Novel Silver-Platinum Nanoparticles for Anticancer and Antimicrobial Applications.

BACKGROUND: Cancer is a disease with an enormous worldwide impact. One of the fatal complications in cancer patients are bacterial opportunistic infections. The use of chemotherapeutic drugs made cancer remission more frequent and prolonged patient survival, but, increased the risk of infections. PURPOSE: Address the current problem with growing pandemic cancer and considering high risks of complications with bacterial infections, the present study synthesized novel dendritic assembly of silver (Ag)-platinum (Pt) nanoparticles. METHODS: Nanoparticles were characterized by TEM analysis, and the composition was confirmed by EDX. Bacterial studies were performed for Gram-positive Staphylococcus aureus, Gram-negative Pseudomonas aeruginosa and Gram-negative multi-drug resistant Escherichia coli. Cell experiments were performed with two different cancer cell lines, glioblastoma and melanoma to determine anticancer activity. Finally, cytotoxicity with fibroblast was tested. RESULTS: The TEM analysis of silver-platinum (AgPt) nanoparticles showed dendrimer shape nanoparticles with a mean size of 42 ± 11nm. Elemental composition was analyzed by EDX, confirming the presence of both Ag and Pt metals. The synthesized nanoparticles significantly inhibited the growth of medically important pathogenic, Gram-positive Staphylococcus aureus, Gram-negative Pseudomonas aeruginosa and Gram-negative multi-drug resistant Escherichia coli. Bactericidal effect of AgPt nanoparticles had greater effectiveness than silver nanoparticles. MTS assay revealed a selective and dose-dependent anticancer activity of AgPt nanoparticles over cancer cell lines glioblastoma and melanoma in the 10-250 µg/mL concentration range. Cytotoxicity experiments with fibroblast cells showed no side effects of nanoparticles against healthy cells at a range of concentrations from 10-50 µg/mL. CONCLUSION: The newly synthesized AgPt nanoparticles have a promising future as a potent anticancer agent with antibacterial properties.

Characterization and study of the antibacterial mechanisms of silver nanoparticles prepared with microalgal exopolysaccharides.

The green synthesis of biomaterials is of significant interest as it enables the safe and sustainable preparation of noble metallic nanoparticles for medical applications. Microalgae polysaccharides have received attention due to their outstanding properties such as biocompatibility, biodegradability and low cost. In addition, due to their variety of remarkable biological and physicochemical properties, polysaccharide-based nanoparticles have advantageous features yet to be explored. The primary objective of the current research was to investigate exopolysaccharides isolated from green microalgae Botryococcus braunii (EPBb) and Chlorella pyrenoidosa (EPCp), as both reducing and stabilizing agents, for the green synthesis of silver nanoparticles (AgNPs). Their antibacterial activity towards Gram-positive bacteria (Staphylococcus aureus), Gram-negative bacteria (Escherichia coli), and antibiotic-resistant bacteria (methicillin-resistant Staphylococcus aureus) was studied, as well as their cytotoxicity to human dermal fibroblasts. The presently synthesized AgNPs were spherical in shape and exhibited characteristic surface plasmon resonance at 430 nm. The main population had a particle size which ranged between 5 and 15 nm as analyzed by transmission electron micrographs. Zeta potentials averaged -51.81 ±â€¯3.01 mV using EPBb and -12.16 ±â€¯2.41 mV using EPCp. More importantly, AgNPs possessed strong antibacterial activity in a dose-dependent manner, even against drug-resistant bacteria. The enhanced antibacterial activity of these particles is explained due to extensive reactive oxygen species generation and bacterial cell membrane damage. In contrast, such AgNPs were not cytotoxic at the same therapeutic range to fibroblasts (0.5-10.0 µg/mL). In summary, these results showed that polysaccharide-capped AgNPs have a strong potential for numerous medical applications, such as antibacterial agents in pharmaceutical and biomedical areas.

Synthesis and study of cell-penetrating peptide-modified gold nanoparticles.

BACKGROUND: In nanomedicine, gold nanoparticles (AuNPs) have demonstrated versatile therapeutic efficiencies and, in particular, have been developed for the treatment of various cancers due to their high selectivity in killing cancer, not healthy, cells. METHODS: In this study, AuNPs were conjugated with the cell-penetrating peptide Cys-(Arg)8-Asp-Ser (CRRRRRRRRGDS) by direct cross-linking of the cysteine's thiol group to the gold surface and a fibronectin-derived RGD group was also used due to its efficacy toward cancer cell targeting and possible promotion of healthy fibroblast functions. RESULTS: Ultraviolet-visible absorbance spectrum and transmission electron microscope images of the synthesized peptide-capped AuNPs (PEP-AuNPs) validated the formation of AuNP aggregates. The presence of peptides on AuNPs was confirmed by Fourier transform infrared spectroscopy and quantified by a bicinchoninic acid assay. After being modified with the arginine-rich peptide, the AuNPs possessed a positive charge, as their zeta potential increased from -23.81±8.43 mV to 8 mV on average. In this manner, an easy method to conjugate AuNPs was shown here. Further, MTS assays were performed using healthy human dermal fibroblasts. After 24 hours of treatment with PEP-AuNPs, the cell density increased dramatically to around 25,000 cells/cm2. Results further showed a very high half-maximal inhibitory concentration of 69.2 µM for the PEP-AuNPs (indicating low toxicity). CONCLUSION: The results showed for the first time the ability of PEP-AuNPs to promote human dermal fibroblast cell viability, which after further investigation, may show an ability to replace cancerous tissue with healthy soft tissue.

