Nano-constructs for polynucleotide delivery

A nano-construct comprising:

• (1) a core particle comprising gold and having a diameter of 40-50 nm;
• (2) a polymer coating comprising polydopamine on the surface of the core particle having a thickness of 4 to 5 nm;
• and
• (3) a polynucleotide non-covalently attached to the polymer coating,
• wherein the polynucleotide comprises a core segment of 15-30 nucleotides in length, a first pairing segment located at the 5′ of the core segment, and a second pairing segment located at the 3′ of the core segment, wherein the polynucleotide is further attached to a fluorescent molecule fluorescein isothiocyanate (FITC) or cyanine 3 (Cy3), wherein:
• when the core segment is not hybridized to its complementary sequence, the first and second pairing segments hybridize with each other so as to allow the polynucleotide to assume a hair-pin configuration and fluorescence from the fluorescent molecule to be quenched, and
• when the core segment is hybridized to its complementary sequence, the first and second pairing segment separate from each other so as to allow the polynucleotide to assume an open configuration and fluorescence from the fluorescent molecule to be detectable.