Nanotoxicity of polyelectrolyte-functionalized titania nanoparticles towards microalgae and yeast: Role of the particle concentration, size and surface charge

We studied the nanotoxicity of titania nanoparticles (TiO₂NPs) of various hydrodynamic diameters and crystallite sizes towards C. reinhardtii microalgae and S. cerevisiae (yeast) upon illumination with UV and visible light. The cell viability was assessed for a range of nanoparticle concentrations and incubation times. We found that bare TiO₂NPs affect the C. reinhardtii cell viability at much lower particle concentrations than for yeast. We observed an increase of the TiO₂NPs toxicity upon illumination with UV light compared with that in dark conditions due to the oxidative stress of the produced reactive oxygen species. We also found an increased TiO₂NPs nanotoxicity upon illumination with visible light which indicates that they may also interfere with the microalgae's photosynthetic system leading to decreased chlorophyll content upon exposure to TiO₂NPs. The results indicate that the larger the hydrodynamic diameter of the TiO₂NPs the lower is their nanotoxicity, with anatase TiO₂NPs generally being more toxic than rutile TiO₂NPs. We also prepared a range of polyelectrolyte-coated TiO₂NPs using a layer by-layer method and studied their nanotoxicity towards yeast and microalgae. We found that the toxicity of the coated TiO₂NPs changes with their surface charge. TiO₂NPs coated with cationic polyelectrolyte as an outer layer exhibit much higher nanotoxicity than the ones with an outer layer of anionic polyelectrolyte. TEM images of sectioned microalgae and yeast cells exposed to different polyelectrolyte-coated TiO₂NPs confirmed the formation of a significant build-up of nanoparticles on the cell surface for bare and cationic polyelectrolyte-coated TiO₂NPs. The effect comes from the increased adhesion of cationic nanoparticles to the cell walls. Significantly, coating the TiO₂NPs with anionic polyelectrolyte as an outer layer led to a reduced adhesion and much lower nanotoxicity due to electrostatic repulsion with the cell walls. This suggest a new way of making cationic TiO₂NPs safer for use in different formulations by pre-coating them with anionic polyelectrolytes. The results of this study give important insights into the various factors controlling the nanotoxicity of TiO₂NPs

Controlling the nanotoxicity of polyelectrolyte-functionalized titania nanoparticles

This study gives important insights of the various factors controlling the nanotoxicity of titania nanoparticles (TiO2NPs). We studied the nanotoxicity of TiO2NPs of various hydrodynamic diameters and crystallite sizes on C. Reinhardtii (microalgae) and S. cerevisiae (yeast) upon illumination with UV/visible light [1]. The cell viability was assessed for a range of nanoparticle concentrations and incubation times. Bare TiO2NPs affect the microalgae viability at much lower particle concentrations than for yeast. We also found an increased nanotoxicity upon illumination with visible light which indicates that they may also interfere with the microalgae photosynthetic system leading to decreased chlorophyll content upon exposure to TiO2NPs. The results indicate that the larger the hydrodynamic diameter of the TiO2NPs the lower is their nanotoxicity, with anatase TiO2NPs generally being more cytotoxic than rutile TiO2NPs. We also prepared a range of polyelectrolyte-coated TiO2NPs using the layer by-layer method and studied their nanotoxicity on yeast and microalgae. The toxicity of the coated TiO2NPs alternates with their surface charge. TiO2NPs coated with cationic polyelectrolyte as an outer layer exhibit much higher nanotoxicity than the ones with an outer layer of anionic polyelectrolyte. TEM images of sectioned microalgae and yeast cells exposed to different polyelectrolyte-coated TiO2NPs confirmed the formation of a significant build-up of nanoparticles on the cell surface for bare- and cationic polyelectrolyte-coated TiO2NPs. The effect is coming from the increased adhesion of cationic nanoparticles to the cell walls. Significantly, coating the TiO2NPs with an anionic polyelectrolyte as an outer layer led to a reduced adhesion and much lower nanotoxicity due to electrostatic repulsion with the cell walls. This suggest a new way of making the TiO2NPs potentially safer for use in different formulations by pre-coating them with anionic polyelectrolytes. Please click Additional Files below to see the full abstract

