Genotoxicity of gold nanoparticles functionalized with indolicidin towards Saccharomyces cerevisiae

Review of Advances in Coating and Functionalization of Gold Nanoparticles: From Theory to Biomedical Application

Nanoparticles, especially gold nanoparticles (Au NPs) have gained increasing interest in biomedical applications. Used for disease prevention, diagnosis and therapies, its significant advantages in therapeutic efficacy and safety have been the main target of interest. Its application in immune system prevention, stability in physiological environments and cell membranes, low toxicity and optimal bioperformances are critical to the success of engineered nanomaterials. Its unique optical properties are great attractors. Recently, several physical and chemical methods for coating these NPs have been widely used. Biomolecules such as DNA, RNA, peptides, antibodies, proteins, carbohydrates and biopolymers, among others, have been widely used in coatings of Au NPs for various biomedical applications, thus increasing their biocompatibility while maintaining their biological functions. This review mainly presents a general and representative view of the different types of coatings and Au NP functionalization using various biomolecules, strategies and functionalization mechanisms.

The Green Synthesis of Silver Nanoparticles from Avena fatua Extract: Antifungal Activity against Fusarium oxysporum f.sp. lycopersici

Using plant extracts as eco-friendly reducing and stabilizing agents for the synthesis of nanoparticles has gained significant attention in recent years. The current study explores the green synthesis of silver nanoparticles (AgNPs) using the Avena fatua extract and evaluates their antifungal activity against Fusarium oxysporum f.sp. lycopersici (Fol), a fungal plant pathogen. A green and sustainable approach was adopted to synthesize silver nanoparticles before these nanoparticles were employed for anti-fungal activity. The primary indication that AgNPs had formed was performed using UV-vis spectroscopy, where a strong peak at 425 nm indicated the effective formation of these nanoparticles. The indication of important functional groups acting as reducing and stabilizing agents was conducted using the FTIR study. Additionally, morphological studies were executed via SEM and AFM, which assisted with more effectively analyzing AgNPs. Crystalline behavior and size were estimated using powder XRD, and it was found that AgNPs were highly crystalline, and their size ranged from 5 to 25 nm. Synthesized AgNPs exhibited significant antifungal activity against Fol at a concentration of 40 ppm. Furthermore, the inhibitory index confirmed a positive correlation between increasing AgNPs concentration and exposure duration. This study suggests that the combined phytochemical mycotoxic effect of the plant extract and the smaller size of synthesized AgNPs were responsible for the highest penetrating power to inhibit Fol growth. Moreover, this study highlights the potential of using plant extracts as reducing and capping agents for the green synthesis of AgNPs with antifungal properties. The study concludes that A. fatua extract can synthesize antifungal AgNPs as a sustainable approach with robust antifungal efficacy against Fol, underscoring their promising potential for integration into plant protection strategies.

Biocompatibility and Cytotoxicity of Gold Nanoparticles: Recent Advances in Methodologies and Regulations

Recent advances in the synthesis of metal nanoparticles (MeNPs), and more specifically gold nanoparticles (AuNPs), have led to tremendous expansion of their potential applications in different fields, ranging from healthcare research to microelectronics and food packaging. The properties of functionalised MeNPs can be fine-tuned depending on their final application, and subsequently, these properties can strongly modulate their biological effects. In this review, we will firstly focus on the impact of MeNP characteristics (particularly of gold nanoparticles, AuNPs) such as shape, size, and aggregation on their biological activities. Moreover, we will detail different in vitro and in vivo assays to be performed when cytotoxicity and biocompatibility must be assessed. Due to the complex nature of nanomaterials, conflicting studies have led to different views on their safety, and it is clear that the definition of a standard biosafety label for AuNPs is difficult. In fact, AuNPs' biocompatibility is strongly affected by the nanoparticles' intrinsic characteristics, biological target, and methodology employed to evaluate their toxicity. In the last part of this review, the current legislation and requirements established by regulatory authorities, defining the main guidelines and standards to characterise new nanomaterials, will also be discussed, as this aspect has not been reviewed recently. It is clear that the lack of well-established safety regulations based on reliable, robust, and universal methodologies has hampered the development of MeNP applications in the healthcare field. Henceforth, the international community must make an effort to adopt specific and standard protocols for characterisation of these products.

