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Characterisation of engineered nanomaterials in nano-enabled products exhibiting priority environmental exposure
(2021-03) Lehutso, Raisibe F; Tancu, Yolanda; Maity, Arjun; Thwala, Melusi
Analytical limitations have constrained the determination of nanopollution character from real-world sources such as nano-enabled products (NEPs), thus hindering the development of environmental safety guidelines for engineered nanomaterials (ENMs). This study examined the properties of ENMs in 18 commercial products: sunscreens, personal care products, clothing, and paints—products exhibiting medium to a high potential for environmental nanopollution. It was found that 17 of the products contained ENMs; 9, 3, 3, and 2 were incorporated with nTiO2, nAg, binaries of nZnO + nTiO2, and nTiO2 + nAg, respectively. Commonly, the nTiO2 were elongated or angular, whereas nAg and nZnO were near-spherical and angular in morphology, respectively. The size ranges (width × length) were 7–48 × 14–200, 34–35 × 37–38, and 18–28 nm for nTiO2, nZnO, and nAg respectively. All ENMs were negatively charged. The total concentration of Ti, Zn, and Ag in the NEPs were 2.3 × 10-4–4.3%, 3.4–4.3%, and 1.0 × 10-4–11.3 × 10-3%, respectively. The study determined some key ENM characteristics required for environmental risk assessment; however, challenges persist regarding the accurate determination of the concentration in NEPs. Overall, the study confirmed NEPs as actual sources of nanopollution; hence, scenario-specific efforts are recommended to quantify their loads into water resources.
Dammarane-type triterpenoids with anti-cancer activity from the leaves of Cleome gynandra
(2021-06) Mzondo, Buntubonke; Dlamini, Nomusa; Malan, FP; Labuschagne, Philip W; Bovilla, VR; Madhunapantula, SV; Maharaj, V
Three dammarane-type triterpernoids including two new ones, cleogynones A and B (1 and 2), were isolated from the leaves of Cleome gynandra. The structures of the new triterpenoids were elucidated by spectroscopic data analysis and confirmed by single crystal X-ray crystallography. All three compounds showed moderate cytotoxicity against breast cancer (MDA-MB-468), cleogynone B (2) and compound (3) further showed cytotoxicity against colorectal cancer (HCT-116 & HCT-15). Cleogynone B was also moderately active against lung cancer (A549).
Efficient catalytic reduction of nitroaromatics by recyclable 2-naphthalene sulfonic acid doped polyaniline nanotubes decorated with NiFe2O4 nanorods
(2021-03) Sypu, VS; Kear, NH; Bhaumik, M; Raju, Kumar; Maity, Arjun
A hybrid nanostructure comprising NiFe2O4 nanorods and 2-naphthalene sulfonic acid (2-NSA) doped polyaniline nanotubes (NiFe2O4@PANI/NSA) has been explored as an efficient catalyst for the reduction of nitroaromatics in the aqueous medium. The obtained NiFe2O4@PANI/NSA nanocomposites (NCs) were characterized using XRD, FE-SEM, HR-TEM, TGA, FT-IR, BET, and XPS, and their catalytic efficiencies were investigated for the reduction of nitroarenes with 4-nitrophenol (4-NP) being used as a model nitroarene. NiFe2O4@PANI/NSA exhibited excellent catalytic activity with a rate constant of 0.00557 s-1 and excellent recyclability, with the identical activity being retained after 15 successive runs. The mechanism of the reaction was proposed based on the kinetics results using the Langmuir-Hinshelwood model. The activation energy (Ea) was calculated to be 30 kJ/mol-1 for 4-NP reduction.
