Antimicrobial activity of kojic acid from endophytic fungus Colletotrichum gloeosporioides isolated from Sonneratia apetala, a mangrove plant of the Sundarbans

Objective: To isolate and evaluate the antimicrobial activity of the active principle(s) from the ethyl acetate (EtOAc) extract of endophytic fungus Colletotrichum gloeosporioides (C. gloeosporioides) isolated from Sonneratia apetala. Methods: Water agar technique was used to isolate the fungus, and both microscopic and molecular techniques were used for identification of the strain. Potato dextrose broth was used to grow the fungus in large-scale. Reversed-phase preparative HPLC analysis was performed to isolate the major active compound, kojic acid. The EtOAc extract and kojic acid were screened for their antimicrobial activity against two Gram-positive and two Gram-negative bacteria as well as a fungal strain using the resazurin 96-well microtitre plate antimicrobial assay. Results: The fungus C. gloeosporioides was isolated from the leaves of Sonneratia apetala. Initial identification of the fugal isolate was carried out using spore characteristics observed under the microscope. Subsequently, the ITS1-5.8S-ITS2 sequencing was employed for species-level identification of the fungus C. gloeosporioides. Five litres of liquid culture of the fungus produced approximately 610 mg of a mixture of secondary metabolites. Kojic acid (1) was isolated as the main secondary metabolite present in the fungal extract, and the structure was confirmed by 1D, 2D NMR and mass spectrometry. The EtOAc extract and compound 1 exhibited considerable antimicrobial activity against all tested microorganisms. Whilst the minimum inhibitory concentration (MIC) values from the EtOAc extract ranged between 2.4× 10-4 mg/mL and 2.5 mg/mL, those of kojic acid (1) were between 0.125 mg/mL and 1 mg/mL. The EtOAc extract and kojic acid (1) were most active against Pseudomonas aeruginosa (MIC = 2.4×10-4 mg/mL) and Micrococcus luteus (MIC = 0.125 mg/mL), respectively. Conclusions: The results revealed that the endophytic fungus C. gloeosporioides could be a good source of commercially important kojic acid, which exhibited antimicrobial properties

The Surfactant Dipalmitoylphophatidylcholine (DPPC) Modifies Acute Responses in Alveolar Carcinoma Cells in Response to Low Dose Silver Nanoparticle Exposure

Nanotechnology is a rapidly growing field with silver nanoparticles (AgNP) in particular utilized in a wide variety of consumer products. This has presented a number of concerns relating to exposure and the associated toxicity to humans and the environment. As inhalation is the most common exposure route, this study investigates the potential toxicity of AgNP to A549 alveolar epithelial carcinoma cells and the influence of a major component of lung surfactant dipalmitoylphosphatidylcholine (DPPC) on toxicity. It was illustrated that exposure to AgNP generated low levels of oxidative stress and a reduction in cell viability. While DPPC produced no significant effect on viability studies its presence resulted in increased reactive oxygen species formation. DPPC also significantly modified the inflammatory response generated by AgNP exposure. These findings suggest a possible interaction between AgNP and DPPC causing particles to become more reactive, thus increasing oxidative insult and inflammatory response within A549 cell

Cytotoxicity of ZnO Nanoparticles Can Be Tailored by Modifying Their Surface Structure: A Green Chemistry Approach for Safer Nanomaterials

ZnO nanoparticles (NP) are extensively used in numerous nanotechnology applications; however, they also happen to be one of the most toxic nanomaterials. This raises significant environmental and health concerns and calls for the need to develop new synthetic approaches to produce safer ZnO NP, while preserving their attractive optical, electronic, and structural properties. In this work, we demonstrate that the cytotoxicity of ZnO NP can be tailored by modifying their surface-bound chemical groups, while maintaining the core ZnO structure and related properties. Two equally sized (9.26 ± 0.11 nm) ZnO NP samples were synthesized from the same zinc acetate precursor using a forced hydrolysis process, and their surface chemical structures were modified by using different reaction solvents. X-ray diffraction and optical studies showed that the lattice parameters, optical properties, and band gap (3.44 eV) of the two ZnO NP samples were similar. However, FTIR spectroscopy showed significant differences in the surface structures and surface-bound chemical groups. This led to major differences in the zeta potential, hydrodynamic size, photocatalytic rate constant, and more importantly, their cytotoxic effects on Hut-78 cancer cells. The ZnO NP sample with the higher zeta potential and catalytic activity displayed a 1.5-fold stronger cytotoxic effect on cancer cells. These results suggest that by modifying the synthesis parameters/conditions and the surface chemical structures of the nanocrystals, their surface charge density, catalytic activity, and cytotoxicity can be tailored. This provides a green chemistry approach to produce safer ZnO NP

Transcriptomics-based characterization of the toxicity of ZnO nanoparticles against chronic myeloid leukemia cells

