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Evariste B. Gueguim-Kana

Bio: Evariste B. Gueguim-Kana is an academic researcher from University of KwaZulu-Natal. The author has contributed to research in topics: Silver nanoparticle & Bacillus safensis. The author has an hindex of 24, co-authored 28 publications receiving 1406 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, the authors reported the biogenic synthesis of silver nanoparticles (AgNPs) using the pod extract of Cola nitida, the evaluation of their antibacterial and antioxidant activities, and their application as an antimicrobial additive in paint.

140 citations

Journal ArticleDOI
TL;DR: In this paper, a crude extracellular keratinase obtained from a novel keratin-degrading bacterial strain, Bacillus safensis LAU 13 (GenBank accession No. KJ461434) was used for the synthesis of silver nanoparti-cles (AgNPs).
Abstract: In this study, crude extracellular keratinase obtained from a novel keratin-degrading bacterial strain, Bacillus safensis LAU 13 (GenBank accession No. KJ461434) was used for the synthesis of silver nanoparti- cles (AgNPs). The particles were characterised by UV- Visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy. The biosynthesised AgNPs exhibited maximum absorbance at 409 nm. They are spherical in shape with the size ranging 5-30 nm. The FTIR spectrum showed peaks at 3410, 2930, 1664, 1618, 1389 and 600 cm -1 , indicating that proteins were the capping and stabilisation molecules in the syn- thesis of AgNPs. Data obtained from XRD showed that the particles have face-centred cubic phase and are crystalline in nature with average size of *8.3 nm. The particles showed effective inhibitory activity against five clinical isolates of Escherichia coli. Therefore, the keratinase of this strain could be used to develop an environmental friendly method for the rapid synthesis of AgNPs. To the best of our knowledge, this is the first report of green synthesis of AgNPs using the metabolite of B. safensis, and the report adds to the growing relevance of B. safensis as a potential industrially viable organism.

138 citations

Journal ArticleDOI
TL;DR: This study demonstrated for the first time the utility of C PHE in the biosynthesis of CPHE-AgNPs with potential applications as antimicrobial and larvicidal agents, and paint additives for coating material surfaces to protect them against microbial growth while improving their shelf life.
Abstract: The present investigation reports utility of cocoa pod husk extract (CPHE), an agro-waste in the biosynthesis of silver nanoparticles (AgNPs) under ambient condition. The synthesized CPHE-AgNPs were characterized by UV–visible spectroscopy, Fourier-transform infrared spectroscopy, Energy dispersive X-ray (EDX) spectroscopy and transmission electron microscopy. The feasibility of the CPHE-AgNPs as antimicrobial agent against some multidrug-resistant clinical isolates, paint additive, and their antioxidant and larvicidal activities were evaluated. CPHE-AgNPs were predominantly spherical (size range of 4–32 nm) with face-centered cubic phase and crystalline conformation pattern revealed by selected area electron diffraction, while EDX analysis showed the presence of silver as a prominent metal. The synthesized nanoparticles effectively inhibited multidrug-resistant isolates of Klebsiella pneumonia and Escherichia coli at a concentration of 40 µg/ml, and enhanced the activities of cefuroxime and ampicillin in synergistic manner at 42.9–100 % concentration, while it completely inhibited the growth of E. coli, K. pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, Pseudomonas aeruginosa, Aspergillus flavus, Aspergillus fumigatus and Aspergillus niger as additive in emulsion paint. The antioxidant activities of the CPHE-AgNPs were found to be excellent, while highly potent larvicidal activities against the larvae of Anopheles mosquito at 10–100 µg/ml concentration were observed. Our study demonstrated for the first time the utility of CPHE in the biosynthesis of CPHE-AgNPs with potential applications as antimicrobial and larvicidal agents, and paint additives for coating material surfaces to protect them against microbial growth while improving their shelf life.