Flower-like structures of carbonaceous nanomaterials obtained from biomass for the treatment of copper ion-containing water and their re-use in organic transformations
(2021-08) Arunachellan, IC; Sypu, VS; Kera, NH; Pillay, K; Maity, Arjun
In the present work, raw waste material obtained from polluting dried tree fibres (raw TF) as a source of natural carbon was used for the removal of contaminating copper ions in water. Through two sequential steps of oxidation, carbonaceous adsorbent materials were obtained. Namely, tree fibre activated carbon treated with sulphuric acid (TFSA) and oxidised activated carbon modified using Hummer's method (TFHM). These materials were then characterized using techniques such as SEM, TEM, XRD, FTIR, XPS, TGA, Raman, and BET. The surface areas were found to have an increase from 0, 0.3109 and 55.0107 m2/g for raw TF, TFSA, and TFHM, respectively. The carbonaceous adsorbents were then used in batch adsorption studies for the removal of copper ions in a test water solution. The maximum adsorption capacities determined by non-linear estimation models at the optimum pH 6, were 11.04 and 80.19 mg/g for TFSA and TFHM, respectively. Furthermore, copper is known to facilitate many organic transformations such as reduction and cyclisation, thus, the spent carbonaceous adsorbents were re-used in cyclocondensation and catalytic reduction reactions to avoid discarding these into the environment and creating secondary pollutants. The initial catalytic studies of cyclocondensation of benzamine lead to 96% and 98% yield of desired product via recrystallization while catalytic reduction of 4-nitrophenol was obtained 92% within 22 min.
Fluorinated quaternary chitosan derivatives: Synthesis, characterization, antibacterial activity, and killing kinetics
(2020-11) Cele, Zamani ED; Somboro, AM; Amoako, DG; Ndlandla, Lindokuhle F; Balogun, Mohammed O
Chitosan has become an established platform biopolymer with applications in biomedical engineering, nanomedicine, and the development of new materials with improved solubility, antimicrobial activity, and low toxicity. In this study, a series of chitosan derivatives were synthesized by conjugating various perfluorocarbon chains to chitosan via Schiff base formation or nucleophilic substitution, followed by quaternization with glycidyl trimethylammonium chloride to confer non-pH-dependent permanent positive charges. Synthesized fluorinated N-(2-hydroxypropyl)-3-trimethylammonium chitosan chloride polymers were characterized and investigated for their antibacterial efficacies against multidrug-resistant bacteria including clinical isolates. The polymers showed activity against both Gram-positive and Gram-negative bacteria (MIC = 64–512 μg/mL) but with greater potency against the former. They displayed rapid bactericidal properties, based on the MBC/MIC ratio, which were further confirmed by the time-kill kinetic assays. Given the properties presented here, fluorinated quaternary chitosan derivatives can serve as great candidates to be investigated as environmentally more benign, nontherapeutic antimicrobial agents that could serve as alternatives to the heavy reliance on antibiotics, which are currently in a very precarious state due to increasing occurrence of drug resistance.
Folic acid–intercalated mg/al layered double hydroxides-a multifunctional nanohybrid delivery system for topical applications
(2024-11) Kleyi, Phumelelo E; Mandiwana, Vusani; De Beer, Miranda; Kesavan Pillai, Sreejarani; Ray, Suprakas S
The delivery of active functional molecules across the skin is laborious due to its structural intricacy and exceptional barrier characteristics. Developments in nanotechnology yielded innovative transport vehicles derived from nanomaterials to reinforce the skin’s ability to interact with active ingredient molecules and increase its bioavailability. The current study employed crystalline inorganic two-dimensional double hydroxides (LDHs) as an efficient carrier and delivery vehicle for folic acid (FA) in a topical skincare formulation. FA was incorporated into the interlayer region of Mg/Al LDHs utilizing a coprecipitation procedure to produce a nanohybrid. The nanohybrid was characterized by XRD and FTIR. FA intercalation into the interlayer galleries of the nanohybrid was confirmed by an XRD diffractogram, which established a shift of the basal d(003) reflection of LDHs to lower 2θ angles. FTIR of the nanohybrids revealed the characteristic absorption frequencies of FA, indicating the existence of FA within the LDH matrix. The FA-intercalated nanohybrid showed antioxidant activity similar to that of free FA. A topical formulation was prepared by dispersing FA-intercalated LDH nanohybrid in an oil-in-water (o/w) emulsion, and it was used to evaluate its properties further. Rheological property evaluation showed that the presence of the nanohybrid resulted in better flow behavior and higher yield stress of the formulation, implying improved stability and quality. The nanohybrid also enhanced the storage modulus and, thus, the dynamic rigidity of the formulation. The test compounds expressed no cytotoxicity in HaCaT cells, as cell viability significantly increased in monolayer cultures after a 24-h incubation period. Release studies conducted in vitro using the nanohybrid showed a pH-dependent controlled release of FA. Transdermal permeation experiments using Franz diffusion cells demonstrated a direct correlation between the concentration of penetrated FA with time, which signified a gradual and effective transfer of FA from the LDH matrix into the oil/water emulsion, demonstrating its efficacy. Thus, the study revealed excellent prospects for the nanohybrid as a multifunctional active ingredient in topical applications.
