Nanoparticles as delivery vehicles for sunscreen agents

Environmental implications and nanotechnological advances in octocrylene-enriched sunscreen formulations: A comprehensive review

Ultraviolet (UV) radiation is a major contributor to skin aging, cancer, and other detrimental health effects. Sunscreens containing FDA-approved UV filters, like avobenzone, offer protection but suffer from photodegradation and potential phototoxicity. Encapsulation, antioxidants, and photostabilizers are strategies employed to combat these drawbacks. Octocrylene, an organic UV filter, utilizes nanotechnology to enhance sun protection factor (SPF). This review examines recent literature on octocrylene-enriched sunscreens, exploring the interplay between environmental impact, nanotechnological advancements, and clinical trial insights. A critical focus is placed on the environmental consequences of sunscreen use, particularly the potential hazards UV filters pose to marine ecosystems. Research in the Mediterranean Sea suggests bacterial sensitivity to these filters, raising concerns about their integration into the food chain. This review aims to guide researchers in developing effective strategies for photostabilization of UV filters. By combining encapsulation, photostabilizers, and antioxidants, researchers can potentially reduce phototoxic effects and contribute to developing more environmentally friendly sunscreens.

Characterization Methods for Nanoparticle-Skin Interactions: An Overview

Research progresses have led to the development of different kinds of nanoplatforms to deliver drugs through different biological membranes. Particularly, nanocarriers represent a precious means to treat skin pathologies, due to their capability to solubilize lipophilic and hydrophilic drugs, to control their release, and to promote their permeation through the stratum corneum barrier. A crucial point in the development of nano-delivery systems relies on their characterization, as well as in the assessment of their interaction with tissues, in order to predict their fate under in vivo administration. The size of nanoparticles, their shape, and the type of matrix can influence their biodistribution inside the skin strata and their cellular uptake. In this respect, an overview of some characterization methods employed to investigate nanoparticles intended for topical administration is presented here, namely dynamic light scattering, zeta potential, scanning and transmission electron microscopy, X-ray diffraction, atomic force microscopy, Fourier transform infrared and Raman spectroscopy. In addition, the main fluorescence methods employed to detect the in vitro nanoparticles interaction with skin cell lines, such as fluorescence-activated cell sorting or confocal imaging, are described, considering different examples of applications. Finally, recent studies on the techniques employed to determine the nanoparticle presence in the skin by ex vivo and in vivo models are reported.

Overcoming limitations of conventional solvent exchange methods: Achieving monodisperse non-equilibrium polymer micelles through equilibration-nanoprecipitation (ENP)

Hypothesis Conventional solvent exchange formulation methods face limitations when trying to control the final non-equilibrium size properties of block copolymer micelles containing a strongly hydrophobicity and a rigid block because the solvent conditions are not well controlled during micelle formation. Therefore, using an alternative formulation method, named Equilibration-Nanoprecipitation (ENP), in which micelles are formed under uniform solvent conditions, will significantly reduce the final dispersity compared a conventional solvent exchange method. EXPERIMENTAL: Size properties of the final aqueous micelle dispersions formed from the ENP method and a conventional solvent exchange are measured using DLS. Also, a parallel modelling study is completed to predict the final size distributions using both methods. Findings The experimental results demonstrate the ENP method is effective producing non-equilibrium micelles with low dispersity below the monodisperse polydispersity index (PDI) cutoff for DLS while the conventional solvent exchange method leads to significantly greater dispersity. Also the experimental results highlight ENP can be used to tune the final size properties which cannot be done using methods which do not properly control the micelle formation conditions. Additionally, the modelling study supports the utility of the ENP approach for producing monodisperse dispersions of nonequilibrium polymer micelles.

