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Stimuli-responsive controlled-release system using quadruplex DNA-capped silica nanocontainers.

Chen C, Pu F, Huang Z, Liu Z, Ren J, Qu X - Nucleic Acids Res. (2010)

Bottom Line: Start from simple conformation changes, the i-motif DNA cap can open and close the pore system in smart response to pH stimulus.A pH-switchable nanoreactor has also been developed to validate the potential of our system for on-demand molecular transport.This proof of concept might open the door to a new generation of carrier materials and could also provide a general route to use other functional nucleic acids/peptide nucleic acids as capping agents in the fields of versatile controlled delivery nanodevices.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Chemical Biology and State Key laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, PR China.

ABSTRACT
A novel proton-fueled molecular gate-like delivery system has been constructed for controlled cargo release using i-motif quadruplex DNA as caps onto pore outlets of mesoporous silica nanoparticles. Start from simple conformation changes, the i-motif DNA cap can open and close the pore system in smart response to pH stimulus. Importantly, the opening/closing and delivery protocol is highly reversible and a partial cargo delivery can be easily controlled at will. A pH-switchable nanoreactor has also been developed to validate the potential of our system for on-demand molecular transport. This proof of concept might open the door to a new generation of carrier materials and could also provide a general route to use other functional nucleic acids/peptide nucleic acids as capping agents in the fields of versatile controlled delivery nanodevices.

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(A) Release profiles of rhodamine B dye from MSN-RhB at pH 5.0 and 8.0. (B) Partial guest release profile of rhodamine B dye from MSN-RhB as function of pH variations.
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Figure 4: (A) Release profiles of rhodamine B dye from MSN-RhB at pH 5.0 and 8.0. (B) Partial guest release profile of rhodamine B dye from MSN-RhB as function of pH variations.

Mentions: To investigate the proton-fueled gating behavior of the MSN-DNA system, rhodamine B was first loaded as guest molecule by soaking MSN-DNA in a phosphate-buffered saline (PBS) solution (pH 7.4). The pore was capped by i-motif quadruplex when the pH value of the solution was adjusted to five. The excess amount of dye was removed by centrifugation and repeated washing with PBS (pH 5.0). The resulting particles (denoted as MSN-RhB) were then dispersed the citrate buffer (25 ml, 25 mM, pH 5.0 or pH 8.0) to test their controlled release property. As can be seen in Figure 4A, a very clear and highly effective pH-operable gating effect was demonstrated by monitoring the absorbance maximum of rhodamine B (553 nm) as a function of time. When the pH value is adjusted to 8.0, 91% release is obtained after 24 h. However, only negligible release occurs at pH 5.0 under the same condition, indicating good capping efficiency and tunable release rate via pH change. The pH-dependent release rate is consistent with the mechanism of operation for the MSN system: release of guest molecules depends on the reversible conformational change between i-motif quadruplex and random coil DNA. Since the diameter of i-motif structure is 1.9 nm (26,27), we speculated that the gate-like structure formed at the closed state (pH 5.0) might be expected to be large enough to gate the ∼2-nm diameter pore and thus prevent rhodamine B molecules from escaping. Indeed, we note that the structural change of DNA could be extremely complicated on the surface. For example, a DNA strand may fold into more than one i-motif structure, while the i-motif could form by association of two or more single strands. Further studies will be required to elucidate the exact mechanisms involved, but these are beyond the scope of this brief communication. In contrast, when the folded four-stranded i-motif domain was denatured into single-stranded form with cross-sectional diameter of 0.6 nm at pH 8.0, the packing of ssDNA displayed poor coverage of the pore and consequently leaded to leakage of entrapped dye molecules. In comparison, the results of unfunctionalized MCM-41 and MSN-cDNA showed remarkable dye liberation at both pH 5.0 and 8.0 (Supplementary Figures S4–S6). These data clearly demonstrated that we were able to close the pore system of MSN with the i-motif quadruplex DNA, and to release the loaded molecules subsequently by unfolding the quadruplex DNA in smart response to pH stimulus. Compared to the fast capping/uncapping response on the basis of the conformational change of i-motif DNA, the relatively slow liberation processes observed is ascribed to the diffusion-controlled kinetics of dye release.Figure 4.


