High-Elongation Fiber Mats by Electrospinning of Polyoxymethylene

A dual-selective thermal emitter with enhanced subambient radiative cooling performance

Radiative cooling is a zero-energy technology that enables subambient cooling by emitting heat into outer space (~3 K) through the atmospheric transparent windows. However, existing designs typically focus only on the main atmospheric transparent window (8-13 μm) and ignore another window (16-25 μm), under-exploiting their cooling potential. Here, we show a dual-selective radiative cooling design based on a scalable thermal emitter, which exhibits selective emission in both atmospheric transparent windows and reflection in the remaining mid-infrared and solar wavebands. As a result, the dual-selective thermal emitter exhibits an ultrahigh subambient cooling capacity (~9 °C) under strong sunlight, surpassing existing typical thermal emitters (≥3 °C cooler) and commercial counterparts (as building materials). Furthermore, the dual-selective sample also exhibits high weather resistance and color compatibility, indicating a high practicality. This work provides a scalable and practical radiative cooling design for sustainable thermal management.

Micro (nano) plastics in wastewater: A critical review on toxicity risk assessment, behaviour, environmental impact and challenges

With millions of tonnes of plastic pollution generated every year, small-sized plastic particles, including micro- and nanoplastics, end up in freshwater systems. Due to the very small size and very large specific surface area of nanoplastics, they are known to be persistent and toxic in our environment. These particles are also known to react with other water-borne contaminants and cause acute toxicity in organisms. Nanoplastics are prone to biomagnification and can be transported to humans through various pathways. This study aims to contribute towards understanding the behaviour of nanoplastics in our environment, specifically through identification of various sources, detection techniques, toxicity estimation, health risk in humans, environmental fate, recovery and reuse, and future challenges and limitations. Detailed review on the toxic effects of nanoplastics on various organisms and their degradation rates in soil and water matrices are provided. The suitability of small- and large-scale separation techniques for the removal of nanoplastics in wastewater treatment plants is also discussed. Current challenges and future perspectives in understanding the fate and transport of nanoplastics in the environment are also discussed. Research gaps, including the development of quantification techniques, estimation of degradation mechanisms, transport in marine ecosystems, and development of sensors to examine nanoplastics in the environment, are explored. Finally, we can limit the release of nanoplastics to the environment through reduction, reuse and recycling (3 Rs) of bulk plastic products.

Polystyrene nanoplastics (20 nm) are able to bioaccumulate and cause oxidative DNA damages in the brain tissue of zebrafish embryo (Danio rerio)

Nano-sized plastic particles formed from both daily use plastics and its debris have become a potential health and environmental problem due to features such as transportation through food webs and maternal transfer. Although many studies on the toxicity of plastics exist more detailed and molecular studies are needed to evaluate and review the effects of plastics especially in nano-size range. For this purpose, we have microinjected polystyrene nanoplastics (PNP) (20 nm) to the zebrafish embryo, which is one of the best model organisms for developmental toxicity studies, to simulate intake with food or maternal. Survival, hatching and malformations evaluated during the experimental period (120 h). Moreover, we have aimed to put forth the presence of reactive oxygen species (ROS) and apoptosis signalling accumulation in the body in addition to bioaccumulation of PNP and immunochemical toxicity (8-OHdG) on the brain of zebrafish larvae at the 120th hour. According to results, it has been demonstrated that 20 nm diameter PNP can reach the brain and bioaccumulate there, moreover lead to oxidative DNA damage in the brain regions where it bioaccumulates. Here we have also imaged the PNP from a vertebrate brain via transmission electron microscopy (TEM) for the first time. As a result of these, it has been detected increasing mortality and prevailing abnormalities in addition to excessive ROS and apoptosis in especially the brain. As a conclusion, obtained data have suggested that precautions, on the use and contamination of the plastic product, to be taken during both pregnancy and baby care/feeding are important for the health of the baby in future.

