Plain Polystyrene Research Articles

Surface functional groups on nanoplastics delay the recovery of gut microbiota after combined exposure to sulfamethazine in marine medaka (Oryzias melastigma)

Nanoplastics can interact with antibiotics, altering their bioavailability and the ensuing toxicity in marine organisms. It is reported that plain polystyrene (PS) nanoplastics decrease the bioavailability and adverse effects of sulfamethazine (SMZ) on the gut microbiota in Oryzias melastigma. However, the influence of surface functional groups on the combined effects with SMZ remains largely unknown. In this study, adult O. melastigma were fed diet amended with 4.62 mg/g SMZ and 3.65 mg/g nanoplastics (i.e., plain PS, PS-COOH and PS-NH2) for 30 days (F0 exposed fish, F0-E), followed by a depuration period of 21 days (F0 depurated fish, F0-D). In addition, the eggs produced on the last day of exposure were cultured under standard protocols without further exposure for 2 months (F1 fish). The results showed that the alpha diversity or the bacterial community of gut microbiota did not differ among the SMZ + PS, SMZ + PS-COOH, and SMZ + PS-NH2 groups in the F0-E and F1 fish. Interestingly, during the depuration, a clear recovery of gut microbiota (e.g., increases in the alpha diversity, beneficial bacteria abundances and network complexity) was found in the SMZ + PS group, but not for the SMZ + PS-COOH and SMZ + PS-NH2 groups, indicating that PS-COOH and PS-NH2 could prolong the toxic effect of SMZ and hinder the recovery of gut microbiota. Compared to plain PS, lower egestion rates of PS-COOH and PS-NH2 were observed in O. melastigma. In addition, under the simulated fish digest conditions, the SMZ-loaded PS-NH2 was found to desorb more SMZ than the loaded PS and PS-COOH. These results suggested that the surface -COOH and -NH2 groups on PS could influence their egestion efficiency and the adsorption/desorption behavior with SMZ, resulting in a long-lasting SMZ stress in the gut during the depuration phase. Our findings highlight the complexity of the carrier effect and ecological risk of surface-charged nanoplastics and the interactions between nanoplastics and antibiotics in natural environments.

Ultrasound-Activated Piezoelectric Polyvinylidene Fluoride-Trifluoroethylene Scaffolds for Tissue Engineering Applications.

Severe peripheral nervous system (PNS) injuries have limited options for therapeutic solutions to regain functional recovery. This can be attributed in part to the lack of regeneration pathways promoted by recapitulating chemical, physical, and electrical cues to direct nerve guidance. To address this, we examined ultrasonic stimulation of a piezoelectric polyvinylidene fluoride-triflouroethylene (PVDF-TrFE) scaffold as a potentially clinically relevant therapy for PNS regeneration. Owing to the piezoelectric modality of PVDF-TrFE, we hypothesize that ultrasound stimulation will activate the scaffold to electrically stimulate cells in response to the mechanical deformation mediated by sound waves. Biocompatible PVDF-TrFE scaffolds were fabricated to be used as an ultrasound-activated, piezoelectric biomaterial to enhance cellular activity for PNS applications. NIH-3T3 fibroblasts were cultured on PVDF-TrFE nanofibers and stimulated with low-, medium-, or high-powered ultrasound. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assays were performed on fibroblasts to measure the metabolic activity of the cells following stimulation. MTT assays showed that ultrasound-stimulated fibroblasts on PVDF-TrFE scaffolds had increased metabolic activity as power was increased, whereas on plain polystyrene, an opposite trend was observed where cells had a decreased metabolic activity with ascending levels of ultrasound power. Ultrasound-stimulated PVDF-TrFE nanofibers hold exciting potential as a therapy for PNS injuries by promoting increased metabolic activity and proliferation. The ability to noninvasively stimulate implantable piezoelectric nanofibers to promote mechanical and electrical stimulation for nerve repair offers a promising benefit to severe trauma patients.

Effects of Cascading Optical Processes: Part III. Impacts on Spectroscopic Measurements of Fluorescent Samples.

