Revealing Trace Nanoplastics in Food Packages─An Electrochemical Approach Facilitated by Synergistic Attraction of Electrostatics and Hydrophobicity.

Most food packages are made of plastics, nanoplastics released from which can be directly ingested and induce serious damage to organisms. Therefore, it is urgent to develop an effective and convenient method for nanoplastic determinations in food packages. In this work, we present a sandwich-based electrochemical strategy for nanoplastic determination. Positively charged Au nanoparticles were coated onto a Au electrode to selectively capture negatively charged nanoplastics in an aqueous environment. Subsequently, the nanoplastics were recognized by the signal molecule ferrocene via the hydrophobic interaction and determined by differential pulse voltammetry. Our sandwich-type detection depends on both electronegativity and hydrophobicity of nanoplastics, which make the method applicable for the assays of packages made of widely commercialized polystyrene (PS), polypropylene (PP), polyethylene (PE), and polyamide (PA). The method displays different sensitivities to above four nanoplastics but the same dynamic range from 1 to 100 µg·L-1. Based on it, the nanoplastics released from several typical food packages were assayed. Teabags were revealed with significant nanoplastic release, while instant noodle boxes, paper cups, and take-out boxes release slightly. The good recoveries in nanoplastic-spiked samples confirm the accuracy and applicability of this method. This work provides a sensitive, low-cost, and simple method without complicated instruments and pretreatment, which is of great significance for the determination of nanoplastics released from food packages.

Silymarin modified polysulfone hollow fiber membranes with antioxidant, anti-M1 macrophage polarization and hemocompatibility for blood purification.

Oxidative stress is highly prevalent in maintenance hemodialysis patients and increases the risk of cardiovascular morbidity and mortality. Silymarin (SM) is a natural compound extracted from plants, and has been shown to have pharmacological effects such as antioxidant, anti-inflammatory, cytoprotective, and anti-nephrotoxicity. SM-modified polysulfone (PSF) hemodialysis membranes were prepared by an immersion-precipitation phase transition method. The experimental results showed that the modified membranes effectively scavenged free radicals, significantly inhibited lipid peroxidation, and had good antioxidant stability (60 days). The PSF/SM antioxidant membranes (H-3) had no pro-inflammatory effect, which was confirmed by the result of anti-M1 macrophage polarization. Furthermore, the hemolysis rate (2%), blood cell deformation (3.7%), and inhibition of erythrocyte and platelet adhesion were improved by the SM-modified PSF membranes. All the results suggest that PSF/SM blended hollow fiber membranes are promising for application in hemodialysis membranes to improve oxidative stress status and reduce inflammation and complications in patients.

Controlling the degradation of covalently cross-linked carboxymethyl chitosan utilizing bimodal molecular weight distribution.

Degradability is often a critical property of materials utilized in tissue engineering. Although chitosan, a naturally derived polysaccharide, is an attractive material due to its biocompatibility and ability to form scaffolds, its slow and uncontrollable rate of degradation can be an undesirable feature. In this study, we characterize chitosan derivatives formed using a combination of carboxymethylation and a bimodal molecular weight distribution. Specifically, chitosan is carboxymethylated to a theoretical extent of approximately 30% as described in our previous work, in which carboxyl groups possessing negative charges are created at a physiological pH. Carboxymethyl chitosan is used to form films and constructs by varying the ratio of high to low molecular weight (MW) while maintaining the mechanical properties of the polymer. The rate of degradation is found to be dependent upon both the carboxymethylation and the ratio of high to low MW polymer, as determined by dry weight loss in lysozyme solution in PBS. Subsequently, biocompatibility is examined to determine the effects of these modifications upon Neuro-2a cells cultured on these films. Neuro-2a cells adhere and proliferate on the modified films at a comparable rate to those cultured on unmodified films. This data indicates that these chitosan derivatives exhibit tunable degradation rates and result in a promising material system for neural tissue engineering.

Function and mechanism of mesoporous bioactive glass adsorbed epidermal growth factor for accelerating bone tissue regeneration.

