Research Publications/Outputs

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2D MXenes nanomaterials for removal of organic wastewater contaminants
(CRC Press, 2024-12) Mdlalose, Lindani M; Hlekelele, Lerato; Chauke, Vongaini P
The research and development of two-dimensional (2D) materials was prompted and advanced after the discovery of the remarkable physical properties of single/multiple layered graphene. This hastily encouraged more research on 2D materials in the form of manipulating the structure of graphene through exfoliation, altering the starting material with readily available layered precursors such as graphite-like hexagonal boron nitride or dichalcogenides or even layered oxides [1]. This then stimulated the development of more 2D materials including the birth of MXenes. MXenes are a group 2D transition metal carbides, carbonitrides, and nitrides discovered in 2011 [2]. Their single flakes are denoted by a chemical formula Mn+1 Xn Tx (n = 1 to 4), which designates transition metals alternating layers (M) enclosed by carbon/nitrogen (X) layers with attached terminations Tx (-O2 , -F2 , -OH2 , -Cl2 ) on the external transition metal surfaces [3]. Due to their intriguing electrical and optical properties, they play numerous roles in photodetectors. Additionally, their distinctive mechanical, chemical, and physical properties allow MXenes to be altered by various surface terminations and transition metals. The atomically narrow structure of 2D MXenes makes it an appropriate alternative material for water purification technologies. Additionally, its large surface area, excellent mechanical strength, and numerous functional groups on their surfaces make it a suitable candidate for the uptake of contaminants from aqueous medium [4]. MXenes water purification interest is facilitated by its unique adsorptive, antibacterial, and reductive properties, which are further augmented by high electrical conductivity. With the intensive industrialization and vast agricultural systems, the release of toxic contaminants into ground and surface water continues to be a strain on the environment. In this chapter, the potential use of 2D MXenes derivatives for organic contaminants (such as dyes, antibiotics, and pharmaceuticals) removal is addressed. This entails mechanistic pathways of using MXene-based materials as adsorbents, water purification membranes, and photocatalysts. The ability of MXenebased composites in showing catalytic activity toward diverse pollutants and superior selectivity toward specific pollutants will be discussed.
A comprehensive review of metal-organic frameworks sorbents and their mixed-matrix membranes composites for biogas cleaning and CO2/ CH4 separation
(2024-09) Duma, Zama G; Makgwane Peter R, MN; Masukume, Mike; Swaartbooi, Ashton M; Rambau, Khavharendwe; Mehlo, Thembelihle; Mavhungu, Tshidzani
Metal-organic framework (MOF) sorbent materials have recently gained considerable attention in gas separation technology. This is because of their unique structural properties, such as high gas permeability and selectivity promoted by large porosity and high surface areas. Integrating MOF fillers with polymer membranes to construct mixed-matrix membranes (MMMs) has enhanced gas separation and capture performance and stability. This review provides a comprehensive current status development in MOFs and their integrated MMMs composites with focused applications in biogas cleaning for the removal of common trace impurities such as hydrogen sulfide (H2S), ammonia (NH3), siloxanes, and moisture and upgrading of the subsequent carbon dioxide/methane (CO2/CH4) mixture to bio-methane and biogenic CO2. We highlight the structural properties and descriptors critical for designing MOF sorbents and MOF-based MMMs to improve their adsorption capacities and separation efficiency in biogas cleaning and upgrading. The tuneable surface modifications of MOFs boasted by the surface-endowed basic-acidic sites and coordinated open metal sites effectively provide high adsorption capacities and separation selectivities in biogas processing. The combination of MOFs and membranes offers high separation efficiencies of biogas-derived CO2 and CH4 for their diverse potential downstream utilisation. Future perspectives on advancing further developments in MOF sorbents and MOFs-based MMMs for biogas cleaning and upgrading to access sustainable and green derivatives with fewer carbon footprints while beneficiating wastes for adopting a circular economy are highlighted to provide solutions to the shortcomings.