Cytotoxicity and genotoxicity of coated-gold nanoparticles on freshwater algae Pseudokirchneriella subcapitata

Gold engineered nanoparticles (nAu) are increasingly detected in ecosystems, and this raises the need to establish their potential effects on aquatic organisms. Herein, cytotoxic and genotoxic effects of branched polyethylenimine (BPEI)- and citrate (cit)-coated nAu (5, 20, and 40 nm) on algae Pseudokirchneriella subcapitata were evaluated. The apical biological endpoints: growth inhibition and chlorophyll a (Chl a) content were investigated at 62.5-1000 µg/L over 168 h. In addition, the apurinic/apyrimidinic (AP) sites, randomly amplified polymorphic deoxyribonucleic acid (RAPD) profiles, and genomic template stability (GTS) were assessed to determine the genotoxic effects of nAu. The results show algal growth inhibition at 5 nm BPEI-nAu up to 96 h, and thereafter cell recovery except at the highest concentration of 1000 µg/L. Insignificant growth reduction for cit-nAu (all sizes), as well as 20 and 40 nm BPEI-nAu, was observed over 96 h, but growth promotion was apparent at all exposures thereafter except for 40 nm BPEI-nAu at 250 µg/L. A decrease in Chl a content following exposure to 5 nm BPEI-nAu at 1000 µg/L corresponded to significant algal growth reduction. In genotoxicity studies, a significant increase in AP sites content was observed relative to the control - an indication of nAu ability to induce genotoxic effects irrespective of their size and coating type. For 5 nm- and 20 nm-sized nAu for both coating types and exposure concentrations no differences in AP sites content were observed after 72 and 168 h. However, a significant reduction in AP sites was observed following algae exposure to 40 nm-sized nAu (irrespective of coating type and exposure concentration) at 168 h compared to 72 h. Thus, AP sites results at 40 nm-size suggest likely DNA damage recovery over a longer exposure period. The findings on AP sites content showed a good correlation with an increase in genome template stability and growth promotion observed after 168 h. In addition, RAPD profiles demonstrated that nAu can induce DNA damage and/or DNA mutation to P. subcapitata as evidenced by the appearance and/or disappearance of normal bands compared to the controls. Therefore, genotoxicity results revealed significant toxicity of nAu to algae at the molecular level although no apparent effects were detectable at the morphological level. Overall, findings herein indicate that long-term exposure of P. subcapitata to low concentrations of nAu may cause undesirable sub-lethal ecological effects.

Antioxidant action and enzyme activity modulation by bioaccessible polyphenols from jambolan (Syzygium cumini (L.) Skeels)

Jambolan is rich in antioxidant polyphenols; however, the bioactivity of these compounds remains poorly investigated. We compared changes in polyphenols and antioxidant capacity by ABTS and FRAP assays of jambolan pulp during in vitro digestion and chemical extraction and evaluated the effects of these changes on oxidative stress in wild and mutant Saccharomyces cerevisiae. Digestion and chemical extraction were performed with enzyme saline solutions, deionized water, and 50% (v/v) aqueous acetone solution. Caffeic, quinic, gallic, and ellagic acids, isomers of myricetin, catechin, and anthocyanins are bioaccessible during gastric digestion. In the duodenum, flavonoids and proanthocyanidins remained stable when the pH changed from acidic to neutral/alkaline, whereas anthocyanins were degraded when exposed to pH 7. In the colon, anthocyanins were not identified. The antioxidant activity of bioaccessible fractions is correlated with non-anthocyanin flavonoids and proanthocyanidins, reflected in the modulation of antioxidant enzymes of S. cerevisiae. The digestion process favors the release of bio-polyphenols from jambolan with preventive, scavenger, and reparative antioxidant action. They also stimulate the production and activity of Sod and Cat, strengthening the endogenous antioxidant system.

