Salt-Induced Adsorption and Rupture of Liposomes on Microplastics.

Microplastics have attracted considerable attention because of concerns regarding their environmental risks to living systems. The interaction between the lipid bilayer and microplastics is important for examining the potential harm to biological membranes in the presence of microplastics. In addition, membrane coatings may change the surface and colloidal properties of microplastics. Herein, phosphatidylcholine (PC) lipids, whose headgroup is most common in cell membranes, were used as model lipids. The adsorption and rupture of PC liposomes on microplastics were systematically studied. We found that divalent metal ions, such as Mg2+ and Ca2+, facilitate liposome adsorption onto microplastics and induce 40-55% liposome leakage at 2.5 mM. In contrast, to achieve a similar effect, 300 mM Na+ was required. Adsorption and rupture followed the same metal concentration requirements, suggesting that liposome adsorption was the rate-limiting step. After adsorption with liposomes, microplastics became more hydrophilic and were better dispersed in water. A similar behavior was observed for all five types of tested microplastics, including PP, PE, PVC, PET, and PS. Leakage also occurred in ocean water. This study provides fundamental insights into the interactions between liposomes and microplastics and has implications for the colloidal and transport properties of microplastics.

Mass Production of Hierarchically Designed Engine-Intake Air Filters by Multinozzle Electroblow Spinning.

Particulate matter damages engines of vehicles when blown into the ventilation system. Conventional engine-intake filter is cellulose microfiber board with an average diameter larger than ten microns, which has low removal efficiency of ultrafine particular matter. In this work, we apply ultrafine polyurethane nanofibers (∼122.8 nm) onto pleated cellulose board using scalable multinozzle electroblow spinning technology, which improves filtration efficiency of particulate matter with a diameter of less than 0.3 µm PM0.3 greatly. The thermoplastic polyurethane 85A nanofiber membranes are transparent, and display superior filtration performance which meets up with the 95% filtration efficiency standard in GB 19083-2010 technical requirements for protective face mask for medical use. The lightweight pleated thermoplastic polyurethane/cellulose composites intercept ∼90% ultrafine PM0.3 under airflow velocity of 32 L min-1 and possess great resistance to shock. These hierarchically designed filters follow a mechanical mechanism and can be used in on-road and off-road cars in the long run.

Liposome-Boosted Peroxidase-Mimicking Nanozymes Breaking the pH Limit.

Peroxidase-mimicking nanozymes such as Fe3 O4 nanoparticles are promising substitutes for natural enzymes like horseradish peroxidase. However, most such nanozymes work efficiently only in acidic conditions. In this work, the influence of various liposomes on nanozyme activity was studied. By introducing negatively charged liposomes, peroxidase-mimicking nanozymes achieved oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in neutral and even alkaline conditions, although the activity towards anionic 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) was inhibited. The Fe3 O4 nanoparticles adsorbed on the liposomes without disrupting membrane integrity as confirmed by fluorescence quenching, dye leakage assays, and cryo-electron microscopy. Stabilization of the blue-colored oxidized products of TMB by electrostatic interactions was believed to be the reason for the enhanced activity. This work has introduced lipids to nanozyme research, and it also has practically important applications for using nanozymes at neutral pH, such as the detection of hydrogen peroxide and glucose.

Growing a Nucleotide/Lanthanide Coordination Polymer Shell on Liposomes.

Coating liposomes with a shell is a useful strategy to increase membrane stability and prevent leakage or fusion. Nucleotide/lanthanide coordination nanoparticles (NPs) are formed by a simple mixing at ambient conditions. Because some lipid headgroups contain lanthanide binding ligands, they may direct the growth of such coordination NPs. Herein, a gadolinium/adenosine monophosphate (Gd3+/AMP) shell was formed on liposomes (liposome@Gd3+/AMP) using lipids containing phosphoserine (PS) or cholinephosphate (CP) headgroups, while phosphocholine liposomes did not support the shell. Liposome binding Gd3+ is confirmed by transmission electron microscopy (TEM). The negatively charged CP and PS liposomes reversed to positive upon Gd3+ binding, while other metals such as Ca2+ and Zn2+ did not reverse the charge. Binding of Gd3+ did not leak the PS liposomes. Then, AMP was further added to cross-link Gd3+ on the liposome surface. A shell was formed as indicated by TEM, and the content inside the liposome remained for the PS liposomes. While adding Triton X-100 still induced leakage of the encapsulated liposomes, the shell protected the liposomes from leakage induced by ZnO NPs, suggesting a porous structure of the Gd3+/AMP shell which allowed penetration of Triton X-100 but not the larger ZnO NPs. This work provides a simple method to coat liposomes, and also offers a fundamental understanding of liposome adsorption of lanthanide ions.

