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A smartphone-based application for the colorimetric detection of lead in wastewater using gold nanoparticles
(2025) Kubheka, Penuel Nkanyezi; Mokhothu, Thabang Hendrica; Shange, Sindisiwe Fortunate; Mdluli, Phumlani Selby
This study was conducted to develop and validate a straightforward, selective, and efficient colorimetric optical sensor that relies on gold nanoparticles for the detection and quantification of Pb(II) in wastewater systems. Gold nanoparticles were synthesized by chemical reduction of gold(III) chloride trihydrate, with trisodium citrate as a stabilizing agent to prevent aggregation. The synthesized AuNPs were characterized by ultraviolet-visible (UV-Vis) spectroscopy and transmission electron microscopy (TEM), confirming a spherical morphology with an average diameter of approximately 20 nm and a characteristic surface plasmon resonance (SPR) peak at 520 nm. The detection mechanism was based on Pb(II)-induced nanoparticle aggregation, resulting in a visible color change from red to blue. Quantitative analysis was conducted using both UVVis spectroscopy and digital image processing in ImageJ. The method was further validated using spiked river and tap water samples across a concentration range of 0.1–20 mg/L. Selectivity was assessed in the presence of potential interfering ions, while colorimetric response was analysed using the CIE Lab* color space. The presence of Pb(II) resulted in a red shift in the UV-Vis spectra, with the identification of two distinct SPR peaks at 520 nm and 680 nm, confirming nanoparticle aggregation. The colorimetric sensor demonstrated a strong linear response over the concentration range of 0.0520.0 mg/L (R² = 0.9901), with a detection limit of 0.01 mg/L. The recovery studies yielded values of 93%-99% for the ImageJ method and 88%-98% for the UV-Vis method. The Analysis of wastewater samples revealed Pb(II) concentrations ranging from 0.0 to 0.0379 mg/L. Then, minimal interference from other metal ions (Cr, Cu, Fe, Ni, Zn, Mn) was observed, indicating high selectivity. Colour analysis showed a systematic transition from red to green in the CIE Lab* space, with increasing Pb(II) concentration strongly correlating with measurable colour variation. The colorimetric sensor based on AuNPs developed provides a swift, cost-efficient, and exceptionally selective means for detecting Pb(II) in wastewater. The robust alignment between ImageJ and UV-Vis results indicates that smartphone image analysis can serve as a reliable alternative to standard spectrophotometric techniques. This strategy holds significant potential for on-site environmental assessments and in settings with limited resources.
Metagenomic fingerprinting of waterborne enteric viruses and their inhibition using phyto-nanomaterials
(2025) Lanrewaju, Adedayo Ayodeji; Swalaha, Feroz Mahomed; Folami, Abimbola Motunrayo; Sabiu, Saheed
Waterborne enteric viruses are major causes of diseases including gastroenteritis, hepatitis, encephalitis, meningitis, conjunctivitis, and respiratory disorders. Transmission occurs primarily through the faecal-oral channel via contaminated water or food, constituting significant public health risks. These viruses have been reported in South Africa following exposure to contaminated surface waters, dams, and wastewater. Nevertheless, limited data exist on their prevalence, diversity and abundance, especially in wastewater treatment plants (WWTPs) in eThekwini Municipality, Durban, KwaZulu-Natal, South Africa, necessitating metagenomic surveillance. In addition, the development of resistance to conventional drugs and high treatment costs necessitates the development of novel approaches to identify inexpensive and efficient antiviral medications. Interestingly, Spondias mombin and Macaranga barteri extracts have exhibited antiviral activity against several enteric viruses while Dicerocaryum eriocarpum with reported antibacterial activity remain unexplored as a reservoir of antiviral drug candidates. Accordingly, for the first time, this study profile the prevalence and diversity of viral families, including human and plant pathogenic viruses at the selected WWTPs and receiving rivers in eThekwini, Durban, Kwazulu-Natal, South Africa, using metagenomics next-generation sequencing (mNGS) approach and evaluates metabolites from S. mombin, M. barteri and D. eriocarpum against severe acute respiratory syndromecoronavirus-2 (SARS-CoV-2) and rotavirus A (RVA) using in silico techniques. The mNGS viral surveillance investigation identified viral families with a wide range of hosts including vertebrates (19.46%), plant (6.89%), insect (1.90%), fungal (0.13%), unclassified (7.25%) and phages (64.37%). Altogether, 30 viral families encompassing 26 different human pathogenic viral species were identified including enteroviruses, hepatovirus A, rotavirus A, norovirus, and astrovirus A. Conversely, plant viruses accounted for eight families dominated by the Virgaviridae. Most phytopathogenic reads belonged to the Tobamovirus genus, with additional representation from the family Bromoviridae detected across all sampling sites except RIVER4. These findings highlight the significance of wastewater surveillance in tracking known infections and unveiling possible emerging viral threats. RVA, one of the commonest waterborne enteric viruses detected in this study and SARS-CoV-2, although not detected in this study, probably due to low circulation within the communities at the time of sampling, were selected due to their clinical relevance and therapeutic limitations for in silico drug discovery