Organic carbon release, denitrification performance and microbial community of solid-phase denitrification reactors using the blends of agricultural wastes and artificial polymers for the treatment of mariculture wastewater.

This paper explored the possibility of heterotrophic denitrification driven by composite solid carbon sources in low carbon/nitrogen ratio marine recirculating aquaculture wastewater. In this study, two agricultural wastes, reed straw (RS), corn cob (CC) and two artificial polymers, polycaprolactone (PCL), poly3-hydroxybutyrate-hydroxypropionate (PHBV) were mixed in a 1:1 ratio to compare the carbon release characteristics of the four composite carbon sources (RS+PCL, RS+PHBV, CC+PCL, and CC+PHBV) and their effects on improving the mariculture wastewater for denitrification. Dissolved organic carbon (DOC) after carbon source release (4.96-1.07 mg/g), total organic carbon/chemical oxygen demand (1.9-0.79) and short-chain fatty acids (SCFAs) (4.23-0.21 mg/g) showed that all the four composite solid carbon sources had excellent organic carbon release ability, and the CC+PCL group had the highest release of DOC and SCFAs. Energy-dispersive X-ray spectroscopy, scanning electron microscopy, and Fourier-transform infrared spectroscopy were used to observe the changes in the surface characteristics of the composite carbon source before and after application. And results showed that the stable internal structure enabled CC+PCL group to have continuous carbon release performance and achieved the maximum denitrification efficiency (93.32 %). The NRE results were supported by the abundance of the Proteobacteria microbial community at the phylum level and Marinobacter at the genus level. Quantitative real-time PCR (q-PCR) indicated CC-containing composite carbon source groups have good nitrate reduction ability, while PCL-containing composite carbon source groups have better nitrite reduction level. In conclusion, the carbon source for agricultural wastes and artificial polymers can be used as an economic and effective solid carbon source for denitrification and treatment of marine recirculating aquaculture wastewater.

Distribution and possible sources of atmospheric microplastic deposition in a valley basin city (Lanzhou, China).

The deposition is an important process of microplastics transporting from atmosphere to water and soil. But the spatial and temporal distribution of microplastics in urban atmospheric deposition and its influencing factors are poorly understood. The current study investigated the possible sources, spatial and temporal distribution, and potential ecological risk of microplastics in deposition from the valley basin of Lanzhou city during the COVID-19 pandemic (from February to August, 2020). The deposition flux of microplastics was 353.83 n m-2 d-1. Most plastic samples were small sized (50～500 µm) and transparent. The dominant chemical composition and shapes were PET, fragments and fibers, respectively. A modified method was conducted to identify the sources of microplastics, and the local sources were suggested as the main possible sources. The distribution of microplastics investigated through the inverse distance weight interpolation showed spatial variation and temporal differentiation which was dominated by the human activity. The rainfall also affected the temporal distribution. The preliminary assessment indicated higher potential ecological risk of microplastics in deposition. This study suggested the dominant effect of human activity on the source and distribution of atmospheric microplastic deposition in city.

A core-skirt designed artificial cornea with orthogonal microfiber grid scaffold.

Artificial cornea is an effective treatment option for cases of severe corneal loss. In this study, we prepared a core-skirt designed artificial cornea with orthogonal microfiber grid scaffold. We fabricated PCL orthogonal microfiber grid scaffolds by a direct writing technique, and then combined them with compressed collagen (CC) to obtain a sandwich-like CC/P (where P is used to represent the PCL microfiber grid scaffold). PHEMA hydrogel and the CC/P served as the core and the skirt, respectively, with the P also serving as an intermediate between the two. The physical properties of the artificial cornea, including the morphology, the mechanical properties and the light transmittance, were evaluated. SEM images showed an effective connection and a lack of phase separation at the interface between the core and the skirt, and the skirt formed a highly porous scaffold that promoted tissue biointegration. In addition, we used the skirt structure to construct a corneal tissue model containing two cells types: corneal stromal stem cells (CSSCs) and mouse hippocampal neurons. The results showed that the cells could grow and differentiate well, and the orthogonal microfiber grid scaffold fibers were good guides for the structural growth of CSSCs and neuronal axons.