120 citations

Journal ArticleDOI
TL;DR: The nanoparticles prevented coagulation of blood, and also completely dissolved blood clots, indicating the biomedical potential of AuNPs and Ag-AuNPs in the management of blood coagulated disorders.
Abstract: This study investigated the green biosynthesis of gold (Au) and silver-gold alloy (Ag-Au) nanoparticles using cell-free extract of Bacillus safensis LAU 13 strain (GenBank accession No: KJ461434). The biosynthesized AuNPs and Ag-AuNPs were characterized using UV-Vis spectroscopy, Fourier-transform infrared spectroscopy, and transmission electron microscopy. Evaluation of the antifungal activities, degradation of malachite green, anti-coagulation of blood, and thrombolysis of human blood clot by the biosynthesized nanoparticles were investigated. The AuNPs and Ag-AuNPs had maximum absorbance at 561 and 545 nm, respectively. The FTIR peaks at 3318, 2378, 2114, 1998, 1636, 1287, 446, $421~\mathrm {cm}^{-1}$ for AuNPs; and 3310, 2345, 2203, 2033, 1636, 1273, 502, 453, 424 $\mathrm {cm}^{-1}$ for Ag-AuNPs indicated that proteins were the capping and stabilization molecules in the biosynthesized nanoparticles. The particles were fairly spherical in shape with size of 10–45 nm for AuNPs and 13–80 nm for Ag-AuNPs. Moreover, energy dispersive X-ray analysis of AuNPs revealed gold as the most prominent metal in the AuNPs solution, while silver and gold were the most prominent in the case of Ag-AuNPs. Selected area electron diffraction showed the biosynthesized nanoparticles as crystal structures with ring shape pattern. AuNPs and Ag-AuNPs displayed growth inhibitions of 66.67–90.78% against strains of Aspergillus fumigatus and A. niger at concentration of 200 $\mu \mathrm {g}/\mathrm {ml}$ , and remarkable degradation (> 90%) of malachite green after 48 h. Furthermore, the nanoparticles prevented coagulation of blood, and also completely dissolved blood clots, indicating the biomedical potential of AuNPs and Ag-AuNPs in the management of blood coagulation disorders. This is the first report of the synthesis of AuNPs and Ag-AuNPs using a strain of B. safensis for biomedical and catalytic applications.

99 citations

Journal ArticleDOI
22 Jun 2016
TL;DR: This study, which is the first of its kind to use nest extract of paper wasp for the synthesis of nanoparticles, has shown that the biosynthesized AgNPs could be deployed for biomedical and catalytic applications.
Abstract: Biosynthesis of silver nanoparticles (AgNPs) using nest extract of paper wasp (Polistes sp) was investigated in this work. The AgNPs were characterized by UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM), and evaluated for antibacterial, antifungal, dye degradation, blood anticoagulation, and blood clot dissolution (thrombolytic) activities. The crystalline polydispersed AgNPs with size range of 12.5–95.55 nm absorbed maximally at 428 nm and showed anisotropic structures of sphere, triangle, hexagon, rod, and rhombus. The FTIR data showed prominent peaks at 3426 and 1641 cm−1, which indicate the involvement of phenolics compounds and proteins in the synthesis of AgNPs. The prominence of Ag in the EDX spectra showed that indeed, AgNPs were formed. The AgNPs showed potent antibacterial activities (12–35 mm) against three multi-drug strains of Pseudomonas aeruginosa and Klebsiella granulomatis. While the growth of Aspergillus flavus and Aspergillus niger was completely suppressed, the AgNPs produced growth inhibition of 75.61 % against Aspergillus fumigatus at 100 µg/ml. Furthermore, the AgNPs degraded malachite green to the tune of 93.1 %. The AgNPs also prevented coagulation of blood, while it completely dissolved preformed blood clots within 5 min showing the potent anticoagulation and thrombolytic activities. This study, which is the first of its kind to use nest extract of paper wasp for the synthesis of nanoparticles, has shown that the biosynthesized AgNPs could be deployed for biomedical and catalytic applications.

93 citations


Cited by
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Journal ArticleDOI
TL;DR: It has been demonstrated that Ag NPs arrest the growth and multiplication of many bacteria such as Bacillus cereus, Staphylococcus aureus, Citrobacter koseri, Salmonella typhii, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia, Vibrio parahaemolyticus and fungus.
Abstract: Use of silver and silver salts is as old as human civilization but the fabrication of silver nanoparticles (Ag NPs) has only recently been recognized. They have been specifically used in agriculture and medicine as antibacterial, antifungal and antioxidants. It has been demonstrated that Ag NPs arrest the growth and multiplication of many bacteria such as Bacillus cereus, Staphylococcus aureus, Citrobacter koseri, Salmonella typhii, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia, Vibrio parahaemolyticus and fungus Candida albicans by binding Ag/Ag+ with the biomolecules present in the microbial cells. It has been suggested that Ag NPs produce reactive oxygen species and free radicals which cause apoptosis leading to cell death preventing their replication. Since Ag NPs are smaller than the microorganisms, they diffuse into cell and rupture the cell wall which has been shown from SEM and TEM images of the suspension containing nanoparticles and pathogens. It has also been shown that smaller nanoparticles are more toxic than the bigger ones. Ag NPs are also used in packaging to prevent damage of food products by pathogens. The toxicity of Ag NPs is dependent on the size, concentration, pH of the medium and exposure time to pathogens.