Dual-functionalised shellac nanocarriers give a super-boost of the antimicrobial action of berberine

We have developed highly efficient antimicrobial nanocarriers for berberine (BRB) based on shellac nanoparticles (NPs) which were surface-functionalised with a surface active polymer, Poloxamer 407 (P407), and the cationic surfactant octadecyltrimethylammonium bromide (ODTAB). These shellac nanocarriers were produced in a two-step process which involves: (i) a pH change from aqueous ammonium shellac solution using P407 as a steric stabilizer in the presence of berberine chloride, and (ii) addition of ODTAB to yield shellac nanocarriers of cationic surface. We determined the BRB encapsulation efficiency and release profiles from such nanocarriers. We explored the antimicrobial action of these nanocarriers at different stages of their preparation which allowed us gain better understanding how they work, fine tune their design and reveal the impact of the nanoparticle coatings on to its antimicrobial effect. The antimicrobial action of BRB loaded within such shellac NPs with cationic surface functionality was examined on three different microorganisms, C. reinhardtii, S. cerevisiae and E. coli and compared with the effect of free BRB as well as non-coated BRB-loaded nanocarriers at the same BRB concentrations. We found that the cationic surface coating of the shellac NPs strongly amplified the efficiency of the encapsulated BRB across all tested microorganisms. The effect was attributed to the increased attraction between the ODTAB-coated BRB-loaded NPs and the anionic surface of the cell walls which delivers locally high BRB concentration. This nanotechnological approach could lead to more effective antimicrobial and disinfecting agents, dental formulations for plaque control, wound dressings, antialgal/antibiofouling formulations and antifungal agents

Enhanced antimicrobial effect of berberine in nanogel carriers with cationic surface functionality

We report a strong enhancement in the antimicrobial action of berberine encapsulated into polyacrylic acid-based nanogels followed by further surface functionalisation with a cationic polyelectrolyte (PDAC). Due to the highly developed surface area, the nanogel carrier amplifies the contact of berberine with microbial cells and increases its antimicrobial efficiency. We show that such cationic nanogel carriers of berberine can adhere directly to the cell membranes and maintain a very high concentration of berberine directly on the cell surface. We demonstrated that the antimicrobial action of the PDAC-coated nanogel loaded with berberine on E. coli and C. reinhardtii is much higher than that of the equivalent solution of free berberine due to the electrostatic adhesion between the positively charged nanogel particles and the cell membranes. Our results also showed a marked increase in their antimicrobial action at shorter incubation times compared to the non-coated nanogel particles loaded with berberine under the same conditions. We attribute this boost in the antimicrobial effect of these cationic nanocarriers to their accumulation on the cell membranes which sustains a high concentration of released berberine causing cell death within much shorter incubation times. This study can provide a blueprint for boosting the action of other cationic antimicrobial agents by encapsulating them into nanogel carriers functionalised with a cationic surface layer. This nanotechnology-based approach could lead to the development of more effective wound dressings, disinfecting agents, antimicrobial surfaces, and antiseptic and antialgal/antibiofouling formulations

Boosting the antimicrobial action of vancomycin formulated in shellac nanoparticles of dual-surface functionality

