A discussion of microplastics in soil and risks for ecosystems and food chains.

Microplastics are among the major contaminations in terrestrial and marine environments worldwide. These persistent organic contaminants composed of tiny particles are of concern due to their potential hazards to ecosystem and human health. Microplastics accumulates in the ocean and in terrestrial ecosystems, exerting effects on living organisms including microbiomes, fish and plants. While the accumulation and fate of microplastics in marine ecosystems is thoroughly studied, the distribution and biological effects in terrestrial soil call for more research. Here, we review the sources of microplastics and its effects on soil physical and chemical properties, including water holding capacity, bulk density, pH value as well as the potential effects to microorganisms and animals. In addition, we discuss the effects of microplastics in combination with other toxic environmental contaminants including heavy metals and antibiotics on plant growth and physiology, as well as human health and possible degradation and remediation methods. This reflect is an urgent need for monitoring projects that assess the toxicity of microplastics in soil and plants in various soil environments. The prospect of these future research activities should prioritize microplastics in agro-ecosystems, focusing on microbial degradation for remediation purposes of microplastics in the environment.

A Space-Time Conversion Vehicle for Programmed Multi-Drugs Delivery into Pancreatic Tumor to Overcome Matrix and Reflux Barriers.

The numerous biological barriers, which limit pharmacotherapy of pancreatic carcinoma, including inadequate drug accumulation in the tumor environment, a dense extracellular matrix (ECM) and efficient drug-efflux mechanisms, illustrate the requirement of multifunctional delivery systems to overcome the individual barriers at the right place at the right time. Herein, a space-time conversion vehicle based on covalent organic framework (COF)-coated mesoporous silica nanospheres (MSN) with a sandwiched polyethyleneimine (PEI) layer (MPCP), is designed. The space-specific drugs-loaded vehicle (MG PP CL P) is obtained by separately incorporating a chemotherapeutic agent (gemcitabine, G) into the MSN core, a P glycoprotein inhibitor (LY 335979, P) into the PEI layer, and an extracellular matrix disruptor (losartan, L) into the COF shell. Thereafter, a programmed drug delivery is achieved via the ordered degradation from COF shell to MSN core. Sequential release of the individual drugs, synergized with a change of nanoparticle surface charge, contribute to an obvious extracellular matrix distraction, distinct drug efflux inhibition, and consequently enhance chemotherapeutic outcomes in pancreatic carcinoma. This MPCP-based vehicle design suggests a robust space-time conversion strategy to achieve programmed multi-drugs delivery and represents a new avenue to the treatment of pancreatic carcinoma by overcoming extracellular matrix and drug reflux barriers.

Progress in microbial biomass conversion into green energy.

The increase in global population size over the past 100 decades has doubled the requirements for energy resources. To mitigate the limited fossil fuel available, new clean energy sources being environmental sustainable for replacement of traditional energy sources are explored to supplement the current scarcity. Biomass containing lignin and cellulose is the main raw material to replace fossil energy given its abundance and lower emission of greenhouse gases and NOx when transformed into energy. Bacteria, fungi and algae decompose lignocellulose leading to generation of hydrogen, methane, bioethanol and biodiesel being the clean energy used for heating, power generation and the automobile industry. Microbial Fuel Cell (MFC) uses microorganisms to decompose biomass in wastewater to generate electricity and remove heavy metals in wastewater. Biomass contains cellulose, hemicellulose, lignin and other biomacromolecules which need hydrolyzation for conversion into small molecules by corresponding enzymes in order to be utilized by microorganisms. This paper discusses microbial decomposition of biomass into clean energy and the five major ways of clean energy production, and its economic benefits for future renewable energy security.

Multimodal theranostics augmented by transmembrane polymer-sealed nano-enzymatic porous MoS2 nanoflowers.

Developing an all-in-one multimodal theranostic platform that can synergistically integrate sensitive photoacoustic (PA) imaging, enhanced photothermal therapy (PTT) and photodynamic therapy (PDT) as well as the nano-enzyme activated chemodynamic therapy (CDT) presents a great challenge for the current nanomedicine design. Herein, a simple hydrothermal method was used to prepare porous molybdenum disulfide (MoS2) nanoflowers. These nanoflowers were assembled by three dimensional (3D)-stacked MoS2 nanosheets with plentiful pores and large surfaces, which thus exhibited enhanced photothermal conversion via light trapping and peroxidase (POD)-like activity via active defects exposure. Consequently, this 3D-MoS2 nanostructure could be well-sealed by polyethylene glycol-polyethylenimine polymer modified with nucleolar translocation signal sequence of the LIM Kinase 2 protein (LNP) via strong electrostatic interaction, which not only benefited to stably deliver anticancer drug doxorubicin (DOX) into the tumor cells for pH/NIR-responsive chemotherapy, but also provided strong photoacoustic, photothermal performances and stimulated generation of reactive oxygen species (ROS) for imaging-guided PTT/PDT/CDT combined therapy. This work promised a simple all-in-one multimodal theranostic platform to augment the potential antitumoral therapeutic outcomes.