Hetero-mixed TiO2-SnO2 interfaced nano-oxide catalyst with enhanced activity for selective oxidation of furfural to maleic acid
(2021-07) Malibo, Pretrus M; Makgwane, Peter R; Baker, PGL
Herein we report on the catalytic activity of hetero-mixed TiO2-SnO2 nano-oxide catalyst for the selective liquidphase oxidation of furfural to maleic acid using H2O2 oxidant. The high surface area and strong interaction of the two oxides with modified electronic structure manifested enhanced effective oxygen vacancies, and redox activity performance of the TiO2-SnO2 catalyst for furfural oxidation reaction. The structure of the catalyst was investigated by the powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transition electron microscopy (HRTEM), electron paramagnetic resonance (EPR) and Brunauer-Emmett-Teller (BET) surface area analyser techniques. The interfaced TiO2-SnO2 oxide catalyst was more catalytically active than its single counterpart SnO2 and TiO2 oxides to give a furfural conversion of 96.2% at up to 63.8% yield of maleic acid. The catalytic performance shown by TiO2-SnO2 present encouraging prospects for an economical solid metal oxide catalyst to access biobased maleic acid from renewable biomass-derived furfural.
Layered double hydroxides: An advanced encapsulation and delivery system for cosmetic ingredients-an overview
(2020-12) Kesavan Pillai, Sreejarani; Kleyi, Phumelele E; De Beer, Marinda; Mudaly, Preensha
Topical delivery of active ingredients is very challenging because of the complex structure and excellent barrier properties of human skin. Advances in nanotechnology resulted in nanomaterial based delivery systems to augment the skin absorption of hydrophilic, hydrophobic and high molecular weight molecules. Nanostructured layered double hydroxides (LDH), owing to its exceptional features; such as large surface area, expandable interlayer space to accommodate active molecules, biocompatibility, high water holding efficiency, rheological and swelling properties, as well as cost effectiveness, have been proposed as innovative carriers of active ingredients for its effective transfer through skin. This is achieved by altering the active molecule release profiles, improving the stability of the active, increasing the solubility and bioavailability. This article intends to give an outline of recent research efforts in the development pertaining LDH based advanced skin delivery systems for cosmetic ingredients, the associated challenges and future perspectives. Special consideration is dedicated to the functionalities of LDH and its prospects in controlled release for cosmetic ingredients. The examples and discussions illustrating the application of LDH in topical delivery are centered around UV protection, skin care and antimicrobial properties.