from selected antiviral plants (S. mombin, M. barteri and D. eriocarpum). Molecular docking identified top-ranked compounds with higher negative docking scores against SARS-CoV-2 and RVA targets from the 77 pooled metabolites identified from the three selected medicinal plants against each of the investigated targets [main protease and RNAdependent RNA polymerase (RdRp)] of SARS-CoV-2 and RVA [capsid protein (VP7A, VP7C, VP7D), RdRp (VP1), spike protein (VP5*, VP8*)]. A minimum of three top-ranked compounds were subsequently identified owing to their physicochemical, pharmacokinetic and toxicological profiles suitable for drug development. The profiled top ranked compounds against the selected druggable targets of SARS-CoV-2 and RVA were subsequently subjected to 120-ns molecular dynamics (MD) simulations using the in-house HEAL1361 program with the Amber 18 package of the Centre for High Performance Computing (CHPC), South Africa. At least three of the top-ranked compounds exhibited higher negative binding free energy across the evaluated targets, suggesting structural and thermodynamic compatibility of the ligands at the binding domain of the targets and their suitability for drug development thereby validating the antiviral potential of the selected medicinal plants. However, against SCMP, only quercetin 3-O-rhamnoside had a higher negative binding free energy, suggesting the need for optimization of other metabolites. Notably, chrysoeriol7-glucuronide and spiraeoside demonstrated broad-spectrum affinity for RdRp of SARS-CoV-2 and RVA. Furthermore, (2S)- 6-(gamma,gamma-dimethylallyl)-3’,4’-dimethoxy-6’’,6’’- dimethylpyran[2’’,3’’:7,8]flavanone (2SG) and sericetin had better broad-spectrum affinities for both RVA VP5* and VP8*, while 2SG, apigenin-4 ′-glucoside and gnetin L exhibited better broad-spectrum affinities for RVA VP7A, VP7C and VP7D, suggesting their potential as multitarget antiviral candidates. However, some compounds induce higher thermodynamic entropy within the proteins relative to the standard. For instance, against VP5*, 2SG (-20.98 kcal/mol, 1.88 Å), sericetin (-20.46 kcal/mol, 1.93 Å) and sacranoside (-16.96 kcal/mol, 1.50 Å), though having higher negative binding free energies, exhibited higher RMSD values compared to the standard (1.30 Å) and unbound VP5* (1.45 Å). A partly similar trend was illustrated against VP8*, where sericetin (-18.31 kcal/mol, 1.27 Å) and 2SG (-20.98 kcal/mol, 1.18 Å) exhibited higher negative binding free energies yet had higher RMSD and RMSF values respectively, compared to the standard (1.19 Å, 1.01 Å). This observation highlights the need for optimizing these leads to improve their thermodynamic stability while boosting their affinity for the target proteins. Thus, due to their critical role in viral entry and infection, silver complexation optimization was limited to VP5* and VP8* of RVA to block the first and most vulnerable stage of infection. Accordingly, the silver complexation approach was employed to model possible silver nanoparticle conjugates for each lead compound, treating the compound as the reducing and capping agent. Thereafter, the effect of the complexation was evaluated whether complexation of the lead compound with silver enhances their binding affinity in silico. Improved binding affinity enhances drug activity through silver complexation which help mitigate drug resistance, broaden activity spectrum and enhance potency in vitro and in vivo. Thus, the study adopted silver complexation approach by conjugating silver with identified lead compounds against VP5* and VP8* via in silico modelling to achieve improved activity, reduced toxicity and maintain favorable pharmacokinetic profiles. To comprehend the effect of the complexation, quantum chemical calculations (density functional theory) were used to compare the molecular features of the silver-complexed leads against the lead compounds alongside assessment of drug-likeness and toxicity profiles. Thereafter, 12 and 19 silvercomplexed leads were docked against VP5* and VP8* respectively, followed by comparative interaction analysis between lead and silver-complexed compounds. Notably, the silvercomplexed leads exhibited enhanced molecular properties, suggesting better reactivity than their corresponding lead compounds without significantly altering their pharmacokinetic properties and toxicity profiles; hence, they remain suitable for drug development. Remarkably, higher negative docking scores were observed in all silver-complexed leads docked against VP5* compared to their corresponding lead compounds, except in the sacranoside A series. Conversely, lower negative docking scores were reported in the apigenin-4'-glucoside series, gnetin L A-E, and sericetin B relative to their lead compounds, while the remaining silvercomplexed leads exhibited improved binding affinity. Comparative interaction analysis identified 2SGC (-6.59 kcal/mol) and 2SGA (-6.77 kcal/mol) against VP5* and 2SGC (-8.06 kcal/mol) and SERA (-7.26 kcal/mol) against VP8* as promising candidates. Further computational investigation, including MD simulation, is recommended to elucidate the thermodynamics profile of the resulting protein and silver-complexed leads. Summarily, the observed enhanced binding capability of the silver-complexed leads could be attributed to their higher reactivity and increased interactions with essential amino acids at the binding pocket of the targets investigated. To validate the therapeutic potential of the profiled silver-complexed leads in combating viral infections, complementary in vitro and in vivo studies are strongly recommended.
