Rational design of wettability-patterned microchips for high-performance attomolar surface-enhanced Raman detection.

Recent progress in wettability-patterned microchips has facilitated the development of ultra-trace detection in multiple biomedical and food safety fields. The existence of a superhydrophilic trap can realize targeted deposition of the analyte. However, the wetting transition from the Cassie-Baxter state to the Wenzel state usually occurs during evaporation and leads to a larger deposition footprint, which has a strong impact on the detection sensitivity and uniformity. In this paper, we report an integrated design, fabrication, and evaporation strategy to avoid the transition for high-performance attomolar surface-enhanced Raman scattering (SERS) detection. An improved force balance model was proposed to design the microstructures of wettability-patterned microchips, which were fabricated by nanosecond laser direct writing and surface fluorination. The microchips were composed of superhydrophobic micro-grooves and superhydrophilic traps, by which the targeted deposition of Au nanoparticles and rhodamine 6G (R6G) onto a minimal area of ∼70 × 70 µm2 was realized after a two-step heated evaporation. Accordingly, the detection limit was down to the attomolar level (5 × 10-18 M) with SERS enhancement factors (EFs) exceeding 1010. More importantly, the Raman signals showed good uniformity (RSD of 11.5%) for the concentration of 2 × 10-17 M. A good linear relationship was obtained in the quantitative concentration range of 10-12 M to 5 × 10-18 M with a high correlation coefficient (R2) of 0.996. These wettability-patterned microchips exhibit high performance (that is, both good sensitivity and good uniformity) in the detection of ultra-trace molecules in aqueous solutions, avoiding the need for expensive equipment and considerable skill in operations. The proposed strategy could also be applied to other microfluidic devices for rapid and simple analyte pre-concentration.

A DNA aptamer with high affinity and specificity for molecular recognition and targeting therapy of gastric cancer.

BACKGROUND: Aptamers have emerged as excellent molecular probes for cancer diagnosis and therapy. The aim of the current study was to determine the feasibility of using DNA aptamer cy-apt 20 developed by live cell-SELEX for detecting and targeting gastric cancer. METHODS: The specificity, sensitivity and biostability of cy-apt 20 in detecting gastric cancer were assessed by binding assay, cell fluorescence imaging, and in vivo tumor imaging in animal model in comparison with non-gastric cancers. RESULTS: Flow cytometric analysis showed that cy-apt 20 had higher than 78% of maximal binding rate to gastric cancer cells, much higher than that of non-gastric cancer cells. Cell fluorescence imaging and in vivo tumor imaging showed that the targeting recognition could be visualized by using minimal dose of fluorochrome labeled cy-apt 20. Meanwhile, strong fluorescence signals were detected and lasted for a period of time longer than 50 min in vitro and 240 min in vivo. The fluorescence intensities of gastric cancer were about seven folds in vitro and five folds of that of non-gastric cancers in vivo. CONCLUSION: Our study demonstrated that cy-apt 20 was an excellent molecular probe with high specificity and sensitivity and a certain degree of biostability for molecular recognition and targeting therapy of gastric cancer.

Evolution of a gastric carcinoma cell-specific DNA aptamer by live cell-SELEX.

Aptamers have emerged as promising molecular probes for disease diagnosis and therapy. In the present study, the entire live cell-SELEX method was used to generate gastric cancer cell­specific aptamers. Human gastric carcinoma AGS cells were used as target cells for positive selections and human normal gastric epithelial GES-1 cells as the negative cells for counter selections. The selection procedure was monitored by gel electrophoresis and flow cytometric analysis. By successive in vitro evolutions and subsequent cloning and sequencing, a gastric carcinoma cell­specific DNA aptamer termed cy-apt 20 with minimal recognition to the controls was identified from the final enriched ssDNA pool. Flow cytometry binding assays revealed that cy-apt 20 had a >70% binding rate to AGS cells and <30% binding affinity to non-gastric cancer cells. Furthermore, the targeting recognition of AGS cells was established by using minimal doses of FITC-cy-apt 20 that continued for a long period of time. As visualized by fluorescence imaging, the majority of AGS cells were stained by FITC-cy-apt 20. The fluorescence intensity of AGS cells was ~6-fold over that of non-AGS cells. The present study demonstrated that the entire live cell-SELEX was simple, but effective in generating gastric cancer cell­specific aptamers, and that the aptamer cy-apt 20 has great potential to be used for the study and diagnosis of gastric cancer.