Introduction: Zinc oxide nanoparticles (ZnO NPs) have recently attracted attention as potential anti-cancer agents. To the best of our knowledge, the toxicity of ZnO NPs against human chronic myeloid leukemia cells (K562 cell line) has not been studied using transcriptomics approach. Objective: The goals of this study were to evaluate the capability of ZnO NPs to induce apoptosis in human chronic myeloid leukemia cells (K562 cells) and to investigate the putative mechanisms of action. Methods: We used viability assay and flowcytometry coupled with Annexin V-FITC and propidium iodide to investigate the toxicity of ZnO NPs on K562 cells and normal peripheral blood mononuclear cells. Next we utilized a DNA microarray-based transcriptomics approach to characterize the ZnO NPs-induced changes in the transcriptome of K562 cells. Results: ZnO NPs exerted a selective toxicity (mainly by apoptosis) on the leukemic cells (p≤ 0.005) and altered their transcriptome; 429 differentially expressed genes (DEGs) with fold change (FC)≥ 4 and p≤ 0.008 with corrected p≤ 0.05 were identified in K562 cells post treatment with ZnO NPs. The over-expressed genes were implicated in “response to zinc”, “response to toxic substance” and “negative regulation of growth” (corrected p≤ 0.05). In contrast, the repressed genes positively regulated “cell proliferation”, “cell migration”, “cell adhesion”, “receptor signaling pathway via JAK-STAT” and “phosphatidylinositol 3-kinase signaling” (corrected p≤ 0.05). Lowering the FC to ≥ 1.5 with p≤ 0.05 and corrected p≤ 0.1 showed that ZnO NPs over-expressed the anti-oxidant defense system, drove K562 cells to undergo mitochondrial-dependent apoptosis, and targeted NF-κB pathway. Conclusion: Taken together, our findings support the earlier studies that reported anti-cancer activity of ZnO NPs and revealed possible molecular mechanisms employed by ZnO NPs to induce apoptosis in K562 cells

Anti-bacterial activity of inorganic nanomaterials and their antimicrobial peptide conjugates against resistant and non-resistant pathogens

This review details the antimicrobial applications of inorganic nanomaterials of mostly metallic form, and the augmentation of activity by surface conjugation of peptide ligands. The review is subdivided into three main sections, of which the first describes the antimicrobial activity of inorganic nanomaterials against gram-positive, gram-negative and multidrug-resistant bacterial strains. The second section highlights the range of antimicrobial peptides and the drug resistance strategies employed by bacterial species to counter lethality. The final part discusses the role of antimicrobial peptide-decorated inorganic nanomaterials in the fight against bacterial strains that show resistance. General strategies for the preparation of antimicrobial peptides and their conjugation to nanomaterials are discussed, emphasizing the use of elemental and metallic oxide nanomaterials. Importantly, the permeation of antimicrobial peptides through the bacterial membrane is shown to aid the delivery of nanomaterials into bacterial cells. By judicious use of targeting ligands, the nanomaterial becomes able to differentiate between bacterial and mammalian cells and, thus, reduce side effects. Moreover, peptide conjugation to the surface of a nanomaterial will alter surface chemistry in ways that lead to reduction in toxicity and improvements in biocompatibility

Factors influencing the development of management skills in South African civil engineers

MBA - WBSThe objective of this research was to identify the factors, both the barriers and facilitators, influencing the development of management skills in South African civil engineers. There were 2 research propositions set up from the literature review. The research method adopted was quantitative factor analysis to test the two propositions. Data was collected through a survey conducted at a case site Grinaker-LTA. A 7-point Likert scale was used as the measuring instrument. The research findings concluded that the factors which are barriers in the development of management skills in civil engineers included the lack of training, the lack of management skills in engineers and job dissatisfaction. The facilitating factors included the use of coaching, management related training, the use of employee feedback systems and the self development of the engineer. The second research proposition produced two new factors which were the learning organisation and the effects of cultural diversity on the management development process of engineers. The key recommendations include that human resource managers in construction firms should use the factors from the research in order to improve the processes within the organisation in order to assist in the development of engineers into manager

Virtual 3D planning and patient specific surgical guides for osteotomies around the knee: a feasibility and proof-of-concept study

We have investigated the benefits of patient specific instrument guides, applied to osteotomies around the knee. Single, dual and triple planar osteotomies were performed on tibias or femurs in 14 subjects. In all patients, a detailed pre-operative plan was prepared based upon full leg standing radiographic and CT scan information. The planned level of the osteotomy and open wedge resection was relayed to the surgery by virtue of a patient specific guide developed from the images. The mean deviation between the planned wedge angle and the executed wedge angle was 0 degrees (-1 to 1, SD 0.71) in the coronal plane and 0.3 degrees (-0.9 to 3, SD 1.14) in the sagittal plane. The mean deviation between the planned hip, knee, ankle angle (HKA) on full leg standing radiograph and the post-operative HKA was 0.3 degrees (-1 to 2, SD 0.75). It is concluded that this is a feasible and valuable concept from the standpoint of pre-operative software based planning, surgical application and geometrical accuracy of outcome