Virus-induced gene silencing of the two squalene synthase isoforms of apple tree (Malus × domestica L.) negatively impacts phytosterol biosynthesis, plastid pigmentation and leaf growth.

MAIN CONCLUSION: The use of a VIGS approach to silence the newly characterized apple tree SQS isoforms points out the biological function of phytosterols in plastid pigmentation and leaf development. Triterpenoids are beneficial health compounds highly accumulated in apple; however, their metabolic regulation is poorly understood. Squalene synthase (SQS) is a key branch point enzyme involved in both phytosterol and triterpene biosynthesis. In this study, two SQS isoforms were identified in apple tree genome. Both isoforms are located at the endoplasmic reticulum surface and were demonstrated to be functional SQS enzymes using an in vitro activity assay. MdSQS1 and MdSQS2 display specificities in their expression profiles with respect to plant organs and environmental constraints. This indicates a possible preferential involvement of each isoform in phytosterol and/or triterpene metabolic pathways as further argued using RNAseq meta-transcriptomic analyses. Finally, a virus-induced gene silencing (VIGS) approach was used to silence MdSQS1 and MdSQS2. The concomitant down-regulation of both MdSQS isoforms strongly affected phytosterol synthesis without alteration in triterpene accumulation, since triterpene-specific oxidosqualene synthases were found to be up-regulated to compensate metabolic flux reduction. Phytosterol deficiencies in silenced plants clearly disturbed chloroplast pigmentation and led to abnormal development impacting leaf division rather than elongation or differentiation. In conclusion, beyond the characterization of two SQS isoforms in apple tree, this work brings clues for a specific involvement of each isoform in phytosterol and triterpene pathways and emphasizes the biological function of phytosterols in development and chloroplast integrity. Our report also opens the door to metabolism studies in Malus domestica using the apple latent spherical virus-based VIGS method.

Characterization of an autonomously replicating sequence in Candida guilliermondii.

Candida guilliermondii is an ascomycetous yeast widely studied due to its clinical importance, biotechnological interest, and biological control potential. During a series of preliminary experiments aiming at optimizing the electroporation procedure of C. guilliermondii cells, we observed that the efficiency of transformation of an ura5 recipient strain with the corresponding dominant marker URA5 was more than a thousand fold higher as compared with the transformation of an ura3 strain with the URA3 wild type allele. This result allowed the identification of an autonomously replicating sequence (ARS) within an A/T rich region located upstream of the URA5 open reading frame (ORF). Interestingly, linear double strand DNAs (dsDNAs) containing this putative ARS are circularized and then autonomously replicated in C. guilliermondii transformed cells. We demonstrated that the C. guilliermondii Lig4p ligase, involved in the canonical non-homologous end-joining (NHEJ) pathway, was responsible for this phenomenon since a lig4 mutant was unable to circularize and to autonomously maintain transforming dsDNAs containing the putative ARS. Finally, a functional dissection of the C. guilliermondii A/T rich region located upstream of the URA5 ORF revealed the presence of a 60 bp-length sequence essential and sufficient to confer ARS properties to shuttle plasmid and linear dsDNAs.

Kava-kava and anxiety: growing knowledge about the efficacy and safety.

Kava-kava (Piper methysticum G. Forster) has been used in social and ceremonial life in the Pacific islands from ancient times for the soporific and narcotic effects. Today several extracts standardized in the biologically active constituents kavalactones are marketed both as herbal medicinal products for anxiety disorders and as dietary supplements to improve stress disorders, nervous tension and restlessness. Unlike other substances used for these purposes, kava-kava has been shown to have minimal negative effects, and possibly positive effects, on reaction time and cognitive processing. Furthermore, it decreases anxiety without the loss of mental acuity. Although kava-kava has been found to be very effective, well tolerated, and non-addictive at therapeutic dosages, potential side effects can occur when very high doses are taken for extended periods. In addition, in the last two years unexpected high liver toxicity has been reported in two patients. Until now no studies support the liver toxicity of kavalactones and it is unknown which compound could have provoked the liver disease. On the other hand, it should be possible that unknown or unexpected constituents are the responsible or contributed to the liver toxicity.