Responsive Nucleic Acid-Based Organosilica Nanoparticles

Abstract

The development of smart nanoparticles (NPs) that encode responsive features in the structural framework promises to extend the applications of NP-based drugs, vaccines, and diagnostic tools. New nanocarriers would ideally consist of a minimal number of biocompatible components and exhibit multiresponsive behavior to specific biomolecules, but progress is limited by the difficulty of synthesizing suitable building blocks. Through a nature-inspired approach that combines the programmability of nucleic acid interactions and sol-gel chemistry, we report the incorporation of synthetic nucleic acids and analogs, as constitutive components, into organosilica NPs. We prepared different nanomaterials containing single-stranded nucleic acids that are covalently embedded in the silica network. Through the incorporation of functional nucleic acids into the organosilica framework, the particles respond to various biological, physical, and chemical inputs, resulting in detectable physicochemical changes. The one-step bottom-up approach used to prepare organosilica NPs provides multifunctional systems that combine the tunability of oligonucleotides with the stiffness, low cost, and biocompatibility of silica for different applications ranging from drug delivery to sensing.

Figure 1

The presence of a covalently embedded nucleic acid (DNA or PNA) building block endows nucleic acid-based organosilica NPs with sequence-specific chemical, physical, and biological responsiveness.

Figure 2

(a) The DNA bis-alkoxysilane (Si-ssDNA-Si) is hydrolyzed in basic aqueous solutions (pH = 8.5) in the presence of the surfactant CTAB to obtain nanometer-sized ssDNA-OSPs as visualized by SEM. (b) SEM images of ssDNA-OSPs before (left image) and after mixing (2 h, right image) with DNase I. All scale bars = 500 nm.

Figure 3

(a) The ssDNA embedded in the silica framework of ssDNA-OSPs is accessible and can hybridize with its complementary strand. When the complementary and Cy5-labeled strand binds to Cy3-labeled ssDNA-OSPs, a partial energy transfer (ET) from the excited state of the donor, Cy3 (blue dot), to the acceptor, Cy5 (red dot), occurs. (b) Fluorescence spectra obtained upon addition of Cy5-ssDNA to a dispersion containing ssDNA-OSPs(Cy3) (0.06 mg·mL^–1 ≙ 1.76 μM of Cy3-labeled DNA, bold line). (c) Relative FRET efficiencies obtained from energy-transfer experiments with the free Cy3-ssDNA strand (3.52 μM) or with the ssDNA-OSPs(Cy3) (0.12 mg·mL^–1 ≙ 3.52 μM) in the presence of Cy5-ssDNA (0–5 μM). All of the experiments were performed in Tris-HCl buffer (10 mM, containing 3 mM MgCl₂ at pH 7.5). All fluorescence spectra and intensities were recorded upon excitation at λ_ex,Cy3 = 520 nm. The FRET intensities were recorded at λ_em,Cy3 = 570 nm and λ_em,Cy5 = 665 nm.

Figure 4

(a) Synthesis scheme for the preparation of ssPNA-OSPs shown in the SEM image (top right). Scale bar: 500 nm. (b) ssPNA-OSPs based FRET study in the presence of the Cy5-labeled and the PNA complementary ssDNA strand.