This work describes the synthesis
and characterization of noncytotoxic
nanocomposites either colloidal or as films exhibiting high antibacterial
activity. The biocompatible and biodegradable polymer chitosan was
used as reducing and stabilizing agent for the synthesis of gold nanoparticles
embedded in it. Herein, for the first time, three different chitosan
grades varying in the average molecular weight and deacetylation degree
(DD) were used with an optimized gold precursor concentration. Several
factors were analyzed in order to obtain antimicrobial but not cytotoxic
nanocomposite materials. Films based on chitosan with medium molecular
weight and the highest DD exhibited the highest antibacterial activity
against biofilm forming strains of Staphylococcus aureus and Pseudomonas aeruginosa. The resulting
nanocomposites did not show any cytotoxicity against mammalian somatic
and tumoral cells. They produced a disruptive effect on the bacteria
wall while their internalization was hindered on the eukaryotic cells.
This selectivity and safety make them potentially applicable as antimicrobial
coatings in the biomedical field.
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.
We describe the synthetic pathway to produce efficient bactericidal, fungicidal and non-cytotoxic chitosan–ascorbic acid–silver composites as solid films.
In this study, we report on the ability of the yeast Yarrowia lipolytica W29 to produce an extracellular melanin‐like brown pigment at high yield (0.5 mg/ml) in culture medium supplemented with L‐tyrosine. This pigment has been characterized as pyomelanin and its synthesis was found to occur by the so‐called HGA‐melanin pathway. The purified pyomelanin was found embedded with antioxidant properties as it exhibited a radical scavenging activity toward 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) with IC50 of 230 μg/ml. It was also characterized as noncytotoxic toward two mammalian cell lines, namely the mouse fibroblast NIH3T3 and human keratinocytes HaCaT. When blended with different commercial sunscreens, the purified pyomelanin increased significantly the sun protection factor (SPF) value, highlighting its potential utilization as UV‐filter in cosmetic preparations.
BackgroundElevated temperatures induce activation of the heat shock transcription factor 1 (HSF1) which in somatic cells leads to heat shock proteins synthesis and cytoprotection. However, in the male germ cells (spermatocytes) caspase-3 dependent apoptosis is induced upon HSF1 activation and spermatogenic cells are actively eliminated.ResultsTo elucidate a mechanism of such diverse HSF1 activity we carried out genome-wide transcriptional analysis in control and heat-shocked cells, either spermatocytes or hepatocytes. Additionally, to identify direct molecular targets of active HSF1 we used chromatin immunoprecipitation assay (ChIP) combined with promoter microarrays (ChIP on chip). Genes that are differently regulated after HSF1 binding during hyperthermia in both types of cells have been identified. Despite HSF1 binding to promoter sequences in both types of cells, strong up-regulation of Hsps and other genes typically activated by the heat shock was observed only in hepatocytes. In spermatocytes HSF1 binding correlates with transcriptional repression on a large scale. HSF1-bound and negatively regulated genes encode mainly for proteins required for cell division, involved in RNA processing and piRNA biogenesis.ConclusionsObserved suppression of the transcription could lead to genomic instability caused by meiotic recombination disturbances, which in turn might induce apoptosis of spermatogenic cells. We propose that HSF1-dependent induction of cell death is caused by the simultaneous repression of many genes required for spermatogenesis, which guarantees the elimination of cells damaged during heat shock. Such activity of HSF1 prevents transmission of damaged genetic material to the next generation.
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