and aptamer motifs
were incorporated into the nanostructure to endow it with active targeting ability
to HeLa cells. DOX was loaded on the SiNP/CNT-DNA nanocomposite to perform
chemotherapy. The in vitro experimental results demonstrated that these designed
materials were more efficient than the pure drug alone.
89
4.4.1.4 Metal-Organic Framework (MOF)
Metal-organic framework (MOF) is a hybrid porous material composed of metal ions
and organic connectors, which is also a commonly used carrier in DDSs, especially
for stimuli-responsive drug delivery, and the detailed mechanisms involved have
been systematically illustrated by Liu group [64]. In a study, Chen et al. [65] fabricated pH-responsive nanosized MOFs (NMOFs) for the transportation of anticancer
drug to inhibit the breast cancer cells’ proliferation. The DOX-loaded NMOFs were
modified with cytosine (C)-rich i-motif sequences for hybridizing with guanine (G)rich AS1411 aptamers. The NMOFs exhibited pH-induced DOX release because the
release efficiency at pH 5.0 was higher than at pH 7.4 and showed higher cytotoxicity to cancer cells than bare NMOFs. Afterward, Chen’s group realized controllable
release of antiblood clotting drugs (Apixaban) through lock-key system of NMOFs,
in which the lock and the key were thrombin aptamer and thrombin, respectively
[66]. Drugs were loaded on MOFs by physical adsorption, and the helices formed by
aptamers and complementary strands were anchored on the surface of MOF to trap
drugs. In the presence of thrombin, the helices were dissociated due to the leaving
of aptamers, resulting in the release of drugs (Fig. 4.5e).
4.4.1.5 Carbon Nanomaterials
Graphene has large surface area, possesses characteristics of high carrier transport
mobility, mechanical flexibility, excellent chemical and thermal stability. Besides,
graphene oxide (GO) is an excellent fluorescence quencher. Liu group modified
GO with fluorescence-labeled aptamers, such as ATP aptamer, achieved intracellular detection of ATP with increased specificity and ability to resistance nonspecific probe displacement (Fig. 4.5f) [67]. Besides, the supramolecular π–π stacking
enabled the adsorption of DOX on GO surface, thus making GO a potential material in theranostic [68]. In another study, Liu group [69] prepared a drug delivery
system, namely, AS1411-GO/B3 for tumor targeting, in which nanographene oxide
(NGO) sheets were employed as the drug carrier, and the aptamer AS1411 was
conjugated onto GO for tumor targeting. GO also had photothermal effect, which
promoted the release of B3 from GO as well as the generation of thermal cytotoxicity to cells. This AS1411-GO/B3 platform with chemo-photothermal synergetic
therapy provided a promising treatment platform for tumors (Fig. 4.5g). In a study,
Hu et al. [70] reported a SiNP/CNT-DNA nanocomposite for traceable and targeted
drug delivery. This nanocomposite was synthesized in a highly modular fashion from
DNA-functionalized carbon nanotubes (CNT) and silica nanoparticles (SiNP) via
enzymatic rolling circle amplification. GC/CG-rich stem loops and aptamer motifs
were incorporated into the nanostructure to endow it with active targeting ability
to HeLa cells. DOX was loaded on the SiNP/CNT-DNA nanocomposite to perform
chemotherapy. The in vitro experimental results demonstrated that these designed
materials were more efficient than the pure drug alone.