Distinctive impact of polystyrene nano-spherules as an emergent pollutant toward the environment

The increasing load of nanoplastic pollution in the environment has become a major concern toward human and environmental safety. The current investigation mainly focused on assessing the toxic behavior of nanoplastics (polystyrene nano-spheres (PNS)) toward blood cells and marine crustacean. The study also investigated the temporal stability of PNS under different water matrices and its size-dependent sedimentation behavior in the sea water dispersion. The nano-dispersion showed mean particle size of 561.4 ± 0.80 and 613.7 ± 0.11 nm for PNS 1 and 781.4 ± 0.80 and 913.7 ± 0.11 nm for PNS 2 in lake and seawater, respectively after 48-h incubation, which is ~ 8-fold increase from its original size. The LC50 value against Artemia salina and lymphocytes were found to be 4.82 and 8.79 μg/mL, and 75 μg/mL, respectively for PNS 1 and PNS 2. The genotoxic study reveals that around 50% of lymphocytes were affected by both PNS at 50 μg/mL concentration, whereas the cytotoxic studies on RBC and lymphocytes showed 50% toxicity only at 100 μg/mL concentration. The genotoxic study displayed numerous tri- and multi-nucleated cells. The biochemical profile of A. salina exposed to lethal concentration demonstrated a significant decrease in the total protein, reduced glutathione, and catalase activity and increase in lipid peroxidation activity as a result of PNS permeation to tissues. In conclusion, the present study demonstrated that the polystyrene nano-spheres are emerging pollutant in the environment and are hazardous to humans.

Highly Sensitive, Anisotropic, and Reversible Stress/Strain-Sensors from Mechanochromic Nanofiber Composites

Mechanochromic polymeric systems are intensively investigated for real-time stress detection applications. However, an effective stress-sensing material must respond to low deformation with a detectable color change that should be quickly reversible upon force unloading. In this work, mechanochromic nanofibers made by electrospinning are used to produce mechanochromic nanofiber/poly(dimethylsiloxane) (PDMS) composites with isotropic and anisoptropic response. Due to chain alignment of spiropyran copolymer chains within the nanofibers, only very small strains are required to yield a mechanochromic response. Composites with aligned and isotropic nanofibers show anisotropic and isotropic mechanochromic behavior, respectively. Due to the special substitution pattern of spiropyran in the copolymer, the mechanochromic response of these nanofiber/PDMS composites shows fast reversibility upon force unloading. The outstanding benefit of using highly sensitive mechanochromic nanofibers as filler in composite materials allows the detection of directional stress and strain, and it is a step forward in the development of smart, mechanically responsive materials.

Enhanced Aerosol Particle Filtration Efficiency of Nonwoven Porous Cellulose Triacetate Nanofiber Mats

Aerosol particle filtration in most penetrating particle size (MPPS) region is of great challenge for conventional nonwoven filter mats. The present work, therefore, redesigns conventional filter mats by introducing porous structure. A combination of thermally induced phase separation and breath figure mechanism was employed to synthesize porous cellulose triacetate fibers, in conjunction with the volatile solvent methylene chloride. The ambient humidity, the concentration of the polyvinylpyrrolidone (PVP) secondary polymer, and the ethanol cosolvent were all adjusted to modify the Taylor cone formation, jet stability, and fiber porosity. After fiber formation, the PVP was removed to obtain a superhydrophobic material. To distinguish the effect of pores, the performance of porous and nonporous nanofibers having similar sizes was conducted. Tests were performed using various dust particle sizes, and the results show that the collection efficiency of the porous fibers, resulting from particle diffusion, inertial impaction, and interception, was improved. Interestingly, the efficiency of the porous fibers in the MPPS region was exceptionally enhanced (up to 95%), demonstrating that the presence of dynamic pores greatly contributes to particle capture.

The use of solvent-soaking treatment to enhance the anisotropic mechanical properties of electrospun nanofiber membranes for water filtration

The solvent-soaking treatment for improving the tensile strength of B-CA mats is proposed. A fibrous structure with changed morphology and molecular orientation resulted. These results showed important influences on the mechanical properties.

Electrospun nanofibers with both surface nanopores and internal interpenetrated nanochannels for oil absorption

We report novel polyoxymethylene nanofibers with both surface nanopores and internal interpenetrated channels. Their novel interesting structure makes them an ideal alternative for oil adsorption, oil/water separation or catalysis in the future.