Ultrafast excited-state energy dissipation pathway of diethylamino hydroxybenzoyl hexyl benzoate (DHHB) via the nanoparticles

The organic UVA filter is popularized in sunscreen cosmetics due to the advantages of excellent light stability and high molar extinction coefficient. However, the poor water solubility of organic UV filters has been a common problem. Given that nanoparticles (NPs) can significantly improve the water solubility of organic chemicals. Meanwhile, the excited-state relaxation pathways of NPs might differ from their solution. Here, the NPs of diethylamino hydroxybenzoyl hexyl benzoate (DHHB), a popular organic UVA filter, were prepared by an advanced ultrasonic micro-flow reactor. The surfactant (sodium dodecyl sulfate) was selected as an effective stabilizer to prevent the self-aggregation of the NPs for DHHB. Femtosecond transient ultrafast spectroscopy (fs-TA) and theoretical calculations were utilized to trace and explain the excited-state evolution of DHHB in NPs suspension and its solution. The results reveal that the surfactant-stabilized NPs of DHHB reserve a similarly good performance of ultrafast excited-state relaxation. The stability characterization experiments demonstrate that the strategy of surfactant-stabilized NPs for sunscreen chemicals can maintain its stability and enhance the water solubility of DHHB compared with that of the solution phase. Therefore, the surfactant-stabilized NPs of organic UV filters are an effective method to improve water solubility and keep the stability from aggregation and photoexcitation.

Preparation of enzymolysis porous corn starch composite microcapsules embedding organic sunscreen agents and its UV protection performance and stability

In this paper, a natural composite wall material sunscreen microcapsule was prepared, which significantly improved the SPF value and photostability of the embedded sunscreen agents. Using modified porous corn starch and whey protein as wall materials, the sunscreen agents 2-[4-(diethylamino)-2-hydroxybenzoyl] benzoic acid hexyl ester and ethylhexyl methoxycinnamate were embedded by adsorption, emulsion, encapsulation and solidification. The embedding rate of the obtained sunscreen microcapsules was 32.71 % and the average size was 7.98 μm; the enzymatic hydrolyzed starch formed a porous structure, its X-ray diffraction pattern did not change significantly, and the specific volume and oil absorption rate increased by 39.89 % and 68.32 %, respectively, compared with those before enzymatic hydrolyzed; The porous surface of the starch after embedding the sunscreen was covered and sealed with whey protein. 120 h sunscreen penetration rate was lower than 12.48 %; Compared with the lotion containing the same amount of sunscreen but not encapsulated, the SPF value of the lotion containing sunscreen microcapsules increased by 62.24 %, and the photostability of sunscreen microcapsules increased by 66.28 % within 8 h under the irradiation intensity of 25 w/m². The wall material and the preparation method are natural and environmentally friendly, and have a good application prospect in low-leakage drug delivery system.

Role of ZnO Nanoparticles Loading in Modifying the Morphological, Optical, and Thermal Properties of Immiscible Polymer (PMMA/PEG) Blends

High-performance hybrid polymer blends can be prepared by blending different types of polymers to improve their properties. However, most polymer blends exhibit phase separation after blending. In this study, polymethylmethacrylate/polyethylene glycol (PMMA/PEG) polymer blends (70/30 and 30/70 w/w) were prepared by solution casting with and without ZnO nanoparticles (NPs) loading. The effect of loading ZnO nanoparticles on blend morphology, UV blocking, glass transition, melting, and crystallization were investigated. Without loading ZnO NP, the PMMA/PEG blends showed phase separation, especially the PEG-rich blend. Loading PMMA/PEG blend with ZnO NPs increased the miscibility of the blend and most of the ZnO NPs dispersed in the PEG phase. The interaction of the ZnO NPs with the blend polymers slightly decreased the intensity of infrared absorption of the functional groups. The UV-blocking properties of the blends increased by 15% and 20%, and the band gap energy values were 4.1 eV and 3.8 eV for the blends loaded with ZnO NPs with a PMMA/PEG ratio of 70/30 and 30/70, respectively. In addition, the glass transition temperature (T_g) increased by 14 °C, the crystallinity rate increased by 15%, the melting (T_m) and crystallization(T_c) temperatures increased by 2 °C and 14 °C, respectively, and the thermal stability increased by 25 °C compared to the PMMA/PEG blends without ZnO NP loading.

