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In this report, gold nanoparticles (GNPS) were synthesized using cell‐free extracts of seven different isolates, namely, Pseudomonas aerogenosa CEBP2, Pseudomonas sp. CEBP1, Pseudomonas pseudoalcaligenes CEB1G, Acinetobactor baumani CEBS1, Cuprividus sp. CEB3, Micrococcus luteus CUB12, and Pandoraea sp. CUB2S. The spectroscopic (UV–vis, FTIR, DLS, XRD, EDS) and microscopic (FESEM, TEM) results confirm the reduction of Au3+ to Au0 in the presence of biomolecules having reducing as well as self‐stabilizing activity. In this green synthesis approach, the average particle size of biosynthesized GNPS might vary (4–60 nm) depending on the bacterial species, pH of the media, incubation time, and temperature. In this study, GSH‐modified BSGNPs (Au‐GSH) have shown antimicrobial activity with better stability against Gram‐positive bacteria. After conjugation of lysozyme with Au‐GSH (lyso@Au‐GSH), the zone of inhibition was enhanced from 12 to 23 mm (Au‐GSH). The TEM study shows the spherical GNP (16.65 ± 2.84) turns into a flower‐shaped GNP (22.22 ± 3.12) after conjugation with lysozyme due to the formation of the protein corona. Furthermore, the nanobioconjugate (lyso@Au‐GSH) was immobilized with Nafion on a glassy carbon electrode to fabricate a label‐free impedance biosensor that is highly sensitive to monitor changes in the transducer surface due to biomolecular interactions. The uniquely designed biosensor could selectively detect Gram‐positive bacteria in the linear range of 3.0 × 101–3 × 1010 cfu mL−1 with RE <5%. The proposed simplest biosensor exhibited good reproducibility (RSD = 3.1%) and excellent correlation (R2 = 0.999) with the standard plate count method, making it suitable for monitoring Gram‐positive bacterial contamination in biofluids, food, and environmental samples. [ABSTRACT FROM AUTHOR]

Biosynthesis of gold nanoparticles (AuNPs) is emerging as a better alternative to traditional chemical-based techniques. During this study, extracts of different marine algae species Ulva rigida (green algae), Cystoseira myrica (brown Algae), and Gracilaria foliifera (red Algae) were utilized as reducing and capping agents to synthesize AuNPs. AuNPs capped by U. rigida, C. myrica, and G. foliifera were confirmed by the appearance of surface plasmonic bands at 528, 540, and 543 nm, respectively. Transmission electron microscopy revealed mostly spherical shapes of AuNPs having a size of about 9 nm, 11 nm, and 13 nm for C. myrica, and G. foliifera extracts, respectively. Fourier transform-infrared spectroscopy (FTIR) illustrated the major chemical constituents of U. rigida, C. myrica, and G. foliifera. LC50 values of the biosynthesized AuNPs against Artemia salina nauplii were calculated at a range of concentrations (5-188 μg ml−1) after 16 to 24h. AuNPs concentration-dependent lethality was noted and U. rigida extracts-mediated AuNPs presented the lowest cytotoxicity. The biosynthesized AuNPs exhibited significant anticancer activity (86.83%) against MCF-7 cell lines (human breast adenocarcinoma cell lines) at 188 µg/ml concentration. G. foliifera demonstrated the highest anticancer value (92.13%) followed by C. myrica (89.82%), and U. rigida (86.83%), respectively. The AuNPs synthesized by different algal extracts showed variable antimicrobial activity against the tested pathogenic microorganisms. AuNPs of U. rigida extracts showed significant antimicrobial activity against dermatophytic fungi Trichosporon cataneum (30 mm) followed by Trichophyton mantigrophytes (25 mm). Furthermore, it also exhibited mild activity against Escherichia coli (17 mm), Cryptococcus neoformans (15 mm), Candida albicans (13 mm), and Staphylococcus aureus (11mm), respectively whereas no effects were observed against Bacillus cereus. To conclude, AuNPs can be effectively synthesized by marine algal species, and particularly U. rigida extracts could be effective reducing agents for the green AuNPs synthesis. These AuNPs could potentially serve as efficient alternative anticancer agents against human breast adenocarcinoma and anti-dermatophytes associated with skin infections.