Bacterial magnetic particles-polyethylenimine vectors deliver target genes into multiple cell types with a high efficiency and low toxicity.

Bacterial magnetic particles (BMPs) are biosynthesized magnetic nano-scale materials with excellent dispersibility and biomembrane enclosure properties. In this study, we demonstrate that BMPs augment the ability of polyethylenimine (PEI) to deliver target DNA into difficult-to-transfect primary porcine liver cells, with transfection efficiency reaching over 30%. Compared with standard lipofection and polyfection, BMP-PEI gene vectors significantly enhanced the transfection efficiencies for the primary porcine liver cells and C2C12 mouse myoblast cell lines. To better understand the mechanism of magnetofection using BMP-PEI/DNA vectors, transmission electron microscopy (TEM) images of transfected Cos-7, HeLa, and HEP-G2 cells were observed. We found that the BMP-PEI/DNA complexes were trafficked into the cytoplasm and nucleus by way of vesicular transport and endocytosis. Our study builds support for the versatile BMP-PEI vector transfection system, which might be exploited to transfect a wide range of cell types or even to reach specific targets in the treatment of disease. KEY POINTS: • We constructed a BMP-PEI gene delivery vector by combining BMPs and PEI. • The vector significantly enhanced transfection efficiencies in eukaryotic cell lines. • The transfection mechanism of this vector was explained in our study.

Preparation, Characterization and Antioxidant Activities of Kelp Phlorotannin Nanoparticles.

Phlorotannins are a group of major polyphenol secondary metabolites found only in brown algae and are known for their bioactivities and multiple health benefits. However, they can be oxidized due to external factors and their bioavailability is low due to their low water solubility. In this study, the potential of utilizing nanoencapsulation with polyvinylpyrrolidone (PVP) to improve various activities of phlorotannins was explored. Phlorotannins encapsulated by PVP nanoparticles (PPNPS) with different loading ratios were prepared for characterization. Then, the PPNPS were evaluated for in vitro controlled release of phlorotannin, toxicity and antioxidant activities at the ratio of phlorotannin to PVP 1:8. The results indicated that the PPNPS showed a slow and sustained kinetic release of phlorotannin in simulated gastrointestinal fluids, they were non-toxic to HaCaT keratinocytes and they could reduce the generation of endogenous reactive oxygen species (ROS). Therefore, PPNPS have the potential to be a useful platform for the utilization of phlorotannin in both pharmaceutical and cosmetics industries.

Conductive Composite Materials Fabricated from Microbially Produced Protein Nanowires.

Protein-based electronic materials have numerous potential advantages with respect to sustainability and biocompatibility over electronic materials that are synthesized using harsh chemical processes and/or which contain toxic components. The microorganism Geobacter sulfurreducens synthesizes electrically conductive protein nanowires (e-PNs) with high aspect ratios (3 nm × 10-30 µm) from renewable organic feedstocks. Here, the integration of G. Sulfurreducens e-PNs into poly(vinyl alcohol) (PVA) as a host polymer matrix is described. The resultant e-PN/PVA composites exhibit conductivities comparable to PVA-based composites containing synthetic nanowires. The relationship between e-PN density and conductivity of the resultant composites is consistent with percolation theory. These e-PNs confer conductivity to the composites even under extreme conditions, with the highest conductivities achieved from materials prepared at pH 1.5 and temperatures greater than 100 °C. These results demonstrate that e-PNs represent viable and sustainable nanowire compositions for the fabrication of electrically conductive composite materials.

Antifouling Stripes Prepared from Clickable Zwitterionic Copolymers.

