Antimicrobial effect of Sargassum plagiophyllum mediated gold nanoparticles on Escherichia coli and Salmonella typhi

Monstera deliciosa mediated single step biosynthesis of gold nanoparticles by bottom-up approach and its non-antimicrobial properties

In this study, we have stated the green biosynthesis of gold nanoparticles (AuNPs) by utilizing the extract of Monstera deliciosa leaves (MDL) as a reducing agent. Biosynthesized flat, thin, and single-crystalline gold nanotriangles obtained through centrifugation are then analyzed by different characterization techniques. The UV - visible absorption spectra of AuNPs exhibited maxima bands in the range of 500-590 nm, indicating a characteristic of AuNPs. XRD analysis revealed the formation of the (111)-oriented face-centered cubic (FCC) phase of AuNPs. ATR-IR spectra showed signatures of stretching vibrations of O-H, C-H, C=C, C=O, C-O, and C-N, accompanied by CH3 rocking vibrations present in functional groups of biomolecules. FESEM images confirmed spherical nanoparticles with an average diameter in the range of 53-66 nm and predominantly triangular morphology of synthesized AuNPs within the size range of 420-800 nm. NMR, GC-MS, and HR-MS studies showed the presence of different biomolecules, including phenols, flavonoids, and antioxidants in MDL extracts, which play a crucial role of both, reducing as well as stabilizing and capping agents to form stable AuNPs by a bottom-up approach. They were then investigated for their antibacterial assay against Gram-positive (S. aureus, B. subtilis) and Gram-negative (E. coli, P. aeruginosa) microorganisms, along with testing of antifungal potential against various fungi (Penicillium sp., Aspergillus flavus, Fusarium oxysporum, Rhizoctonia solani) using the well diffusion method. Here, biosynthesized AuNPs showed non-antimicrobial properties against all four used bacteria and fungi, showing their suitability as a contender for biomedical applications in drug delivery ascribed to their inert and biocompatible nature.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03898-0.

Mannosylated preactivated hyaluronic acid-based nanostructures for bacterial infection treatment

Salmonella Typhi is an intracellular bacterium causing a variety of enteric diseases, being typhoid fever the most common. Current modalities for treating S. typhi infection are subjected to multi-drug resistance. Herein, a novel macrophage targeting approach was developed via coating bioinspired mannosylated preactivated hyaluronic acid (Man-PTHA) ligands on a self-nanoemulsifying drug delivery system (SNEDDS) loaded with the anti-bacterial drug ciprofloxacin (CIP). The shake flask method was used to determine the drug solubility in the different excipients (oil, surfactants and co-surfactants). Man-PTHA were characterized by physicochemical, in vitro, and in vivo parameters. The mean droplet size was 257 nm, with a PDI of 0.37 and zeta potential of -15 mV. In 72 h, 85 % of the drug was released in a sustained manner, and the entrapment efficiency was 95 %. Outstanding biocompatibility, mucoadhesion, muco-penetration, anti-bacterial action and hemocompatibility were observed. Intra-macrophage survival of S. typhi was minimal (1 %) with maximum nanoparticle uptake, as shown by their higher fluorescence intensity. Serum biochemistry evaluation showed no significant changes or toxicity, and histopathological evaluation confirmed the entero-protective nature of the bioinspired polymers. Overall, results confirm that Man-PTHA SNEDDS can be employed as novel and effective delivery systems for the therapeutic management of S. typhi infection.

Macroalgae as biofactories of metal nanoparticles; biosynthesis and food applications

Nanotechnology has opened a new frontier in recent years, capable of providing new ways of controlling and structuring products with greater market value and offering significant opportunities for the development of innovative applications in food processing, preservation, and packaging. Macroalgae (MAG) are the major photoautotrophic group of living beings known as a potential source of secondary metabolites, namely phenolic compounds, pigments, and polysaccharides. Biosynthesis based on the abilities of MAG as "nanobiofactories" targets the use of algal secondary metabolites as reducing agents to stabilize nanoparticles (NPs). Nowadays, most of the studies are focused on the use of metal (Ag, Au) and metal-oxide (CuO, ZnO) NPs derived from algae. The eco-friendly biosynthesis of metal NPs reduces the cost and production time and increases their biocompatibility, due to the presence of bioactive compounds in MAG, making them suitable for a wide variety of applications. These compounds have been attributed to the antimicrobial and antioxidant properties responsible for their application through innovative technologies such as nanoencapsulation, nanocomposites, or biosensors in the food industry. Nevertheless, toxicity is a key factor that should be considered, so the applicable regulation needs to guarantee the safe use of metal NPs. Consequently, the aim of this review will be to compile the available information on MAG-mediated metal NPs, their biosynthesis, and potential food applications.

