Phototheranostic nanoparticles with aggregation-induced emission as a four-modal imaging platform for image-guided photothermal therapy and ferroptosis of tumor cells.

Due to the aggregation-caused quenching (ACQ) and weak photo-penetrating ability, the application of phototheranostic agents in drug delivery field is greatly limited. Ferroptosis, a newly discovered cell death mode, has not been extensively studied in the field of phototherapy up to now. Here, a new near-infrared II (NIR-II) molecule with aggregation-induced emission (AIE) property (named TSST) co-assembled with DHA-PEG and ferrocene as nanoparticles (DFT-NP), which was rationally designed and synthesized. The DFT-NP exhibited enhanced NIR-II fluorescence, photothermal, photoacoustic, magnetic resonance imaging, AIE and ferroptosis capacities. The NIR-II fluorescence intensity of obtained nanoparticles was improved, owing to the strong interaction between DHA and TSST, which limited the intramolecular rotation restriction and non-radiative attenuation of TSST to discourage energy dissipation in aggregation state. Inspiringly, the generated photothermal effect by DFT-NP can promote the Fenton reaction of ferrocene and H2O2, resulting in dissolution of the nanoparticles and cancer cells expedited ferroptosis via accumulation lipid free radicals of DHA. The released TSST enhanced the photothermal and photoacoustic imaging effects through removing the DHA restriction to restore the non-radiative attenuation. This work is the first example of nanoparticles that integrates four-mode imaging, photothermal and ferroptosis-induced therapy functions, which offers great advantages for potential clinical applications.

pH-activated nanoplatform for visualized photodynamic and ferroptosis synergistic therapy of tumors.

To overcome drug resistance and improve precision theranostics for hepatocellular carcinoma (HCC), a nanoplatform with an "off/on" function for multimodality imaging (near-infrared-II (NIR-II) fluorescence imaging, magnetic resonance imaging (MRI), and photoacoustic imaging) and synergistic therapy (photodynamic therapy and ferroptosis) activated by an acidic pH in the tumor microenvironment is proposed. Although many photosensitizers with photodynamic effects have been reported, very few of them have outstanding photodynamic effect and high stability with response to endogenous stimuli capable of NIR-II imaging. Herein, a new amphiphilic photosensitizer SR780 derived from croconaine dye, was developed with satisfactory photodynamic effects and pH-responsive NIR-II imaging. Interestingly, it was deactivated by coordination with Fe3+ (SR780@Fe) and activated during their release under mild acidic condition. Ferroptosis can generate hydroxyl free radical and lipid peroxide, which aggravate the oxidative stress of tumor cells and mediate their death while depleting glutathione (GSH) to enhance photodynamic effect. In situ pH-activatable theranostic nanoplatform, SR780@Fe-PAE-GP, was thus developed by loading SR780@Fe with pH-responsive polymers, modified by a glypican-3 (GPC-3) receptor-targeting peptide. The synergistic antitumor effects were confirmed both in vitro and in vivo, and the tumor inhibition rate of the SR780@Fe-PAE-GP + L treatment group reached 98%.

A short DNA sequence confers strong bleomycin binding to hairpin DNAs.

Bleomycins A5 and B2 were used to study the structural features in hairpin DNAs conducive to strong BLM-DNA interaction. Two members of a 10-hairpin DNA library previously found to bind most tightly to these BLMs were subsequently noted to share the sequence 5'-ACGC (complementary strand sequence 5'-GCGT). Each underwent double-strand cleavage at five sites within, or near, an eight base pair region of the DNA duplex which had been randomized to create the original library. A new hairpin DNA library was selected based on affinity for immobilized Fe(III)·BLM A5. Two of the 30 newly identified DNAs also contained the sequence 5'-ACGC/5'-GCGT. These DNAs bound to the Fe(II)·BLMs more tightly than any DNA characterized previously. Surface plasmon resonance confirmed tight Fe(III)·BLM B2 binding and gave an excellent fit for a 1:1 binding model, implying the absence of significant secondary binding sites. Fe(II)·BLM A5 was used to assess sites of double-strand DNA cleavage. Both hairpin DNAs underwent double-strand cleavage at five sites within or near the original randomized eight base region. For DNA 12, four of the five double-strand cleavages involved independent single-strand cleavage reactions; DNA 13 underwent double-strand DNA cleavage by independent single-strand cleavages at all five sites. DNA 14, which bound Fe·BLM poorly, was converted to a strong binder (DNA 15) by insertion of the sequence 5'-ACGC/5'-GCGT. These findings reinforce the idea that tighter DNA binding by Fe·BLM leads to increased double-strand cleavage by a novel mechanism and identify a specific DNA motif conducive to strong BLM binding and cleavage.