Cascading optical processes involve sequential photon-matter interactions triggered by the same individual excitation photons. Parts I and II of this series explored cascading optical processes in scattering-only solutions (Part I) and solutions with light scatterers and absorbers but no emitters (Part II). The current work (Part III) focuses on the effects of cascading optical processes on spectroscopic measurements of fluorescent samples. Four types of samples were examined: (1) eosin Y (EOY), an absorber and emitter; (2) EOY mixed with plain polystyrene nanoparticles (PSNPs), which are pure scatterers; (3) EOY mixed with dyed PSNPs, which scatter and absorb light but do not emit; and (4) fluorescent PSNPs that are simultaneous light absorbers, scatterers, and emitters. Interference from both forward scattered and emitted photons can cause nonlinearity and spectral distortion in UV-vis extinction measurements. Sample absorption by nonfluorogenic chromophores reduces fluorescence intensity, while the effect of scattering on fluorophore fluorescence is complicated by several competing factors. A revised first-principles model is developed for correlating the experimental fluorescence intensity with the sample absorbance in solutions containing both scatterers and absorbers. The optical properties of fluorescent PSNPs of three different sizes were systematically investigated by using integrating-sphere-assisted resonance synchronous spectroscopy, linearly polarized resonance synchronous spectroscopy, UV-vis, and fluorescence spectroscopy. The insights and methodology provided in this work should help improve the reliability of spectroscopic analyses of fluorescent samples, where the interplay among light absorption, scattering, and emission can be complex.

Combined effects of microplastics and excess boron on Microcystis aeruginosa

Both microplastics (MPs) and excess boron (B) have adverse effects on microalgae. However, the combined toxic effects of MPs and excess B on microalgae have not been studied. The aim of this study was to investigate the combined effects of excess B and three types of surface-modified microplastics, including plain polystyrene (PS-Plain), amino-modified polystyrene (PS-NH2), and carboxyl-modified polystyrene (PS-COOH), on chlorophyll a content, oxidative damage, photosynthetic activity and microcystin (MC) production in Microcystis aeruginosa. The results showed that PS-NH2 inhibited the growth of M. aeruginosa, with the maximum inhibition rate of 18.84 %, while PS-COOH and PS-Plain showed stimulatory effects with the maximum inhibition rates of −2.56 % and − 8.03 % respectively. PS-NH2 aggravated the inhibition effects of B, while PS-COOH and PS-Plain alleviated the inhibition effects. Furthermore, the combined exposure of PS-NH2 and excess B had a much greater effect on oxidative damage, cell structure, and production of MCs in algal cells than the combined effects of PS-COOH and PS-Plain. The charges on microplastics affected both B adsorption on microplastics and the aggregation of microplastics with algal cells, indicating that the charge on microplastics is a dominant factor influencing the combined effects of microplastics and excess B on microalgae. Our findings can provide direct evidence for the combined effects of microplastics and B on freshwater algae and improve the understanding of the potential risks of microplastics in aquatic ecosystems.

Antiadhesive and Antibiofilm Effect of Malvidin-3-Glucoside and Malvidin-3-Glucoside/Neochlorogenic Acid Mixtures upon Staphylococcus.

Several reports on the biological activity of anthocyanin-rich extracts have been made. However, despite the association of said activity with their anthocyanin content, to the best of our knowledge, there are no previous works regarding the antimicrobial, antibiofilm and/or antiadhesive properties of anthocyanins alone. Therefore, the present work aimed to determine the effects of malvidin-3-glucoside, a major component of a previously reported extract, and the impact of its association with neochlorogenic acid (the only non-anthocyanin phenolic present in said extract), upon several Staphylococcus strains with varying resistance profiles. Results show that, while malvidin-3-glucoside and malvidin-3-glucoside/neochlorogenic acid mixtures were unable to considerably inhibit bacterial growth after 24 h, they still possessed an interesting antibiofilm activity (with reductions of biofilm entrapped cells up to 2.5 log cycles, metabolic inhibition rates up to 81% and up to 51% of biomass inhibition). When considering the bacteria's capacity to adhere to plain polystyrene surfaces, the inhibition ranges were considerably lower (21% maximum value). However, when considering polystyrene surfaces coated with plasmatic proteins this value was considerably higher (45% for adhesion in the presence of extract and 39% for adhesion after the surface was exposed to extract). Overall, the studied anthocyanins showed potential as future alternatives to traditional antimicrobials in adhesion and biofilm formation prevention.