Facile marriage of Gd3+ to polymer-coated carbon nanodots with enhanced biocompatibility for targeted MR/fluorescence imaging of glioma.

Overcoming blood-brain barrier (BBB) for precise glioma diagnosis remains an urgent challenge due to its peculiar location in central nervous system (CNS). Herein, polymer-coated carbon nanodots with high hydrophilicity were facilely married with Gd-DTPA to construct a dual-modal imaging system (NCDDG). This system was demonstrated with obviously decreased toxicity and enhanced magnetic resonance imaging (MRI) ability compared to traditional Gd-DTPA. Meanwhile, NCDDG reserved the bright fluorescence of biocompatible carbon nanodots with increased spatial resolution. Attributed to small size and hydrophilic polymer coating, NCDDG was capable of overcoming the BBB and permeating leaky microvascular walls into surrounding glioma tissues via prolonged in vivo circulation and enhanced retention effect. As a result, dual1-modal targeted MR/fluorescence imaging of glioma was synergistically achieved with high sensitivity and resolution. This work promised a potential contrast agent for sensitive clinical diagnosis of glioma.

A compound scaffold with uniform longitudinally oriented guidance cues and a porous sheath promotes peripheral nerve regeneration in vivo.

Scaffolds with inner fillers that convey directional guidance cues represent promising candidates for nerve repair. However, incorrect positioning or non-uniform distribution of intraluminal fillers might result in regeneration failure. In addition, proper porosity (to enhance nutrient and oxygen exchange but prevent fibroblast infiltration) and mechanical properties (to ensure fixation and to protect regenerating axons from compression) of the outer sheath are also highly important for constructing advanced nerve scaffolds. In this study, we constructed a compound scaffold using a stage-wise strategy, including directionally freezing orientated collagen-chitosan (O-CCH) filler, electrospinning poly(ε-caprolactone) (PCL) sheaths and assembling O-CCH/PCL scaffolds. Based on scanning electron microscopy (SEM) and mechanical tests, a blend of collagen/chitosan (1:1) was selected for filler fabrication, and a wall thickness of 400 µm was selected for PCL sheath production. SEM and three-dimensional (3D) reconstruction further revealed that the O-CCH filler exhibited a uniform, longitudinally oriented microstructure (over 85% of pores were 20-50 µm in diameter). The electrospun PCL porous sheath with pore sizes of 6.5 ±â€¯3.3 µm prevented fibroblast invasion. The PCL sheath exhibited comparable mechanical properties to commercially available nerve conduits, and the O-CCH filler showed a physiologically relevant substrate stiffness of 2.0 ±â€¯0.4 kPa. The differential degradation time of the filler and sheath allows the O-CCH/PCL scaffold to protect regenerating axons from compression stress while providing enough space for regenerating nerves. In vitro and in vivo studies indicated that the O-CCH/PCL scaffolds could promote axonal regeneration and Schwann cell migration. More importantly, functional results indicated that the CCH/PCL compound scaffold induced comparable functional recovery to that of the autograft group at the end of the study. Our findings demonstrated that the O-CCH/PCL scaffold with uniform longitudinal guidance filler and a porous sheath exhibits favorable properties for clinical use and promotes nerve regeneration and functional recovery. The O-CCH/PCL scaffold provides a promising new path for developing an optimal therapeutic alternative for peripheral nerve reconstruction. STATEMENT OF SIGNIFICANCE: Scaffolds with inner fillers displaying directional guidance cues represent a promising candidate for nerve repair. However, further clinical translation should pay attention to the problem of non-uniform distribution of inner fillers, the porosity and mechanical properties of the outer sheath and the morphological design facilitating operation. In this study, a stage-wise fabrication strategy was used, which made it possible to develop an O-CCH/PCL compound scaffold with a uniform longitudinally oriented inner filler and a porous outer sheath. The uniform distribution of the pores in the O-CCH/PCL scaffold provides a solution to resolve the problem of non-uniform distribution of inner fillers, which impede the clinical translation of scaffolds with longitudinal microstructured fillers, especially for aligned-fiber-based scaffolds. In vitro and in vivo studies indicated that the O-CCH/PCL scaffolds could provide topographical cues for axonal regeneration and SC migration, which were not found for random scaffolds (with random microstructure resemble sponge-based scaffolds). The electrospun porous PCL sheath of the O-CCH/PCL scaffold not only prevented fibroblast infiltration, but also satisfied the mechanical requirements for clinical use, paving the way for clinical translation. The differential degradation time of the O-CCH filler and the PCL sheath makes O-CCH/PCL scaffold able to provide long protection for regenerating axons from compression stress, but enough space for regenerating nerve. These findings highlight the possibility of developing an optimal therapeutic alternative for nerve defects using the O-CCH/PCL scaffold.