Toxicity profiling of metallosurfactant based ruthenium and ruthenium oxide nanoparticles towards the eukaryotic model organism Saccharomyces cerevisiae

In the present study, a facile method was used to synthesize the ruthenium and ruthenium oxide (RuO₂) nanoparticles (NPs) derived from three different metallosurfactants. Firstly, three metallosurfactants were fabricated i.e. RuCTAC (Bishexadecyltrimethylammonium ruthenium tetrachloride), RuDDA (Bisdodecylamine ruthenium dichloride), and RuHEXA (Bishexadecylamine ruthenium dichloride) and characterized by CHN, FTIR, and ¹HNMR. These metallosurfactants were further utilized to fabricate the mixed type of NPs (Ru and RuO₂ NPs) using the biocompatible microemulsion technique and NPs were then characterized. Subsequently, the nanotoxicity of mixed NPs (Ru & RuO₂) was studied towards Saccharomyces cerevisiae. The detailed study of nanotoxicity against the S. cerevisiae cells was done by employing optical microscopy, FESEM, anti-yeast activity assay, circular dichroism, and gel electrophoresis techniques. FESEM and optical microscopy analyses indicated that RuCTAC nanosuspension (Ns) has the most toxic effect on the S. cerevisiae cells. FESEM analysis confirmed the harmful impact of Ru and RuO₂ NPs on the S. cerevisiae cells. From the FESEM analysis, complete alteration in the morphology, cell membrane breakage, and formation of the holes on the cell wall of S. cerevisiae was affirmed in presence of all three types of Ns i.e. RuCTAC, RuDDA, and RuHEXA Ns. Genotoxicity of the NPs was confirmed by circular dichroism and gel electrophoresis and it was found that RuCTAC and RuHEXA Ns have the most damaging influence on the yeast genomic DNA.

Enhanced cytotoxicity of highly water-soluble gold nanoparticle-cyclopeptide conjugates in cancer cells

Conjugation of cytostatic drugs to nanomaterials seeks to improve their low bioavailability and selectivity to overcome the important associated side effects. In this work, we aimed to synthesize water-soluble gold nanoparticles as transporters for synthetic cyclic peptides with a potential anticancer activity but with a limited bioavailability. The highly water-soluble nanoparticles (2.5 nm diameter gold core) are coated with a mixture of polyethylene glycol linkers, one bearing a terminal hydroxyl group for increasing dispersibility in water, and the second bearing a carboxylic acid group for peptide conjugation through amide bond formation. Peptide-functionalized particles have a 9.7 ± 1.8 nm hydrodynamic diameter and are highly water-soluble and stable in solution for at least one year. The morphology of the gold cores as well as their organic coating was studied using Transmission Electron Microscopy, showing that the attachment of a limited number of peptides per nanoparticle leads to a uneven organic coating of two different thicknesses, one of 2.0 ± 0.6 nm formed by polyethylene glycol linkers, and a second of 3.6 ± 0.5 nm which includes the peptide. GNP significantly enhance the internalization of the cyclic peptide BPC734 in cells as compared to peptide in solution, with improved uptake in cancerous HT29 cells. Cytotoxicity studies show that peptide BPC734 in solution is toxic in the micromolar range, whereas peptide-functionalized particles are toxic at nanomolar peptide concentrations and with a significantly higher toxicity for cancerous cells. All these results, besides the stability and expected passive tumor targeting, make these particles a promising option for improving the bioavailability, efficacy, and selectivity in cancer therapy.

Ecotoxicity Evaluation of Pristine and Indolicidin-coated Silver Nanoparticles in Aquatic and Terrestrial Ecosystem

BACKGROUND

Metallic nanoparticles (NPs) are highly exploited in manufacturing and medical processes in a broad spectrum of industrial applications and in the academic sectors. Several studies have suggested that many metallic nanomaterials including those derived by silver (Ag) are entering the ecosystem to cause significant toxic consequences in cell culture and animal models. However, ecotoxicity studies are still receiving limited attention when designing functionalized and non.-functionalized AgNPs.