Dietary exposure to four sizes of spherical polystyrene, polylactide and silica nanoparticles does not affect mortality, behaviour, feeding and energy assimilation of Gammarus roeseli

The abundance and persistence of plastic nanoparticles in aquatic habitats are considered a threat to marine and freshwater biota. However, the risk assessment of plastic particles is complicated due to various factors that need to be considered, including composition, size and environmental abundance. This study investigated the behavioural response of a key river species, Gammarus roeseli, to dietary exposure of plain biodegradable and non-biodegradable plastic as well as to natural small micro- and nanoparticles. Mortality, feeding, swimming velocity and energy assimilation endpoints were examined by considering four particles sizes ranging from 30 to 1000 nm in two concentrations. Contrary to our expectations, neither decreasing size nor increasing abundance of each tested particle impacted any of the examined endpoints. Likewise, dietary exposition with biodegradable plain polylactide did not induce other or stronger effects than non-biodegradable plain polystyrene or natural silica micro- and nanoparticles, as all three particle types did not lead to adverse effects on G. roeseli. These findings also suggest that the functional role of Gammarus roeseli as a shredder is not impaired due to particle occurrence within the exposure range of this study.

The Effect of Submicron Polystyrene on the Electrokinetic Potential of Cell Membranes of Red Blood Cells and Platelets.

In recent years, many scientists have studied the effects of polymer micro- and nanostructures on living organisms. As it turns out, plastic can be a component of the blood of livestock, eaten by humans around the globe. Thus, it seems important to investigate possible changes in the physicochemical parameters and morphology of the cell membranes of blood morphotic elements (red blood cells and platelets) under the influence of polymer particles. The article presents research in which cell membranes were exposed to plain polystyrene (PS) and amino-functionalized polystyrene (PS-NH2) of two different sizes. The polymers were characterized by infrared spectroscopy and dynamic light-scattering methods. To analyze possible changes caused by polymer exposure in the structure of the membranes, their zeta potentials were measured using the electrophoretic light-scattering technique. The concentration of the polymers, as well as the exposure time, were also taken into the consideration during the research. Based on the obtained results, we concluded that 100 and 200 nm PS, as well as 100 nm PS-NH2, internalize into the cells. On the contrary, 200 nm PS-NH2 particles attach to cell membranes. Our study clearly shows that particle size and surface chemistry determine the interaction with biological membranes.

Uptake and accumulation of microplastic particles by two freshwater ciliates isolated from a local river in South Africa.

Microplastics are considered environmental pollutants of serious concern. In freshwater environments, they can affect aquatic biota and accumulate along the food web. Therefore, this study investigated the capacity of bacterivorous freshwater ciliates, essential members of the aquatic food chain, to ingest plain and fluorescently-labeled polystyrene microspheres. Two holotrich ciliates were isolated from a stream in KwaZulu-Natal (South Africa) and identified as members of the genera Paramecium and Tetrahymena based on morphological characteristics and 18S rRNA gene sequence analysis. While the larger bacterivorous ciliate Paramecium sp. strain RB1 ingested all three sizes of plain polystyrene microbeads tested (2,5,10μm), the smaller sized Tetrahymena sp. strain RB2 only ingested microbeads of 2 and 5μm. The two ciliates ingested polystyrene microbeads at rates ranging from 1650 to 3870 particles x ciliate-1 x hour-1 for all particle sizes ingested, matching rates determined for selected microbial prey (E. coli, S. cerevisiae) of similar size. The ability to ingest non-nutritious microplastic particles was confirmed for both ciliates using fluorescently-labeled microbeads as these were detected in food vacuoles by fluorescence microscopy. Therefore, ciliates such as Paramecium sp. strain RB1 and Tetrahymena sp. strain RB2 can contribute to the transfer and bioaccumulation of microplastics in freshwater food webs in South Africa.

