Validation of Selective Capture of Fimbriated Uropathogenic Escherichia coli by a Label-free Engineering Detection System Using Mannosylated Surfaces.

Label-free detection of pathogens is of major concern to the microbiologist community. Most procedures require several steps and amplification techniques. Carbohydrates are well-established receptors for host-pathogen interactions, which can be amplified using glycodendritic architectures on the basis of multivalent binding interactions. Given that uropathogenic Escherichia coli bacterial FimH is based on such mannopyranoside-binding interactions, we demonstrate herein that synthetic monomeric and trimeric thiolated α-d-mannosides can be effectively bound to gold substrate-functionalized self-assembled monolayers (SAMs) preactivated with maleimide functionalities. Mannosides grafted onto SAMs were followed using Quartz Crystal Microbalance with Dissipation (QCM-D). Binding recognition efficiency was first evaluated using the plant lectin from Canavalia ensiformis (ConA) also using QCM-D. We showed a direct correlation between the amount of mannoside bound and the lectin attachment. Even though there was less trimer bound (nM/cm2) to the surface, we observed a 7-fold higher amount of lectin anchoring, thus further demonstrating the value of the multivalent interactions. We next examined the relative fimbriated E. coli selective adhesion/capture to either the monomeric or the trimeric mannoside bound to the surface. Our results established the successful engineering of the surfaces to show E. coli adhesion via specific mannopyranoside binding but unexpectedly, the monomeric derivative was more efficient than the trimeric analog, which could be explained by steric hindrance. This approach strongly suggests that it could be broadly applicable to other Gram-negative bacteria sharing analogous carbohydrate-dependent binding interactions.

Surface Grafted MSI-78A Antimicrobial Peptide has High Potential for Gastric Infection Management.

As we approach the end of the antibiotic era, newer therapeutic options, such as antimicrobial peptides (AMPs), are in urgent demand. AMP surface grafting onto biomaterials has been described as a good strategy to overcome problems associated with their in vivo stability. Helicobacter pylori is among the bacteria that pose greatest threat to human health, being MSI-78A one of the few bactericidal AMPs against this bacterium. Here, we report that MSI-78A grafted onto model surfaces (Self-Assembled Monolayers -SAMs), in a concentration of 30.3 ± 1.2 ng/cm2 determined by quartz crystal microbalance with dissipation (QCM-D), was able to kill, by contact, 98% of planktonic H. pylori in only 2 h. This fact was not verified against the control bacteria (Staphylococcus epidermidis), although the minimal inhibitory concentration (MIC) of MSI-78A in solution is much lower for S. epidermidis (2 µg/mL) than for H. pylori (64 µg/mL). Our results also demonstrated that, in opposite to other bacteria, H. pylori cells were attracted to ethylene glycol terminated (antiadhesive) surfaces, which can explain the high bactericidal potential of grafted MSI-78A. This proof of concept study establishes the foundations for development of MSI-78A grafted nanoparticles for gastric infection management within a targeted nanomedicine concept.

Development of a rapid antibody test for point-of-care diagnosis of animal African trypanosomosis.

Trypanosoma congolense and T. vivax are the main causative agents of animal African trypanosomosis (AAT), a disease which hinders livestock production throughout sub-Saharan Africa and in some parts of South America. Although two trypanocidal drugs are currently available, the level of treatment is low due to the difficulty in diagnosing the disease in the field. The major clinical signs of AAT such as anaemia, weight loss, and infertility, are common to several other endemic livestock diseases. Current diagnostic methods, based on the visualization of the parasite in the blood, or on the detection of its DNA or the antibodies it triggers in the host, are not suitable for direct use in the field as they require specialized equipment and personnel. Thus, we developed a quick-format diagnostic test (15min) based on the recombinant TcoCB and TvGM6 antigens for detection of T. congolense and T. vivax, respectively, aimed at providing farmers and veterinarians in the field with the means to conduct a quick diagnosis. The specificity and sensitivity of the test were evaluated using sera from experimentally infected cattle, and fresh blood when possible. The prototype, which includes both antigens, shows a specificity of 95.9 (95% C.I., 90.4%-100%) and a sensitivity of 92.0% (95% C.I., 85.9%-98.1%) for T. congolense and 98.2% (95% C.I., 94.7%-100%) for T. vivax. The high levels of sensitivity and specificity of this rapid test, the possibility of using directly whole blood, and the ease of interpreting the result, all contribute to make of this test a valuable candidate to contribute to the control of AAT in the field. However, further tests with more representative, numerous and fresh reference samples are necessary in order to compare this test with the ELISA, the current gold standard serological test for trypanosomosis.

Vitamin B3 metal-organic frameworks as potential delivery vehicles for therapeutic nitric oxide.

The synthesis and structural characterization of two isostructural metal (M=Ni, Co) 3D framework structure that integrate vitamin B3 building blocks with NO delivery capabilities and low toxicity is presented. The compounds with a formula [M2(µ2-H2O)(µ-vitamin B3)4]·2H2O contain two crystallographic distinct divalent metal centres connected by a bridging water and carboxylate group from vitamin B3. The porous compounds have the capability of storing and releasing nitric oxide (NO) in a slow and reversible manner, with released amounts of 2.6 and 2.0µmol NOmgsolid-1, on the Ni and Co compound, respectively. The NO release followed a convenient slow release kinetic profile in both gas and liquid phases. Haemoglobin tests demonstrated that NO is released to the medium in a biologically active form, thus suitable to trigger the desired response in biological systems. The toxicity of the samples with and without loaded NO was evaluated from cytotoxicity tests in HeLa and HEKn cells, showing low toxicity of the compounds at concentrations below 180µgcm-3. The overall results indicate that these bio based MOFs are of interest for therapeutic applications related with NO delivery. STATEMENT OF SIGNIFICANCE.