In vitro and in vivo evaluation of the wound healing capability of electrospun gelatin/PLLCL nanofibers

Recent progress in tissue-engineered skin grafts has alleviated the demand for autologous split thickness skin grafts for treatment of large skin wounds. In this study, a series of cost-effective nanofibrous scaffolds aimed at full-thickness wound healing are fabricated by blending gelatin (Gel) with poly(l-lactic acid)-b-poly( ε-caprolactone) (PLLCL) and electrospun to obtain composite Gel/PLLCL nanofibers in four different weight ratios (w/w) of 80:20 [Gel/PLLCL(20)], 70:30 [Gel/PLLCL(30)], 60:40 [Gel/PLLCL(40)], and 50:50 [Gel/PLLCL(50)]. The mechanical properties of these nanofibrous scaffolds were evaluated in both dry and wet conditions, and the Gel/PLLCL(40) retained suitable tensile stress (1.16 ± 0.03 MPa) to be handled even in wet conditions. Moreover, the proliferations of fibroblast cells on Gel/PLLCL(40) were 15%, 7% and 10% higher compared to cell proliferations on Gel/PLLCL(20), Gel/PLLCL(30), and Gel/PLLCL(50), respectively. In vitro results confirmed Gel/PLLCL(40) as the optimized scaffold composition suitable for skin tissue engineering. The healing ability of this scaffold was studied in vivo using mouse models. The Gel/PLLCL(40) greatly accelerated wound closure and regeneration occurring in the first 10 days of implantation compared to the control group. In addition, newly regenerated epidermis was only found in the nanofibrous scaffolds–treated group, and it was comparable to the epidermis of normal skin.

Electrospun PGS:PCL microfibers align human valvular interstitial cells and provide tunable scaffold anisotropy

Tissue engineered heart valves (TEHV) can be useful in the repair of congenital or acquired valvular diseases due to their potential for growth and remodeling. The development of biomimetic scaffolds is a major challenge in heart valve tissue engineering. One of the most important structural characteristics of mature heart valve leaflets is their intrinsic anisotropy, which is derived from the microstructure of aligned collagen fibers in the extracellular matrix (ECM). In the present study, a directional electrospinning technique is used to fabricate fibrous poly(glycerol sebacate):poly(caprolactone) (PGS:PCL) scaffolds containing aligned fibers, which resemble native heart valve leaflet ECM networks. In addition, the anisotropic mechanical characteristics of fabricated scaffolds are tuned by changing the ratio of PGS:PCL to mimic the native heart valve's mechanical properties. Primary human valvular interstitial cells (VICs) attach and align along the anisotropic axes of all PGS:PCL scaffolds with various mechanical properties. The cells are also biochemically active in producing heart-valve-associated collagen, vimentin, and smooth muscle actin as determined by gene expression. The fibrous PGS:PCL scaffolds seeded with human VICs mimick the structure and mechanical properties of native valve leaflet tissues and would potentially be suitable for the replacement of heart valves in diverse patient populations.

Resin composites reinforced by nanoscaled fibers or tubes for dental regeneration

It has been stated clearly that nanofillers could make an enhancement on the mechanical performances of dental composites. In order to address current shortage of traditional dental composites, fillers in forms of nanofibers or nanotubes are broadly regarded as ideal candidates to greatly increase mechanical performances of dental composites with low content of fillers. In this review, the efforts using nanofibers and nanotubes to reinforce mechanical performances of dental composites, including polymeric nanofibers, metallic nanofibers or nanotubes, and inorganic nanofibers or nanotubes, as well as their researches related, are demonstrated in sequence. The first purpose of current paper was to confirm the enhancement of nanofibers or nanotubes' reinforcement on the mechanical performances of dental restorative composite. The second purpose was to make a general description about the reinforcement mechanism of nanofibers and nanotubes, especially, the impact of formation of interphase boundary interaction and nanofibers themselves on the advanced mechanical behaviors of the dental composites. By means of the formation of interface interaction and poststretching nanofibers, reinforced effect of dental composites by sorts of nanofibers/nanotubes has been successfully obtained.

Photosensitive and biomimetic core-shell nanofibrous scaffolds as wound dressing

Tissue engineered skin grafts that mimic the native extracellular matrix of skin has gained huge popularity among clinicians since they increase the survival rate of the patients. Phototherapy shows promising results with respect to acute and chronic pain relief, treatment of inflammatory conditions and promotion of wound healing. Here, we encapsulated a photosensitive polymer poly (3-hexylthiophene) (P3HT) and epidermal growth factor in the core-shell-structured Gelatin/poly(L-lactic acid)-co-poly-(ε-caprolactone) nanofibers [Gel/PLLCL/P3GF(cs)] by coaxial spinning and studied the potential application of the Gel/PLLCL/P3GF(cs) nanofibrous scaffold as a novel skin graft. The proliferation of fibroblasts was significantly improved on Gel/PLLCL/P3GF(cs) under light stimulation compared to fibroblasts on the same scaffold under dark condition. Studies on the in vitro wound healing ability of Gel/PLLCL/P3GF(cs) showed complete closure of wound after 9 days under "light stimulation" too. Furthermore, the potential of adipose-derived stem cells (ASCs) to differentiate to epidermal cells on Gel/PLLCL/P3GF(cs) was evaluated. The differentiated ASCs with keratinocytes morphology were only found on the light stimulated Gel/PLLCL/P3GF(cs). Our results suggest that the photosensitive core-shell Gel/PLLCL/P3GF(cs) nanofibers could be a novel substrate to aid in the reestablishment of skin architecture.