Two new Co(II) and Ni(II) complexes with 3-(2-Pyridyl)pyrazole-based ligand: synthesis, crystal structures, and bioactivities.

Two new Co(II) and Ni(II) complexes exhibiting DNA cytotoxic activities with 3-(2-pyridyl)pyrazole-based ligand, [Co(L)(3)](ClO(4))(2) (1) and [Ni(L)(3)](ClO(4))(2) (2) (L=1-[3-(2-pyridyl)-pyrazol-1-ylmethyl]-naphthalene) were synthesized and structurally characterized. Both 1 and 2 crystallized in the monoclinic system, space group P2(1)/c, for 1, a=12.8324(8), b=12.1205(8), c=33.27(2) A, beta=93.92(3) degrees and Z=4; for 2, a=12.8764(3), b=12.1015(3), c=33.2415(9) A, beta=93.998(1) degrees and Z=4. Among them, the Co(II) and Ni(II) ions were all coordinated by six N donors from three distinct L ligands. In addition, the cytotoxic activities of 1, 2 and L in vitro were evaluated against three different cancer cell lines HL-60 (human leukemia), BGC-823 (stomach cancer) and MDA-MB-435 (mammary cancer), respectively. The results showed that 1 exhibited significantly high cytotoxic activities against HL-60 and moderate activities against BGC-823 and MDA-MB-435. In order to further investigate the relationships between structures and DNA-binding behaviors of these complexes, the interactions of 1, 2 and L with calf thymus DNA (CT-DNA) were then subjected to thermal denaturation, viscosity measurements and spectrophotometric methods. The results indicated that 1 and 2 intercalated with DNA via L ligand. The intrinsic binding constants of 1, 2 and L with DNA were 1.6x10(4), 5.6x10(3) and 2.76x10(3) M(-1), respectively.

Syntheses, crystal structures, and magneto-structural correlations of novel Cu(II) complexes containing a planar [Cu(mu-L1)]2 (HL1 = 3-(2-pyridyl)pyrazole) unit: from dinuclear to tetranuclear and then to one-dimensional compounds.

Seven new Cu(II) complexes based on a binuclear planar unit [Cu(mu-L(1))](2), [[Cu(mu-L(1))(NO(3))(H(2)O)](2) (1), [Cu(mu-L(1))(HL(1))(ClO(4))](2) (2), [Cu(4)(mu-L(1))(6)(NO(3))(2)] (3), [Cu(4)(mu-L(1))(6)(L(1))(2)] (4), [Cu(4)(mu-L(1))(6)(mu-L(2))](n) (5), [Cu(4)(mu-L(1))(6)(mu-L(3))](n) (6), [[Cu(4)(mu-L(1))(4)(mu-L(4))(2)](H(2)O)(3)](n) (7) (HL(1) = 3-(2-pyridyl)pyrazole, L(2) = 1,8-naphthalenedicarboxylate, L(3) = terephthalate, L(4) = 2,6-pyridinedicarboxylate)}, have been synthesized and characterized by elemental analysis, IR, and X-ray diffraction. In 1 and 2, the Cu(II) centers are linked by deprotonated pyrazolyl groups to form dinuclear structures. 3 and 4 have similar gridlike tetranuclear structures in which two additional deprotonated L(1) ligands bridge two [Cu(mu-L(1))](2) units perpendicularly. 5 and 6 consist of similar one-dimensional (1-D) chains in which gridlike tetranuclear copper(II) units similar to that of 3 are further linked by L(2) or L(3) ligands, respectively. And, in 7, L(4) ligands link [Cu(mu-L(1))](2) binuclear units to form a tetranuclear gridlike structure in chelating/bridging mode and simultaneously bridge the tetranuclear units to form a 1-D chain. The magnetic properties of all complexes were studied by variable-temperature magnetic susceptibility and magnetization measurements. The obtained parameters of J range from -33.1 to -211 cm(-1), indicating very strong antiferromagnetic coupling between Cu(II) ions. The main factor that affects the |J| parameter is the geometry of the Cu(N(2))(2)Cu entity. From the magnetic point of view, 1 and 2 feature "pure" dinuclear, 3 and 5 tetranuclear, and 4, 6, and 7 pseudodinuclear moieties.