Fig. 2

Demonstration of lysozyme selectivity of LBA-Au NPs by fluorescence imaging. To achieve the fluorescent function of LBA-Au NPs, both Hex- (fluorescent molecule) and thiol-modified LBAs (5′-H S-TTTTTTATCAGGGCTAAAGAGTGCAGAGTTACTTAG-Hex-3′) were used to replace thiol modified-LBAs in these experiments. The three regions defined by black dotted circles on the glass microscope slide (from left to right) were dropped with 10 µL of aqueous solution respectively containing 10 µM of PBS, bovine serum albumin (BSA), and lysozyme; the slide was then dried by air. Subsequently, the three regions were treated with LBA-Au NPs for 1 h, followed by washing with deionized water to remove non-binding LBA-Au NPs. Finally, the region in each black dotted circle was observed using fluorescence microscopy. The left region (PBS-treated region) exhibited no fluorescence after treatment with THPC-Au NPs, indicating that THPC-Au NPs had no non-specific targeting on the glass microscope slide. No fluorescence was observed in the middle region (BSA-existed region) after treatment with LBA-Au NPs because LBA-Au NPs could not bind to BSA and were thus removed during washing. The right region (lysozyme-existed region) had an obvious fluorescence after treatment with LBA-Au NPs because of the specific lysozyme-targeting of the LBA-Au NPs. These results indicated that LBA-Au NPs still had excellent selectivity for lysozyme after the LBAs were conjugated on the surface of the Au NPs