A review of weathering studies in plastics and biocomposites— Effects on mechanical properties and emissions of volatile organic compounds (VOCs)
(2024-04) Nzimande, Monwabisi C; Mtibe, Asanda; Tichapondwa, S; Mathew, Maya J
Polymeric materials undergo degradation when exposed to outdoor conditions due to the synergistic effects of sunlight, air, heat, and moisture. The degradation can lead to a decline in mechanical properties, fading, surface cracking, and haziness, attributed to the cleavage of the polymer chains and oxidation reactions. Accelerated weathering testing is a useful technique to evaluate the comparative photodegradation of materials within a reasonable timeframe. This review gives an overview of the different degradation mechanisms occurring in conventional plastics and bio-based materials. Case studies on accelerated weathering and its effect on the mechanical properties of conventional plastics and biocomposites are discussed. Different techniques for analysing volatile organic emissions (VOCs) have been summarized and studies highlighting the characterization of VOCs from aged plastics and biocomposites after aging have been cited.
A review on thermally induced phase separation technology in the fabrication of microporous polymer membrane devices for sustained-repellent delivery: Crystallization and morphological studies
(2024-08) Tewo, RK; Mapossa, AB; Ray, Suprakas S; Mhike, W; Sundararaj, U
This article reports recent advances in thermally induced phase separation technology in fabricating microporous scaffold polymeric membranes as devices suitable for the controlled release of insect repellent. The key aspects, such as the crystallization behavior and morphological study of the polymeric membrane-based repellent, were reported and discussed. Studies demonstrated that trapping of such repellents into microporous polymeric materials can be achieved by spinodal decomposition of the polymer/liquid repellent system. Usually, solubility is enhanced at elevated temperatures. Rapid cooling of such solution below the UCST leads to the formation of cocontinuous phase structures by decomposition. The polymer then forms an open-cell structure with the repellent trapped inside. Approaches to forming such an open-cell polymer structure containing mosquito repellent were successfully performed and confirmed with the SEM and POM techniques. It showed the structure of a polymer and liquid repellent prepared by spinodal decomposition, providing proof that thermally induced spinodal decomposition is a route to trap liquid mosquito repellent into a microporous polymer matrix. Additionally, the effects of polymer type, repellent nature, cooling conditions, and fillers on the morphology and performance of TIPS membranes are also discussed. Finally, challenges in developing microporous polymeric membrane-based repellent using TIPS technology are addressed.
Active nanocomposite films based on low density polyethylene/organically modified layered bouble hydroxides/thyme oil to retain retail shelf life and quality of hass avocados
(2020-12) Kesavan Pillai, Sreejarani; Sivakumar, D; Ray, Suprakas S; Obianom, P; Eggers, Sharon K; Mhlabeni, T
In this study, the ability of an active film containing volatile bioactives in post-harvest disease control and preservation of quality in avocados is explored as a non-traditional treatment method. Antimicrobial transparent flexible trilayer low density polyethylene (LDPE) films containing organically modified layered double hydroxides (OLDH) and plant bioactive-thyme oil (TO) were made using single step blown film extrusion. Antifungal effects of the packaging in comparison to commercial treatment and untreated control showed considerable reduction in anthracnose disease events in ‘Hass’ cultivar of avocados while improving the fruit quality. 2wt% OLDH loading improved the oxygen and moisture barrier properties while not affecting the transparency of the film. The results suggest that the synergistic effect of barrier and antimicrobial properties of the controlled volatile bioactive release of the nanocomposite film can be utilised as a prospective strategy to modify the headspace gas composition to combat anthracnose disease in avocados.
