An injectable pH neutral bioactive glass-based bone cement with suitable bone regeneration ability.

Background: As a class of promising bone augmentation materials, bone cements have attracted particular attention. Due to various limitations, the current bone cements are still imperfect. In this study, an injectable pH neutral bioactive bone cement (PSC/CSC) was developed by mixing phosphosilicate bioactive glass (PSC) and α-calcium sulfate hemihydrate (CSH), with the goal of optimizing bone defects repairs. Methods: A range of compositions (PSC/CSC: 10P/90C, 30P/70C, 50P/50C) were developed and their physicochemical properties evaluated. Their bone regeneration ability was compared to those of two widely used bone cements as controls (calcium phosphate cement (CPC) and Genex®) in rabbit femoral condyle bone defect models for 4, 8 and 12 weeks. Based on physicochemical properties and in vivo bone regeneration ability, the PSC/CSC exhibited the best outcomes was selected. Then, in vitro, the effects of selected PSC/CSC, CPC and Genex® extracts on MC3T3-E1 cell proliferation, migration and osteogenesis as well as angiogenesis of HUVECs were examined. Results: Based on physicochemical properties, the 30P/70C formula exhibited suitable operability and compressive strength (3.5 ±â€¯0.3 MPa), which fulfilled the requirements for cancellous bone substitutes. In vivo, findings from micro-CT and histological analyses showed that the 30P/70C formula better promoted bone regeneration, compared to 10P/90C, 50P/50C, CPC and Genex®. Hence, 30P/70C was selected as the ideal PSC-based cement. In vitro, the 30P/70C extracts showed better promotion of cell viability, alkaline phosphatase (ALP) activity, calcium mineral deposition, mRNA and protein expression levels of osteogenesis in MC3T3-E1 cells, further supporting its superiority. Meanwhile, the 30P/70C extracts also showed better stimulation of HUVECs proliferation and angiogenesis. Conclusion: The new composite cement, 30P/70C, is a favorable bioactive glass-based bone cement with suitable operability, compressive strength and bone regeneration ability. The translational potential of this article: Clinically, treatment of large bone defects is still a major challenge for orthopaedic trauma. We showed that 30P/70C has the potential to be clinically used as an injectable cement for rapid bone repairs and reconstruction of critical sized bone defects.

Visible-light-induced cleavage of 4-α-amino acid substituted naphthalimides and its application in DNA photocleavage.

A new kind of visible-light photocleavable molecule, 4-α-amino acid substituted naphthalimide, is reported. The cleavage occurred at the C-N bond between the 4-amino and the amino acid residue and released a 4-aminonaphthalimide. A lysine substituted naphthalimide exhibited a strong DNA photocleavage activity when irradiated with a blue light LED.

A turn-on fluorescent sensor for zinc and cadmium ions based on perylene tetracarboxylic diimide.

In this paper, we describe a turn-on fluorescent probe for Zn(2+) and Cd(2+) ion detection and discrimination. This probe, N'-bis-(N,N-di-(2-pyridylmethyl)-ethane-1,2-diamine)-perylene-3,4,9,10-tetracarboxylic-diimide (PDI-DIDPA), exhibits very low fluorescence at pH above 6.0 due to the photo-induced electron transfer (PET) process from 2-pyridylmethyl-amine (DPA) to perylene tetracarboxylic diimide (PDI). Zn(2+) and Cd(2+) can chelate PDI-DIDPA to form a stable complex at pH 6.0-7.0 and 9.0 respectively, and inhibit the PET process, which result in the fluorescence recovery of PDI-DIDPA. This fluorescence turn-on behavior allows the detection of Zn(2+) in the range of 0.1-4.0 µM and Cd(2+) in the range of 0.1-5.0 µM. The limit of detection for Zn(2+) and Cd(2+) is as low as 32 nM and 48 nM. The high selectivity, high sensitivity and easy operation make this probe suitable for the rapid detection of Zn(2+) and Cd(2+) respectively. The different response of PDI-DIDPA to Zn(2+) and Cd(2+) at different pH makes it possible to discriminate Zn(2+) and Cd(2+) by simply adjusting the pH of the working solution.

A pH sensitive ratiometric fluorophore and its application for monitoring the intracellular and extracellular pHs simultaneously.