Cu2+-Directed Liposome Membrane Fusion, Positive-Stain Electron Microscopy, and Oxidation.

Natural lipid headgroups contain a few types of metal ligands, such as phosphate, amine, and serine, which interact with metal ions differently. Herein, we studied the binding between Cu2+ and liposomes with four types of headgroups: phosphocholine (PC), phosphoglycerol (PG), phosphoserine (PS), and cholinephosphate (CP). Using fluorescently headgroup-labeled liposomes, Cu2+ strongly quenched the CP and PS liposomes, whereas quenching of PC and PG was weaker. Dynamic light scattering indicated that all of the four liposomes aggregated at high Cu2+ concentrations, and ethylenediaminetetraacetic acid (EDTA) only restored the original size of the PC liposome, implying fusion of the other three types of liposomes. The leakage tests revealed that the integrity of PC liposomes was not affected by Cu2+, but the other three liposomes leaked. Under TEM, all of the liposomes show a positive-stain feature in the presence of Cu2+ and Cu2+-stained individual liposomes with a short incubation time (<1 min). The oxidative catalytic property of Cu2+ was also tested, and a tight binding by the PS liposome inhibited the activity of Cu2+. Finally, a model of interaction for each liposome was proposed, and each one has a different metal-binding and interaction mechanism.

Headgroup-Inversed Liposomes: Biointerfaces, Supported Bilayers and Applications.

Phospholipids are a major component of the cell membrane. In most natural phospholipids, the phosphate acts as a bridge, connecting the other portion of the polar headgroup with the hydrophobic tails. Such bridging phosphate is chemically quite inert. Synthetic lipids inversing the headgroup polarity of phosphocholine (PC) have been recently reported, and these are named CP lipids with a terminal phosphate, or CPe with the terminal phosphate capped by an ethyl group. This Feature Article summarizes the properties and applications of such inversed lipids. First, CPe liposomes were found to be highly resistant to protein adsorption with an even longer blood circulation time than PC liposomes, allowing for enhanced accumulation in tumor sites. CPe liposomes do not interact with PC liposomes either, and this observation was different from that reported using CP polymers, which adhere strongly to cells. Second, CP liposomes interact strongly with many metal oxide nanoparticles (but not silica) forming supported lipid bilayers, while PC liposomes only form supported bilayers on silica. Finally, CP liposomes are good metal ligands based on their exposed terminal phosphate. Zn2+ binds to CP liposomes so strongly that Zn2+ sandwiched multilayered lipid structures were observed. Aside from these fundamental aspects, the potential applications of these headgroup-inversed lipids in drug delivery and biosensor development have also been described, which in turn has promoted fundamental biointerface insights.

Zn2+ Induced Irreversible Aggregation, Stacking, and Leakage of Choline Phosphate Liposomes.

The interaction between lipids and metal ions is important for metal sensing, cellular signal transduction, and oxidative lipid damage. While most previous work overlooked the phosphate group of lipids for metal binding, we herein highlight its importance. Phosphocholine (PC) and its headgroup inversed choline phosphate (CP) lipids were used to prepare liposomes. From dynamic light scattering (DLS), Zn2+ causes significant aggregation or fusion of the CP liposomes, but not PC liposomes. The size change induced by Zn2+ is not fully reversed by adding EDTA, implying liposome fusion induced by Zn2+. Isothermal titration calorimetry (ITC) shows that binding between Zn2+ and CP liposomes is endothermic with a Kd of 110 µM Zn2+, suggesting an entropy driven reaction likely due to the release of bound water. In comparison, no heat was detected by titrating Zn2+ into PC liposomes or Ca2+ into CP liposomes. Furthermore, Zn2+ causes a transient leakage of the CP liposomes, and further leakage is observed upon removing Zn2+ by EDTA. Transmission electron microscopy (TEM) with negative stained samples showed multilamellar CP lipid structures attributable to Zn2+ sandwiched between lipid bilayers, leading to a proposed reaction mechanism. This work provides an interesting system for studying metal interacting with terminal phosphate groups in liposomes, affecting the size, charge, and membrane integrity of the liposomes.