Noncovalent Bonding of RGD and YIGSR to an Electrospun Poly(ε-Caprolactone) Conduit through Peptide Self-Assembly to Synergistically Promote Sciatic Nerve Regeneration in Rats.

The nerve conduit with biofunctionalities can regulate neurite outgrowth, as well as the migration, proliferation, and myelination activity of Schwann cells. In the present study, polycaprolactone (PCL) conduits are coated with Naphthalene-phenylalanine-phenylalanine-glycine-arginine-glycine-aspartic (Nap-FFGRGD) and Naphthalene-phenylalanine-phenylalanine-glycine-cysteine-aspartic-proline-glycine-tyrosine-isoleucine-glycine-serine-arginine (Nap-FFGCDPGYIGSR) by self-assembly. In vitro studies demonstrate that arginine-glycine-aspartic (RGD) and tyrosine-isoleucine-glycine-serine-arginine (YIGSR) are capable of synergistically enhancing the ability of PCL to support the adhesion and proliferation of Schwann cells, as well as increasing neurite outgrowth from dorsal root ganglions explants. This synergistic effect may occur via the activation of both the phosphoinositide 3-kinase/protein kinase B and mitogen-activated protein kinase/extracellular signal-regulated protein kinase pathways. RGD/YIGSR modifications demonstrate beneficial effects across a 15 mm sciatic nerve gap in axonal regeneration and functional recovery. In addition, increased vascularization is observed in the RGD/YIGSR-PCL group, which might contribute to their beneficial effects on nerve regeneration. These findings indicate the potential of the RGD/YIGSR-PCL conduit to promote axonal regeneration and functional recovery, making the RGD/YIGSR-PCL conduit an attractive candidate for the treatment of a critical nerve defect.

Activation of Schwann cells in vitro by magnetic nanocomposites via applied magnetic field.

Schwann cells (SCs) are attractive seed cells in neural tissue engineering, but their application is limited by attenuated biological activities and impaired functions with aging. Therefore, it is important to explore an approach to enhance the viability and biological properties of SCs. In the present study, a magnetic composite made of magnetically responsive magnetic nanoparticles (MNPs) and a biodegradable chitosan-glycerophosphate polymer were prepared and characterized. It was further explored whether such magnetic nanocomposites via applied magnetic fields would regulate SC biological activities. The magnetization of the magnetic nanocomposite was measured by a vibrating sample magnetometer. The compositional characterization of the magnetic nanocomposite was examined by Fourier-transform infrared and X-ray diffraction. The tolerance of SCs to the magnetic fields was tested by flow-cytometry assay. The proliferation of cells was examined by a 5-ethynyl-2-deoxyuridine-labeling assay, a PrestoBlue assay, and a Live/Dead assay. Messenger ribonucleic acid of BDNF, GDNF, NT-3, and VEGF in SCs was assayed by quantitative real-time polymerase chain reaction. The amount of BDNF, GDNF, NT-3, and VEGF secreted from SCs was determined by enzyme-linked immunosorbent assay. It was found that magnetic nanocomposites containing 10% MNPs showed a cross-section diameter of 32.33±1.81 µm, porosity of 80.41%±0.72%, and magnetization of 5.691 emu/g at 8 kOe. The 10% MNP magnetic nanocomposites were able to support cell adhesion and spreading and further promote proliferation of SCs under magnetic field exposure. Interestingly, a magnetic field applied through the 10% MNP magnetic scaffold significantly increased the gene expression and protein secretion of BDNF, GDNF, NT-3, and VEGF. This work is the first stage in our understanding of how to precisely regulate the viability and biological properties of SCs in tissue-engineering grafts, which combined with additional molecular factors may lead to the development of new nerve grafts.