title: Two-Way Gold Nanoparticle Label-Free Sensing of Specific Sequence and Small Molecule Targets Using Switchable Concatemers.
abstract: A two-way colorimetric biosensor based on unmodified gold nanoparticles (GNPs) and a switchable double-stranded DNA (dsDNA) concatemer have been demonstrated. Two hairpin probes (H1 and H2) were first designed that provided the fuels to assemble the dsDNA concatemers via hybridization chain reaction (HCR). A functional hairpin (FH) was rationally designed to recognize the target sequences. All the hairpins contained a single-stranded DNA (ssDNA) loop and sticky end to prevent GNPs from salt-induced aggregation. In the presence of target sequence, the capture probe blocked in the FH recognizes the target to form a duplex DNA, which causes the release of the initiator probe by FH conformational change. This process then starts the alternate-opening of H1 and H2 through HCR, and dsDNA concatemers grow from the target sequence. As a result, unmodified GNPs undergo salt-induced aggregation because the formed dsDNA concatemers are stiffer and provide less stabilization. A light purple-to-blue color variation was observed in the bulk solution, termed the light-off sensing way. Furthermore, H1 ingeniously inserted an aptamer sequence to generate dsDNA concatemers with multiple small molecule binding sites. In the presence of small molecule targets, concatemers can be disassembled into mixtures with ssDNA sticky ends. A blue-to-purple reverse color variation was observed due to the regeneration of the ssDNA, termed the light-on way. The two-way biosensor can detect both nucleic acids and small molecule targets with one sensing device. This switchable sensing element is label-free, enzyme-free, and sophisticated-instrumentation-free. The detection limits of both targets were below nanomolar.
authors.affiliation: Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science & Nutritional Engineering, China Agricultural University , Beijing 100083, China.|Beijing Laboratory for Food Quality and Safety, College of Food Science & Nutritional Engineering, China Agricultural University , Beijing 100083, China.
authors.forename: Longjiao
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science & Nutritional Engineering, China Agricultural University , Beijing 100083, China.
authors.forename: Xiangli
authors.initials: X
authors.lastname: Shao
authors.affiliation: Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science & Nutritional Engineering, China Agricultural University , Beijing 100083, China.
authors.forename: Yunbo
authors.initials: Y
authors.lastname: Luo
authors.affiliation: Beijing Laboratory for Food Quality and Safety, College of Food Science & Nutritional Engineering, China Agricultural University , Beijing 100083, China.
authors.forename: Kunlung
authors.initials: K
authors.lastname: Huang
authors.affiliation: Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Food Science & Nutritional Engineering, China Agricultural University , Beijing 100083, China.|Beijing Laboratory for Food Quality and Safety, College of Food Science & Nutritional Engineering, China Agricultural University , Beijing 100083, China.
authors.forename: Wentao
authors.identifier: 0000-0002-8572-8257
authors.initials: W
authors.lastname: Xu
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry; D015374:Biosensing Techniques / Q000379:methods* / Q000592:standards; D003124:Colorimetry / Q000379:methods; D004277:DNA, Single-Stranded / Q000737:chemistry; D006046:Gold; D057230:Limit of Detection; D053768:Metal Nanoparticles / Q000737:chemistry*; D015335:Molecular Probes / Q000737:chemistry* / Q000592:standards
chemical_list: D052157:Aptamers, Nucleotide; D004277:DNA, Single-Stranded; D015335:Molecular Probes; D006046:Gold