Toxicity evaluation of nano-TiO2 in the presence of functionalized microplastics at two trophic levels: Algae and crustaceans

The rising use of contaminants such as nanoparticles and microplastics has taken a heavy toll on the marine environment. However, their combined toxic effects on the species across various trophic levels remain quite unexplored. The aim of this study was to explore the effects of three surface-functionalized (carboxylated, plain, and aminated) polystyrene microplastics on nano-TiO2 toxicity across two trophic levels containing Chlorella sp. as the prey and Artemia salina as the predator. The experiments carried out on Chlorella sp. include the toxicity assessment, oxidative stress determination, and uptake of nano-TiO2 (both in the presence and absence of microplastics). Results revealed that the aminated and plain polystyrene microplastics enhanced nano-TiO2 toxicity, while carboxylated microplastics decreased the toxic effects in Chlorella sp. On the other hand, toxicity assessment in Artemia salina was carried out using two different modes of exposure: aqueous and dietary routes. The aqueous route involving the direct exposure of nano-TiO2 and microplastics indicated greater toxicity, uptake, and accumulation in Artemia salina than the dietary route of exposure. Since dietary exposure decreased the toxicity, uptake, and accumulation of nano-TiO2, no change (p > 0.05) in the biomagnification factors of nano-TiO2 was noted for all the test concentrations of nano-TiO2 combined with and without microplastics. The computed values were less than 1, indicating negligible transfer of nano-TiO2 from Chlorella sp. to Artemia salina. Overall, the study highlights the two-level trophic toxicity and the transfer potential of nano-TiO2 under the influence of different microplastics.

Microplastics decrease the toxicity of triphenyl phosphate (TPhP) in the marine medaka (Oryzias melastigma) larvae

Plastics have been recognized as a serious threat to the environment. Besides their own toxicity, microplastics can interact with other environmental pollutants, acting as carriers and potentially modulating their toxicity. In this study, the toxicity of polystyrene (PS) microplastic fragments (plain PS; carboxylated PS, PS-COOH and aminated PS, PS-NH2) and triphenyl phosphate (TPhP) (an emerging organophosphate flame retardant) at the environmentally relevant concentrations to the marine medaka (Oryzias melastigma) larvae was investigated. Larvae were exposed to 20 μg/L of microplastic fragments or 20 and 100 μg/L of TPhP or a combination of both for 7 days. The results showed that the three microplastics did not affect the larval locomotor activity. For TPhP, the larval moving duration and distance moved were significantly decreased by the TPhP exposure, with a maximum decrease of 43.5% and 59.4% respectively. Exposure to 100 μg/L TPhP respectively down-regulated the expression levels of sine oculis homeobox homologue 3 (six3) and short wavelength-sensitive type 2 (sws2) by 19.1% and 41.7%, suggesting that TPhP might disturb eye development and photoreception and consequently the low locomotor activity in the larvae. Interestingly, during the binary mixture exposure, the presence of PS, PS-COOH or PS-NH2 reversed the low locomotor activity induced by 100 μg/L TPhP to the normal level. Relative to the larvae from the 100 μg/L TPhP group, the movement duration and distance moved were increased by approximately 60% and 100%, respectively, in the larvae from the TPhP + PS, TPhP + PS-COOH and TPhP + PS-NH2 groups. However, the gene expression profiles were distinct among the fish from the TPhP + PS, TPhP + PS-COOH and TPhP + PS-NH2 groups, implying different mechanisms underlying the reversal of the locomotor activity. The findings in this study challenge the general view that microplastics aggravate the toxicity of the adsorbed pollutants, and help better understand the environmental risk of microplastic pollution.