Exposure to polystyrene nanoplastics impairs lipid metabolism in human and murine macrophages in vitro

The use of polystyrene micro and nanoplastics in cosmetics and personal care products continues to grow every day. The harmful effects of their biological accumulation in organisms of all trophic levels including humans have been reported by several studies. While we have accumulating evidence on the impact of nanoplastics on different organ systems in humans, only a handful of reports on the impact of polystyrene nanoplastics upon direct contact with the immune system at the cellular level are avialable. The present study offers significant evidence on the cell-specific harmful impact of sulfate-modified nanoplastics (S-NPs) on human macrophages. Here we report that exposure of human macrophages to S-NPs (100 µg/mL) stimulated the accumulation of lipids droplets (LDs) in the cytoplasm resulting in the differentiation of macrophages into foam cells. The observed effect was specific for human and murine macrophages but not for other cell types, especially human keratinocytes, liver, and lung cell models. Furthermore, we found that S-NPs mediated LDs accumulation in human macrophages was accompanied by acute mitochondrial oxidative stress. The accumulated LDs were further delivered and accumulated into lysosomes leading to impaired lysosomal clearance. In conclusion, our study reveals that exposure to polystyrene nanoplastics stabilized with anionic surfactants can be a potent stimulus for dysregulation of lipid metabolism and macrophage foam cell formation, a characteristic feature observed during atherosclerosis posing a serious threat to human health.

Photoprotection and Photostability of a New Lignin-Gelatin-Baccharis antioquensis-Based Hybrid Biomaterial

The aim of this study was to develop a new hybrid biomaterial that could photo-stabilize and improve the photoprotective capacity of a Baccharis antioquensis extract. Different combinations of lignin/gelatin/natural extract were applied to prepare hybrid biomaterial nanoparticles (NPs), which were then incorporated into an emulsion. The in vitro photoprotection and photostability were evaluated. The methanolic extract showed high phenolic content (646.4 ± 9.5 mg GAE/g dry extract) and a DPPH radical assay revealed that the antiradical capacity of the extract (0.13 to 0.05 g extract/mmol DPPH) was even better than that of BHT. The particle size of the hybrid biomaterial ranged from 100 to 255 nm; a polydispersity index (PdI) between 0.416 and 0.788 is suitable for topical use in dermocosmetic products. The loading capacity of the extract ranged from 27.0 to 44.5%, and the nanoparticles (NPs) showed electrostatic stability in accordance with the zeta potential value. We found that the formulation based on lignin: extract (1:1 ratio) and gelatin: lignin: extract (0.5:0.5:1 ratio) demonstrated photoprotection qualities with a sun protection factor (SPF) ranging from 9.4 to 22.6. In addition, all the hybrid NP-formulations were time-stable with %SPFeff and %UVAPFeff greater than 80% after exposure to 2 h of radiation. These results suggest that the hybrid biopolymer-natural extract improved the photoprotection and photostability properties, as well as the antiradical capacity, of the B. antioquensis extract, and may be useful for trapping high polyphenol content from natural extracts, with potential application in cosmeceutical formulations.

Polystyrene nanoplastics dysregulate lipid metabolism in murine macrophages in vitro

Micro and nanoplastics are one of the major emerging environmental contaminants. Their impact on human health is less explored. There are several in vitro studies on their cellular uptake and accumulation, where micro and nanoplastics were mostly reported to be non-cytotoxic. The effects caused by the direct contact of nanoplastics with the immune system, especially at the cellular level is less known. Here we report that RAW 264.7 macrophages undergo differentiation into lipid laden foam cells when exposed to polystyrene nanoplastics (50 μg/mL). We found that exposure of RAW 264.7 macrophages to sulfate-modified polystyrene nanoplastics results in the accumulation of lipid droplets in the cytoplasm leading to foam cell formation. Exposure to high concentration of polystyrene nanoplastics (100 and 200 μg/mL) results in increased reactive oxygen species and impair lysosomes in macrophages. The exposure of BV2 microglial cells to polystyrene nanoplastics (50 μg/mL) induces lipid accumulation. In addition, our results indicate the role of polystyrene nanoplastics in altering the lipid metabolism in murine macrophages in vitro. In the present study we reported that polystyrene nanoplastics stabilized with anionic surfactants can be potent stimuli for lipotoxicity and foam cell formation leading to the pathogenesis of atherosclerosis posing major threat for animal and human health.

