TELEX HEBDOMADAIRE NR 95 DU 17.09.82 DESTINE A L'ENSEMBLE DES DELEGATIONS EXTERIEURES ET BUREAUX DE PRESS ET D'INFORMATION INDEPENDANTS DANS LES PAYS TIERS = WEEKLY MEMO NO. 95 FOR 17.09.82 TO FOREIGN DELEGATIONS AND PRESS BUREAUS OF THIRD COUNTRIES

<p>High-performance liquid chromatography (HPLC) results of (A) commercial surfactin sample, and (B) our extract surfactin of <i>B</i>. <i>subtilis</i> HH2 in LB medium. There were three main peaks (Peak A-C) of the extract and the surfactin standard in the same location.</p

Quantum Dots Encapsulated with Canine Parvovirus-Like Particles Improving the Cellular Targeted Labeling

<div><p>Quantum dots (QDs) have a promising prospect in live-cell imaging and sensing because of unique fluorescence features. QDs aroused significant interest in the bio-imaging field through integrating the fluorescence properties of QDs and the delivery function of biomaterial. The natural tropism of Canine Parvovirus (CPV) to the transferrin receptor can target specific cells to increase the targeting ability of QDs in cell imaging. CPV virus-like particles (VLPs) from the expression of the CPV-VP2 capsid protein in a prokaryotic expression system were examined to encapsulate the QDs and deliver to cells with an expressed transferrin receptor. CPV-VLPs were used to encapsulate QDs that were modified using 3-mercaptopropionic acid. Gel electrophoresis, fluorescence spectrum, particle size, and transmission electron microscopy verified the conformation of a complex, in which QDs were encapsulated in CPV-VLPs (CPV-VLPs-QDs). When incubated with different cell lines, CPV-VLPs-QDs significantly reduced the cytotoxicity of QDs and selectively labeled the cells with high-level transferrin receptors. Cell-targeted labeling was achieved by utilizing the specific binding between the CPV capsid protein VP2 of VLPs and cellular receptors. CPV-VLPs-QDs, which can mimic the native CPV infection, can recognize and attach to the transferrin receptors on cellular membrane. Therefore, CPV-VLPs can be used as carriers to facilitate the targeted delivery of encapsulated nanomaterials into cells via receptor-mediated pathways. This study confirmed that CPV-VLPs can significantly promote the biocompatibility of nanomaterials and could expand the application of CPV-VLPs in biological medicine.</p></div

Optimization of QDs encapsulation using CPV-VLPs.

<p>(<b>a</b>) Particle size of CPV-VLPs-QDs under different CPV-VLPs/QDs ratios. (<b>b</b>)Absorbance of complex at different CPV-VLPs/QDs ratios.</p

Expression and purification of CPV-VP2 proteins.

<p>Protein detection using SDS-PAGE (<b>a</b>): lane 1, His-Sumo-VP2 (85 kDa); lane 2, VP2 protein (65 kDa). Identification of proteins using Western blot (<b>b</b>): lane 1, His-Sumo-VP2; lane 2, VP2 protein. Mouse anti-CPV monoclonal antibody was used as the primary antibody (1:1000).</p

Targeting labeling of cells using CPV-VLPs-QDs.

<p>DAPI-labeled nucleus (blue), QDs (red), and FITC-labeled goat anti-mouse secondary antibody (green). Anti-CPV mouse monoclonal antibody was used as the primary antibody. Hela and F81 cells show high uptake (red), whereas no obvious fluorescence signal was detected in BHK-21 cells.</p

Cytotoxicity of the CPV-VLPs-QDs and MPA-QDs in BHK-21(a), F81 (b), and Hela (c) cells.

<p>The relative cell viability (%) related to control wells containing cell culture medium without nanoparticles was calculated as [<i>A</i>]_sample /[<i>A</i>]_control × 100%, where [<i>A</i>]_Sample is the absorbance of the test sample and [A]_control is the absorbance of control sample. To determine 50% inhibitory concentration, namely, IC50, concentration—response curves were generated relative to the negative control. IC50 values were calculated from the non-linear regression analyses. In comparison with MPA-QDs, the encapsulated QDs, i.e., CPV-VLPs-QDs with low cytotoxicity (<b>d</b>), show that CPV-VLPs can be employed as safe delivery carriers. *p value<0.05, **p value<0.01.</p

Characterization of CPV-VLPs-QDs complex.

<p>(<b>a</b>) Absorbance spectrum of CPV-VLPs-QDs complex. (<b>b</b>) Particle size of CPV-VLPs-QDs complex using a nano sizer; (<b>c</b>) MPA-QDs (blue line) are approximately 5 nm in diameter; the CPV-VLPs (green line) are approximately 20 nm in diameter; the CPV-VLPs-QDs (purple line) are approximately 24 nm in diameter. (<b>d</b>) Gel electrophoresis of different nanoparticles. Modified QDs moved toward the anode, whereas the unmodified QDs are still in the well; TEM pictures of CPV-VLPs; (<b>e</b>) TEM pictures of CPV-VLPs-QDs complex; <b>(f)</b> TEM pictures of soluble MPA-QDs.</p

Stability of CPV-VLPs-QDs complex.

<p>The CPV-VLPs-QDs were in dialysis under a buffer with different pH values. The QDs concentrations in the buffer were determined at 6, 12, 24, 36, 48, and 72 hours. The released QDs were calculated according to the formula indicated in the <b>Determination of release rate of QDs encapsulated in CPV-VLPs</b> of the <b>Materials and Methods</b> section. *p value<0.05, **p value<0.01</p

Modification of QDs with MPA.

<p>(<b>a</b>) Zeta potential of MPA-QDs and QDs. The QDs surface had no charge, but this surface became negative after modification with MPA; (<b>b</b>) Gel electrophoresis of MPA-QDs and QDs in the presence of an electric field. QDs without charge stayed only in the well, and MPA-QDs ran to anode. (<b>c</b>) Fluorescent emission spectra of MPA-QDs and QDs.</p

Schematic of encapsulation of QDs with CPV-VLPs.

<p>The CPV capsid protein VP2 was expressed in <i>Escherichia coli</i>. QDs modified with 3-mercaptopropionic acid (MPA) were then added into VP2 protein solution. During the CPV-VP2 assembly into VLPs, encapsulation of MPA-QDs into VLPs was achieved. The artwork was created using Adobe Illustrator CS6 software.</p