Plain polystyrene microplastics reduce the toxic effects of ZnO particles on marine microalgae Dunaliella salina

Abstract A critical literature survey on marine ecotoxicology reveals a lack of comprehensive studies to assess the impact of microplastics on the toxicity of engineered nanomaterials at environmentally relevant doses. Though ZnO and microplastics both are well known to be marine pollutants, the combined toxicity of ZnO particles with plain polystyrene (PS) microplastics are yet to be studied. Preliminary characterization of ZnO particles included examining particle size, morphology, and surface area. The amount of nominal and dissolved ions in the suspensions containing nano-sized ZnO particles was determined. The toxicity of bulk and nano-sized ZnO particles in combination with plain PS microplastics at low concentration (1 mg/ L) was assessed towards marine algae Dunaliella salina at three exposure concentrations 1.22, 12.28 and 122.88 μM under UV-A and dark exposure conditions. As expected, a dose-dependent increment in the toxicity, ROS (extracellular & intracellular) generation and lipid peroxidation were noted for both bulk and nano-sized ZnO particles. The harmful effects of bulk and nano-sized ZnO particles were considerably reduced in the presence of plain PS microplastics. This study opens up new dimensions regarding the positive impact of microplastics at low concentration, where they lessen the toxic effects of co-pollutants in the marine ecosystem.

Static Polystyrene Gate Charge Density Modulation of Dinaphthothienothiophene with Tetrafluorotetracyanoquinodimethane Layer Doping: Evidence from Conductivity and Seebeck Coefficient Measurements and Correlations

We relate the static charging of organic field effect transistor (OFET) gate dielectric polymers, the resulting change in threshold voltage shift, and the modulation of thermoelectric properties of the transistor semiconductor. We utilize a bottom gate OFET structure with cross-linkable polystyrene and plain polystyrene (XLPS/PS) bilayer dielectrics and dinaphthothienothiophene (DNTT) organic molecular semiconductor with tetrafluorotetracyanoquinodimethane (F4TCNQ) doping layer. The conductivity and Seebeck coefficient are measured before and after charging. We find that the conductivity increases significantly, while the Seebeck coefficient decreases correspondingly in a trend of S ∝ ln(σ) after the dielectrics were negatively charged, resulting in an average of 5-fold increase in power factor at the maximum charging level. Additionally, temperature-dependent conductivity measurements show that the activation energy decreases with the increasing conductivity. We calculate the Seebeck coefficient based on the activation energy and find the result is consistent with the Mott mobility edge model. This work confirms the charging mechanism in our previous published work, including the location of static charges in the bulk of the dielectric, and demonstrates modulation and enhancement of the thermoelectric properties of organic thermoelectric materials by adjacent chargeable dielectrics without changing the molecular microstructure or applying external gate voltage during operation.

Investigating the toxicities of different functionalized polystyrene nanoplastics on Daphnia magna

Nanoplastics (NPs) spread widely with water and air current, and they can accumulate in aquatic organisms, even penetrating biofilms, which may cause persistent toxicity and potential hazards. This current study aimed to reveal the toxicological mechanism of different functionalized polystyrene (PS) NPs on Daphnia magna (D. magna) by investigating toxicity endpoints in individual level and biochemical level. In this study, acute toxicity, behavioral parameters and biomarker responses of D. magna was measured in the exposure of different functionalized PS NPs (plain PS, PS-p-NH2, PS-n-NH2 and PS-COOH). The results indicated that when exposed to the plain PS, ROS induction would activate MAPKs, thereby causing lethality and adverse behavior effects on D. magna; while the functionalized PS NPs were less toxic than the plain PS, especially for PS-p-NH2 which was severely flocculated after exposure, thus showing no immobilization at the investigated concentrations. Also, the antioxidant system was mainly stimulated due to the direct interaction with the cell surface receptor, which was different from the plain PS. Consequently, this work suggests significant effects of functional groups on NPs for environmental toxicity studies, and provides a better understanding of the toxicological mechanism on the toxicity of PS NPs toward D. magna.