Active nanocomposite films based on low density polyethylene/organically modified layered bouble hydroxides/thyme oil to retain retail shelf life and quality of hass avocados
(2020-11) Kesavan Pillai, Sreejarani; Sivakumar, D; Ray, SS; Obianom, P; Eggers, SK; Mhlabeni, T
In this study, the ability of an active film containing volatile bioactives in post-harvest disease control and preservation of quality in avocados is explored as a non-traditional treatment method. Antimicrobial transparent flexible trilayer low density polyethylene (LDPE) films containing organically modified layered double hydroxides (OLDH) and plant bioactive-thyme oil (TO) were made using single step blown film extrusion. Antifungal effects of the packaging in comparison to commercial treatment and untreated control showed considerable reduction in anthracnose disease events in ‘Hass’ cultivar of avocados while improving the fruit quality. 2wt% OLDH loading improved the oxygen and moisture barrier properties while not affecting the transparency of the film. The results suggest that the synergistic effect of barrier and antimicrobial properties of the controlled volatile bioactive release of the nanocomposite film can be utilised as a prospective strategy to modify the headspace gas composition to combat anthracnose disease in avocados.
Adsorption of NH3 and NO2 molecules on sn-doped and undoped ZnO (101) surfaces using density functional theory
(2022) Dima, Ratshilumela S; Tshwane, David M; Shingange, Katekani; Modiba, Rosinah; Maluta, NE; Maphanga, Rapela R
The adsorption and interaction mechanisms of gaseous molecules on ZnO surfaces have received considerable attention because of their technological applications in gas sensing. The adsorption behavior of NH3 and NO2 molecules on undoped and Sn-doped ZnO (101) surfaces was investigated using density functional theory. The current findings revealed that both molecules adsorb via chemisorption rather than physisorption, with all the adsorption energy values found to be negative. The calculated adsorption energy revealed that the adsorption of the NH3 molecule on the bare ZnO surface is more energetically favorable than the adsorption of the NO2 molecule. However, a stable adsorption configuration was discovered for the NO2 molecule on the surface of the Sn-doped ZnO surface. Furthermore, the adsorption on the undoped surface increased the work function, while the adsorption on the doped surface decreased. The charge density redistribution showed charge accumulation and depletion on both adsorbent and adsorbate. In addition, the density of states and band structures were studied to investigate the electronic behavior of NH3 and NO2 molecules adsorbed on undoped and Sn-doped ZnO (101) surfaces.
Advancements and perspectives in folate-based anticancer drugs: Bridging quantum and classical mechanics in folate receptor research
(2024) Josiah, Andrea J; Govender, KK; Govender, PP; Ray, Suprakas S
This review highlights the role of computational chemistry, specifically quantum and molecular mechanics, in the development of folate-based anticancer drugs. Folate receptors (FRs) are overexpressed in cancerous cells, rendering these receptors a key focus in the design of targeted drug delivery systems. These computational tools are fundamental for analyzing drug–receptor interactions and overcoming the limitations of traditional drug development processes. A 10-year literature survey demonstrated advancements in employing FRs for targeted cancer therapy. Key findings reveal that structural modifications to folate derivatives consistently enhance binding affinities and specificity toward FRα and FRβ. Computational methodologies predicted and analyzed molecular interactions, validated by experimental data. Functional groups play a crucial role in enhancing binding stability and interaction strength within FR binding pockets. Detailed structural insights into folate derivatives and antifolates interacting with FRs have identified critical residues involved in binding, aiding the design of targeted therapeutics.
Advances in CRISPR-Cas systems for blood cancer
(2024-08) Monchusi, Bernice A; Dube, Phumzile; Takundwa, Mutsa M; Kenmogne, Vanelle L; Thimiri Govinda Raja, Deepak B
CRISPR-Cas systems have revolutionised precision medicine by enabling personalised treatments tailored to an individual's genetic profile. Various CRISPR technologies have been developed to target specific disease-causing genes in blood cancers, and some have advanced to clinical trials. Although some studies have explored the in vivo applications of CRISPR-Cas systems, several challenges continue to impede their widespread use. Furthermore, CRISPR-Cas technology has shown promise in improving the response of immunotherapies to blood cancers. The emergence of CAR-T cell therapy has shown considerable success in the targeting and correcting of disease-causing genes in blood cancers. Despite the promising potential of CRISPR-Cas in the treatment of blood cancers, issues related to safety, ethics, and regulatory approval remain significant hurdles. This comprehensive review highlights the transformative potential of CRISPR-Cas technology to revolutionise blood cancer therapy.
