Silica-coated superparamagnetic nanoparticles as contrast agent for magnetic resonance imaging: Synthesis and physicological charaterizations

International audienc

Superparamagnetic nanohybrids with cross-linked polymers providing higher in vitro stability

International audienceA method for facile synthesis of high stable cross-linked superparamagnetic nanohybrids using pre-coating of biocompatible polymer, hydroxyl polyvinyl alcohol (PVA-OH) was demonstrated as a simple, controllable, fast, reproducible, and upscalable method. To improve stability, morphology and functionalization of the particles, the PVA-OH was first coated onto superparamagnetic iron oxide nanoparticle (SPION) surfaces before a cross-linking condensation with silica precursor. The obtained magnetic nanohybrid with compact silica layer was monodispersed with uniform morphology with the size of 50.0 ± 3.7 nm. The particles showed colloidal stability region at pH 7.35-7.45 which is applicable in biomedical applications and long shelf life upon storage of over 9 months. In vitro study in aspect of cytotoxicity and stability of the particle reveled that these original nanohybrids are non-toxic and highly robust in endosomal/lysosomal condition for up to 42 days without dissolution of the particles. In order to demonstrate the efficient targeting of the magnetic nanohybrid for their further use as targeting detection for example in MRI, we prepared folate reactive cross-linked magnetic nanohybrid which showed an interesting affinity to folate receptor (FR)-positive cervix (HeLa) cells. Our work to develop the characteristics of non-toxic and stable cross-linked magnetic nanohybrids would be beneficial for the further development of safer and more efficient targeting MRI contrast agent for diagnosis of various cancers

Rapid Molecular Detection of Multidrug-Resistant Tuberculosis by PCR-Nucleic Acid Lateral Flow Immunoassay.

Several existing molecular tests for multidrug-resistant tuberculosis (MDR-TB) are limited by complexity and cost, hindering their widespread application. The objective of this proof of concept study was to develop a simple Nucleic Acid Lateral Flow (NALF) immunoassay as a potential diagnostic alternative, to complement conventional PCR, for the rapid molecular detection of MDR-TB. The NALF device was designed using antibodies for the indirect detection of labeled PCR amplification products. Multiplex PCR was optimized to permit the simultaneous detection of the drug resistant determining mutations in the 81-bp hot spot region of the rpoB gene (rifampicin resistance), while semi-nested PCR was optimized for the S315T mutation detection in the katG gene (isoniazid resistance). The amplification process additionally targeted a conserved region of the genes as Mycobacterium tuberculosis (Mtb) DNA control. The optimized conditions were validated with the H37Rv wild-type (WT) Mtb isolate and Mtb isolates with known mutations (MT) within the rpoB and katG genes. Results indicate the correct identification of WT (drug susceptible) and MT (drug resistant) Mtb isolates, with the least limit of detection (LOD) being 104 genomic copies per PCR reaction. NALF is a simple, rapid and low-cost device suitable for low resource settings where conventional PCR is already employed on a regular basis. Moreover, the use of antibody-based NALF to target primer-labels, without the requirement for DNA hybridization, renders the device generic, which could easily be adapted for the molecular diagnosis of other infectious and non-infectious diseases requiring nucleic acid detection

Targeted Mutagenesis of Burkholderia thailandensis and Burkholderia pseudomallei through Natural Transformation of PCR Fragments▿ †

Burkholderia pseudomallei is the causative agent of melioidosis, an overwhelming, rapidly fatal septic infection, and B. thailandensis is a closely related, less virulent species. Both organisms are naturally competent for DNA transformation, and this report describes a procedure exploiting this property for the rapid generation of marked deletion mutations by using PCR products. The method was employed to create 61 mutant strains. Several selectable elements were employed, including elements carrying loxP and FRT recombinase recognition sites to facilitate resistance marker excision. Chromosomal mutations could also be transferred readily between strains by transformation. The availability of simple procedures for creating defined chromosomal mutations and moving them between strains should facilitate genetic analysis of virulence and other traits of these two Burkholderia species

Dengue virus-specific memory T cell responses in human volunteers receiving a live attenuated dengue virus type 2 candidate vaccine

A live attenuated dengue virus type 2 candidate vaccine (16681-PDK53) was evaluated in a phase I trial in 10 nonimmune adult volunteers. The dengue virus-specific memory T cell responses were analyzed as part of this study. Dengue virus-specific T cell proliferative responses were observed in all subjects after stimulating their peripheral blood mononuclear cells with live viruses or noninfectious viral antigens. The highest proliferative response was against dengue virus type 2, although cross-reactivity with other flaviviruses was detected to a lesser degree in some subjects. Dengue virus type 2-specific CD4+ and CD8+ cytotoxic T lymphocytes were generated in all vaccinees. This study investigated whether the candidate vaccine was efficacious in inducing dengue virus-specific CD4+ and CD8+ T cell memory after a single immunization in nonimmune recipients

NALF and agarose gel electrophoresis results for the <i>rpoB</i> assay.

<p><b>(A)</b> The use of SM primers demonstrate an effective template distinction with the appearance of NALF T1 and T2 for all MT templates to indicate RIF resistant Mtb isolates, which relates to the inner and outer DNA bands on agarose gel for the MT templates. As for WT templates, the assays correctly resulted in the appearance of NALF T2 only, to indicate RIF susceptible Mtb isolates, which corresponds to PCR product size 314 bp on agarose gel.</p

PCR Amplification Products.

<p><b>(A)</b> Multiplex PCR amplification products for the <i>rpoB</i> assay and <b>(B)</b> Semi-nested PCR amplification products for the <i>katG</i> assay, on agarose gel electrophoresis.</p