Morphology modulated photocatalytic activity of CeO2 nanostructures for selective oxidation of biobased alphaPinene to oxygenates
(2020-11) Mavuso, MA; Makgwane, Peter R; Ray, Suprakash S
The effective Ce3+/Ce4+ redox and oxygen mobility of CeO2 induced by tunable nanostructure morphology has attracted a great interest in photocatalytic organic synthesis. Herein, we report on the microwave‐assisted synthesis of CeO2 with nanoparticles (NPs), nanorods (NRs) and nanocubes (NCs) morphologies. The optical‐electronic properties of the nanostructure CeO2 catalysts varied relatively with the respective morphologies. Ce‐NPs catalyst showed a significant blue shift while a red shift was observed for Ce‐NCs and a slight blue shift for Ce‐NRs. The Ce‐NRs and Ce‐NPs showed high charge recombination suppression, which was due to the formation of surface defects associated with dislocations, steps and oxygen vacancies (Vo) as elucidated from the photolumiscence, X‐ray photoelectron spectroscopy and electron paramagnetic resonance results. The surface oxygen defects populated with reactive superoxide oxygens of Ce‐NRs and its high surface showed better photocatalytic activity for oxidation of alpha‐pinene to pinene oxide, verbenol and verbenone as major products. A pinene conversion of 33.6 % to pinene oxide with the selectivity of 54.3 % was achieved with Ce‐NRs. The effective photocatalytic activity of the Ce‐NRs was attributed to its enhanced efficient charge recombination suppression and oxygen vacancies. Ce‐NRs catalyst was recyclable without any significant loss of its initial photoactivity.
Performance evaluation of polypyrrole-montmorillonite clay composite as a re-usable adsorbent for Cr(VII) remediation
(2020-08) Mdlalose, Lindani M; Balogun, Mohammed O; Setshedi, Katlego Z; Chimuka, L; Chetty, Avashnee
A flexible composite adsorbent combination of polypyrrole and montmorillonite clay (PPy-MMT) has been prepared by in situ oxidative polymerization method. This well-achieved adsorbent has amphoteric characteristics and has been explored in many adsorption processes related to heavy metals removal, more especially Cr(VI) from the water phase. However, the progressive accumulation of Cr(VI) onto the adsorbent surface reduces its adsorption capacity before adsorbent depletion. This factor limits the application of the adsorbent due to high cost and environmental impact related to adsorbent disposal after use. Here, we report the feasibility of different regenerating agents to recover adsorbed Cr(VI) and activate the tunable surface charge of the adsorbent composite to restore its initial adsorption capacity until exhaustion. The recycled PPy-MMT adsorbents were characterized by FTIR, TGA and EDS analysis. At low solution pH, PPy-MMT is protonated resulting in high adsorption capacity for Cr(VI) through electrostatic attraction and ion exchange while simultaneously reducing Cr(VI) to less toxic Cr(III). The spent adsorbents were reversibly subjected to sequential adsorption–desorption cycles between adsorbent neutral state and the oxidized state using different concentrations of regenerating agents including NaOH, NH4OH, HCl, NH4Cl and HNO3, respectively. The results suggested that with 0.01 M NaOH and 0.5 M HCl, PPy-MMT could be used for over five cycles for Cr(VI) removal with more than 80% regeneration efficiency indicating potential applicability as a re-usable adsorbent for Cr(VI) removal.
Preclinical assessment addressing intravenous administration of a [68 Ga]Ga-PSMA-617 microemulsion: Acute in vivo toxicity, tolerability, PET imaging, and biodistribution
(2021-04) Mandiwana, Vusani; Kalombo, Lonji; Hayeshi, R; Zeevaart, JR; Ebenhan, T
It has been herein presented that a microemulsion, known to be an effective and safe drug delivery system following intravenous administration, can be loaded with traces of [68Ga]Ga-PSMA-617 without losing its properties or causing toxicity. Following tolerated IV injections the capability of the microemulsion in altering [68Ga]Ga-PSMA-617 distribution was presented at 120 min post injection based on its ex vivo biodistribution results.