OBJECTIVE

This study aimed to investigate different ecotoxicological profiles of AgNPs, which were analyzed in two different states: in pristine form uncoated AgNPs and coated AgNPs with the antimicrobial peptide indolicidin. These two types of AgNPs are exploited for a set of different tests using Daphnia magna and Raphidocelis subcapitata, which are representatives of two different levels of the aquatic trophic chain, and seeds of Lepidium sativum, Cucumis sativus and Lactuca sativa.

RESULTS

Ecotoxicological studies showed that the most sensitive organism to AgNPs was crustacean D. magna, followed by R. subcapitata and plant seeds, while AgNPs coated with indolicidin (IndAgNPs) showed a dose-dependent decreased toxicity for all three.

CONCLUSION

The obtained results demonstrate that high ecotoxicity induced by AgNPs is strongly dependent on the surface chemistry, thus the presence of the antimicrobial peptide. This finding opens new avenues to design and fabricate the next generation of metallic nanoparticles to ensure the biosafety and risk of using engineered nanoparticles in consumer products.

Antifungal effects of indolicidin-conjugated gold nanoparticles against fluconazole-resistant strains of Candida albicans isolated from patients with burn infection

Background:Candida albicans as an opportunistic fungus is one of the most important causes of late-onset morbidity and mortality in patients with major burns and severely impaired immune system. In recent years, the emergence of resistance to opportunistic fungi and toxicity of antimicrobial drugs make it necessary to develop new drugs.

Methods: In the present study, we investigated anticandidal effects of indolicidin, as a representative of host defense peptide, conjugated with gold nanoparticles in fluconazole-resistant clinical isolates of C. albicans. After characterizing the conjugation of indolicidin using biophysical methodologies, the cytotoxicity and hemolytic activity of the nanocomplex were examined. In addition, the expression level of ERG11, responsible for antifungal resistance, and the immunomodulatory effect of peptide-nanomaterial conjugates were assessed.

Results: Our data indicated that the nanocomplex was nontoxic for the fibroblast cells and erythrocytes. Treatment with the nanocomplex significantly reduced the expression levels of the ERG11 gene in fluconazole-resistant C. albicans isolates and the iNOS gene in macrophages.

Conclusion: The study data provides a chance to develop innovative therapies for the treatment of C. albicans burn infections. However, further investigation is required to examine the efficiency of the nanocomplex.

Genotoxicity of gold nanoparticles in the gilthead seabream (Sparus aurata) after single exposure and combined with the pharmaceutical gemfibrozil

Due to their diverse applications, gold nanoparticles (AuNPs) are expected to increase of in the environment, although few studies are available on their mode of action in aquatic organisms. The genotoxicity of AuNPs, alone or combined with the human pharmaceutical gemfibrozil (GEM), an environmental contaminant frequently detected in aquatic systems, including in marine ecosystems, was examined using gilthead seabream erythrocytes as a model system. Fish were exposed for 96 h to 4, 80 and 1600 μg L^-1 of 40 nm AuNPs with two coatings - citrate or polyvinylpyrrolidone; GEM (150 μg L^-1); and a combination of AuNPs and GEM (80 μg L^-1 AuNPs + 150 μg L^-1 GEM). AuNPs induced DNA damage and increased nuclear abnormalities levels, with coating showing an important role in the toxicity of AuNPs to fish. The combined exposures of AuNPs and GEM produced an antagonistic response, with observed toxic effects in the mixtures being lower than the predicted. The results raise concern about the safety of AuNPs and demonstrate interactions between them and other contaminants.

Melittin Inhibition and Eradication Activity for Resistant Polymicrobial Biofilm Isolated from a Dairy Industry after Disinfection

The emerging concern about the increase of antibiotic resistance and associated biofilm has encouraged scientists to look for alternative antibiotics such as antimicrobial peptides (AMPs). This study evaluated the ability of melittin to act as an antibacterial biofilm inhibitor and biofilm remover considering isolates from dairy industry. Minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), minimum biofilm inhibitory concentrations (MBICs), and biofilm removal activities were studied in polymicrobial biofilms produced from isolates. MIC and MBC were set at 1–3 µg/mL and 25–50 µg/mL for Gram-positive and Gram-negative bacteria, respectively. Results demonstrated a good MBIC reaching 85% inhibition ability and a good activity and better penetration in deeper layers against the mixed preformed biofilm, thereby increasing its activity against all isolates also at the lowest tested concentrations. Melittin showed interesting characteristics suggesting its potential to act as an antimicrobial agent for polymicrobial biofilm from dairy industry even in environmental isolates.