Production of mycosporine-like amino acids from Euhalothece sp. for use as a photoprotectant
(2025) Mahmud, Uwais; Rawat, Ismail; Mogany, Trisha; Bux, Faizal
Protecting skin from harmful UV radiation is a well-recognized health imperative. Given that UV exposure is a primary cause of sunburn, premature skin aging, and significantly increases the risk of skin cancers including melanoma, the use of sunscreens has become a vital tool in public health strategies, leading to their widespread use. Whilst effective, there are concerns about the longterm effects of synthetic sunscreen ingredients that are driving the search for natural alternatives. Cyanobacteria are constantly exposed to short-wave ultraviolet (UV) radiation as they require solar energy to perform processes such as photosynthesis and nitrogen fixation. These microorganisms have developed multiple UV defence mechanisms to protect themselves from the higher amounts of UV radiation in the environment. Some of these strategies include mat formation, active repair mechanisms, accumulation of detoxifying enzymes and antioxidants, and synthesis of photo-protectants such as mycosporine-like amino acids (MAAs) (Rastogi et al., 2014). Mycosporine-like amino acids have gained a lot of interest in cosmetics and pharmaceutical industries since they act as natural photoprotectants and have shown to aid in overcoming rashes, pigmentation, aging as well as possess anticancer properties. Mycosporine-like amino acids are secondary metabolites produced by cyanobacteria in response to environmental stress such as salinity, temperature, high light irradiance and UV wavelengths. Cyanobacteria are a good source of MAAs, can be easily cultivated and requires a very short generation time, making them an environmentally friendly source of alternate photoprotectants. This study focuses on elucidating factors affecting MAA production using indigenous halophilic cyanobacteria Euhalothece sp. Light, salinity, and nitrogen concentration were optimised using response surface methodology to maximise MAA production. UV light irradiance was used to further induce expression of the protein. DNA was extracted and purified for gene expression analysis targeting the mys gene cluster. Purified MAAs were tested for their antioxidant activity and their stability under a range of temperatures, pH and UV irradiance to assess their potential for commercial use. Preliminary experiments confirmed the individual influence of abiotic factors, with light and salinity significantly impacting MAA production (p = 0,0395 and p = 0,0009 respectively). Using response surface methodology (RSM), the effects of light irradiance, salinity, nitrogen concentration, and UV exposure were optimized. A significant model (p = 0,0099) was developed, predicting optimal MAA production under 92 hours of UV exposure, nitrogen deficiency, and high salinity (90 or 120 g/L). Using 90 g/L salt was more cost-effective, requiring 28% less salt for a 5,36% reduction in MAA production. Molecular analysis through PCR confirmed the presence of the MAA biosynthetic gene cluster utilizing the OMT and DHQS and demonstrated its upregulation in response to UV exposure through qPCR. The UV-exposed culture showed amplification around cycle 14 while the control showed amplification around cycle 26. Purified MAAs demonstrated antioxidant activity and high stability across varying conditions over 48 hours. This included room temperature and neutral pH (p = 0,02), 4°C (p = 0,046), 40°C (p = 0,041) and UV irradiance (p = 0,04). These compounds showed excellent stability across various conditions, effectively maintaining their protective abilities. While their antioxidant capacity was measured (50,15%), it was clear that the main strength of MAAs lies in their strong UV protecting ability, making them highly suitable as active ingredients. This study demonstrates the potential of MAAs from Euhalothece sp. as a highly stable, effective, naturally derived, and industrially viable product. The optimized culture conditions, validated by molecular techniques, coupled with the high stability and additional beneficial properties of MAAs, position them as a compelling natural resource. Mycosporine-like amino acids can significantly advance photoprotection strategies and offer several other valuable applications in the cosmetic and pharmaceutical industries.
