Gold@silver nanodumbbell based inter-nanogap aptasensor for the surface enhanced Raman spectroscopy determination of ochratoxin A.

Here, a plasmonic nanogap structure was fabricated with its specific surface enhanced Raman spectroscopy (SERS) effect to construct an aptasensor for the sensitive detection of ochratoxin A (OTA). Gold nanorod (AuNR) were synthesized first by seed-mediated method. Then, silver was reduced and grown on its surface. In the presence of glycine, Ag0 was preferred to grow at both ends of AuNR to form gold@silver nanodumbbell (Au@AgND). The thiolated OTA aptamer and its complementary sequence were modified on Au@AgND respectively using Ag-SH bond. Under the base complementary pairing principle, Au@AgND assembly formed with certain inter distances. The inter-nanogap structure generated more hot spots which enhanced the Raman signal of 4-hydroxybenzoic acid (4-MBA) immobilized on Au@AgND. When OTA was present, the aptamer preferentially combined to OTA and the Au@AgND assembly disintegrated. Thus, the SERS signal of 4-MBA decreased. Under the optimal conditions, the OTA concentrations were inversely proportional to SERS signal. The linear range was 0.01 ng/mL-50 ng/mL and the limit of detection (LOD) was 0.007 ng/mL. The method can be successfully applied to the detection of real sample (beer/peanut oil).

Construction of near infrared light triggered nanodumbbell for cancer photodynamic therapy.

The application of photodynamic therapy (PDT) in deep tissue has been severely restricted by the poor photosensitizers loading and tissue-penetration of visible light for exciting the photosensitizers. How to prepare a nanocarrier with high drug loading amount and remote controllability still remains the challenge. In this article, a novel drug delivery system nanodumbbell was designed. The nanodumbbell was assembled from the hydrophobic upconverting nanoparticle (UCN) core and hydrophilic polymersome shell. The "nanodumbbell" offers possibilities to overcome the problem mentioned above. The UCN core works as a transducer to convert deeply penetrating near-infrared light to visible light to activate photosensitizers zinc (II) phthalocyanine (ZnPc) for photodynamic therapy. The polymersome lipid shell is used for loading ZnPc and protecting the whole system from nonspecific absorbance or corrosion during the transportation. The nanodumbbell is appealing because it can simultaneously achieve the high loading amount of ZnPc while avoiding UCNs aggregation. The reactive oxygen species (ROS) production test and PDT test in vitro suggested that the fluorescence emitted from the UCNs can be effectively transferred to the photosensitizers to produce cytotoxic ROS. When the UCN@lipid@polymersome nanodumbbell was decorated with targeting peptide (RGD), it presented better target specificity to cells. Our data suggest that this nanoparticle may serve as a useful nanoplatform for PDT treatment in deep-cancer therapy based on upconverting mechanism.