Photoprotective activity of zirconia nanoparticles

The increasing incidence of diseases caused by the harmful effects of UV radiation in skin, predominantly skin cancer, induce the search for more efficient photoprotector agents. Nowadays, titanium dioxide (TiO₂) and zinc oxide (ZnO) are the most widely used photoprotectors and therefore form the main components of commercially available sunscreens. Although the outstanding efficiency in absorbing and scattering UV radiation, mainly as nanoparticles, recent studies have raised concerns regarding the safe use of these nanoparticles, especially due to their high generation of reactive oxygen species (ROS). Thereby, this work focus on the evaluation of the photoprotective activity of zirconia nanoparticles (ZrO₂ NPs) and their cytotoxicity study in the presence and absence of UV irradiation. The ZrO₂ NPs were synthesized by hydrothermal method and their hydrodynamic diameter, Zeta potential and colloidal stability were characterized by dynamic light scattering. The morphology and size were observed by transmission electron microscopy. The synthesis resulted in ZrO₂ NPs with 50 nm of diameter and 56 nm of hydrodynamic diameter. The high colloidal stability was evidenced by the high value of Zeta potential (+48 mV) and low polydispersity index (0.09). The UV-vis spectrum of the ZrO₂ NPs in aqueous suspension showed an intense light scattering below 250 and a wide absorption band at 285 nm. The poor generation of ROS by ZrO₂ NPs was confirmed by the absence of photodegradation of methylene blue after long periods of irradiation. The in vitro assays performed with HaCaT cell line showed that the cell viability did not decrease in the absence of irradiation. However, after 24 h of incubation, the cell viability decreased under UV-irradiation in comparison with irradiated cells that were not incubated with ZrO₂ NPs. Notably, in these assays, the cells were incubated with the ZrO₂ NPs and after 24 h, they were replaced by fresh culture medium before the cell viability assay. Nevertheless, another in vitro assay was performed in order to evaluate the photoprotective activity of ZrO₂ NPs. The cells were irradiated in the presence of ZrO₂ NPs suspension. In this case, cell viability did not decrease even after long period of UV-irradiation and at higher concentration of ZrO₂ NPs. The present results showed that ZrO₂ NPs could be an interesting material to be used for skin photoprotection since they showed low cytotoxicity, absence of ROS generation and protection under UV irradiation. Additionally, the ZrO₂ NPs suspension was transparent as usually required for applications in sunscreens.

Flash Technology-Based Self-Assembly in Nanoformulation: From Fabrication to Biomedical Applications

Advances in nanoformulation have driven progress in biomedicine by producing nanoscale tools for biosensing, imaging, and drug delivery. Flash-based technology, the combination of rapid mixing technique with the self-assembly of macromolecules, is a new engine for the translational nanomedicine. Here, we review the state-of-the-art in flash-based self-assembly including theoretical and experimental principles, mixing device design, and applications. We highlight the fields of flash nanocomplexation (FNC) and flash nanoprecipitation (FNP), with an emphasis on biomedical applications of FNC, and discuss challenges and future directions for flash-based nanoformulation in biomedicine.

Block copolymer [(L-GluA-5-BE)-b-(L-AspA-4-BE)]-based nanoflower capsules with thermosensitive morphology and pH-responsive drug release for cancer therapy

Herein, the synthesis of an amino-acid-based di-block copolymer (di-BCP) in-between an l-glutamic acid-5-benzyl ester and l-aspartic acid-4-benzyl ester [(l-GluA-5-BE)-b-(l-AspA-4-BE)] has been reported. However, the synthesis of di-BCP of [(l-GluA-5-BE)-b-(l-AspA-4-BE)] was carried out through the facile modified ring-opening polymerization (ROP) without using any surfactants and harmful chemicals. Interestingly, the synthesized [(l-GluA-5-BE)-b-(l-AspA-4-BE)] has been used to design nanoflower capsules (NFCs) with surface-functionalized nanoflakes and petals. Notably, the simple solvent propanol has been used as a dispersing medium for the di-BCP-based powder to observe morphology of NFCs. Moreover, these amino-acid-based NFCs are biocompatible, biodegradable, and bio-safe for mankind usage. Consequently, di-BCP-based NFCs show changes in morphology with different temperature conditions, i.e., at ∼10 °C, ∼25 °C (RT), and ∼37 °C (body temperature). Furthermore, the average thickness of the surface-functionalized nanopetals has been calculated as ∼324 nm (in diameter). Similarly, the average distance between petals is calculated as 3.6 μm and the pore depth is ∼21 nm. Additionally, the porosity throughout the surface of capsules in-between nanopetals is an advantageous characteristic feature to improve the drug/paclitaxel (PTX) loading capacity. It is a unique and novel approach to design NFCs, which are a potential payload for nanomedicine and cancer therapy. Furthermore, NFCs were used to evaluate the loading efficacy of drugs and showed ∼78% (wt/wt%) of the PTX loading. Moreover, NFCs showed ∼74% drug release at physiological body temperature. Thus, NFCs showed remarkable release at acidic pH medium. However, PTX released from NFCs showed greater cell inhibition (i.e., ∼79%) with an increase of the PTX concentration after 24 h incubation over HeLa (human epithelial cervical cancer) cells. Besides, PTX released from NFC showed significant (∼34%) cell killing capacity. Such promising NFCs are recommended for breast, liver, and lung cancer therapeutics.