PGS:Gelatin nanofibrous scaffolds with tunable mechanical and structural properties for engineering cardiac tissues

A significant challenge in cardiac tissue engineering is the development of biomimetic grafts that can potentially promote myocardial repair and regeneration. A number of approaches have used engineered scaffolds to mimic the architecture of the native myocardium tissue and precisely regulate cardiac cell functions. However, previous attempts have not been able to simultaneously recapitulate chemical, mechanical, and structural properties of the myocardial extracellular matrix (ECM). In this study, we utilized an electrospinning approach to fabricate elastomeric biodegradable poly(glycerol sebacate) (PGS):gelatin nanofibrous scaffolds with a wide range of chemical composition, stiffness and anisotropy. Our findings demonstrated that through incorporation of PGS, it is possible to create nanofibrous scaffolds with well-defined anisotropy that mimic the left ventricular myocardium architecture. Furthermore, we studied attachment, proliferation, differentiation and alignment of neonatal rat cardiac fibroblast cells (CFs) as well as protein expression, alignment, and contractile function of cardiomyocyte (CMs) on PGS:gelatin scaffolds with variable amount of PGS. Notably, aligned nanofibrous scaffold, consisting of 33 wt. % PGS, induced optimal synchronous contractions of CMs while significantly enhanced cellular alignment. Overall, our study suggests that the aligned nanofibrous PGS:gelatin scaffold support cardiac cell organization, phenotype and contraction and could potentially be used to develop clinically relevant constructs for cardiac tissue engineering.

Elastomeric electrospun scaffolds of poly(L-lactide-co-trimethylene carbonate) for myocardial tissue engineering

In myocardial tissue engineering the use of synthetically bioengineered flexible patches implanted in the infarcted area is considered one of the promising strategy for cardiac repair. In this work the potentialities of a biomimetic electrospun scaffold made of a commercial copolymer of (L)-lactic acid with trimethylene carbonate (P(L)LA-co-TMC) are investigated in comparison to electrospun poly(L)lactic acid. The P(L)LA-co-TMC scaffold used in this work is a glassy rigid material at room temperature while it is a rubbery soft material at 37 °C. Mechanical characterization results (tensile stress-strain and creep-recovery measurements) show that at 37 °C electrospun P(L)LA-co-TMC displays an elastic modulus of around 20 MPa and the ability to completely recover up to 10% of deformation. Cell culture experiments show that P(L)LA-co-TMC scaffold promotes cardiomyocyte proliferation and efficiently preserve cell morphology, without hampering expression of sarcomeric alpha actinin marker, thus demonstrating its potentialities as synthetic biomaterial for myocardial tissue engineering.

Spray-spinning: a novel method for making alginate/chitosan fibrous scaffold

The subject of our investigations was the process of obtaining alginate/chitosan polyelectrolyte complex (PEC) fibers. In this study, a novel method named "spray-spinning" was developed for the making of these hybrid fibers. In spray-spinning, a chitosan solution was sprayed into a flowing sodium alginate solution and sheared into streamlines. The elongated streamlines subsequently transformed into alginate/chitosan PEC fibers. Average diameter of the fibers increased with the increasing of chitosan concentration used in spinning. The fibers showed a high water-absorbability of about 45 folds of water to their dry weight and retained their integrity after incubation in Minimum Essential Medium (MEM) for up to 30 days. In vitro co-culture experiments indicated that the fibers could support the three-dimensional growth of HepG2 cells and did not display any cyto-toxicity. Moreover, in vivo implanting experiments indicated that the connective tissue cells infiltrated into the implanted fibrous scaffolds in 3 weeks after surgery. These results demonstrated the potential applications of the as-spun fibers in regenerative medicine and tissue engineering.