Intracellular and extracellular pH plays a key role in many cell biological processes. Probes for simultaneously monitoring the pH change inside and outside living cells are rarely available. In this paper, we describe a new ratiometric pH fluorophore that was synthesized by condensation of 4-bromine-1,8-naphthalimides and 3-amino-1,2,4-triazole. In the range of pH 5-8, the only N-H in the heterocycle-fused aromatic ring system of this fluorophore undergoes a reversible deprotonation-protonation process, which results in a large red shift of the absorption and emission spectra. In aqueous solution, this fluorophore exhibits good pH selectivity, high photostability, high tolerance to ionic strength, and high fluorescence quantum yield in both the acid and base forms. A long chain derivative of this fluorophore (HNNA) was designed for cellular pH sensing. HNNA was found to locate on the membrane structure of the cells, and was successfully used for mapping the pH change in both the extracellular microenvironment and the inner cells by confocal imaging.

Characterization of G-quadruplex/hemin peroxidase: substrate specificity and inactivation kinetics.

Recently, G-quadruplex/hemin (G4/hemin) complexes have been found to exhibit peroxidase activity, and this feature has been extensively exploited for colorimetric detection of various targets. To further understand and characterize this important DNAzyme, its substrate specificity, inactivation mechanism, and kinetics have been examined by comparison with horseradish peroxidase (HRP). G4/hemin DNAzyme exhibits broader substrate specificity and much higher inactivation rate than HRP because of the exposure of the catalytic hemin center. The inactivation of G4/hemin DNAzyme is mainly attributed to the degradation of hemin by H(2)O(2) rather than the destruction of G4. Both the inactivation rate and catalytic oxidation rate of G4/hemin DNAzyme depend on the concentration of H(2)O(2), which suggests that active intermediates formed by G4/hemin and H(2)O(2) are the branch point of catalysis and inactivation. Reducing substrates greatly inhibit the inactivation of G4/hemin DNAzyme by rapidly reacting with the active intermediates. A possible catalytic and inactivation process of G4/hemin has been proposed. These results imply a potential cause for the hemin-mediated cellular injury and provide insightful information for the future application of G4/hemin DNAzyme.

Mercury(II)-mediated formation of imide-Hg-imide complexes.

Three different kinds of cyclic imides with imido protons are chosen to interact with Hg(II): succinimide, the simplest cyclic imide (five-membered ring); phthalimide (conjugated five-membered ring); and 1,8-naphthalimide (conjugated six-membered ring). Based on the results of MS, (1)H-NMR, XPS, IR spectroscopy and fluorescence response analyses, it is suggested that N-unsubstituted cyclic imides react specifically with Hg(II) and form imide-Hg-imide complexes through an imido proton-metal exchange process. The reaction is reversible and occurs rapidly at moderate to high pH. This discovery expands the comprehension of the specific interaction of Hg(II) with the nucleobase thymine, and may open up new possibilities in designing novel ligands for sensing and removing Hg(II) based on cyclic imides.

Characterization and application of a DNA aptamer binding to L-tryptophan.

DNA aptamers for specific recognition of L-tryptophan have been evolved by a SELEX (systematic evolution of ligands by exponential enrichment) technique. Truncation-mutation experiments suggest that a 34-mer sequence, Trp3a-1, possesses the strongest binding ability to L-tryptophan. Trp3a-1 is predicted to adopt a loop-stem secondary structure, in which the loop may further fold into a binding pocket for L-tryptophan with the help of the stem. The specificity investigation shows that Trp3a-1 strongly binds to L-tryptophan, has almost no binding to other amino acids, and weakly binds to some tryptophan analogs and peptides containing the L-tryptophan residue. The binding of Trp3a-1 to L-tryptophan is mainly contributed to by hydrogen bonds and precise stacking formed between the binding pocket of Trp3a-1 and all groups on L-tryptophan. This aptamer has also been proved to be an effective ligand for the chiral separation of D/L-tryptophan. L-tryptophan and its derivatives are known to play important biological roles; this aptamer ligand could be used as a tool for the analysis of tryptophan and other related studies.

Visual detection of Hg2+ with high selectivity using thymine modified gold nanoparticles.

Here, we describe a colorimetric sensor for detecting Hg(2+) in aqueous media, which is simply constructed by the self-assembly of thymine acetamidoethanethiol (T-SH) on gold nanoparticles (AuNPs). Based on the specific interaction of Hg(2+) with two thymines (T), the T-SH modified AuNPs can be induced to aggregate through the formation of a stable T-Hg-T complex in the presence of Hg(2+), resulting in a color change from red to blue-gray. As low as 0.5 µM of Hg(2+) can be easily monitored by the naked eye using this sensor. Other metal ions, including Zn(2+), Cd(2+), Pb(2+), Ni(2+), Cu(2+), Co(2+), Mn(2+), Ba(2+), Fe(2+), Ca(2+), Mg(2+), Al(3+), and Fe(3+), could not cause any response, even at concentrations 100-fold higher than Hg(2+). The high selectivity, high stability and easy operation enable this sensor suitable for the rapid on-site detection of Hg(2+) pollution.