Mesoporous bioactive glass (MBG) has been demonstrated to play a vital role in bone tissue engineering due to its bioactivity, biocompatibility, and osteoinduction properties. Here, we report that MBG grafted with an amino group (MBG-NH2) and MBG-NH2 adsorbed epidermal growth factor (EGF) (MBG-NH2/EGF) sustained-release EGF, and MBG-NH2/EGF could accelerate osteoblast differentiation and mineralization in MC3T3-E1 cells. We found that MBG-NH2 could promote bone-like deposit formation and Ca deposition in vitro. Intriguingly, we observed that MBG-NH2/EGF enhanced MC3T3-E1 cell adhesion. We also showed that extracellular signal-regulated kinase 1/2 (ERK1/2) was phosphorylated when MC3T3-E1 cells were cultured on MBG-NH2/EGF. Interestingly, the transcription factor Runx2, important for osteoblast differentiation, was also activated when MC3T3-E1 cells were cultured on MBG-NH2/EGF. We showed that MC3T3-E1 cells cultured on MBG-NH2/EGF activating Runx2 was through ERK1/2 phosphorylation. Consistent with this survey, we observed that MC3T3-E1 cells cultured on MBG-NH2/EGF accelerated osteoblastic marker gene expressions, including osteopontin (Opn) and osteocalcin (Ocn). Taken together, we conclude that the osteoblast differentiation and mineralization were accelerated in MC3T3-E1 cells cultured on MBG-NH2/EGF through ERK-activated Runx2 pathway. These findings support the idea that MBG-NH2/EGF is a potential biomaterial for bone tissue repair in bone defect-related diseases.

The mechanism of a chitosan-collagen composite film used as biomaterial support for MC3T3-E1 cell differentiation.

Natural composite biomaterials are good structural supports for bone cells to regenerate lost bone. Here, we report that a chitosan-collagen composite film accelerated osteoblast proliferation, differentiation and matrix mineralization in MC3T3-E1 cells. Intriguingly, we observed that the film enhanced the phosphorylation of Erk1/2. We showed that the chitosan-collagen composite film increased the transcriptional activity of Runx2, which is an important factor regulating osteoblast differentiation downstream of phosphorylated Erk1/2. Consistent with this observation, we found that the chitosan-collagen composite film increased the expression of osteoblastic marker genes, including Type I Collagen and Runx2 in MC3T3-E1 cells. We conclude that this film promoted osteoblast differentiation and matrix mineralization through an Erk1/2-activated Runx2 pathway. Our findings provide new evidence that chitosan-collagen composites are promising biomaterials for bone tissue engineering in bone defect-related diseases.

An integrated approach to optimize the conditioning chemicals for enhanced sludge conditioning in a pilot-scale sludge dewatering process.

An integrated approach incorporating response surface methodology (RSM), grey relational analysis, and fuzzy logic analysis was developed to quantitatively evaluate the conditioning chemicals in sludge dewatering process. The polyacrylamide (PAM), ferric chloride (FeCl(3)) and calcium-based mineral powders were combined to be used as the sludge conditioners in a pilot-scale sludge dewatering process. The performance of conditioners at varied dosages was comprehensively evaluated by taking into consideration the sludge dewatering efficiency and chemical cost of conditioner. In the evaluation procedure, RSM was employed to design the experiment and to optimize the dosage of each conditioner. The grey-fuzzy logic was established to quantify the conditioning performance on the basis of grey relational coefficient generation, membership function construction, and fuzzy rule description. Based on the evaluation results, the optimal chemical composition for conditioning was determined as PAM at 4.62 g/kg DS, FeCl(3) at 55.4 g/kg DS, and mineral powders at 30.0 g/kg DS.

The effect of topology of chitosan biomaterials on the differentiation and proliferation of neural stem cells.

Neural stem cells (NSCs) are capable of self-renewal and differentiation into three principle central nervous system cell types under specific local microenvironments. Chitosan films (Chi-F), chitosan porous scaffolds (Chi-PS) and chitosan multimicrotubule conduits (Chi-MC) were used to investigate their effects on the differentiation and proliferation of NSCs isolated from the cortices of fetal rats. In the presence of 10% fetal bovine serum most NSCs cultured on Chi-F differentiated into astrocytes, NSCs cultured on Chi-MC showed a significant increase in neuronal differentiation, while Chi-PS somewhat promoted NSCs to differentiate into neurons. However, in serum-free medium with 20 ng ml(-1) basic fibroblast growth factor NSCs cultured on Chi-F showed the greatest proliferation, NSCs cultured on Chi-MC showed moderate cell proliferation, but NSCs cultured on Chi-PS exhibited the least cell proliferation. These observations indicate that chitosan topology can play an important role in regulating differentiation and proliferation of NSCs and raise the possibility of the utilization of chitosan in various structural biomaterials in neural tissue engineering.

