Nanoparticle synthesis under environmentally friendly conditions has been conducted utilizing natural resources in order to reduce the reliance on hazardous chemicals. For example, the utilization of microbial synthesis has enabled the production of nanoparticles that exhibit biocompatibility, stability, and safety. Microorganisms facilitate the growth of crystals while preventing aggregation. They serve as both reducing agents and capping agents by offering enzymes, peptides, poly(amino acids), polyhydroxyalkanoate, and polysaccharides. In this review, we present an overview of nanoparticle synthesis based on microorganisms including bacteria, fungi, algae, and actinobacteria, encompassing metals such as gold (Au), silver (Ag), platinum (Pt), palladium (Pd), copper (Cu), titanium dioxide ((TiO₂), zinc oxide (ZnO), iron oxide (Fe₂O₃), and selenium (Se). The nanoparticles typically vary in size from 1 to 100 nm and exhibit various shapes including spherical, rod-shaped, triangular, cubic, and hexagonal shapes. Additionally, this review discusses the mechanisms behind the synthesis of metal nanoparticles by microorganisms, whether they occur intracellularly or extracellularly.

This study developed a lysozyme–dequalinium chloride-loaded Zn–Fe layered double hydroxide (LDH)–chia seed mucilage matrix for enhanced antimicrobial efficacy and sustained drug delivery. The optimized formulation (15% w/v Zn–Fe LDH–chia seed hybrid) achieved encapsulation efficiencies of 93.30 ± 1.92% (lysozyme) and 88.74 ± 1.71% (dequalinium), with a particle size of 153.77 ± 5.79 nm, PDI of 0.18, and zeta potential of +26.44 ± 1.21 mV, ensuring stability and mucoadhesion. Surface morphology, structure, drug loading, and thermostability were confirmed using various techniques. In vitro release studies showed sustained drug release over 24 h. Antimicrobial assays demonstrated inhibition zones against S. mutans (24.33 ± 2.03 mm), S. aureus (14.67 ± 0.88 mm), S. sobrinus (11.45 ± 0.887 mm), and K. pneumoniae (20.33 ± 2.03 mm). MIC/MBC analysis indicated high susceptibility of K. pneumoniae (MIC = 13.00 ± 2.60 μg mL⁻¹, MBC = 20.83 ± 5.23 μg mL⁻¹, P < 0.001) and S. mutans (MIC = 15.60 ± 1.05 μg mL⁻¹, MBC = 26.07 ± 5.23 μg mL⁻¹, P < 0.01), with S. sobrinus showing moderate sensitivity (MIC = 49.66 ± 4.32 μg mL⁻¹, MBC = 72.93 ± 6.43 μg mL⁻¹). MBC/MIC ratios below 4 confirmed bactericidal action. The formulation reduced S. mutans biofilm formation by 90.1 ± 1.2% at the highest tested concentration. Cytotoxicity evaluation showed a CC50 of 306.6 μg mL⁻¹, demonstrating improved cytocompatibility compared to the free components.

This work emphasizes the importance of utilizing cuttlebone waste as a sustainable solution for waste management and the development of antimicrobial materials by incorporating it as a supporting phase for polyaniline (PANI) to form a nanocomposite. The three prepared materials were fully characterized using various techniques, including FTIR, XRD, SEM, EDX for elemental analysis, Brunauer–Emmett–Teller (BET) surface area measurements, particle size distribution analysis, and zeta potential measurements. The study focuses on the development of novel molecules with potential antibacterial and antifungal activity against clinical pathogens responsible for infectious diseases. The antibacterial and antifungal activities of the polyaniline/cuttlebone (PANI/CB) composite were evaluated using methods such as minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and disk diffusion for bacterial samples, as well as MIC, minimum fungicidal concentration (MFC), antifungal percentage, and disk diffusion for fungal samples. Notably, the PANI/CB composite exhibited a distinct crystallite size and characteristic XRD pattern, along with a significant BET surface area, demonstrating strong antimicrobial properties. Cuttlebone not only serves as a bioactive agent but also acts as a sustainable support to enhance the properties of polyaniline, forming a nanocomposite with a low MIC range (8–66 μg mL⁻¹) and effective action against Gram-positive bacteria such as S. aureus, although it showed less susceptibility against Gram-negative bacteria like E. coli. The MTT assay results demonstrated that while PANI and CB alone exhibited minimal cytotoxicity on Huh7 cells, the combination of doxorubicin (DOX) with PANI/CB significantly enhanced the cytotoxic effect, suggesting a synergistic interaction that could improve the therapeutic efficacy of DOX. Additionally, the effectiveness of the polyaniline/cuttlebone composite in protecting against DOX-induced hepatic and renal damage in rats was evaluated. Tissue damage was assessed using serum markers such as alanine transaminase (ALT), aspartate transaminase (AST), urea, and creatinine. The results demonstrated a decrease in oxidative damage and significant improvements in liver and kidney function markers in the polyaniline/cuttlebone-treated groups compared to those treated with individual components. Specifically, ALT levels decreased from 48 ± 2.8 IU L⁻¹ to 21 ± 0.4 IU L⁻¹, AST from 195 ± 0.7 IU L⁻¹ to 13 ± 1.08 IU L⁻¹, urea from 86 ± 1.4 mg dL⁻¹ to 39 ± 0.7 mg dL⁻¹, and creatinine from 1.05 ± 0.03 mg dL⁻¹ to 0.53 ± 0.01 mg dL⁻¹. These findings highlight the potential of utilizing cuttlebone waste as a sustainable material in antimicrobial applications, offering an eco-friendly solution for waste management while contributing to the development of potent antimicrobial nanocomposites.