Stimuli-responsive controlled-release system using quadruplex DNA-capped silica nanocontainers.

Chen C, Pu F, Huang Z, Liu Z, Ren J, Qu X - Nucleic Acids Res. (2010)

(A) Release profiles of rhodamine B dye from MSN-RhB at pH 5.0 and 8.0. (B) Partial guest release profile of rhodamine B dye from MSN-RhB as function of pH variations.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3045591&req=5

Figure 4: (A) Release profiles of rhodamine B dye from MSN-RhB at pH 5.0 and 8.0. (B) Partial guest release profile of rhodamine B dye from MSN-RhB as function of pH variations.
Mentions: To investigate the proton-fueled gating behavior of the MSN-DNA system, rhodamine B was first loaded as guest molecule by soaking MSN-DNA in a phosphate-buffered saline (PBS) solution (pH 7.4). The pore was capped by i-motif quadruplex when the pH value of the solution was adjusted to five. The excess amount of dye was removed by centrifugation and repeated washing with PBS (pH 5.0). The resulting particles (denoted as MSN-RhB) were then dispersed the citrate buffer (25 ml, 25 mM, pH 5.0 or pH 8.0) to test their controlled release property. As can be seen in Figure 4A, a very clear and highly effective pH-operable gating effect was demonstrated by monitoring the absorbance maximum of rhodamine B (553 nm) as a function of time. When the pH value is adjusted to 8.0, 91% release is obtained after 24 h. However, only negligible release occurs at pH 5.0 under the same condition, indicating good capping efficiency and tunable release rate via pH change. The pH-dependent release rate is consistent with the mechanism of operation for the MSN system: release of guest molecules depends on the reversible conformational change between i-motif quadruplex and random coil DNA. Since the diameter of i-motif structure is 1.9 nm (26,27), we speculated that the gate-like structure formed at the closed state (pH 5.0) might be expected to be large enough to gate the ∼2-nm diameter pore and thus prevent rhodamine B molecules from escaping. Indeed, we note that the structural change of DNA could be extremely complicated on the surface. For example, a DNA strand may fold into more than one i-motif structure, while the i-motif could form by association of two or more single strands. Further studies will be required to elucidate the exact mechanisms involved, but these are beyond the scope of this brief communication. In contrast, when the folded four-stranded i-motif domain was denatured into single-stranded form with cross-sectional diameter of 0.6 nm at pH 8.0, the packing of ssDNA displayed poor coverage of the pore and consequently leaded to leakage of entrapped dye molecules. In comparison, the results of unfunctionalized MCM-41 and MSN-cDNA showed remarkable dye liberation at both pH 5.0 and 8.0 (Supplementary Figures S4–S6). These data clearly demonstrated that we were able to close the pore system of MSN with the i-motif quadruplex DNA, and to release the loaded molecules subsequently by unfolding the quadruplex DNA in smart response to pH stimulus. Compared to the fast capping/uncapping response on the basis of the conformational change of i-motif DNA, the relatively slow liberation processes observed is ascribed to the diffusion-controlled kinetics of dye release.Figure 4.

Bottom Line: Start from simple conformation changes, the i-motif DNA cap can open and close the pore system in smart response to pH stimulus.A pH-switchable nanoreactor has also been developed to validate the potential of our system for on-demand molecular transport.This proof of concept might open the door to a new generation of carrier materials and could also provide a general route to use other functional nucleic acids/peptide nucleic acids as capping agents in the fields of versatile controlled delivery nanodevices.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Chemical Biology and State Key laboratory of Rare Earth Resources Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, PR China.

ABSTRACT
A novel proton-fueled molecular gate-like delivery system has been constructed for controlled cargo release using i-motif quadruplex DNA as caps onto pore outlets of mesoporous silica nanoparticles. Start from simple conformation changes, the i-motif DNA cap can open and close the pore system in smart response to pH stimulus. Importantly, the opening/closing and delivery protocol is highly reversible and a partial cargo delivery can be easily controlled at will. A pH-switchable nanoreactor has also been developed to validate the potential of our system for on-demand molecular transport. This proof of concept might open the door to a new generation of carrier materials and could also provide a general route to use other functional nucleic acids/peptide nucleic acids as capping agents in the fields of versatile controlled delivery nanodevices.

Show MeSH
Related in: MedlinePlus