Efficiency of gold nanoparticles coated with the antimicrobial peptide indolicidin against biofilm formation and development of Candida spp. clinical isolates

BACKGROUND

This article examines the use of a novel nano-system, gold nanoparticles coated with indolicidin (AuNPs-indolicidin), against pathogenic Candida albicans biofilms. Candida species cause frequent infections owing to their ability to form biofilms, primarily on implant devices.

MATERIALS AND METHODS

We used an integrated approach, evaluating the effect of AuNPs-indolicidin on prevention and eradication of Candida biofilms formed in multi-well polystyrene plates, with relative gene expression assays. Four biofilm-associated genes (FG1, HWP1, ALS1 and ALS3, and CDR1 and CDR2) involved in efflux pump were analyzed using reverse transcription polymerase chain reaction.

RESULTS

Treatment with the nano-complex significantly inhibits the capacity of C. albicans to form biofilms and impairs preformed mature biofilms. Treatment with AuNPs-indolicidin results in an increase in the kinetics of Rhodamine 6G efflux and a reduction in the expression of biofilm-related genes.

CONCLUSION

These data provide a chance to develop novel therapies against nosocomially acquired refractory C. albicans biofilms.

Toxicity Effects of Functionalized Quantum Dots, Gold and Polystyrene Nanoparticles on Target Aquatic Biological Models: A Review

Nano-based products are widespread in several sectors, including textiles, medical-products, cosmetics, paints and plastics. Nanosafety and safe-by-design are driving nanoparticle (NP) production and applications through NP functionalization (@NPs). Indeed, @NPs frequently present biological effects that differ from the parent material. This paper reviews the impact of quantum dots (QDs), gold nanoparticles (AuNPs), and polystyrene-cored NPs (PSNPs), evidencing the role of NP functionalization in toxicity definition. Key biological models were taken into consideration for NP evaluation: Saccharomyces cerevisiae, fresh- (F) and saltwater (S) microalgae (Raphidocelis subcapitata (F), Scenedesmus obliquus (F) and Chlorella spp. (F), and Phaeodactylum tricornutum (S)), Daphnia magna, and Xenopus laevis. QDs are quite widespread in technological devices, and they are known to induce genotoxicity and oxidative stress that can drastically change according to the coating employed. For example, AuNPs are frequently functionalized with antimicrobial peptides, which is shown to both increase their activity and decrease the relative environmental toxicity. P-NPs are frequently coated with NH₂⁻ for cationic and COOH⁻ for anionic surfaces, but when positively charged toxicity effects can be observed. Careful assessment of functionalized and non-functionalized NPs is compulsory to also understand their potential direct and indirect effects when the coating is removed or degraded.

Cyclic Peptides as Novel Therapeutic Microbicides: Engineering of Human Defensin Mimetics

Cyclic peptides are receiving significant attention thanks to their antimicrobial activity and high serum stability, which is useful to develop and design novel antimicrobial agents. Antimicrobial peptides appear to be key components of innate defences against bacteria, viruses, and fungi. Among the others, defensins possess a strong microbicidial activity. Defensins are cationic and amphipathic peptides with six cysteine residues connected by three disulfide bonds found in plants, insects, and mammals; they are divided in three families: α-, β-, and θ-defensins. α-Defensins are contained in the primary granules of human neutrophils; β-defensins are expressed in human epithelia; and θ-defensins are pseudo-cyclic defensins not found in humans, but in rhesus macaques. The structural diversities among the three families are reflected in a different antimicrobial action as well as in serum stability. The engineering of these peptides is an exciting opportunity to obtain more functional antimicrobial molecules highlighting their potential as therapeutic agents. The present review reports the most recent advances in the field of cyclic peptides with a specific regard to defensin analogs.