In this study, we have fabricated robust patterned surfaces that contain biocompatible and antifouling stripes, which cause microorganisms to consolidate into bare silicon spaces. Copolymers of methacryloyloxyethyl phosphorylcholine (MPC) and a methacrylate-substituted dihydrolipoic acid (DHLA) were spin-coated onto silicon substrates. The MPC units contributed biocompatibility and antifouling properties, and the DHLA units enabled cross-linking and the formation of robust thin films. Photolithography enabled the formation of 200-µm-wide poly(MPC-DHLA) stripped patterns that were characterized using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and rhodamine 6G staining. Regardless of the spacing between poly(MPC-DHLA) stripes (10, 50, or 100 µm), Escherichia coli rapidly adhered to the bare silicon gaps that lacked the copolymer, confirming the antifouling nature of MPC. Overall, this work provides a surface modification strategy for generating alternating biofouling and nonfouling surface structures that are potentially applicable for researchers studying cell biology, drug screening, and biosensor technology.

Conductive Polymer Binder for High-Tap-Density Nanosilicon Material for Lithium-Ion Battery Negative Electrode Application.

High-tap-density silicon nanomaterials are highly desirable as anodes for lithium ion batteries, due to their small surface area and minimum first-cycle loss. However, this material poses formidable challenges to polymeric binder design. Binders adhere on to the small surface area to sustain the drastic volume changes during cycling; also the low porosities and small pore size resulting from this material are detrimental to lithium ion transport. This study introduces a new binder, poly(1-pyrenemethyl methacrylate-co-methacrylic acid) (PPyMAA), for a high-tap-density nanosilicon electrode cycled in a stable manner with a first cycle efficiency of 82%-a value that is further improved to 87% when combined with graphite material. Incorporating the MAA acid functionalities does not change the lowest unoccupied molecular orbital (LUMO) features or lower the adhesion performance of the PPy homopolymer. Our single-molecule force microscopy measurement of PPyMAA reveals similar adhesion strength between polymer binder and anode surface when compared with conventional polymer such as homopolyacrylic acid (PAA), while being electronically conductive. The combined conductivity and adhesion afforded by the MAA and pyrene copolymer results in good cycling performance for the high-tap-density Si electrode.

Enhancement of Friction against a Rough Surface by a Ridge-Channel Surface Microstructure.

We report on a study of the sliding friction of elastomeric surfaces patterned with ridges and channels (and unstructured flat controls), against both smooth and roughened spherical indenters. Against the smooth spherical indenter, all of the structured surfaces have highly reduced sliding friction due to the reduction in actual area of contact. Against roughened spherical indenters, however, the sliding force for structured samples can be up to 50% greater than that of an unstructured flat control. The mechanism of enhanced friction against a rough surface is due to a combination of increased actual area of contact, interlocking between roughness and the surface structure, and attendant dynamic instabilities that dissipate energy.

Effect of hydraulic retention time on denitrification performance and microbial communities of solid-phase denitrifying reactors using polycaprolactone/corncob composite.

This study investigated the effect of hydraulic retention time (HRT) on the denitrification performance and microbial composition of reactors, packed with composite polycaprolactone and corncob carbon sources, during the treatment mariculture wastewater. The optimal HRT was 3 h, and average nitrogen removal efficiency was 99.00 %, 99.07 %, and 98.98 % in the HRT =3, 5, and 7 h groups, respectively. However, the 3 h group (DOC 2.91 mg/L) was the only group with a lower DOC concentration than that of the influent group (3.31 mg/L). Moreover, species richness was lower at HRT =3 h, with a greater proportion of denitrification-dominant phyla, such as Proteobacteria. The abundance of the NarG, NirK, and NirS functional genes suggested that the HRT =3 h group had a significant advantage in the nitrate and nitrite reduction phases. Under a short HRT, the composite carbon source achieved a good denitrification effect.

Understanding the multi-functionality and tissue-specificity of decellularized dental pulp matrix hydrogels for endodontic regeneration.

