An ultra-sensitive biosensor using only two DNA oligos to initiate multiple signal amplification cycles.

To advance anti-tumor efficiency and lessen the adverse effect caused by nanodrug residues in the body, a smart nanoagent system is developed and successfully used in intracellular ATP imaging and in vivo chemo-photothermal synergetic therapy. The nanoagent system is facilely prepared using a DNA complex to modify gold nanoparticles (AuNPs). The DNA complex is formed by three oligonucleotides (ATP aptamer, rC-DNA, and rG-DNA). The CG-rich structure in a ternary DNA complex could be exploited for payload of chemotherapeutic medicine doxorubicin (DOX), thus making efficient DOX transport into the tumor site possible. In tumor cells, especially in acidic organelles (e.g., endosome and lysosome), DOX could be rapidly released via the dual stimuli of overexpressed ATP and pH. What is more, the specific recognition of a fluorescently labeled aptamer strand to ATP can achieve the intracellular ATP imaging. pH-controlled reversible folding and unfolding of intermolecular i-motif formed by C-rich strands can lead to intracellular in situ assembly of AuNP aggregates with high photothermal conversion efficiency and promote relatively facile renal clearance of AuNPs through the disassociation of the aggregates in extracellular environments. Experiments in vivo and vitro present feasibility for a synergetic chemo-photothermal therapy. Such an in situ reversible assembly strategy of a chemo-photothermal agent also presents a new paradigm for a smart and highly efficient disease treatment with reduced side effects.

Metal−organic frameworks (MOFs) are powerful toolkits to directly correlate structure−function relationships due to their well-defined structures. In this work, 5,15di(3,4,5-trihydroxyphenyl)porphyrin (DTPP) and 5,10,15,20-tetra(3,4,5-trihydroxyphenyl)porphyrin (TTPP) are reacted with zirconium ions to afford two MOFs (Zr-DTPP and Zr-TTPP) with acid and base tolerance in the pH range of 1.0−14.0. Powder X-ray diffraction investigation combined with Rietveld refinement reveals the J-aggregated porphyrin building blocks confined by benzene-1,2,3-trisolate-zirconium chains in the newly prepared Zr-DTPP. Electron spin-resonance, singlet-oxygen determination, and sulfides oxidation experiments demonstrate a much better singlet-oxygen evolution of J-aggregated Zr-DTPP than that of unaggregated Zr-TTPP reported previously, in good contrast to the weaker photocatalytic capability disclosed for DTPP than that for TTPP in solution, consummating the theory of photosensitizer J-aggregation in boosting heterogeneous photoinduced singlet-oxygen generation.

Demands related to clean energy and environmental protection promote the development of novel supramolecular assemblies for photocatalysis. Because of the distinctive aggregation behaviors, bolaamphiphiles with two hydrophilic end groups could be theoretically the right candidates for the fabrication of high-performance photocatalysis. However, photocatalytic applications based on bolaamphiphilic assemblies were still rarely investigated. Especially, the relationship between diverse assembled nanostructures and the properties for different applications is urgently needed to be studied. Herein, we demonstrate that using the hierarchical assembly of bolaamphiphiles could correctly induce the porphyrin supramolecular architectures with much better photocatalytic performances than the aggregations containing 450 times of the porphyrin molecules, even though both molecular structures as well as the J-aggregations of porphyrin building blocks are same in two different systems. Thus, the co-assembly of l -phenylalanine terminated bolaamphiphile (Bola-F) and the porphyrin containing four hydroxyl groups (tetrakis-5,10,15,20-(4-hydroxyphenyl)porphyrin) can form microtube in methanol and forms fibers/spheres in methanol/water mixture. For catalyzing the photodegradation of rhodamine B, the small amount of J-aggregated porphyrin within Bola-F microtubes show much better photocatalytic performance comparing with that of huge porphyrin J-aggregations in fibers/spheres. The supramolecular assemblies as well as the photocatalysis were thoroughly characterized by different spectroscopies and electron microscopy. It is demonstrated that the co-assembly with bolaamphiphiles could inhibit the energy transfer of porphyrin aggregation and subsequently benefit the electron transfer and corresponding photocatalysis under photo-irradiation. This work is not only useful for further understanding the hierarchically supramolecular assembly but also provides a new strategy for making novel functional supramolecular architectures based on the assembly of bolaamphiphiles and porphyrins.