766 citations

Journal ArticleDOI
Li Xu, Yi Yi Wang1, Jie Huang1, Chun-Yuan Chen1, Zhen-Xing Wang1, Hui Xie 
TL;DR: The state-of-the-art advances of AgNPs in the synthesis methods, medical applications and biosafety, and a new type of Ag particles, silver Ångstrom (Å, 1 Å = 0.1 nm) particles (AgÅPs), which exhibit better biological activity and lower toxicity compared with AgNps are reviewed.
Abstract: Silver nanoparticles (AgNPs) have been one of the most attractive nanomaterials in biomedicine due to their unique physicochemical properties. In this paper, we review the state-of-the-art advances of AgNPs in the synthesis methods, medical applications and biosafety of AgNPs. The synthesis methods of AgNPs include physical, chemical and biological routes. AgNPs are mainly used for antimicrobial and anticancer therapy, and also applied in the promotion of wound repair and bone healing, or as the vaccine adjuvant, anti-diabetic agent and biosensors. This review also summarizes the biological action mechanisms of AgNPs, which mainly involve the release of silver ions (Ag+), generation of reactive oxygen species (ROS), destruction of membrane structure. Despite these therapeutic benefits, their biological safety problems such as potential toxicity on cells, tissue, and organs should be paid enough attention. Besides, we briefly introduce a new type of Ag particles smaller than AgNPs, silver Angstrom (A, 1 A = 0.1 nm) particles (AgAPs), which exhibit better biological activity and lower toxicity compared with AgNPs. Finally, we conclude the current challenges and point out the future development direction of AgNPs.

372 citations

Journal ArticleDOI
TL;DR: This review discusses the various methods available for the dissolution and extraction of keratin with emphasis on their advantages and limitations, and reports the properties of various keratin-based biomaterials and critically examines how these materials are influenced by the keratin extraction procedure.
Abstract: Keratinous materials such as wool, feathers and hooves are tough unique biological co-products that usually have high sulfur and protein contents A high cystine content (7–13%) differentiates keratins from other structural proteins, such as collagen and elastin Dissolution and extraction of keratin is a difficult process compared to other natural polymers, such as chitosan, starch, collagen, and a large-scale use of keratin depends on employing a relatively fast, cost-effective and time efficient extraction method Keratin has some inherent ability to facilitate cell adhesion, proliferation, and regeneration of the tissue, therefore keratin biomaterials can provide a biocompatible matrix for regrowth and regeneration of the defective tissue Additionally, due to its amino acid constituents, keratin can be tailored and finely tuned to meet the exact requirement of degradation, drug release or incorporation of different hydrophobic or hydrophilic tails This review discusses the various methods available for the dissolution and extraction of keratin with emphasis on their advantages and limitations The impacts of various methods and chemicals used on the structure and the properties of keratin are discussed with the aim of highlighting options available toward commercial keratin production This review also reports the properties of various keratin-based biomaterials and critically examines how these materials are influenced by the keratin extraction procedure, discussing the features that make them effective as biomedical applications, as well as some of the mechanisms of action and physiological roles of keratin Particular attention is given to the practical application of keratin biomaterials, namely addressing the advantages and limitations on the use of keratin films, 3D composite scaffolds and keratin hydrogels for tissue engineering, wound healing, hemostatic and controlled drug release

289 citations

Journal ArticleDOI
TL;DR: The current review focuses on the comparison among different proteases and the current problems faced during production and application at the industrial level to promote microbial proteases economically and commercially around the world.
Abstract: The use of chemicals around the globe in different industries has increased tremendously, affecting the health of people. The modern world intends to replace these noxious chemicals with environmental friendly products for the betterment of life on the planet. Establishing enzymatic processes in spite of chemical processes has been a prime objective of scientists. Various enzymes, specifically microbial proteases, are the most essentially used in different corporate sectors, such as textile, detergent, leather, feed, waste, and others. Proteases with respect to physiological and commercial roles hold a pivotal position. As they are performing synthetic and degradative functions, proteases are found ubiquitously, such as in plants, animals, and microbes. Among different producers of proteases, Bacillus sp. are mostly commercially exploited microbes for proteases. Proteases are successfully considered as an alternative to chemicals and an eco-friendly indicator for nature or the surroundings. The evolutionary relationship among acidic, neutral, and alkaline proteases has been analyzed based on their protein sequences, but there remains a lack of information that regulates the diversity in their specificity. Researchers are looking for microbial proteases as they can tolerate harsh conditions, ways to prevent autoproteolytic activity, stability in optimum pH, and substrate specificity. The current review focuses on the comparison among different proteases and the current problems faced during production and application at the industrial level. Deciphering these issues would enable us to promote microbial proteases economically and commercially around the world.

277 citations