Dental pulp is the only soft tissue in the tooth which plays a crucial role in maintaining intrinsic multi-functional behaviors of the dentin-pulp complex. Nevertheless, the restoration of fully functional pulps after pulpitis or pulp necrosis, termed endodontic regeneration, remained a major challenge for decades. Therefore, a bioactive and in-situ injectable biomaterial is highly desired for tissue-engineered pulp regeneration. Herein, a decellularized matrix hydrogel derived from porcine dental pulps (pDDPM-G) was prepared and characterized through systematic comparison against the porcine decellularized nerve matrix hydrogel (pDNM-G). The pDDPM-G not only exhibited superior capabilities in facilitating multi-directional differentiation of dental pulp stem cells (DPSCs) during 3D culture, but also promoted regeneration of pulp-like tissues after DPSCs encapsulation and transplantation. Further comparative proteomic and transcriptome analyses revealed the differential compositions and potential mechanisms that endow the pDDPM-G with highly tissue-specific properties. Finally, it was realized that the abundant tenascin C (TNC) in pDDPM served as key factor responsible for the activation of Notch signaling cascades and promoted DPSCs odontoblastic differentiation. Overall, it is believed that pDDPM-G is a sort of multi-functional and tissue-specific hydrogel-based material that holds great promise in endodontic regeneration and clinical translation. STATEMENT OF SIGNIFICANCE: Functional hydrogel-based biomaterials are highly desirable for endodontic regeneration treatments. Decellularized extracellular matrix (dECM) preserves most extracellular matrix components of its native tissue, exhibiting unique advantages in promoting tissue regeneration and functional restoration. In this study, we prepared a porcine dental pulp-derived dECM hydrogel (pDDPM-G), which exhibited superior performance in promoting odontogenesis, angiogenesis, and neurogenesis of the regenerating pulp-like tissue, further showed its tissue-specificity compared to the peripheral nerve-derived dECM hydrogel. In-depth proteomic and transcriptomic analyses revealed that the activation of tenascin C-Notch axis played an important role in facilitating odontogenic regeneration. This biomaterial-based study validated the great potential of the dental pulp-specific pDDPM-G for clinical applications, and provides a springboard for research strategies in ECM-related regenerative medicine.

The Uptake and Distribution Evidence of Nano- and Microplastics in vivo after a Single High Dose of Oral Exposure.

Objective: Tissue uptake and distribution of nano-/microplastics was studied at a single high dose by gavage in vivo. Methods: Fluorescent microspheres (100 nm, 3 µm, and 10 µm) were given once at a dose of 200 mg/(kg∙body weight). The fluorescence intensity (FI) in observed organs was measured using the IVIS Spectrum at 0.5, 1, 2, and 4 h after administration. Histopathology was performed to corroborate these findings. Results: In the 100 nm group, the FI of the stomach and small intestine were highest at 0.5 h, and the FI of the large intestine, excrement, lung, kidney, liver, and skeletal muscles were highest at 4 h compared with the control group ( P < 0.05). In the 3 µm group, the FI only increased in the lung at 2 h ( P < 0.05). In the 10 µm group, the FI increased in the large intestine and excrement at 2 h, and in the kidney at 4 h ( P < 0.05). The presence of nano-/microplastics in tissues was further verified by histopathology. The peak time of nanoplastic absorption in blood was confirmed. Conclusion: Nanoplastics translocated rapidly to observed organs/tissues through blood circulation; however, only small amounts of MPs could penetrate the organs.

Grafting zwitterionic brushes from the surface of an epoxy-based transparent hydrogel for antifouling performance.