Renewable sources: applications in personal care formulations

A global tendency for products considered environmentally sustainable, and ecologically obtained led the industry related to personal care formulations to fund the research and the development of personal care/cosmetics containing ingredients from natural resources. Furthermore, consumers are aware of environmental and sustainability issueans, thus not harming the environment represents a key consideration when developing a new cosmetic ingredient. In this study we review some examples of active ingredients or raw materials used in cosmetics/personal care/biomedical products that are coming from either through biotechnological systems, or as byproducts of several industries. A skin formulation containing biosynthetic actives, prepared by us and the study regarding its dermocosmetic properties are also described. The need for the standardization processes, the safety assessment tools, the improvement of the exploitation methods of these renewable sources in order the production to be ecologically and economically better are also discussed.

Synthesis and Characterization of Nanostructured Lipid Nanocarriers for Enhanced Sun Protection Factor of Octyl p-methoxycinnamate

Sunlight is important to health, but higher exposure to radiation causes early aging of the skin and skin damage that can lead to skin cancers. This study aimed at producing a stable octyl p-methoxycinnamate (OMC)-loaded nanostructured lipid carrier (NLC) sunscreen, which can help in the photoprotective effect. NLC was produced by emulsification-sonication method and these systems were composed of myristyl myristate (MM), caprylic capric triglyceride (CCT), Tween® 80 (TW), and soybean phosphatidylcholine (SP) and characterized by dynamic light scattering (DLS), zeta potential (ZP) measurement, atomic force microscopy (AFM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and in vitro release studies. Pre-formulation studies were performed changing TW concentrations and no differences were found at concentrations of 1.0 and 2.0%. Two selected formulations were designed and showed an average size of 91.5-131.7, polydispersity index > 0.2, and a negative value of ZP. AFM presented a sphere-like morphology and SEM showed ability to form a thin film. DSC exhibited that the incorporation of OMC promoted reduction of enthalpy due to formation of a more amorphous structure. Drug release shows up to 55.74% and 30.57%, and this difference could be related to the presence of SP in this formulation that promoted a more amorphous structure; the release mechanism study indicated Fickian diffusion and relaxation. Sun protection factor (SPF) evaluation was performed using NLC and presented values around 40, considerably higher than those observed in the literature. The developed formulations provide a beneficial alternative to conventional sunscreen formulations.

Materials Science Challenges in Skin UV Protection: A Review

UV radiation is one of the critical environmental stress factors for human skin, which can trigger various problems such as pruritus, burning, erythema, premature skin aging and skin cancer. Hence, UV protection has become an indispensable daily routine and the use of topical sunscreen products is rapidly increasing. However, there are emerging concerns over the efficiency and safety of existing chemical and physical UV filters used in consumer products. Furthermore, there is no universally approved method for assessing sun protection efficiency regardless of the immediate end user need to develop safer sunscreen products that afford broad-spectrum photoprotection. It is evident that the current organic and inorganic UV filters have significant unfavorable impacts on human, environmental, and marine safety. Therefore, effective alternative UV filters should be established. This article comprehensively reviews the properties, safety, health and ecological concerns of various UV filters including TiO₂ and ZnO nanoparticles as well as the limitations of the testing protocols and guidelines provided by major regulatory bodies. The photoreactivity of UV filters used in sunscreen remains a major challenge, and it is crucial to develop new sunscreen ingredients, which not only protect the consumer, but also the environment.