DNA methylation reduces binding and cleavage by bleomycin.

In a recent study, we described the enhanced double-strand cleavage of hairpin DNAs by Fe·bleomycin (Fe·BLM) that accompanies increasingly strong binding of this antitumor agent and suggested that this effect may be relevant to the mechanism by which BLM mediates its antitumor effects. Because the DNA in tumor cells is known to be hypomethylated on cytidine relative to that in normal cells, it seemed of interest to study the possible effects of methylation status on BLM-induced double-strand DNA cleavage. Three hairpin DNAs found to bind strongly to bleomycin, and their methylated counterparts, were used to study the effect of methylation on bleomycin-induced DNA degradation. Under conditions of limited DNA cleavage, there was a significant overall decrease in the cleavage of methylated hairpin DNAs. Cytidine methylation was found to result in decreased BLM-induced cleavage at the site of methylation and to result in enhanced cleavage at adjacent nonmethylated sites. For two of the three hairpin DNAs studied, methylation was accompanied by a dramatic decrease in the binding affinity for Fe·BLM, suggesting the likelihood of diminished double-strand cleavage. The source of the persistent binding of BLM by the third hairpin DNA was identified. Also identified was the probable molecular mechanism for diminished binding and cleavage of the methylated DNAs by BLM. The possible implications of these findings for the antitumor selectivity of bleomycin are discussed.

Outer membrane protein OmpW of Escherichia coli is required for resistance to phagocytosis.

Eight-stranded ß-barrel outer membrane proteins can confer bacterial virulence via resistance to host innate defenses. This resistance function of OmpW, which was recently identified as an eight-stranded ß-barrel protein, was investigated in this study. Our results demonstrated that upregulation of OmpW correlated with increased bacterial survival during phagocytosis. Bacterial mutants harboring a deletion of ompW exhibited a significantly increased phagocytosis rate. Both observations suggest that the OmpW protein protects bacteria against host phagocytosis. In addition, expression of ompW is regulated by iron, which implies that the resistance provided by OmpW may be an important factor in iron-related infectious diseases. Furthermore, OmpW has been identified as a protective antigen that protects mice against bacterial infection and is therefore a promising target for vaccine development against infectious diseases.

Dynamics of bleomycin interaction with a strongly bound hairpin DNA substrate, and implications for cleavage of the bound DNA.

Recent studies involving DNAs bound strongly by bleomycins have documented that such DNAs are degraded by the antitumor antibiotic with characteristics different from those observed when studying the cleavage of randomly chosen DNAs in the presence of excess Fe·BLM. In the present study, surface plasmon resonance has been used to characterize the dynamics of BLM B(2) binding to a strongly bound hairpin DNA, to define the effects of Fe(3+), salt, and temperature on BLM-DNA interaction. One strong primary DNA binding site, and at least one much weaker site, were documented. In contrast, more than one strong cleavage site was found, an observation also made for two other hairpin DNAs. Evidence is presented for BLM equilibration between the stronger and weaker binding sites in a way that renders BLM unavailable to other, less strongly bound DNAs. Thus, enhanced binding to a given site does not necessarily result in increased DNA degradation at that site; i.e., for strongly bound DNAs, the facility of DNA cleavage must involve other parameters in addition to the intrinsic rate of C-4' H atom abstraction from DNA sugars.

