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Magnetic resonance imaging (MRI) and optical imaging (OI) are attractive for constructing bimodal probes due to their complementary imaging characteristics. The combination of these two techniques could be a useful tool to simultaneously obtain both anatomical and molecular information as well as to significantly improve the accuracy of detection. In this study, we found that β-diketonate-lanthanide complexes, BHHBCB-Ln3+, could covalently bind to proteins to exhibit long-lived and intense luminescence (Ln3+ = Eu3+, τ = 0.52 ms, Φ = 0.40) and remarkably high relaxivity (Ln3+ = Gd3+, r1 = 35.67 mM-1 s-1, r2 = 43.25 mM-1 s-1) with excellent water solubility, stability and biocompatibility. Hence, we conjugated BHHBCB-Ln3+ with a tumor-targetable biomacromolecule, transferrin (Tf), to construct the probes, Tf-BHHBCB-Ln3+, for time-gated luminescence (TGL, Ln3+ = Eu3+) and MR (Ln3+ = Gd3+) imaging of cancerous cells in vitro and in vivo. As expected, the as-prepared probes showed high specificity to bind with the transferrin receptor-overexpressed cancerous cells, to enable the probe molecules to be accumulated in these cells. Using Tf-BHHBCB-Ln3+ as probes, the cultured cancerous cells and the tumors in tumor-bearing mice have been clearly visualized by background-free TGL and in vivo MR imaging. The research outcomes suggested the potential of β-diketonate-lanthanide complexes for use in constructing bimodal TGL/MR imaging bioprobes.

Probes combining luminescence and magnetic resonance (MR) imaging activities have attracted tremendous attention since they can offer both molecular and anatomical information to effectively improve the accuracy of detection. In this work, a β-diketone ligand (CDHH) was modified by covalent conjugation with an MRI contrast agent (DO3A–Gd) and a tumor-targetable biomacromolecule transferrin (Tf). When Eu3+ ions were added into the mixture of two functionalized β-diketone ligands, they triggered a self-assembly to form a heteropolymetallic lanthanide complex that was conjugated to Tf. The as-prepared bioconjugate, i.e., Tf–Eu–Gd, exhibited intense long-lived luminescence (ϕ = 0.20, τ = 0.34 ms), remarkably high MR relaxivities (r1 = 9.18 mM−1 s−1 and r2 = 12.03 mM−1 s−1), as well as good water solubility, stability, and biocompatibility. Time-gated luminescence (TGL) imaging of live cells using Tf–Eu–Gd as a probe demonstrated that the probe can distinguish Tf-receptor-overexpressed cancerous cells, which enables the probe to be specifically accumulated in these cells. On the basis of magnetoluminescent properties of Tf–Eu–Gd, it was further used as a bimodal probe for both TGL and MR imaging of cancerous cells in tumor-bearing nude mice. The results indicated that Tf–Eu–Gd could significantly increase the T1-weighted MRI contrast value in the tumor region, and the TGL imaging of tumor tissue sections provided clear histological validation of the MRI signals. The research outcomes revealed the feasibility of Tf–Eu–Gd for the tracing and precise detection of cancerous cells, which suggested its potential for serving to the clinical diagnosis, therapy, and medical research of tumor diseases.

Odor is an important factor influencing the acceptance of clams by the consumer. In order to better understand the flavor characteristics of different clams, the volatiles in raw and cooked Meretri...

Phosphate-solubilizing bacteria have the ability of solubilizing mineral phosphate in soil and promoting growth of plants, but the activity of phosphate solubilization is influenced by exogenous soluble phosphate. In the present study, the effects of soluble phosphate on the activity of phosphate solubilization, acidification of media, growth, and organic acid secretion of phosphate-solubilizing bacterium Pseudomonas frederiksbergensis JW-SD2 were investigated under six levels of soluble phosphate conditions. The activity of phosphate solubilization decreased with the increase of soluble phosphate concentration, accompanying with the increase of media pH. However, the growth was promoted by adding soluble phosphate. Production of gluconic, tartaric, and oxalic acids by the strain was reduced with the increase of concentration of soluble phosphate, while acetic and pyruvic acids showed a remarkable increase. Gluconic acid predominantly produced by the strain at low levels of soluble phosphate showed that this acid was the most efficient organic acid in phosphate solubilization. Pyrroloquinoline quinone-glucose dehydrogenase gene gcd (pg5SD2) was cloned from the strain, and the expressions of pg5SD2 gene were repressed gradually with the increase of concentration of soluble phosphate. The soluble phosphate regulating the transcription of the gcd gene is speculated to underlie the regulation of the secretion of gluconic acid and subsequently the regulation of the activity of phosphate solubilization. Future research needs to consider a molecular engineering strategy to reduce the sensitivity of PSB strain to soluble phosphate via modification of the regulatory mechanism of gcd gene, which could improve the scope of PSB strains' application.

The rhizospheric bacterium JW-SD2 was identified as Pseudomonas frederiksbergensis based on phenotypic features, the Biolog Identification System and 16S rRNA sequence analysis. The phosphate-solubilizing activity, acidification in culture media, growth rate and organic acid secretion of JW-SD2 were investigated during 192 h of cultivation. The phosphate solubilized by JW-SD2 reached 7.75 mM. The decrease of pH and increase of titratable acidity were closely correlated (Pearson’s r = −0.953 and 0.969, respectively) with the phosphate-solubilizing activity. High concentrations of gluconic, 2-ketogluconic, pyruvic, maleic and malic acids were detected before 96 h of culture, when the strain displayed a high level of phosphate-solubilizing activity, indicating that these organic acids were efficient components in phosphate solubilization. However, acetic acid did not affect phosphate solubilization as shown by a remarkable increase at 144 h of culture when the phosphate-solubilizing activity decreased. The phosphate-solubilizing ability of JW-SD2 was significantly (P