Laila Saad Alqarni

Lead contamination in water systems poses a serious environmental and public health concern, necessitating the development of efficient and selective adsorbents. In this study, a NiO‐decorated activated carbon (NiO@AC) nanocomposite was synthesized via chemical activation followed by a precipitation‐assisted method. The resulting material exhibited well‐dispersed NiO nanoparticles on a porous carbon matrix. The adsorption performance toward Pb(II) ions was strongly dependent on solution conditions, with optimal removal achieved at pH 5. The NiO@AC nanocomposite demonstrated a maximum removal efficiency of 95% and maintained 89% removal at an initial Pb(II) concentration of 200 mg/L. Equilibrium data were best described by the Langmuir isotherm model ( R ² = 0.9786), indicating monolayer adsorption with a maximum adsorption capacity of 826.9 mg/g. Kinetic analysis showed that the adsorption process followed the pseudo‐second‐order model, suggesting that both physical and chemisorption are the dominant mechanism. Furthermore, the nanocomposite exhibited strong selectivity toward Pb(II) ions in the presence of competing metal ions and retained good performance over repeated adsorption–desorption cycles, confirming its stability and reusability. These results highlight NiO@AC as an efficient, selective, and sustainable adsorbent with strong potential for practical wastewater treatment applications.

In this work, novel quinoline-2-carboxamide–phenylacetamide hybrids 23a–d were designed, synthesised, and evaluated through antimicrobial and breast cancer-cell cytotoxicity screening. The compounds showed moderate antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, and Candida albicans, with compound 23b showing the lowest MIC values of 0.125 and 0.039 mg/mL against MRSA and P. aeruginosa, respectively. Cytotoxicity screening against MCF-7 and MDA-MB-231 breast cancer cell lines identified compound 23d as the most active member of the series against MCF-7 cells, with an IC₅₀ of 6.249 ± 0.30 µg/mL, corresponding to 14.55 ± 0.70 µM using the molecular weight applied in this study. Molar comparison showed that the activity profile was cell-line dependent: 23d displayed a lower molar IC₅₀ than cisplatin against MCF-7 under the assay conditions used, whereas cisplatin remained more potent against MDA-MB-231 cells. Molecular docking against activated CDC42-associated kinase 1 (ACK1) suggested that 23d can adopt a favourable predicted binding pose within the ACK1 ATP-binding pocket, with a GlideScore of − 8.112 kcal/mol compared with − 9.651 kcal/mol for the co-crystallised inhibitor. However, docking alone cannot confirm ACK1 inhibition or establish the mechanism of cytotoxicity. Because non-cancerous-cell cytotoxicity was not performed, cancer-cell selectivity remains unresolved and selectivity indices could not be calculated. Accordingly, compounds 23a–d are presented as preliminary antimicrobial and cytotoxic hits requiring further optimisation, analytical validation, non-cancerous-cell cytotoxicity testing, and mechanistic confirmation.

SERS is an emerging technique for the rapid sensing of key bioactive molecules, such as glucose, which has relatively low signal levels using normal Raman spectroscopy. SERS of glucose at extremely low concentration levels or high enhancement factors (EFs) is demonstrated here using relatively inexpensive, commercial multilayer graphene nanoplatelet (GNP) substrates produced from natural graphite. Three approaches for modifying the GNPs for SERS were used: the first method involved drop-coating of gold nanoparticles from solution on the GNPs, the second method used a combination of drop-coating the gold nanoparticles followed by the deposition of tri-ethylene glycol (TEG) layers to partition the glucose on the surfaces of the gold nanoparticles to further increase the SERS signal, and the third method used irradiation of the GNPs in a nitrogen-argon radio frequency (RF) plasma to create nitrogenous defect sites on the graphene layers to increase the SERS signal. Glucose in aqueous solutions was detected at concentrations down to 10-8 M, 10-10 M and 10-11 M, respectively, with corresponding high enhancement factors (EFs) for the three types of modified GNP substrates.

In this study, silver-decorated magnetite nanoparticles (Ag@Fe₃O₄) were synthesized via a green method using Brachychiton populneus leaf extract and employed as an efficient support matrix for immobilization of horseradish peroxidase (HRP). The biosynthesized nanocomposite exhibited magnetic properties that facilitated easy separation and reuse, while the silver loading imparted enhanced stability and potential antimicrobial activity. Comprehensive physicochemical characterizations, including XRD, FTIR, FESEM, EDX, BET, and VSM, confirmed the successful formation of Ag@Fe₃O₄ and effective enzyme loading. The immobilization yield of HRP on Ag@Fe₃O₄ reached 93%, and the immobilized enzyme showed improved tolerance toward temperature and pH variations, with an optimal pH of 7.5 and optimal temperature of 60 °C, compared to 7.0 and 50 °C for the free enzyme. Kinetic studies revealed a moderate increase in Km but maintained or slightly increased Vmax, indicating preserved catalytic efficiency. The immobilized enzyme demonstrated excellent reusability over 15 cycles (66% residual activity) and long-term storage stability (81% activity after 60 days at 4 °C). These enhancements are attributed to the protective microenvironment provided by the Ag@Fe₃O₄ matrix, which mitigates denaturation and leaching. This work highlights the potential of Ag@Fe₃O₄ as a sustainable and reusable platform for enzyme immobilization in biocatalytic applications, particularly in environmental remediation and industrial bioprocessing.