Selective and facile assay of human immunodeficiency virus protease activity by a novel fluorogenic reaction.

A highly selective and facile assay of human immunodeficiency virus protease (HIV-PR) has been required for the screening of medicinal inhibitors and also for classifying the subtypes of HIV in the therapeutic treatment of acquired immune deficiency syndrome (AIDS). This article describes a novel assay method of HIV-PR based on the selective fluorogenic reaction of peptides. A peptide fragment generated from a substrate by the enzymatic digestion with HIV-PR could be selectively quantified by the spectrofluorometric detection after the fluorogenic reaction with catechol in the presence of sodium periodate and sodium borate (pH 7.0). This assay system uses an N-terminal acetyl peptide as the substrate and crude extracts from Escherichia coli expressing recombinant HIV-PR. The activity obtained by the proposed assay correlated with that obtained by a conventional HIV-PR assay based on fluorescence resonance energy transfer detection.

Alternative splicing in exon 9 of glucocorticoid receptor pre-mRNA is regulated by SRp40.

Increasing evidence indicates that alternative splicing of human glucocorticoid receptor (GR) transcripts is implicated in the development of glucocorticoid resistance but the underlying mechanism was not well known. Serine/arginine-rich (SR) proteins and heterogeneous nuclear ribonucleoprotein (hnRNP) A1 play an important role in the spliceosome assembly. In this study, we analyzed the effects of different SR proteins and hnRNP A1 on the alternative splicing of GR pre-mRNA in HeLa and 293T cells using a minigene transfection assay. Our results revealed that only SRp40 could induce a GRalpha to GRbeta shift of pre-mRNA splicing in exon 9 in HeLa cells and this effect induced by SRp40 was further confirmed by small interfering RNA study. However, in 293T cells, SRp40 could not induce this shift. These results indicated that SRp40 may influence the alternative splicing of GR pre-mRNA to regulate the ratio of GRalpha to GRbeta, and this effect is cell-dependent.

Facile assay of telomerase activity utilizing a DNA-detectable chemiluminogenic reagent.

Telomerase shows increased activity in most human cancers and germ line cells, but not in normal human somatic cells. We describe a novel chemiluminescence method for the facile assay of telomerase activity in human cells. The telomerase substrate was incubated with the cell lysate containing various amounts of telomerase, and then the telomerase product was amplified by the polymerase-chained reaction (PCR). The PCR products were separated from the excess substrate, primer and deoxyribonucleotide triphosphates by a centrifugal filter, which distinguished different molecular sizes. The isolated products were reacted with a DNA-detectable chemiluminogenic reagent, 3,4,5-trimethoxyphenylglyoxal. The proposed assay method gave linearity for the telomerase activity in 100 to 10000 cells (r2=0.997), and allowed the assay not only of lower activity, but also of higher activity of telomerase without the requirement of any special labeled-PCR primers in the assay system.

A selective fluorescence reaction for peptides and chromatographic analysis.

A novel and selective fluorescence reaction is proposed for the quantitative determination of peptides by reversed-phase liquid chromatography (RPLC). A single fluorescent product was formed when a peptide was heated at 120 degrees C for 20 min in a neutral aqueous medium (pH 7.0) containing catechol, sodium periodate, and sodium borate. The fluorescent products of four peptides such as Leu-Gly, Ala-Leu-Gly, Tyr-Gly-Gly-Phe-Leu, and Leu-Leu-Leu were easily separated on a reversed-phase column by gradient elution of methanol in a mobile phase containing sodium borate (pH 7.0), and then quantitatively detected by fluorimetry. The lower limits (S/N=3) of the detection for the tested peptides were 0.5-1.0 pmol per an injection volume (40 microl). In addition, the fluorescent products of phenylalanine amide and Leu-Leu-Leu were identified by electrospray ionization-time of flight-mass spectrometry (ESI-TOF/MS) for the elucidation of their chemical structures.