Synthesis, physicochemical characterization, toxicity and efficacy of a PEG conjugate and a hybrid PEG conjugate nanoparticle formulation of the antibiotic moxifloxacin
(2020-05) Tshweu, Lesego L; Shemis, MA; Abdelghany, C; Gouda, A; Pilcher, LA; Sibuyi, NRS; Meyer, M; Dube, A; Balogun, Mohammed O
Antibiotic resistance is increasing at such an alarming rate that it is now one of the greatest global health challenges. Undesirable toxic side-effects of the drugs lead to high rates of non-completion of treatment regimens which in turn leads to the development of drug resistance. We report on the development of delivery systems that enable antibiotics to be toxic against bacterial cells while sparing human cells. The broad-spectrum fluoroquinolone antibiotic moxifloxacin (Mox) was successfully conjugated to poly(ethylene glycol) (PEG) which was further encapsulated into the hydrophobic poly(3- caprolactone) (PCL) nanoparticles (NPs) with high efficiency, average particle size of 241.8 4 nm and negative zeta potential. Toxicity against erythrocytes and MDBK cell lines and drug release in human plasma were evaluated. Hemocompatibility and reduced cytotoxicity of the PEG–Mox and PCL(PEG– Mox) NPs were demonstrated in comparison to free Mox. Antimicrobial activity was assessed against drug sensitive and resistant: Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae. The antibacterial activity of Mox was largely maintained after conjugation. Our data shows that the toxicity of Mox can be effectively attenuated while, in the case of PEG–Mox, retaining significant antibacterial activity. At the conditions employed in this study for antimicrobial activity the encapsulated conjugate (PCL(PEG–Mox) NPs) did not demonstrate, conclusively, significant antibacterial activity. These systems do, however, hold promise if further developed for improved treatment of bacterial infections.
Use of herbal extract-based nanoemulsions for hair care application
(Elsevier, 2022-03) Okole, Blessed N; Kesavan Pillai, Sreejarani; Ndzotoyi, Phatheka, T; Phasha, Vivey M; Setapar, SM; Ahmad, A; Jawaid, M
Hair is considered an aspect of body appeal and its appearance is a gage of health in every culture. Natural hair products are becoming more in demand than synthetic products because they are considered safe and without severe side effects. The main driver of growth in natural products is the consumer’s trend towards healthier lifestyles because of the perceived health benefits and higher living standards. Hair-care product manufacturers are now capitalizing on consumers’ interest in health and wellness and have invested in new products containing natural ingredients.
Zero valent nickel nanoparticles decorated polyaniline nanotubes for the efficient removal of Pb(II) from aqueous solution: Synthesis, characterization and mechanism investigation
(2020-12) Bhaumik, M; Maity, Arjun; Brink, HG
Zero valent nickel nanoparticles (Ni0 NPs) have exhibited potential applicability in various fields including, chemical cells, fuel cells and catalysis. Alike zero valent iron NPs, Ni0 NPs and their composite nanostructures would have great prospect in remediating heavy metal pollutants from water bodies. To establish this fact composite nanotubes (CNs) of naphthalene sulfonic acid doped polyaniline (PANI-NSA) and Ni0 NPs (PANI-NSA@Ni0 CNs) were synthesized by immobilization of Ni0 NPs onto the PANI-NSA surface and effectively used for the removal of Pb(II) ions from aqueous solution. Morphological and structural characterization established that aggregation of ferromagnetic Ni0 NPs was greatly diminished by immobilization onto the matrix of PANI-NSA. Improved specific surface area and greater reactivity of the PANI-NSA@Ni0 CNs enabled superior removal performance towards Pb(II) ions in comparison with its constituents. The highest removal efficiency (90.9%) was observed using 0.5 g/L CNs at pH 5.0. Pb(II) sorption kinetics was very rapid and equilibrium was reached within 30–90 min for 50–150 mg/L concentrations at pH 5.0. The Langmuir isotherm model provided the best description of the isotherm data, with a deduced maximum Pb(II) removal capacity of 414.6 mg/g at 25 °C. Thermodynamic analysis revealed exothermic and spontaneous adsorption onto the adsorbent surface. Co-existing heavy metal ions had slight impacts on Pb(II) removal performance of the PANI-NSA@Ni0 with associated implications for the treatment of industrial wastewater. XRD and XPS analyses allude that Pb(II) adsorption onto deprotonated surface sites followed by reduction to Pb0 were the leading removal mechanism associated with the current CNs structure.

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