Draya Michele Slammed For Complaining About Son’s Homework
Draya Micheleis being criticized for complaining about the amount of homework that her eldest son has. The former Basketball Wives LA star posted a message on social media, explaining how she felt her son Kniko’s teacher relied too heavily on a parent’s participation.
Draya & son Kniko
Specifically, she isn’t a fan of how often she had to listen to her son recite his speech and how many times she had to sign his homework. See her message below, which she later deleted.
Apparently, some folk found her post offensive and tweeted their reactions. Check them out below.
Do you agree or disagree with Draya’s perspective on her son’s homework?
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In recent years, the convergence of nanometre size scale technologies and biological technologies has created the new field of nanobiotechnology. This relatively new field is focused on the creation, manipulation, and use of materials at the nanometre scale for advanced biotechnology . At the forefront of this field is the synthesis of nanometre size scale particles via biological entities. Nanoparticles are of great interest due to their novel physicochemical, magnetic, and optoelectronic properties that are governed by their size, shape, and size distribution [2,3,4,5,6]. It is predominantly the nanoparticles’ extremely small size and large surface area to volume ratio that leads to the significant differences in properties (e.g., biological, catalytic activity, mechanical properties, melting point optical absorption, thermal and electrical conductivity) not seen in the same material at larger scales in their bulk form . Because of these unique physicochemical and optoelectronic properties, nanoparticles are of particular interest for a number of applications ranging from as catalysts, chemical sensors, electronic components, medical diagnostic imaging, pharmaceutical products, and medical treatment protocols. For example, metallic nanoparticles of noble metals such as gold, silver, platinum, and palladium have been widely used in products ranging from cosmetic to medical and pharmaceuticals. Gold nanoparticles have been extensively used in biomedical applications [8,9,10], separation sciences , disease diagnostics , and pharmaceuticals [13,14]. Silver nanoparticles have been found to possess both anti-bacterial and anti-inflammatory properties that can promote faster wound healing. Because of these advantageous properties, silver nanoparticles have been integrated into commercially available wound dressings, pharmaceutical preparations, and medical implant coatings [15,16,17,18,19,20]. Platinum nanoparticles have been widely used in biomedical applications in either pure form or alloyed with other nanoparticles  and palladium nanoparticles in catalysis and electro-catalysis applications [22,23,24], chemical sensors , optoelectronics , and anti-bacterial applications . In addition, non-noble metallic nanoparticles such as iron [28,29], copper , zinc oxide , and selenium  have also been used in medical treatments, cosmetic formulations, and anti-bacterial applications.
Due to the increased demand for various metallic and non-metallic nanoparticles over the past two decades, a wide range of physical and chemical techniques have been developed to produce nanoparticles of different sizes, shapes, and compositions. Traditionally, nanoparticles have been synthesized and stabilised via physical and chemical techniques. The physical approach includes techniques such as laser ablation , lithography  and high-energy irradiation . While the chemical approach uses techniques such as: chemical reduction, electrochemistry, and photochemical reduction [36,37,38,39,40]. Studies have shown that during the synthesis process, size, shape, stability, and physicochemical properties of the nanoparticles are strongly influenced by a variety of factors. These factors include process parameters (temperature, concentrations, etc.), process kinetics involving the interplay between the metal ion precursors and the reducing agent, and adsorption kinetics involving the stabilizing agent and the nanoparticles [41,42]. Consequently, designing a process that effectively controls the size, shape, stability, and physicochemical properties is currently at the forefront of research into nanoparticle synthesis [43,44]. Conventional synthesis of nanoparticles can involve expensive chemical and physical processes that often use toxic materials with potential hazards such as environmental toxicity, cytotoxicity, and carcinogenicity . The toxicity problems arise from the hazardous substances, such as organic solvents, reducing agents, and stabilizers that are used to prevent unwanted agglomeration of the colloids. In addition, some nanoparticles have also been found to be toxic due to factors such as composition, size, shape, and surface chemistry. As a result, the presence of these toxic formation agents on the synthesized nanoparticles and potentially the nanoparticles themselves has prevented their clinical and biomedical application. Importantly, all these factors can be potentially controlled via biological mediated production. As a result, there is currently widespread interest in developing clean, reliable, biologically compatible, benign, and environment-friendly green processes to synthesize nanoparticles [44,46].