Nanocarriers and Microcarriers for Enhancing the UV Protection of Sunscreens: An Overview

This review addresses a major question of importance to pharmaceutical scientists: how can novel drug delivery systems play a role in maximizing the UV protection of sunscreens? Because more and more people are being diagnosed with skin cancer each year than all other cancers combined, adequate sun protective measures are pivotal. In this context, the present review is to give an up-to-date overview on the different nanocarrier systems that have been explored so far for encapsulating different types of UV filters present on the market. The aim of these carrier systems is to prevent skin penetration and to enhance the photoprotective potential of sunscreen actives. For each supramolecular system, a brief description along with the studies, achievements, and pitfalls, on the type of UV actives inside them, ranging from classical UV filters to new generation of UV actives is given. A brief overview of UV filters encapsulated in microcarriers is also discussed.

Biodegradable bioadhesive nanoparticle incorporation of broad-spectrum organic sunscreen agents

Conventional emulsion-based sunscreen formulations are limited by postapplication epicutaneous penetration that increases the risk of allergic dermatitis, cellular damage, and filter photodegradation upon ultraviolet radiation (UVR) exposure. Encapsulation of the UVB filter padimate O within bioadhesive biodegradable nanoparticles (BNPs) composed of poly(d,l-lactic acid)-hyperbranched polyglycerol was previously shown to enhance UVR protection while preventing skin absorption. Herein, we assess the capacity of BNP co-incorporation of avobenzone and octocrylene to provide broad-spectrum UVR protection. The ratio of UV filters within nanoparticles (NPs) was optimized for filter-filter stabilization upon UV irradiation and maximum drug loading. In vitro water-resistance test showed significant particle retention at 85% over 3 hr. In a pilot clinical study, protection against UVR-induced erythema of BNPs was found to be comparable to the FDA standard P2. Thus, sunscreen formulations utilizing BNP incorporation of a combination of organic filters may offer key safety and performance advantages.

Preparation and Characterization of PMMA Particles Incorporating a Chemical Sunscreen Agent for Improvement of UV Protection Ability

UV protection ability is an important concern in the application of sunscreen. Modifying well-known UV filters is one of the most important ways to develop sunscreens. In this study, poly(methyl methacrylate)–ethylhexyl salicylate (PMMA-EHS) particles were prepared via miniemulsion polymerization using a redox initiator at low temperature. Compared with free EHS, the sun protection factor (SPF) value of PMMA-EHS particles was increased by ~40 %, which indicated a significant improvement in UV protection ability from encapsulating EHS in PMMA. Prepared PMMA-EHS particles proved non-leaky in application and can greatly reduce skin irritation by preventing direct contact of EHS with skin.

Microwave-irradiation-assisted hybrid chemical approach for titanium dioxide nanoparticle synthesis: microbial and cytotoxicological evaluation

Titanium dioxide nanoparticles (TNPs) are widely used in the pharmaceutical and cosmetics industries. It is used for protection against UV exposure due to its light-scattering properties and high refractive index. Though TNPs are increasingly used, the synthesis of TNPs is tedious and time consuming; therefore, in the present study, microwave-assisted hybrid chemical approach was used for TNP synthesis. In the present study, we demonstrated that TNPs can be synthesized only in 2.5 h; however, the commonly used chemical approach using muffle furnace takes 5 h. The activity of TNP depends on the synthetic protocol; therefore, the present study also determined the effect of microwave-assisted hybrid chemical approach synthetic protocol on microbial and cytotoxicity. The results showed that TNP has the best antibacterial activity in decreasing order from Escherichia coli, Bacillus subtilis, and Staphylococcus aureus. The IC50 values of TNP for HCT116 and A549 were found to be 6.43 and 6.04 ppm, respectively. Cell death was also confirmed from trypan blue exclusion assay and membrane integrity loss was observed. Therefore, the study determines that the microwave-assisted hybrid chemical approach is time-saving; hence, this technique can be upgraded from lab scale to industrial scale via pilot plant scale. Moreover, it is necessary to find the mechanism of action at the molecular level to establish the reason for greater bacterial and cytotoxicological toxicity. Graphical abstract A graphical representation of TNP synthesis.