Antimicrobial benefits of flavonoids and their nanoformulations

Abstract:

Nowadays, there is an urgent need to discover and develop long-term and effective antimicrobial and biofilm-inhibiting compounds. Employing combination therapies using novel drug delivery systems and also natural antimicrobial substances is a promising strategy in this field. Nanoparticles (NPs)-based materials have become well appreciated in recent times due to serve as antimicrobial agents or the carriers for promoting the bioavailability and effectiveness of antibiotics. Flavonoids belong to the promising groups of bioactive compounds abundantly found in fruits, vegetables, spices, and medicinal plants with strong antimicrobial features. Flavonoids and NPs have potential as alternatives to the conventional antimicrobial agents, both on their own as well as in combination. Different classes of flavonoid NPs may be particularly advantageous in handling microbial infections. The most important antimicrobial mechanisms of flavonoid NPs include oxidative stress induction, non-oxidative mechanisms, and metal ion release. However, the efficacy of flavonoid NPs against pathogens and drug-resistant pathogens changes according to their physicochemical characteristics as well as the particular structure of microbial cell wall and enzymatic composition. In this review, we provide an outlook on the antimicrobial mechanism of flavonoid-based NPs and the crucial factors that are involved.

Nano drug delivery in intracellular bacterial infection treatments

The present work aimed to review the potential mechanisms used by macrophages to kill intracellular bacteria, their entrance to the cell, and mechanisms of escape of cellular immunity and applications of various nanoparticles. Since intracellular bacteria such as Mycobacterium and Brucella can survive in host cells and can resist the lethal power of macrophages, they can cause chronic disease or recur in 10-30% of cases in improved patients Nano drug-based therapeutics are promising tools for treating intracellular bacteria and preventing recurrence of the disease caused by these bacteria. In addition, among their unique features, we can mention the small size and the ability of these compounds to purposefully reach the target location.

Synthesis and Characterization of Carbon Dots Coated CaCO3 Nanocarrier for Levofloxacin Against Multidrug Resistance Extended-Spectrum Beta-Lactamase Escherichia coli of Urinary Tract Infection Origin

The multidrug resistance (MDR) Escherichia coli having Extended-Spectrum Beta-Lactamase (ESBL) genes and the capacity to create a biofilm acts as a major reduction in the therapeutic effectiveness of antimicrobials. In search of a novel nanocarrier (NC) for targeted delivery of antibiotics, carbon dots (CDs) coated calcium carbonate nanocarriers (CCNC) from organic chicken eggshells conjugated with levofloxacin (Lvx) were synthesized. Our main objectives were to explore the antimicrobial, antibiofilm, and NC potential of CDs coated CaCO₃ Nanocarrier conjugated with levofloxacin (CD-CCNC-Lvx) to combat biofilm-producing MDR ESBL E. coli of urinary tract infection origin. The synthesized NC system was physiochemically characterized, validating the synthesis of CCNC and CD-CCNC-Lvx with a particle size of 56 and 14 nm, respectively. Scanning electron microscopy (SEM) showed rod shape morphology. X-ray diffraction results discovered crystalline and dispersed nanoparticles. In vitro release drug kinetics illustrated sustained release of Lvx. NC system exhibited strong antibacterial and antibiofilm potential against E. coli with a noticeable low minimal inhibitory concentration (MIC). MIC of CCNC was found to be 30 ± 0.1 μg/mL and CD-CCNC-Lvx was 20 ± 0.1 μg/mL for MDR ESBL-producing E. coli. The synergistic effect of NC upon conjugation with Lvx showed incredible activity with 30 mm zone of inhibition and 68% biofilm inhibition. Flow cytometry analysis revealed treated E. coli cells showed 58.69% reduction in cell viability. SEM images of treated bacterial cells showed morphological changes, which were also confirmed by our flow cytometry findings leading to cell membrane damage in E. coli. NC system also downregulated the bla_CTX-M gene in E. coli. The hemolytic analysis proved biocompatibility with human red blood cells (RBCs). It is concluded that CCNC has the potential to be used as NC for target delivery of antibiotics and may combat toxicity of antibiotics as the inhibition of E. coli was noticed at low MIC concentration.

Macroalgae as a Source of Valuable Antimicrobial Compounds: Extraction and Applications

In the last few decades, attention on new natural antimicrobial compounds has arisen due to a change in consumer preferences and the increase in the number of resistant microorganisms. Macroalgae play a special role in the pursuit of new active molecules as they have been traditionally consumed and are known for their chemical and nutritional composition and their biological properties, including antimicrobial activity. Among the bioactive molecules of algae, proteins and peptides, polysaccharides, polyphenols, polyunsaturated fatty acids and pigments can be highlighted. However, for the complete obtaining and incorporation of these molecules, it is essential to achieve easy, profitable and sustainable recovery of these compounds. For this purpose, novel liquid-liquid and solid-liquid extraction techniques have been studied, such as supercritical, ultrasound, microwave, enzymatic, high pressure, accelerated solvent and intensity pulsed electric fields extraction techniques. Moreover, different applications have been proposed for these compounds, such as preservatives in the food or cosmetic industries, as antibiotics in the pharmaceutical industry, as antibiofilm, antifouling, coating in active packaging, prebiotics or in nanoparticles. This review presents the main antimicrobial potential of macroalgae, their specific bioactive compounds and novel green extraction technologies to efficiently extract them, with emphasis on the antibacterial and antifungal data and their applications.