IN-VITRO ANTIMICROBIAL ACTIVITY OF BIOLOGICAL SYNTHESIZED SILVER NANOPARTICLES USING STENOTROPHOMONAS MALTOPHILIA STRAIN NS-24 FROM NON-RHIZOSPHERE SOIL

Objective: The present goals of our study were biological synthesis, characterizations of silver nanoparticles, and evaluation of its antimicrobial activity against microbial pathogens like Escherichia coli, Enterococcus faecalis, Streptococcus pneumoniae and Staphylococcus aureus. Methods: The bacterial Strain NS-24 was isolated on nutrient agar medium and was selected for the synthesis of silver nanoparticles based on its gram-negative characteristics. The characterizations of silver nanoparticles were done by UV-Visible spectroscopy, Atomic Force Microscopy (AFM), High Resolution-Transmission Electron Microscopy (HR-TEM), Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDX), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Later, the molecular characterization of the Strain NS-24 was done by DNA extraction and 16S rRNA gene sequencing. Results: The UV-visible spectrophotometric observation of the Strain NS-24 supernatant and AgNO3 solution showed maximum absorbance at 423 nm. The AFM data confirmed that the particles were polydispersed and spherical in shape. Additionally, the FTIR analysis revealed the IR spectral band patterning and TEM analyzes showed the size of biological AgNPs was in the range of 12.56 nm to 27.32 nm, with an average of 18.06 nm in size. Further, the 16S rRNA gene sequencing revealed the identity of Strain NS-24 as Stenotrophomonas maltophilia. The antimicrobial activity of AgNPs was studied on different gram-negative and gram-positive bacterial strains like Escherichia coli (MTCC 40), Enterococcus faecalis (MTCC 6845), Streptococcus pneumoniae (MTCC 8874) and Staphylococcus aureus (MTCC 2825), which showed good inhibition of their growth at varying concentrations of AgNPs against all the pathogens. Conclusion: Our findings showed that the synthesized AgNPs from the isolated bacterium was small in size and had profound antibacterial activity against pathogenic micro-organisms

Mechanical and tribological behaviour of three-dimensional printed almond shell particles reinforced polylactic acid bio-composites

Recently, composite filament development for three-dimensional printing has emerged and is used for numerous applications. The present research work develops neat polylactic acid and Almond Shell Particles reinforced polylactic acid bio-composites for three-dimensional printing and investigates the effects of printing orientation, including 0°, 45° and 90° orientation, on the tribological and mechanical behaviours of three-dimensional printed materials. The novel almond shell particles reinforced polylactic acid filaments are extruded by the filament extrusion method with the presence of 10% almond shell particles in the polylactic acid matrix, and the samples are three-dimensional printed by the fused filament fabrication technique. Mechanical characteristics such as tensile, flexural, compressive strength, and shore hardness are evaluated with respect to various three-dimensional printing orientations. The surface quality of the three-dimensional printed polylactic acid composite samples is analysed with respect to length and diameter deviation. Length accuracy of the 90° oriented polylactic acid and almond shell particles reinforced polylactic acid bio-composite samples exploits a better accuracy of 99.12% and 98.81%, respectively. It is shown that adding almond shell particles to the polylactic acid matrix decreases the flexural and tensile strength. Among the printing orientations, 0° flat samples result in the maximum tensile strength of 36 and 28 MPa for the neat polylactic acid and almond shell particles reinforced polylactic acid composites, respectively. The lowest contact angle of 54° is observed on the almond shell particles reinforced polylactic acid bio-composites three-dimensional printed with a 90° orientation. The highest contact angle value of 94° is observed on the neat polylactic acid three-dimensional printed with a 0° printing orientation. A tribological study is carried out under dry conditions on the pin-on-disc tribometer by varying the sliding speed (1, 2, and 3 m/s) and load (10, 20, and 30 N). The result shows that the lowest coefficient of friction of 0.22 is achieved for the almond shell particles reinforced polylactic acid bio-composite samples with a 0° printing orientation under a sliding load of 10 N. These kinds of newly developed compostable materials can be used for developing disposable orthotic foot appliances

Retinal changes in Alzheimer's disease— integrated prospects of imaging, functional and molecular advances

Alzheimer's Disease (AD) is a devastating neurodegenerative disorder of the brain, clinically characterised by cognitive deficits that gradually worsen over time. There is, at present, no established cure, or disease-modifying treatments for AD. As life expectancy increases globally, the number of individuals suffering from the disease is projected to increase substantially. Cumulative evidence indicates that AD neuropathological process is initiated several years, if not decades, before clinical signs are evident in patients, and diagnosis made. While several imaging, cognitive, CSF and blood-based biomarkers have been proposed for the early detection of AD; their sensitivity and specificity in the symptomatic stages is highly variable and it is difficult to justify their use in even earlier, pre-clinical stages of the disease. Research has identified potentially measurable functional, structural, metabolic and vascular changes in the retina during early stages of AD. Retina offers a distinctively accessible insight into brain pathology and current and developing ophthalmic technologies have provided us with the possibility of detecting and characterising subtle, disease-related changes. Recent human and animal model studies have further provided mechanistic insights into the biochemical pathways that are altered in the retina in disease, including amyloid and tau deposition. This information coupled with advances in molecular imaging has allowed attempts to monitor biochemical changes and protein aggregation pathology in the retina in AD. This review summarises the existing knowledge that informs our understanding of the impact of AD on the retina and highlights some of the gaps that need to be addressed. Future research will integrate molecular imaging innovation with functional and structural changes to enhance our knowledge of the AD pathophysiological mechanisms and establish the utility of monitoring retinal changes as a potential biomarker for AD

Limnology: A critical review

The word Limnology is derived from Greek limne-marsh, pond and evaluates how physical, chemical and biological environment regulates these relationships. The type of life which is supported by lentic communities will depend greatly on biotic components of the fresh water ecosystems. Phytoplanktons are microscopic plants which obtain their energy via photosynthesis. They are important to the ecosystem because they are part of the primary producing community and assist in recycling of elements such are carbon and sulphur. A biotic factors are essentially non living components that affect the living organisms of fresh water communities. Most biological assessments have dealt with conditions arising out of organic pollution since chemical conditions are rather difficult to monitor. Therefore both biological and chemical parameters are essential to monitor pollution. Curiosity prompted researchers to ascertain facts regarding limnology and hence publications on the ecology of freshwater biota have occurred quite occasionally.233 references are quoted in the present text. The review literature indicates that publications were high during 1980-1989(29.4) and 1990-1999(26.5). In the present paper an attempt has been made to give an extensive review of literature related to limnology