Co-exposure of ZnO nanoparticles and UV radiation to Daphnia magna and Danio rerio: Combined effects rather than protection

The application of nanoparticles (NPs) in consumer products has been increasing over the past few years. Their release into the environment is likely to happen at any stage of production or during the use of products containing NPs. Zinc oxide NPs (ZnO-NP) are among the most-used NPs on the market due to its intrinsic properties, such as ultraviolet (UV) absorption. The aim of the present study was to assess the combined effects of ZnO-NP and UV radiation on 2 freshwater species: Daphnia magna and Danio rerio. The initial hypothesis was that the presence of ZnO-NP in the aquatic media would decrease the damaging effects of UV radiation for both species. The endpoints assessed for D. magna were immobilization, feeding inhibition, and reproduction output. For D. rerio, egg development was studied during 96 h and mortality, hatching delay, and abnormal development were the endpoints recorded. Combined exposures were designed based on the single toxicity of both stressors and analyzed based on the independent action concept and exploring possible deviations for synergism/antagonism, dose level, and dose ratio. Combined exposures with D. magna induced synergism on reproduction, decreasing the number of neonates produced more than expected based on both stressors' individual toxicity. Single exposures of D. rerio embryos to both stressors induced negative effects. The combined exposures caused a dose-ratio deviation pattern on mortality and hatching, with a synergism observed when ZnO-NP was the dominant stressor, changing to antagonism when UV radiation dominated the combined exposure. Regarding the results attained, studying ZnO toxicity under laboratory conditions may underestimate the risks when considering the potential interaction on effects when combined with UV radiation.

Ionic liquids for nano- and microstructures preparation. Part 2: Application in synthesis

Ionic liquids (ILs) are widely applied to prepare metal nanoparticles and 3D semiconductor microparticles. Generally, they serve as a structuring agent or reaction medium (solvent), however it was also demonstrated that ILs can play a role of a co-solvent, metal precursor, reducing as well as surface modifying agent. The crucial role and possible types of interactions between ILs and growing particles have been presented in the Part 1 of this review paper. Part 2 of the paper gives a comprehensive overview of recent experimental studies dealing with application of ionic liquids for preparation of metal and semiconductor based nano- and microparticles. A wide spectrum of preparation routes using ionic liquids is presented, including precipitation, sol-gel technique, hydrothermal method, nanocasting and ray-mediated methods (microwave, ultrasound, UV-radiation and γ-radiation). It was found that ionic liquids formed of a 1-butyl-3-methylimidazolium [BMIM] combined with tetrafluoroborate [BF4], hexafluorophosphate [PF6], and bis(trifluoromethanesulfonyl)imide [Tf2N] are the most often used ILs in the synthesis of nano- and microparticles, due to their low melting temperature, low viscosity and good transportation properties. Nevertheless, examples of other IL classes with intrinsic nanoparticles stabilizing abilities such as phosphonium and ammonium derivatives are also presented. Experimental data revealed that structure of ILs (both anion and cation type) affects the size and shape of formed metal particles, and in some cases may even determine possibility of particles formation. The nature of the metal precursor determines its affinity to polar or nonpolar domains of ionic liquid, and therefore, the size of the nanoparticles depends on the size of these regions. Ability of ionic liquids to form varied extended interactions with particle precursor as well as other compounds presented in the reaction media (water, organic solvents etc.) provides nano- and microstructures with different morphologies (0D nanoparticles, 1D nanowires, rods, 2D layers, sheets, and 3D features of molecules). ILs interact efficiently with microwave irradiation, thus even small amount of IL can be employed to increase the dielectric constant of nonpolar solvents used in the synthesis. Thus, combining the advantages of ionic liquids and ray-mediated methods resulted in the development of new ionic liquid-assisted synthesis routes. One of the recently proposed approaches of semiconductor particles preparation is based on the adsorption of semiconductor precursor molecules at the surface of micelles built of ionic liquid molecules playing a role of a soft template for growing microparticles.

