Upconversion Nanoparticle@Au Core-Satellite Assemblies for In Situ Amplified Imaging of MicroRNA in Living Cells and Combined Cancer Phototherapy.

Stimuli-responsive therapy of cancer with spatial and temporal control is crucial in improving the treatment efficacy and minimizing the side effects. MicroRNA (miRNA) as an important biomarker has become one of the most promising endogenous stimuli for cancer therapy. However, the therapy efficacy is often impeded by the low expression amount of miRNA. Herein, the upconversion nanoparticle@Au (UCNP@Au) core-satellite nanostructures are rationally fabricated for isothermal amplification detection and in situ imaging of microRNA-21 (miR-21) in living cells based on the toehold-mediated strand displacement (TMSD) reaction, which is further applied to miRNA-responsive combined photothermal and photodynamic therapy of breast cancer. The UCNP@Au are constructed by linking AuNPs to photosensitizers Rose Bengal (RB)-loaded UCNPs through DNA hybridization. The upconversion luminescence (UCL) is quenched by AuNPs, resulting in the attenuation of singlet oxygen generation of RB. Once UCNP@Au are internalized into MCF-7 cells, the overexpressed intracellular miR-21 trigger the cyclic disassembly of UCNP@Au through cascade TMSD reactions, which facilitate the restoration of UCL for in situ imaging of miR-21 with signal amplification. Moreover, the released AuNPs are aggregated for photothermal therapy (PTT), while the singlet oxygen generated by RB is enhanced for photodynamic therapy (PDT). Compared with single-mode therapy, the miRNA-activated combinational phototherapy has demonstrated a greatly improved therapeutic efficacy for breast cancer. Therefore, our proposed core-satellite nanostructures cannot only achieve in situ amplified imaging of endogenous miRNA but also provide an effective nanoplatform for stimuli-responsive combinational phototherapy, which hold great prospects in early diagnosis and treatment of cancers.

Versatile electrochemical biosensor based on bi-enzyme cascade biocatalysis spatially regulated by DNA architecture.

The regulation of biocatalytic cascades in microenvironments for high performance and extended applications is still challenging. Herein, we develop a rolling circle amplification (RCA)-based one-pot method to prepare the micron-sized DNA flowers (DFs), which achieve the co-encapsulation and spatial regulation of bi-enzyme molecules, glucose oxidase (GOx) and horseradish peroxidase (HRP). In this system, GOx and HRP are integrated into the DFs simultaneously during RCA with the bridging of magnesium between enzyme residues and phosphate backbones on DFs. The cascade of GOx/HRP is regulated with the formation of highly ordered and hydrogen-bonded water environment in the cavity of DFs, resulting in an enhanced cascade catalytic efficiency compared with that in homogeneous solution. Moreover, the high density of DNA scaffold ensures the encapsulation of GOx/HRP with high efficiency. Accordingly, a glucose electrochemical biosensor with amplified signal response is fabricated using the as-prepared GOx/HRP DFs as biosensing interface, realizing sensitive detection of glucose. Further, through designing the complementary sequence of aptamer into the programmable circular template of RCA, the bi-enzyme co-encapsulated DFs are versatilely applied to sensitive and selective detection of cancerous exosomes and thrombin in "signal-on" and "signal-off" modes, respectively, which are further applied to the analysis of complex biological samples successfully. Overall, the encapsulation of multi-enzyme with DFs proposes a promising strategy to regulate the microenvironment of biocatalytic cascades, which hold great potential in biotechnology, bioanalysis and disease diagnosis.

DNA flower-encapsulated horseradish peroxidase with enhanced biocatalytic activity synthesized by an isothermal one-pot method based on rolling circle amplification.

DNA nanotechnology has been developed to construct a variety of functional two- and three-dimensional structures for versatile applications. Rolling circle amplification (RCA) has become prominent in the assembly of DNA-inorganic composites with hierarchical structures and attractive properties. Here, we demonstrate a one-pot method to directly encapsulate horseradish peroxidase (HRP) in DNA flowers (DFs) during RCA. The growing DNA strands and Mg2PPi crystals lead to the construction of porous DFs, which provide sufficient interaction sites for spontaneously incorporating HRP molecules into DFs with high loading capacity and good stability. Furthermore, in comparison with free HRP, the DNA flower-encapsulated HRP (termed HRP-DFs) demonstrate enhanced enzymatic activity, which can efficiently biocatalyze the H2O2-mediated etching of gold nanorods (AuNRs) to generate distinct color changes since the longitudinal localized surface plasmon resonance (LSPR) frequency of AuNRs is highly sensitive to the changes in the AuNR aspect ratio. Through rationally incorporating the complementary thrombin aptamer sequence into the circular template, the synthesized HRP-DF composites are readily used as amplified labels for visual and colorimetric detection of thrombin with ultrahigh sensitivity and excellent selectivity. Therefore, our proposed strategy for direct encapsulation of enzyme molecules into DNA structures shows considerable potential applications in biosensing, biocatalysis, and point-of-care diagnostics.