Advances in yeast probiotic production and formulation for preventative health
(2024-11) Moonsamy, Ghaneshree; Roets-Dlamini, Yrielle; Langa, Cebeni N; Ramchur, Santosh O
The use of probiotics has been gaining popularity in terms of inclusion into human diets over recent years. Based on properties exerted by these organisms, several benefits have been elucidated and conferred to the host. Bacteria have been more commonly used in probiotic preparations compared to yeast candidates; however, yeast exhibit several beneficial properties, such as the prevention and treatment of diarrhea, the production of antimicrobial agents, the prevention of pathogen adherence to intestinal sites, the maintenance of microbial balance, the modulation of the immune system, antibiotic resistance, amongst others. Saccharomyces boulardii is by far the most studied strain; however, the potential for the use of other yeast candidates, such as Kluyveromyces lactis and Debaryomyces hansenii, amongst others, have also been evaluated in this review. Furthermore, a special focus has been made regarding the production considerations for yeast-based probiotics and their formulation into different delivery formats. When drafting this review, evidence suggests that the use of yeasts, both wild-type and genetically modified candidates, can extend beyond gut health to support skin, the respiratory system, and overall immune health. Hence, this review explores the potential of yeast probiotics as a safe, effective strategy for preventative health in humans, highlighting their mechanisms of action, clinical applications, and production considerations.
Aldolase: A desirable biocatalytic candidate for biotechnological applications
(2024-01) Mathipa-Mdakane, Moloko G; Steenkamp, Lucia H
The utilization of chemical reactions is crucial in various industrial processes, including pharmaceutical synthesis and the production of fine chemicals. However, traditional chemical catalysts often lack selectivity, require harsh reaction conditions, and lead to the generation of hazardous waste. In response, biocatalysis has emerged as a promising approach within green chemistry, employing enzymes as catalysts. Among these enzymes, aldolases have gained attention for their efficiency and selectivity in catalyzing C-C bond formation, making them versatile biocatalysts for diverse biotechnological applications. Despite their potential, challenges exist in aldolase-based biocatalysis, such as limited availability of natural aldolases with desired catalytic properties. This review explores strategies to address these challenges, including immobilization techniques, recombinant expression, and protein engineering approaches. By providing valuable insights into the suitability of aldolases as biocatalysts, this review lays the groundwork for future research and the exploration of innovative strategies to fully harness the potential of aldolases in biotechnology. This comprehensive review aims to attract readers by providing a comprehensive overview of aldolase-based biocatalysis, addressing challenges, and proposing avenues for future research and development.
Algae infused enhancement of PBAT stiffness: Investigating the influence of algae content on mechanical and thermal properties
(2024) Letwaba, J; Motloung, Mpho P; Muniyasamy, Sudhakar; Mavhungu, L; Mbaya, R; Okpuwhara, R
This study investigates the impact of algae loading on the properties of PBAT/algae bio-composites produced through a melt extrusion process. The integration of algae as a filler demonstrated a reinforcing effect on the PBAT matrix,leading to an increase in modulus with higher algae loading. Concurrently, the tensile strength and maximum tensile strain of PBAT decreased with an increase in algae content. The thermal stability of PBAT was affected by adding algae, resulting in bio-composites exhibiting an intermediate behavior compared with their neat precursors. The optimal formulation is achieved with 20 wt.% of algae incorporated into the PBAT matrix. The produced PBAT/algae bio-composites, demonstrated versatile applications across a wide range of products.
An African perspective on genetically diverse human induced pluripotent stem cell lines
(2024-10) Hurrell, Tracey; Naidoo, Jerolen; Ntlhafu, Tiro; Scholefield, Janine
Human induced pluripotent stem cell-derived models are a well-established preclinical tool, with the ability to retain the genetics of the individual from which they are derived. Here we comment on the global representation and accessibility of such cellular tools from African population groups.