High-efficiency nitrene-based crosslinking agent for robust dielectric layers and high-performance solution-processed organic field-effect transistors

High-performance organic field-effect transistors (OFETs) need not only high-mobility organic semiconductors, but also suitable organic dielectric layers. OFETs with the polystyrene (PS) dielectric layer have shown superior electrical characteristics and operational stability levels due to the hydrophobicity of PS. However, PS is usually compatible with vacuum-evaporated semiconductors because the solution process dissolves the bottom PS layer, making it difficult to obtain a high-quality semiconducting film. In this study, we develop the chemically robust dielectric film ‘FPS’, made up of 5 wt% ethylene glycol bis(4-azido-2,3,5,6-tetrafluoro-benzoate) (sFPA) in a PS film. Addition of UV-responsive sFPA causes the film to become crosslinked after UV irradiation while maintaining its surface properties compared to the PS film. Crosslinking with a very small amount of sFPA is possible due to high crosslinking efficiency of sFPA, not requiring two specific functional groups. In addition, an as-cast FPS film is readily photo-patterned by UV irradiation with a shadow mask. The solution-processed TES-ADT semiconductor film shows a highly crystalline morphology on the FPS layer, and its OFETs show much higher field-effect mobility levels than those with the plain PS layer. These results are attributed to the chemical robustness of the FPS layer, and its favorable environment for growth of TES-ADT crystals. Therefore, we expect the FPS layer to be used as a versatile dielectric layer with various solution-processed semiconductors.

Fabrication of silver nanoparticles-embedded antibacterial polymer surface through thermal annealing and soft molding technique

The major challenge faced in biomedical field is the formation of biofilm on polymer devices like catheters. It is important to functionalize the biomedical devices with a bactericidal agent through an easy and safe process in order to protect them from bacterial attack. In this article, the new method of impregnation of silver nanoparticles (AgNPs) into polymer film was proposed and tested against bacterial cells. The different sizes of silver nanoparticles were embedded in polystyrene film using thermal annealing and soft molding technique. Silver films having different thickness were deposited on the highly polished machinable glass ceramic (MACOR) substrate using direct current (DC) sputtering and subjected to at 750 °C for 15 min. After the heat treatment, AgNPs were formed on MACOR sample. It was then characterized using field emission scanning electron microscope (FE-SEM). Image-J software was used to analysed shape, size and distribution of AgNPs. The spin coating method was adopted to coat polystyrene film on to MACOR substrate supported AgNPs and allow it to cure for 24 h. After curing, the polystyrene film was peeled off and finally, AgNPs got transferred to polystyrene film. The AgNPs embedded polystyrene film was analyzed using FE-SEM and atomic force microscopy (AFM). Spread plate (plate counting) method was used to evaluate the bacterial killing potential of modified polystyrene film against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. The modified polystyrene film shows effective antibacterial ability against both the types of bacteria compared to the plain polystyrene surface.

Multiple particle tracking study of thermally-gelling nanoemulsions.

We perform multiple particle tracking (MPT) on a thermally-gelling oil-in-water nanoemulsion system. Carboxylated and plain polystyrene probes are used to investigate the role of colloidal probe size and surface chemistry on MPT in the nanoemulsion system. As temperature increases, hydrophobic groups of PEG-based gelators (PEGDA) partition into the oil/water interface and bridge droplets. This intercolloidal attraction generates a wide variety of microstructures consisting of droplet-rich and droplet-poor phases. By tailoring the MPT colloidal probe surface chemistry, we can control the residence of probes in each domain, thus allowing us to independently probe each phase. Our results show stark differences in probe dynamics in each domain. For certain conditions, the mean squared displacement (MSD) can differ by over four orders of magnitude for the same probe size but different surface chemistry. Carboxylated probe surface chemistries result in "slippery" probes while plain polystyrene probes appear to tether to the nanoemulsion gel network. We also observe probe hopping between pores in the gel for carboxylated probes. Our approach demonstrates that probes with different surface chemistries are useful in probing the local regions of a colloidal gel and allows the measurement of local properties within structurally heterogeneous hydrogels.

On the effect of thermophoretic force, gravitational force, and particle–particle interactions in field-flow fractionation

ABSTRACTThe theoretical calculations confirmed that the gravitational force cannot be neglected in all field-flow fractionation techniques separating nanometer-sized colloidal particles whenever particle diameter is approximately 200 nm and larger. Particle–particle repulsive interactions, mostly electrostatic repulsions, influence substantially concentration distribution established by any effective field acting across the fractionation channel, as confirmed explicitly for thermophoretic force generated by temperature gradient in microthermal field-flow fractionation. The ionic strength of the carrier liquid causes the screening of the electrostatic double layer around the dispersed particles and thus influences the retention. The attractive particle–particle forces occur when the zeta potential of the particles approaches to 0 mV, the electrostatic repulsions are screened, and the aggregation of the particles is observed. The pH influences differently the size and zeta potential of the plain polystyrene latex particles and of the particles modified on the surface by the groups –COOH and –NH2. The role of a detergent in carrier liquid is non-negligible, as demonstrated by its presence or absence in carrier liquid.