In recent years, biological synthesis has emerged as an attractive alternative to traditional synthesis methods for producing nanoparticles. Biosynthesis involves using an environment-friendly green chemistry based approach that employs unicellular and multicellular biological entities such as actinomycetes [47,48], bacteria [49,50,51,52,53], fungus [54,55,56,57], plants [58,59], viruses [60,61], and yeast [62,63,64]. Synthesising nanoparticles via biological entities acting as biological factories offers a clean, nontoxic and environment-friendly method of synthesizing nanoparticles with a wide range of sizes, shapes, compositions, and physicochemical properties . Another interesting feature of many biological entities is their ability to act as templates in the synthesis, assembly and organisation of nanometre scale materials to fabricate well-defined micro and macro scale structures. For example, viruses have been used to assemble gold and iron oxide nanoparticles to form microstructures , bacteriophages have also been used to form intricate nanometre and micrometre scale structures [67,68,69] and phage based assemblies of liposomes have been used in targeted drug delivery procedures [70,71,72,73]. Comparing the above-mentioned biological identities and their potential to become efficient biological factories, synthesizing nanoparticles via plants, is a relatively straight forward and advantageous approach [74,75]. In comparison with microorganisms, the plant approach is more advantageous since it does not need any special, complex, and multi-step procedures such as isolation, culture preparation, and culture maintenance. Furthermore, synthesis in plants tends to be faster than microorganisms, is more cost-effective and is relatively easy to scale up for the production of large quantities of nanoparticles [74,76,77,78,79]. The aim of this review is to present a brief overview of the techniques used to characterise nanoparticles, microbial routes for synthesising metal and metal oxide nanoparticles, use of plants extracts for synthesis of nanoparticles, factors influencing the synthesis process, possible mechanisms involved in nanoparticle formation and growth, and potential applications of nanoparticles synthesised using natural biological factories found in plants.
2. Characterisation Techniques
To date, there are numerous techniques for synthesizing nanoparticles. However, these techniques fall into two broad approaches and can be defined as either a top down approach or a bottom up approach [80,81,82]. The top down approach starts with a material of interest, which then undergoes size reduction via physical and chemical processes to produce nanoparticles. Importantly, nanoparticles are highly dependent on their size, shape, and surface structure and processing tends to introduce surface imperfections. These surface imperfections can significantly impact on the overall nanoparticle surface physicochemical properties . In the bottom up approach, nanoparticles are built from atoms, molecules and smaller particles/monomers [84,85,86]. In either approach, the resulting nanoparticles are characterized using various techniques to determine properties such as particle size, size distribution, shape, and surface area. This is of particular importance if the properties of nanoparticles need to be homogeneous for a particular application.
In the case of chemical and biological synthesis of nanoparticles, the aqueous metal ion precursors from metal salts are reduced and as a result a colour change occurs in the reaction mixture. This is the first qualitative indication that nanoparticles are being formed. One interesting property of colloidal particles in solution, due to their size and shape, is their ability to be seen when a laser beam passes through the colloidal solution. This effect is known as the Tyndall effect and is a simple and straightforward technique that can be used to detect the presence of nanoparticles in solution . After the reaction, nanoparticles can be separated from the colloid by high speed centrifugation and then examined using advanced nanocharacterization techniques.
Some of the spectroscopy and microscopy techniques routinely used include UV-visible spectroscopy (UV-vis), dynamic light scattering (DLS), atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and Raman spectroscopy. Microscopy based techniques such as AFM, SEM and TEM are considered direct methods of obtaining data from images taken of the nanoparticles. In particular, both SEM and TEM have been extensively used to determine size and morphological features of nanoparticles [87,88,89,90].