Analytical techniques to quantify modifiers in bitumen for the South African asphalt pavement industry
(2021-07) Makhari, A; Hawes, Nomashaka BN; Mturi, George AJ; Ojijo, Vincent O
Modifying bitumen is currently a common practice in South Africa. The asphalt pavement industry has seen an increase in use of different types of modifiers in an attempt to improve or extend the properties of bitumen. Common modifiers used in South Africa include plastomers (e.g. ethylene vinyl acetate or EVA), elastomers (e.g. styrene-butadiene-styrene or SBS) and warm mix additives (e.g. waxes). Bitumens are already complex materials which can be represented mechanically and rheologically with mathematical models. Recently, the need to also characterise the in situ structural and chemistry effect of modifiers within bitumen has been appreciated, in order to determine their influence on modified bitumen performance. This paper explores the analysis of bitumen with various modifiers using Fourier Transform Infra-Red (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC). Special attention is paid to quantification of these modifiers in bitumen as a quality control and forensic investigative tool, due to the current asphalt failure challenges facing the industry. The aim is to accurately determine the extent of modification through analytical techniques as a monitoring tool for the better construction of asphalt pavement roads. The paper shows such analytical scientific techniques have the potential to quantify locally used modifiers in South African bitumen.
Anti-mycobacterial peroxides: A new class of agents for development against tuberculosis
(2020) Van der Westhuyzen, Christiaan W; Haynes, J; Panayides, Jenny-Lee; Wiid, I; Parkinson, C
Background: With few exceptions, existing tuberculosis drugs were developed many years ago and resistance profiles have emerged. This has created a need for new drugs with discrete modes of action. There is evidence that tuberculosis (like other bacteria) is susceptible to oxidative pressure and this has yet to be properly utilised as a therapeutic approach in a manner similar to that which has proven highly successful in malaria therapy. Objective: To develop an alternative approach to the incorporation of bacterial siderophores that results in the creation of antitubercular peroxidic leads for subsequent development as novel agents against tuberculosis. Methods: Eight novel peroxides were prepared and the antitubercular activity (H37Rv) was compared to existing artemisinin derivatives in vitro. The potential for toxicity was evaluated against the L6 rat skeletal myoblast and HeLa cervical cancer lines in vitro. Results: The addition of a pyrimidinyl residue to an artemisinin or, preferably, a tetraoxane peroxidic structure results in antitubercular activity in vitro. The same effect is not observed in the absence of the pyrimidine or with other heteroaromatic substituents. Conclusion: The incorporation of a pyrimidinyl residue adjacent to the peroxidic function in an organic peroxide results in anti-tubercular activity in an otherwise inactive peroxidic compound. This will be a useful approach for creating oxidative drugs to target tuberculosis.
Antibiotic 3D printed Materials for healthcare applications
(Elsevier Inc, 2020-05) Mokhena, Teboho C; John, Maya J; Mochane, MJ; Sadiku, ER; Motsoeneng, TS; Mtibe, Asanda; Tsipa, PC; Kokkarachedu, V; Kanikireddy, V; Sadiku, R
Since its introduction in the past 25 years, three-dimensional (3D) printing has been a major research topic owing to its potential to overcome the limitations of conventional 3D manufacturing techniques, that is, to control the overall architecture toward various applications. In the third (2013–present) decade, 3D printing enters a new phase in which researchers fabricate clinical constructs that benefit the current society. In this chapter, we briefly discuss the recent progress of 3D printing and challenges related to the antibiotic materials and manufacturing process for biomedical applications.
Application of electrospun materials in oil–water separations
(Scrivener Publishing LLC, 2020-04) Mokhena, Teboho C; John, Maya J; Mochane, MJ; Tsipa, PC; Boddula, RI; Ahamed, MI; Asiri, AM
There has been ever-increasing pressure to come up with novel strategies for oily wastewater treatment since it affect the available water sources, crop production, aquatic life and human health. Electrospun nanofibrous materials with attractive attributes, such as interconnected porous structure, large surface-to-area ratio, malleable mechanical properties, tuneable wettability, and porosity have a huge potential for oily wastewater treatment. In this chapter, the recent progress of oil/ water separation using electrospun nanofibrous materials is reviewed. The challenges and future prospects of this new field are also described.