Responsive foams for nanoparticle delivery

We have developed responsive foam systems for nanoparticle delivery. The foams are easy to make, stable at room temperature, and can be engineered to break in response to temperature or moisture. Temperature-responsive foams are based on the phase transition of long chain alcohols and could be produced using medical grade nitrous oxide as a propellant. These temperature-sensitive foams could be used for polyacrylic acid (PAA)-based nanoparticle delivery. We also discuss moisture-responsive foams made with soap pump dispensers. Polyethylene glycol (PEG)-based nanoparticles or PMMA latex nanoparticles were loaded into Tween 20 foams and the particle size was not affected by the foam formulation or foam break. Using biocompatible detergents, we anticipate this will be a versatile and simple approach to producing foams for nanoparticle delivery with many potential pharmaceutical and personal care applications.

Synthesis of polyurea–polyether nanoparticles via spontaneous nanoprecipitation

Synthesis of polyurea–polyether core–shell nano-particles via spontaneous precipitation.

Preparation and ageing-resistant properties of polyester composites modified with functional nanoscale additives

This study investigated ageing-resistant properties of carboxyl-terminated polyester (polyethylene glycol terephthalate) composites modified with nanoscale titanium dioxide particles (nano-TiO2). The nano-TiO2 was pretreated by a dry coating method, with aluminate coupling agent as a functional grafting additive. The agglomeration resistance was evaluated, which exhibited significant improvement for the modified nanoparticles. Then, the effects of the modified nano-TiO2 on the crosslinking and ageing-resistant properties of the composites were studied. With a real-time Fourier transform infrared (FT-IR) measurement, the nano-TiO2 displayed promoting effect on the crosslinking of polyester resin with triglycidyl isocyanurate (TGIC) as crosslinking agent. Moreover, the gloss retention, colour aberration and the surface morphologies of the composites during accelerated UV ageing (1500 hours) were investigated. The results demonstrated much less degree of ageing degradation for the nanocomposites, indicating an important role of the nano-TiO2 in improving the ageing-resistant properties of synthetic polymer composites.

Separation and measurement of silver nanoparticles and silver ions using magnetic particles

The recent surge in consumer products and applications using metallic nanoparticles has increased the possibility of human or ecosystem exposure due to unintentional release into the environment. To protect consumer health and the environment, there is an urgent need to develop tools that can characterize and quantify these materials at low concentrations and in complex matrices. In this study, magnetic nanoparticles coated with either dopamine or glutathione were used to develop a new, simple and reliable method for the separation/pre-concentration of trace amounts of silver nanoparticles followed by their quantification using inductively coupled plasma mass spectrometry (ICP-MS). The structurally modified magnetic particles were able to capture trace amounts of silver nanoparticles (~2 ppb) and concentrate (up to 250 times) the particles for analysis with ICP-MS. Under laboratory conditions, recovery of silver nanoparticles was >99%. More importantly, the magnetic particles selectively captured silver nanoparticles in a mixture containing both nano-particulate and ionic silver. This unique feature addresses the challenges of separation and quantification of silver nanoparticles in addition to the total silver in environmental samples. Spiking experiments showed recoveries higher than 97% for tap water and both fresh and saline surface water.

Flash nanoprecipitation: particle structure and stability

Flash nanoprecipitation (FNP) is a process that, through rapid mixing, stabilizes an insoluble low molecular weight compound in a nanosized, polymer-stabilized delivery vehicle. The polymeric components are typically amphiphilic diblock copolymers (BCPs). In order to fully exploit the potential of FNP, factors affecting particle structure, size, and stability must be understood. Here we show that polymer type, hydrophobicity and crystallinity of the small molecule, and small molecule loading levels all affect particle size and stability. Of the four block copolymers (BCP) that we have studied here, poly(ethylene glycol)-b-poly(lactic-co-glycolic acid) (PEG-b-PLGA) was most suitable for potential drug delivery applications due to its ability to give rise to stable nanoparticles, its biocompatibility, and its degradability. We found little difference in particle size when using PLGA block sizes over the range of 5 to 15 kDa. The choice of hydrophobic small molecule was important, as molecules with a calculated water-octanol partition coefficient (clogP) below 6 gave rise to particles that were unstable and underwent rapid Ostwald ripening. Studies probing the internal structure of nanoparticles were also performed. Analysis of differential scanning calorimetry (DSC), cryogenic transmission electron microscopy (cryo-TEM), and (1)H NMR experiments support a three-layer core-shell-corona nanoparticle structure.