Spectroscopy based techniques such as UV-vis, DLS, XRD, EDS, FT-IR, and Raman are considered indirect methods of determining data related to composition, structure, crystal phase, and properties of nanoparticles. The UV-visible spectroscopy covers the UV range between 190 and 380 nm and the visible range between 380 and 800 nm. Both types of radiation interact with matter and promote electronic transitions from the ground state to higher energy states. Wavelengths between 300 and 800 nm are generally used for characterizing metallic nanoparticles ranging in size from 2 nm up to around 100 nm . For example, absorption measurements for silver (Ag) nanoparticles are usually between 400 and 450 nm [91,92], while gold (Au) nanoparticles are generally detected by the presence of peaks between 500 and 550 nm [93,94]. DLS spectroscopy can be used to determine size distribution and quantify the surface charge of nanoparticles suspended in a liquid [87,95]. The elemental composition of nanoparticles can be determined via EDS mapping. Whereas XRD examination produces a diffraction pattern that is subsequently compared with data contained in a standard crystallographic database to determine structural information. Analysis of the XRD data identifies crystallite size, structure, preferred crystal orientation, and phases present in samples [96,97]. FT-IR spectroscopy can be used to investigate surface chemistry and identify surface residues such as functional groups like carbonyls and hydroxyls moieties that attach to the surface during nanoparticle synthesis. Raman spectroscopy is useful in detecting vibrational modes of molecules and can be used to identify vibrational signals of a variety of chemical species that are attached to the surface of nanoparticles during synthesis . For example, using surface-enhanced Raman scattering (SERS) it was possible to measure single molecular attachments on Ag nanoparticles .
3. Biological Synthesis of Nanoparticles
Recent studies have shown that green biologically based methods using microorganisms and plants to synthesize nanoparticles are safe, inexpensive, and an environment-friendly alternative [99,100]. Both microorganisms and plants have long demonstrated the ability to absorb and accumulate inorganic metallic ions from their surrounding environment. These attractive properties make many biological entities efficient biological factories capable of significantly reducing environmental pollution and reclaiming metals from industrial waste. Importantly, the ability of a biological entity to use its inherent biochemical processes to transform inorganic metallic ions into metal nanoparticles has led to a relatively new and largely unexplored field of research . To date, the ability of microorganisms to interact, extract, and accumulate metallic materials from their surroundings has been capitalized on in a number of biotechnology applications such as bioremediation and bioleaching [102,103]. The capability of microorganisms to actively interact with their surrounding environment stems from the composition of their lipid-based amphipathic membranes enables a variety of oxidation-reduction mechanisms to take place and promote biochemical conversions [104,105,106]. Studies have shown that both unicellular and multicellular organisms achieve both extracellular and intracellular synthesis of inorganic micron and nano-sized materials as presented in Table 1, and in the case of nanoparticle synthesis, culturing microorganisms in particular environments can also assist them in promoting coupled oxidation and reduction phenomenon [104,107]. The specific oxidation-reduction mechanisms, nucleation, and subsequent nanoparticle growth kinetics and the interaction of these processes with the microorganism metabolic processes have yet to be fully explained [108,109,110,111]. Hence, there is still a considerable level of research that needs to be undertaken to fully investigate and elucidate differences in nanoparticle size and morphology between different metals when synthesized using the same microorganism [65,105]. This is also true when considering the use of plants for synthesizing nanoparticles. The advantage of using plants over other eco-friendly biologically based systems such bacteria and fungi, is that it avoids the use of specific, well-conditioned culture preparation and isolation techniques that tend to be expensive and elaborate. Conversely, biosynthesis of nanoparticles using plants or plant based extracts tends to be safe, have relatively short production times, and have a lower cultivation cost compared to other biological systems . Furthermore, plant based biosynthesis is a relatively straightforward process that can be easily scaled up for large-scale production of nanoparticles.
As mentioned above, nanoparticles can be synthesised from a wide variety of biological entities such as actinomycetes, algae, bacteria, fungus, plants, viruses, and yeast. Each biological entity has varying degrees of biochemical processing capabilities that can be effectively used to synthesize particular metallic or metallic oxide nanoparticles. Not all biological entities can synthesize nanoparticles due to their enzyme activities and intrinsic metabolic processes. Therefore, careful selection of the appropriate biological entity is necessary to produce nanoparticles with well-defined properties such as size and morphology. Generally, biological entities with a potential to accumulate heavy metals have the best chance of synthesizing metallic nanoparticles [113,114,115,116]. In the case of a microorganism, culturing methods are very important. Hence optimisation of culturing parameters such as nutrients, light, medium pH, temperature, mixing speed, and buffer strength can significantly increase enzyme activity [74,117]. Recently, the biological synthesis of nanoparticles using plants and plant extracts appears be to an attractive alternative to conventional chemical synthesis and the more complex culturing and isolation techniques needed for many microorganisms. Moreover, combinations of molecules found in plant extracts perform as both reducing and stabilizing (capping) agents during nanoparticle synthesis [118,119,120]. These biological molecules are chemically complex, but have the advantage of being environment-friendly.