Application of monoclonal anti-mycolate antibodies in serological diagnosis of tuberculosis
(2024-11) Truyts, Alma E; Du Preez, Ilse; Maesela, Maushe E; Scriba, Manfred R; Baillie, L; Jones, AT; Land, KJ; Verschoor, JA; Lemmer, Yolandy
Patient loss to follow-up caused by centralised and expensive diagnostics that are reliant on sputum is a major obstacle in the fight to end tuberculosis. An affordable, non-sputum biomarker-based, point-of-care deployable test is needed to address this. Serum antibodies binding the mycobacterial cell wall lipids, mycolic acids, have shown promise as biomarkers for active tuberculosis. However, anti-lipid antibodies are of low affinity, making them difficult to detect in a lateral flow immunoassay—a technology widely deployed at the point-of-care. Previously, recombinant monoclonal anti-mycolate antibodies were developed and applied to characterise the antigenicity of mycolic acid. We now demonstrate that these anti-mycolate antibodies specifically detect hexane extracts of mycobacteria. Secondary antibody-mediated detection was applied to detect the displacement of the monoclonal mycolate antibodies by the anti-mycolic acid antibodies present in tuberculosis-positive guinea pig and human serum samples. These data establish proof-of-concept for a novel lateral flow immunoassay for tuberculosis provisionally named MALIA—mycolate antibody lateral flow immunoassay.
Assessing a sustainable manufacturing route to lapatinib
(2022-08) Stark, RT; Rye, DR; Newton, OJ; Deadman, BJ; Miller, PW; Panayides, Jenny-Lee; Riley, Darren L; Helldardt, K; Hii, KK
A synthetic route to an anti-cancer drug, lapatinib, was devised to support the development of a sustainable manufacturing process in South Africa. Quantitative metrics were employed to evaluate the sustainability of the key steps of the reaction.
Assessing potential drug-drug interactions between clofazimine and other frequently used agents to treat drug-resistant tuberculosis
(2024-04) Kengo, A; Nabeemeeah, F; Denti, P; Sabet, R; Okyere-Manu, G; Abraham, P; Weisner, L; Mosala, MH; Tshabalala, Sibongile; Scholefield, Janine
Clofazimine is included in drug regimens to treat rifampicin/drug-resistant tuberculosis (DR-TB), but there is little information about its interaction with other drugs in DR-TB regimens. We evaluated the pharmacokinetic interaction between clofazimine and isoniazid, linezolid, levofloxacin, and cycloserine, dosed as terizidone. Newly diagnosed adults with DR-TB at Klerksdorp/Tshepong Hospital, South Africa, were started on the then-standard treatment with clofazimine temporarily excluded for the initial 2 weeks. Pharmacokinetic sampling was done immediately before and 3 weeks after starting clofazimine, and drug concentrations were determined using validated liquid chromatography-tandem mass spectrometry assays. The data were interpreted with population pharmacokinetics in NONMEM v7.5.1 to explore the impact of clofazimine co-administration and other relevant covariates on the pharmacokinetics of isoniazid, linezolid, levofloxacin, and cycloserine. Clofazimine, isoniazid, linezolid, levofloxacin, and cycloserine data were available for 16, 27, 21, 21, and 6 participants, respectively. The median age and weight for the full cohort were 39 years and 52 kg, respectively. Clofazimine exposures were in the expected range, and its addition to the regimen did not significantly affect the pharmacokinetics of the other drugs except levofloxacin, for which it caused a 15% reduction in clearance. A posteriori power size calculations predicted that our sample sizes had 97%, 90%, and 87% power at P < 0.05 to detect a 30% change in clearance of isoniazid, linezolid, and cycloserine, respectively. Although clofazimine increased the area under the curve of levofloxacin by 19%, this is unlikely to be of great clinical significance, and the lack of interaction with other drugs tested is reassuring.

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