We report a strong amplification of the antimicrobial action of vancomycin (VCM) encapsulated in shellac nanoparticles (NPs) with dual surface functionalisation. These shellac nanocarriers for VCM were produced in two steps: (i) a pH drop from aqueous ammonium shellac solution containing Poloxamer 407 (P407) as a steric stabilising polymer in solution of vancomycin hydrochloride, and (ii) subsequent doping with the insoluble cationic surfactant octadecyltrimethylammonium bromide (ODTAB) though a solvent change to yield cationic surface functionality. We evaluated the encapsulation efficiency of VCM and its release profiles from these nanocarriers. This study explored the antibiotic action of these VCM nanocarriers at the various stages of their preparation which helped us to evaluate how they could be made to work efficiently, to adapt their design and demonstrate the role of the nanocarrier dual functionalisation on its antibiotic action and delivery. The antibiotic effect of VCM loaded in such versatile functionalised shellac nanocarriers was tested on three different proxy microorganisms, C. reinhardtii, S. cerevisiae and E. coli. We also compared the antibiotic effect of free VCM with non-coated VCM-loaded nanocarriers at the same overall concentrations. The ODTAB coating of the shellac NPs strongly enhanced the antibiotic action of the encapsulated VCM across all tested microorganisms. The enhanced VCM action is explained with the increased electrostatic adhesion between the ODTAB-coated VCM-loaded shellac NPs and the negatively charged surface of the microbial cell walls which allows local delivery of VCM with a high concentration directly on the cell membrane. This nanocarrier-mediated boost of the antibiotic action may potentially breathe new life into old antibiotics and help to fight off antibiotic resistance by making them more effective

Toxicity of polyelectrolyte-functionalized titania nanoparticles in zebrafish (Danio rerio) embryos

We investigated the effects of short-term exposure of bare TiO2NPs and polyelectrolyte-coated TiO2NPs in the 5-25 nm size range, at relatively high concentrations (of 500 and 1000 mg/L) under light or dark conditions, in D. rerio embryos. The biological endpoints investigated included embryo viability and mRNA transcript levels of antioxidant and membrane transport genes relative to control embryos. The presence of nanoparticles on the surface of embryos was assessed using TEM. The results confirm an accumulation of TiO2NPs on the outer surface (chorion) of the embryo, but not within the embryo. No significant difference in embryo viability was detected following each exposure regime. The expression of antioxidant biomarker, SOD2, was significantly impacted by the type of TiO2NP, with TiO2NPs/PSS/PAH coating exposure showing down regulation; the concentration of the nanoparticles, with down regulation at 500 mg/L; and dark/light condition with down regulation in the light. The expression levels of the hypoxia and membrane markers, HIF1 and Pxmp2, were not significantly impacted by any factor. The study indicates that SOD2 mRNA expression levels may be useful in the detection of apparent oxidative stress induced by the titania nanoparticle build up on the embryo chorion surface

Amplified antimicrobial action of chlorhexidine encapsulated in PDAC-functionalized acrylate copolymer nanogel carriers

We have developed and tested a novel functionalised nanocarrier for chlorhexidine (CHX) which provides a very strong enhancement of its antimicrobial action. The nanocarrier was based on lightly-cross-linked acrylate copolymer nanogel particles loaded with CHX followed by a surface functionalisation with the cationic polyelectrolyte poly(diallyldimethylammonium chloride (PDAC). We explored the antimicrobial effect of the PDAC-coated CHX-loaded nanogel carriers on E. coli, S. auresus, C. cerevisiae and C. reinhardtii and discovered that it is much higher than that of solution with equivalent overall concentration of free CHX. Our experiments also showed a marked increase of the cationic CHX-loaded nanocarriers antimicrobial action on these microorganisms at shorter incubation times compared with the non-coated CHX-loaded nanogel particles at the same CHX concentration and other conditions. We attribute the increase in the antimicrobial activity of the cationically-functionalised nanogel carrier to its electrostatic adhesion to the microbial cells walls which allows much higher CHX concentration to be delivered directly onto the cell surface. The results of this study can be used for development of novel more efficient antialgal, antifungal and antbacterial formulations based on cationically functionalised nanogels. Our method can also be used for boosting the effect of other cationic antimicrobial agents by encapsulating them in cationically-functionalised nanogel carriers. This nanotechnological approach could lead to developing more effective antimicrobial and disinfecting agents, dental formulations for plaque control, wound dressings, antialgal/antibiofouling formulations and novel antifungal agents