Aligned carbon nanotube containing scaffolds for neural tissue regeneration.

Neuropathologies include the deterioration and damage of the nervous system, especially neurons present in the brain, spinal cord and peripheral nervous system. Damage or alternations in neurons makes their structure and functionality abnormal. Every year over 90,000 people get affected by neurodegenerative diseases in the USA. Among all the neurological pathologies, the spinal cord injuries alone influence 10,000 people in the USA every year. Millions of cases of neurodegenerative pathologies are registered worldwide. Without proper treatment and cure to these cases, the toll for patients suffering from neurode-generative disease is expected to reach at least 12 million in the USA 30 years from now (John, 2015).

Reaction of monocytes to polystyrene and silica nanoparticles in short-term and long-term exposures.

Nanoparticles (NPs) are increasingly used in industrial, health and consumer products. In addition to the intended effects, NPs may also cause cell damage. Typical cytotoxicity assays assess short-term effects in adherent cells but do not evaluate longer exposure times and do not focus on cells in suspension. Since NPs are not removed easily from the organism, non-biodegradable NPs may persist in the systemic circulation and affect monocyte function at low concentrations. To mimic this situation, THP-1 monocytes were exposed to low concentrations of plain polystyrene particles (PPP) in different sizes for short (24 h) and prolonged (16 d) time periods. CELLine CL350, a small two-chamber bioreactor, and sub-culturing in flasks were compared regarding prolonged cytotoxicity testing. Uptake rates of the particles, cytotoxicity screening assays, and interleukin secretion were used for the identification of adverse effects. After 24 h, 50 μg ml-1 20 nm PPP did not affect cellular viability and interleukin secretion, while at higher concentrations the cytotoxicity of PPP (20 nm-500 nm) was correlated to surface area. After 16 d of exposure at 50 μg ml-1 20 nm PPP, the decrease in cell number and the increase in interleukins were significant. 200 nm PPP, by contrast, caused only minimal effects. Due to lower reproducibility, CELLine proved to be less suitable for the assessment as compared to sub-culturing in flasks. After prolonged exposure, silica Aerosil OX50 particles also were more cytotoxic towards THP-1 monocytes. The data suggest that prolonged exposure to NPs leads to cytotoxicity at low doses and that induction of cell death may be involved in the observed pro-inflammatory action of NPs.

Novel strontium-doped bioactive glass nanoparticles enhance proliferation and osteogenic differentiation of human bone marrow stromal cells

The present study investigates a new family of bioactive glass nanoparticles with and without Sr-doping focusing on the influence of the nanoparticles on human bone marrow stromal cells (hBMSCs) in vitro. The bioactive glass nanoparticles were fabricated by flame spray synthesis and a particle diameter of 30–35 nm was achieved. Glass nanoparticles were undoped (BG 13-93-0Sr) or doped with 5 wt% strontium (Sr) (BG 13-93-5Sr) and used at concentrations of 10 and 100 μg/cm² (particles per culture plate area), respectively. Cells were cultured for 14 days after which the samples were analysed regarding metabolic activity and expression of various bone-specific genes. Cell growth and morphology indicated the high cytocompatibility of the nanoparticulate bioactive glass. The presence of the nanoparticles enhanced cell growth compared to the plain polystyrene control group. At a concentration of 100 μg/cm², Sr-doped particles led to significantly enhanced gene expression of osteocalcin, collagen type 1 and vascular endothelial growth factor. Thus, Sr-doped nanoparticles showing a dose-dependent increase of osteogenic differentiation in hBMSCs are a promising biomaterial for bone regeneration purposes.