Non-specific biofilm formation (biofouling) commonly occurs to the surface of biomedical devices, which causes infection to the human tissues and function loss after implantation. To enhance the antifouling properties on the bioinert hydrogel-based biomaterials, a novel surface grafting approach was developed using surface radical chain-transfer reaction mediated by DL-dithiothreitol (DTT), rather than catalyzed by cytotoxic metal ions. Zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) brushes were grafted on the surface of poly(2-hydroxyethyl methacrylate-co-glycidyl methacrylate) (PHG) to obtain PHG-graft-PMPC (PHG-g-PMPC) hydrogel, which were shown to have tunable surface hydrophilicity while maintaining high water content and transparency. Elemental composition analysis and micromorphology demonstrated the success of surface grafting. Protein adhesion assays were carried out, showing the reduction of bovine serum albumin, lactoferrin, and lysozyme adhesion by ∼90%, 80%, and 70%, respectively, compared to the pristine hydrogels. Significant resistance of bacterial attachment was observed on the surface-modified hydrogels using gram-negativeEscherichia. coliand gram-positiveStaphylococcus aureus, respectively. The PHG-g-PMPC hydrogel is potentially feasible in various biomedical applications, especially for preventing surface biofouling of ophthalmic implants and devices. Furthermore, this de novo approach provides a universal platform for surface functionalization via thiol-epoxy click chemistry and surface radical chain-transfer reaction.

Spatiotemporal distribution and potential sources of atmospheric microplastic deposition in a semiarid urban environment of Northwest China.

In this study, the spatiotemporal distribution of microplastic deposition was investigated through ordinary Kriging interpolation, and the potential sources of microplastic deposition were identified by using Hybrid Single-Particle Lagrangian Integrated Trajectory model. The results showed that the total deposition flux of microplastics ranged from 79.5 to 810.0 p/(m2·d). The shapes of microplastics could be divided into 4 shapes: fiber, fragment, film, and pellet. Seven polymer types of microplastics were identified, including polyamide (PA), polyethylene (PE), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC). Most microplastics were tiny and small sizes (≤ 500 µm) and colorless. Through model analysis and survey, microplastic deposition came from the study region, and the potential sources might be plastic products and wastes. The seasons with the highest and lowest total deposition flux were summer (535.5 p/(m2·d)) and winter (197.5 p/(m2·d)), respectively. The months of the highest and lowest total deposition flux were June 2021 (681.4 p/(m2·d)) and January 2022 (112.2 p/(m2·d)), respectively. Most fibers (PET, PA, PP) and fragments (PP) were distributed in populous areas such as commercial centers and residential areas. Abundant fragments (PET, PS, PE) and films (PE, PVC) were distributed around salvage stations. Almost all of the pellets (PE, PMMA) were found in the factory. Our results suggested that the temporal distribution of microplastic deposition was influenced by precipitation and mean temperature of air, and the spatial distribution of microplastic deposition was influenced by sources and population density.

Injectable decellularized extracellular matrix hydrogel promotes salivary gland regeneration via endogenous stem cell recruitment and suppression of fibrogenesis.

Saliva is key to the maintenance of oral homeostasis. However, several forms of salivary gland (SG) disorders, followed by hyposalivation, often result in dental caries, oral infection, and decreased taste, which dramatically affect the quality of patient's life. Functional biomaterials hold great potential for tissue regeneration in damaged or dysfunctional SGs and maintaining the good health of oral cavity. Herein, we prepared an injectable hydrogel derived from decellularized porcine submandibular glands (pDSG-gel), the material and biological properties of the hydrogel were systematically investigated. First, good biocompatibility and bioactivities of the pDSG-gel were validated in 2D and 3D cultures of primary submandibular gland mesenchymal stem cells (SGMSCs). Especially, the pDSG-gel effectively facilitated SGMSCs migration and recruitment through the activation of PI3K/AKT signaling pathway, suggested by transcriptomic analysis and immunoblotting. Furthermore, proteomic analysis of the pDSG revealed that many extracellular matrix components and secreted factors were preserved, which may contribute to stem cell homing. The recruitment of endogenous SG cells was confirmed in vivo, upon in situ injection of the pDSG-gel into the defective SGs in rats. Acinar and ductal-like structures were evident in the injury sites after pDSG-gel treatment, suggesting the reconstruction of functional SG units. Meanwhile, histological characterizations showed that the administration of the pDSG-gel also significantly suppressed fibrogenesis within the injured SG tissues. Taken together, this tissue-specific hydrogel provides a pro-regenerative microenvironment for endogenous SG regeneration and holds great promise as a powerful and bioactive material for future treatments of SG diseases. STATEMENT OF SIGNIFICANCE: Decellularized extracellular matrix (dECM) has been acknowledged as one of the most promising biomaterials that recapitalizes the microenvironment in native tissues. Hydrogel derived from the dECM allows in situ administration for tissue repair. Herein, a tissue-specific dECM hydrogel derived from porcine salivary glands (pDSG-gel) was successfully prepared and developed for functional reconstruction of defective salivary gland (SG) tissues. The pDSG-gel effectively accelerated endogenous SG stem cells migration and their recruitment for acinar- and ductal-like regeneration, which was attributed to the activation of PI3K/AKT signaling pathway. Additionally, the introduction of the pDSG-gel resulted in highly suppressed fibrogenesis in the defective tissues. These outcomes indicated that the pDSG-gel holds great potential in clinical translation toward SG regeneration through cell-free treatments.

