The intrinsic antimicrobial activity of citric acid-coated manganese ferrite nanoparticles is enhanced after conjugation with the antifungal peptide Cm-p5.

Diseases caused by bacterial and fungal pathogens are among the major health problems in the world. Newer antimicrobial therapies based on novel molecules urgently need to be developed, and this includes the antimicrobial peptides. In spite of the potential of antimicrobial peptides, very few of them were able to be successfully developed into therapeutics. The major problems they present are molecule stability, toxicity in host cells, and production costs. A novel strategy to overcome these obstacles is conjugation to nanomaterial preparations. The antimicrobial activity of different types of nanoparticles has been previously demonstrated. Specifically, magnetic nanoparticles have been widely studied in biomedicine due to their physicochemical properties. The citric acid-modified manganese ferrite nanoparticles used in this study were characterized by high-resolution transmission electron microscopy, which confirmed the formation of nanocrystals of approximately 5 nm diameter. These nanoparticles were able to inhibit Candida albicans growth in vitro. The minimal inhibitory concentration was 250 µg/mL. However, the nanoparticles were not capable of inhibiting Gram-negative bacteria (Escherichia coli) or Gram-positive bacteria (Staphylococcus aureus). Finally, an antifungal peptide (Cm-p5) from the sea animal Cenchritis muricatus (Gastropoda: Littorinidae) was conjugated to the modified manganese ferrite nanoparticles. The antifungal activity of the conjugated nanoparticles was higher than their bulk counterparts, showing a minimal inhibitory concentration of 100 µg/mL. This conjugate proved to be nontoxic to a macrophage cell line at concentrations that showed antimicrobial activity.

Proteomic analysis of Metarhizium anisopliae secretion in the presence of the insect pest Callosobruchus maculatus.

Crop improvement in agriculture generally focuses on yield, seed quality and nutritional characteristics, as opposed to resistance to biotic stresses. Consequently, natural antifeedant toxins are often rare in seed material, with commercial crops being prone to insect pest predation. In the specific case of cowpea (Vigna unguiculata), smallholder cropping is affected by insect pests that reproduce inside the stored seeds. Entomopathogenic organisms can offer an alternative to conventional pesticides for pest control, producing hydrolases that degrade insect exoskeleton. In this study, protein secretions of the ascomycete Metarhizium anisopliae, which conferred bioinsecticidal activity against Callosobruchus maculatus, were characterized via 2D electrophoresis and mass spectrometry. Proteases, reductases and acetyltransferase enzymes were detected. These may be involved in degradation and nutrient uptake from dehydrated C. maculatus. Proteins identified in this work allowed description of metabolic pathways. Their potential applications in biotechnology include both novel compound development and production of genetically modified plants resistant to insect pests.