There is a growing need to improve facile, eco-friendly, and cheap approaches for nanoparticle (NP) synthesis. Green protocols have been investigated for the fabrication of NPs using several natural sources as plants, algae, fungi, and bacteria. Thus, the present study proposed a rapid, convenient, and efficient biosynthesis of gold NPs (Au-NPs) using the ethanolic extracts of three macroalgae, i.e., Cystoseira myrica, C. trinodis, and Caulerpa prolifera. The reduction of Au ions and the fabrication of Au-NPs were validated using ultraviolet-visible (UV–Vis) spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and zeta potential analysis. The produced Au-NPs were tested for their antibacterial, antifungal, anti-inflammatory, and schistolarvicidal activity. Results revealed the formation of Au-NPs with an average size of 12.6–15.5 nm and different shapes that are mainly spherical with pure crystalline nature. The strong antibacterial activities of C. trinodis– and C. myrica–based Au-NPs against E. coli (inhibition zones of 22 and 19 mm) and against Staphylococcus aureus (inhibition zones of 18 and 20.5 and mm) were recorded, respectively. On the other hand, the high antifungal activity of C. trinodis Au-NPs against Aspergillus niger and Alternaria alternate showed the inhibition zones of 18 and 17 mm, respectively. The high antifungal activity of C. trinodis Au-NPs against Candida albicans (inhibition zone 16 mm) was also recorded. Regarding anti-inflammatory and schistolarvicidal activity, Au-NPs fabricated using C. myrica showed 64.2% of the inhibitory effect on protein denaturation and recorded the highest schistolarvicidal activity against Schistosoma mansoni cercariae that sank and died after 7 min. Overall, these findings proved that macroalgal ethanolic extracts can be effectively used for the biosynthesis of Au-NPs. These Au-NPs offer a significant alternative antimicrobial, anti-inflammatory, and schistolarvicidal agents. for biomedical uses.

Biosynthesis of gold nanoparticles (AuNPs) is emerging as a better alternative to traditional chemical based techniques. During this study, extracts of different marine algae species Ulva rigida (green algae), Cystoseira myrica (brown Algae), and Gracilaria foliifera (red Algae) were utilized as reducing and capping agents to synthesize AuNPs. AuNPs capped by U. rigida, C. myrica, and G. foliifera were confirmed by the appearance of surface plasmonic bands at 528, 540, and 543 nm, respectively. Transmission electron microscopy revealed mostly spherical shapes of AuNPs having a size of about 9 nm, 11 nm, and 13 nm for C. myrica, and G. foliifera extracts, respectively. Fourier transform-infrared spectroscopy (FTIR) illustrated the major chemical constituents of U. rigida, C. myrica, and G. foliifera. LC50 values of the biosynthesized AuNPs against Artemia salina nauplii were calculated at a range of concentrations (5-188 μg ml−1) after 16 to 24h. AuNPs concentration-dependent lethality was noted and U. rigida extracts-mediated AuNPs presented the lowest cytotoxicity. The biosynthesized AuNPs exhibited significant anticancer activity (86.83%) against MCF-7 cell lines (human breast adenocarcinoma cell lines) at 188 μg/ml concentration. G. foliifera demonstrated the highest anticancer value (92.13%) followed by C. myrica (89.82%), and U. rigida (86.83%), respectively. The AuNPs synthesized by different algal extracts showed variable antimicrobial activity against the tested pathogenic microorganisms. AuNPs of U. rigida extracts showed significant antimicrobial activity against dermatophytic fungi Trichosporon cataneum (30 mm) followed by Trichophyton mantigrophytes (25 mm). Furthermore, it also exhibited mild activity against Escherichia coli (17 mm), Cryptococcus neoformans (15 mm), Candida albicans (13 mm), and Staphylococcus aureus (11mm), respectively whereas no effects were observed against Bacillus cereus. To conclude, AuNPs can be effectively synthesized by marine algal species, and particularly U. rigida extracts could be effective reducing agents for the green AuNPs synthesis. These AuNPs could potentially serve as efficient alternative anticancer agents against human breast adenocarcinoma and anti-dermatophytes associated with skin infections. [ABSTRACT FROM AUTHOR]