Characterisation and antiproliferative effect of okra seed protein isolate on human cancer cell lines
(2025) Maistry, Letisha; Mellem, John Jason; Gerrano, Abe Shegro
The increasing interest in plant-derived bioactive compounds has led to significant focus on okra seed protein isolate (OSPI) due to its notable nutritional and therapeutic properties. This research explores the structural and molecular characteristics of OSPI, aiming to assess its potential application as a nutraceutical in cancer therapy. A comprehensive amino acid profile showed that OSPI is rich in glutamic acid (14.46 g/100g), aspartic acid (7.56 g/100g), and arginine (9.42 g/100g), with a high proportion of hydrophobic (31.39 g/100g), and branched-chain amino acids (14.24 g/100g), known to support immune modulation and antitumour activity. Solubility analysis demonstrated peak protein solubility (91.86%) at pH 9, which is a critical factor affecting its functional efficacy. Molecular weight profiling indicated the presence of 7S and 11S globulin polypeptides, which are associated with encapsulation efficiency in nutraceutical development. Spectroscopic analysis, including FTIR and XRD, established the presence of α-helices and β-sheet structures, further supporting the protein’s conformational stability and amorphous nature, promoting bioavailability in pharmaceutical formulations. Particle size denoted monomodal distributions with the smallest size depicted at 0.144±0.10 µm, highlighting its suitability in drug delivery systems. The cytotoxic and antiproliferative effect of OSPI was evaluated using human cancer cell lines. In lung carcinoma cells (A549), OSPI reduced viability to 37.73% at 15 µg/mL and demonstrated a lower IC50 (21.80 µg/mL) than the standard chemotherapeutic agent camptothecin (524.85 µg/mL). Defatted okra flour (DOF) and OSPI significantly upregulated p53 levels with apoptotic induction against A549, as presented by Annexin V-binding. In hepatocellular carcinoma cells (Hep-G2), OSPI activated caspase-3/7, -8, and -9 at levels comparable to camptothecin, suggesting the initiation of both intrinsic and extrinsic apoptotic pathways. Furthermore, okra flour (OF) promoted reactive oxygen species (ROS) generation more effectively than camptothecin in A549 and Hep-G2 cells, reinforcing its potential oxidative stress-mediated apoptotic effects. These findings collectively underscore OSPI as a potential candidate for pharmaceutical and nutraceutical applications, particularly in cancer therapy. Its structural stability, solubility, and bioactive profile support its utilisation in the development of plant-based therapeutic interventions.
Social context and the use of technology in teaching African languages : a case study of public universities in KwaZulu-Natal
(2024-12) Adedokun, Theophilus Adedayo; Awung, Felix Nkwatta; Usadolo, Sam Erevbenagie
This study uses the concepts of Bourdieu’s sociological theory to investigate factors influencing technology use in teaching African languages. The study contends that language lecturers’ choices in teaching with technology were affected by the social phenomena of the field in which they operate. By adopting Bourdieu’s concepts of habitus, capital, and field, the study offers a multi-pronged approach to understanding the complex nature of the relationship between practices of individuals and social structures. A thematic textual analysis was used to investigate the attitudes of lecturers who taught African languages in selected public universities in KwaZulu Natal, South Africa. The analysis reveals a mutually reinforcing relationship between individuals who operate in the teaching field and their behavioural attitudes towards using technology in teaching African languages. The study contributes to understanding how individuals and groups navigate different social and cultural contexts and how they could use their resources to the advantage of their fields. In addition, the study showed how agents actively try to shape their current teaching practices and adopt new approaches while subtly resisting external pressures that conflict with the practical realities of their field and their audience (students). The results of the interviews indicate that individuals' behaviours were influenced by the forces of the field where they operated, external factors and their habitus. This study recommends that policymakers collaborate with stakeholders like communities, governments, institutions, and lecturers to ensure technology development for teaching African languages yields desirable results. It also suggests African countries create an enabling environment for African languages to thrive, and future research adopts an integrated approach examining various factors influencing technology use in language teaching.