Adhesion of microchannel-based complementary surfaces.

We show that highly enhanced and selective adhesion can be achieved between surfaces patterned with complementary microchannel structures. An elastic material, poly(dimethylsiloxane) (PDMS), was used to fabricate such surfaces by molding into a silicon master with microchannel profiles patterned by photolithography. We carried out adhesion tests on both complementary and mismatched microchannel/micropillar surfaces. Adhesion, as measured by the energy release rate required to propagate an interfacial crack, can be enhanced by up to 40 times by complementary interfaces, compared to a flat control, and slightly enhanced for some special noncomplementary samples, despite the nearly negligible adhesion for other mismatched surfaces. For each complementary surface, we observe defects in the form of visible striations, where pillars fail to insert fully into the channels. The adhesion between complementary microchannel surfaces is enhanced by a combination of a crack-trapping mechanism and friction between a pillar and channel and is attenuated by the presence of defects.

Bioactive Decellularized Extracellular Matrix Hydrogel Microspheres Fabricated Using a Temperature-Controlling Microfluidic System.

Hydrogel microspheres have drawn great attention as functional three-dimensional (3D) microcarriers for cell attachment and growth, which have shown great potential in cell-based therapies and biomedical research. Hydrogels derived from a decellularized extracellular matrix (dECM) retain the intrinsic physical and biological cues from the native tissues, which often exhibit high bioactivity and tissue-specificity in promoting tissue regeneration. Herein, a novel two-stage temperature-controlling microfluidic system was developed which enabled production of pristine dECM hydrogel microspheres in a high-throughput manner. Porcine decellularized peripheral nerve matrix (pDNM) was used as the model raw dECM material for continuous generation of pDNM microgels without additional supporting materials or chemical crosslinking. The sizes of the microspheres were well-controlled by tuning the feed ratios of water/oil phases into the microfluidic device. The resulting pDNM microspheres (pDNM-MSs) were relatively stable, which maintained a spherical shape and a nanofibrous ultrastructure for at least 14 days. Schwann cells and PC12 cells preseeded on the pDNM-MSs not only showed excellent viability and an adhesive property, but also promoted cell extension compared to the commercially available gelatin microspheres. Moreover, primary neural stem/progenitor cells attached well to the pDNM-MSs, which further facilitated their proliferation. The successfully fabricated dECM hydrogel microspheres provided a highly bioactive microenvironment for 3D cell culture and functionalization, which showed promising potential in versatile biomedical applications.

A new species of tick, Ixodes (Ixodes) mojavensis (Acari: Ixodidae), from the Amargosa Valley of California.