Parents’ experiences of health visiting for children with Down syndrome

© MA Healthcare Limited.Children with Down syndrome have an increased likelihoodof experiencing serious health conditions. Health visitors canhave an important role in monitoring and promoting healthand development for young children with Down syndrome.This study aimed to explore parents’ experiences of healthvisiting services for children with Down syndrome. Twentyfour parents of children with Down syndrome aged 0–5 yearscompleted a brief questionnaire about the number and natureof visits from health visitors in the previous 12 months andtheir support needs. Some parents commented that otherprofessionals met the needs of their child, whereas others saidthat they would like more advice and support from healthvisitors. A further exploration of broader health serviceprovision, including health visiting, for young children withDown syndrome is needed.Peer reviewedFinal Accepted Versio

Genome-wide association reveals three SNPs associated with sporadic amyotrophic lateral sclerosis through a two-locus analysis

<p>Abstract</p> <p>Background</p> <p>Amyotrophic lateral sclerosis (ALS) is a fatal, degenerative neuromuscular disease characterized by a progressive loss of voluntary motor activity. About 95% of ALS patients are in "sporadic form"-meaning their disease is not associated with a family history of the disease. To date, the genetic factors of the sporadic form of ALS are poorly understood.</p> <p>Methods</p> <p>We proposed a two-stage approach based on seventeen biological plausible models to search for two-locus combinations that have significant joint effects to the disease in a genome-wide association study (GWAS). We used a two-stage strategy to reduce the computational burden associated with performing an exhaustive two-locus search across the genome. In the first stage, all SNPs were screened using a single-marker test. In the second stage, all pairs made from the 1000 SNPs with the lowest p-values from the first stage were evaluated under each of the 17 two-locus models.</p> <p>Results</p> <p>we performed the two-stage approach on a GWAS data set of sporadic ALS from the SNP Database at the NINDS Human Genetics Resource Center DNA and Cell Line Repository <url>http://ccr.coriell.org/ninds/</url>. Our two-locus analysis showed that two two-locus combinations--rs4363506 (SNP1) and rs3733242 (SNP2), and rs4363506 and rs16984239 (SNP3) -- were significantly associated with sporadic ALS. After adjusting for multiple tests and multiple models, the combination of SNP1 and SNP2 had a p-value of 0.032 under the Dom∩Dom epistatic model; SNP1 and SNP3 had a p-value of 0.042 under the Dom × Dom multiplicative model.</p> <p>Conclusion</p> <p>The proposed two-stage analytical method can be used to search for joint effects of genes in GWAS. The two-stage strategy decreased the computational time and the multiple testing burdens associated with GWAS. We have also observed that the loci identified by our two-stage strategy can not be detected by single-locus tests.</p

Identification of novel Angiogenin (ANG) gene missense variants in German patients with amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal progressive neurodegenerative disease characterized by the selective death of motor neurons in the motor cortex, brain stem and spinal cord. Recently, missense variants in the angiogenin gene (ANG), an angiogenic factor expressed in ventral horn motor neurons that is up-regulated by hypoxia, have been found in ALS patients of Irish/Scottish, North American, Italian, French and Dutch descent. To investigate the role of ANG in the German population, we screened for mutations by sequencing the entire coding region of the ANG gene in a large sample of 581 German ALS cases and 616 sex- and age-matched healthy controls. We identified two heterozygous missense variants, F(−13)L and K54E, in two German sporadic ALS cases but not in controls. Both missense variants are novel and have not been previously found in ALS cases. Our results suggest that missense variants in the ANG gene play a role in ALS in the German population and provide further evidence to support the hypothesis that angiogenic factors up-regulated by hypoxia are involved in the pathophysiology of ALS