Rat hepatocyte aggregate formation on discrete aligned nanofibers of type-I collagen-coated poly(L-lactic acid).

Primary hepatocytes cultured in three dimensional tissue constructs composed of multicellular aggregates maintain normal differentiated cellular function in vitro while cultured monolayers do not. Here, we report a technique to induce hepatocyte aggregate formation using type-I collagen-coated poly(L-lactic acid) (PLLA) discrete aligned nanofibers (disAFs) by providing limited cell-substrate adhesion strength and restricting cell migration to uniaxial movement. Kinetics of aggregate formation, morphology and biochemical activities of rat hepatocyte aggregates were tested over a 15 day culture period. Evidence was provided that physical cues from disAFs quickly induced the formation of aggregates. After 3 days in culture, 88.3% of free hepatocytes on disAFs were incorporated into aggregates with an average diameter of 61 +/- 18 microm. Hepatocyte aggregates formed on disAFs displayed excellent cell retention, cell activity and stable functional expression in terms of albumin secretion, urea synthesis and phase I and II (CYP1A and UGT) metabolic enzyme activity compared to monolayer culture of hepatocytes on tissue culture plastic (TCP) with type-I collagen as well as on meshes of type-I collagen-coated PLLA random nanofibers (meshRFs). These results suggest that disAFs may be a suitable method to maintain large-scale hepatic cultures with high activity for tissue engineering research and potential therapeutic applications, such as bioartificial liver devices.

Surface characterization and cytocompatibility of three chitosan/polycation composite membranes for guided bone regeneration.

Guided bone regeneration is a promising surgical procedure for reconstructing bone defects. In this study, three chitosan/polycation composite membranes for guided bone regeneration are produced by blending chitosan with poly-L-lysine, polyethyleneimine, and poly-L-ornithine. For all composite membranes, the surface characteristics including surface topography, chemistry, and wettability are examined by atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle assay. Their cytocompatibility is also evaluated with MC3T3-E1 osteoblast-like cells at cell, protein, and gene levels through cell biology assays, western blot, and RT-PCR analysis. On chitosan/poly-L-lysine composite membrane, MC3T3-E1 cells present well-developed cytoskeletal organization and significantly higher adhesion, proliferation, and differentiation than those on chitosan and the other two composite membranes. Furthermore, MC3T3-E1 cells on chitosan/poly-L-lysine membrane exhibit increased phosphorylation levels of focal adhesion kinase and extracellular signal-regulated kinase 1/2, and achieve an enhanced mRNA expression of fibronectin, Runx 2, RhoA, integrin alpha 5, and integrin beta1. From our results, we conclude that chitosan/ poly-L-lysine composite membrane possesses improved cytocompatibility with osteoblasts when compared to chitosan and holds potential for guided bone regeneration in the near future.

Study on novel hydrogels based on thermosensitive PNIPAAm with pH sensitive PDMAEMA grafts.

A series of novel hydrogels based on poly(N-isopropylacrylamide) (PNIPAAm) with pendant poly(N-(2-(dimethylamino) ethyl)-methacrylamide) (PDMAEMA) grafts were designed and synthesized. The influence of the pendant PDMAEMA grafts on the properties of the resulted hydrogels was examined in terms of morphology observed by scanning electron microscopy (SEM), thermal property characterized by differential scanning calorimetry (DSC) and shrinking/swelling kinetics upon external temperature changes. In comparison with the conventional PNIPAAm hydrogels, resulting hydrogels presented favorable pH sensitivity as well as improved thermosensitive properties, including enlarged water containing capability at room temperature and faster shrinking/swelling rate upon heating. In addition, fish DNA, used as a model drug, was loaded into the hydrogels, and the controlled release behavior of the drug-loaded hydrogels at different temperatures (22 and 37 degrees C) was further studied.