Ixodes (Ixodes) mojavensis, n. sp. (Acari: Ixodidae), is described from all parasitic stages collected from the endangered vole Microtus californicus scirpensis Bailey, 1900 (Rodentia: Cricetidae), Mus musculus L. 1758 (Rodentia: Muridae), and Reithrodontomys megalotis (Baird; 1857) (Rodentia: Cricetidae) in the Amargosa Valley of California. When first collected in 2014, this tick was tentatively identified as Ixodes minor Neumann, 1902 because the nucleotide similarity between its 16S rDNA sequence and a homologous GenBank sequence from an I. minor from the eastern U.S. was 99.51%. Nevertheless, adults of I. mojavensis differ morphologically from I. minor by hypostomal dentition, absence of a spur on palpal segment I, and punctation patterns; nymphs by the shapes of basis capituli, auriculae, cervical grooves and external files of hypostomal denticles; and larvae by the length of idiosomal setae and hypostomal dentition. DNA sequencing of fragments of 4 different genes, 12S rDNA, 16S rDNA, cytochrome c oxidase subunit I (COI), and intergenic transcribed spacer 2 (ITS2) of I. mojavensis and of closely related species of Ixodes shows that the mitochondrial gene sequences of the new tick species are almost identical to the I. minor homologous genes. Phylogenetically, the two species do not cluster in mutually exclusive monophyletic clades. However, ITS2 sequences of I. mojavensis and I. minor diverge deeply (≥ 5.74% maximum likelihood divergence) and are as different as homologous genes from other recognized species. The discrepancy between the two sets of genes is suggestive of past mitochondrial introgression or incomplete mitochondrial lineage sorting.

Evidence on Invasion of Blood, Adipose Tissues, Nervous System and Reproductive System of Mice After a Single Oral Exposure: Nanoplastics versus Microplastics.

Objective: This study was designed to provide the evidences on the toxicokinetics of microplastics (MPs) and nanoplastics (NPs) in the bodies of mammals. Methods: 100 nm, 3 µm, and 10 µm fluorescent polystyrene (PS) beads were administered to mice once by gavage at a dose of 200 mg/kg body weight. The levels and change of fluorescence intensity in samples of blood, subcutaneous fat, perirenal fat, peritesticular fat, cerebrum, cerebellum, testis, and epididymis were measured at 0.5, 1, 2, and 4 h after administration using an IVIS Spectrum small-animal imaging system. Histological examination, confocal laser scanning, and transmission electron microscope were performed to corroborate the findings. Results: After confirming fluorescent dye leaching and impact of pH value, increased levels of fluorescence intensity in blood, all adipose tissues examined, cerebrum, cerebellum, and testis were measured in the 100 nm group, but not in the 3 and 10 µm groups except in the cerebellum and testis at 4 h for the 3 µm PS beads. The presence of PS beads was further corroborated. Conclusion: After a single oral exposure, NPs are absorbed rapidly in the blood, accumulate in adipose tissues, and penetrate the blood-brain/testis barriers. As expected, the toxicokinetics of MPs is significantly size-dependent in mammals.

Size Dependence of Particulate Calcium Phosphate Fillers in Dental Resin Composites.

Resin composites that consist of polymeric resins and functional fillers are commonly used as restorative materials for dental caries. Various types of calcium phosphates (CaPs) are studied as remineralizing fillers in the formulation of dental resin composites, which are generally inhibitory to demineralization of teeth, but the performance of resin composites has not yet been investigated comprehensively with respect to the size of CaP particles. In this study, the same tricalcium phosphate (TCP) particles within two different size ranges, the as-received TCP particles (TCP) and those resulted from grinding (TCP-G), were tested to determine the size dependence of CaP fillers in dental resin composites. The buffering capability, mechanical properties, ion release, antibacterial performance, and remineralization effect of TCP/TCP-G-containing composites were experimentally characterized and compared against two other commercial dental materials. The integration of micrometer-sized TCP particles resulted in a similar buffering effect and Ca2+/PO4 3- release behaviors compared to the resin composite containing much smaller TCP-G particles. The flexural strength of the TCP-G resin composite was lower than that of the TCP composite after immersion in water for 30 days. However, the TCP-G composite facilitated crystal deposition toward better gap-closing performance at the dentin-composite interface. This study explored detailed insights about the size effect of CaP fillers, which is useful for the development of functional dental resin composites and their clinical translation.