Adsorption of Nanoceria by Phosphocholine Liposomes.

Nanoceria (CeO2 nanoparticle) possesses a number of enzyme-like activities. In particular, it scavenges reactive oxygen species based on in vitro and in vivo antioxidation studies. An important aspect of fundamental physical understanding is its interaction with lipid membranes that are the main components of the cell membrane. In this work, adsorption of nanoceria onto phosphocholine (PC) liposomes was performed. PC lipids are the main constituents of the cell outer membrane. Using a fluorescence quenching assay, a nanoceria adsorption isotherm was determined at various pH values and ionic strengths. A non-Langmuir isotherm occurred at pH 4 because of lateral electrostatic repulsion among the adsorbed cationic nanoceria. The phosphate group in the PC lipid is mainly responsible for the interaction, and the adsorbed nanoceria can be displaced by free inorganic phosphate. The tendency of the system to form large aggregates is a function of pH and the concentration of nanoceria, attributable to nanoceria being positively charged at pH 4 and neutral at physiological pH. Calcein leakage tests indicate that nanoceria induces liposome leakage because of transient lipid phase transition, and cryo-transmission electron microscopy indicates that the overall shape of the liposome is retained although deformation is still observed. This study provides fundamental biointerfacial information at a molecular level regarding the interaction of nanoceria and model cell membranes.

Profiling Metal Oxides with Lipids: Magnetic Liposomal Nanoparticles Displaying DNA and Proteins.

Metal oxides include many important materials with various surface properties. For biomedical and analytical applications, it is desirable to engineer their biocompatible interfaces. Herein, a phosphocholine liposome (DOPC) and its headgroup dipole flipped counterpart (DOCP) were mixed with ten common oxides. Using the calcein leakage assay, cryo-TEM, and ζ-potential measurement, these oxides were grouped into three types. The type 1 oxides (Fe3 O4 , TiO2 , ZrO2 , Y2 O3 , ITO, In2 O3 , and Mn2 O3 ) form supported bilayers only with DOCP. Type 2 (SiO2 ) forms supported bilayers only with DOPC; type 3 (ZnO and NiO) are cationic and damage lipid membranes. Magnetic Fe3 O4 nanoparticles were further studied for conjugation of fluorophores, proteins, and DNA to the supported DOCP bilayers via lipid headgroup labeling, covalent linking, or lipid insertion. Delivery of the conjugates to cells and selective DNA hybridization were demonstrated. This work provides a general solution for coating the type 1 oxides with a simple mixing in water, facilitating applications in biosensing, separation, and nanomedicine.

Microstructural Characteristics and Properties of Laser-Welded Diamond Saw Blade with 30CrMo Steel.

In order to enhance the quality of diamond composite materials, this work employs a Cu-Co-Fe and Ni-Cr-Cu pre-alloyed powder mixture as a transition layer, and utilizes laser-welding technology for saw blade fabrication. By adjusting the laser-welding process parameters, including welding speed and welding power, well-formed welded joints were achieved, and the microstructure and mechanical properties of the welded joints were investigated. The results demonstrate that the best welding performance was achieved at a laser power of 1600 W and a welding speed of 1400 mm/min, with a remarkable tooth engagement strength of up to 819 MPa. The fusion zone can be divided into rich Cu phase and rich Fe phase regions, characterized by coarse grains without apparent preferred orientation. The microstructure of the heat-affected zone primarily consists of high-hardness brittle quenched needle-like martensite, exhibiting a sharp increase in microhardness up to 550 HV. Fracture occurred at the boundary between the fusion zone and the heat-affected zone of the base material, where stress concentration was observed. By adjusting the welding parameters and transition layer materials, the mechanical properties of the joints were improved, thereby achieving a reliable connection between diamond composite materials and the metal substrate.

Migration insertion polymerization (MIP) of cyclopentadienyldicarbonyldiphenylphosphinopropyliron (FpP): a new concept for main chain metal-containing polymers (MCPs).

We report a conceptually new polymerization technique termed migration insertion polymerization (MIP) for main chain metal-containing polymer (MCP) synthesis. Cyclopentadienyldicarbonyldiphenylphosphinopropyliron (FpP) is synthesized and polymerized via MIP, resulting in air stable poly(cyclopentadienylcarbonyldiphenylphosphinobutanoyliron) (PFpP) displaying narrow molecular weight distribution. The backbone of PFpP contains asymmetric iron units connected by both phosphine coordination and Fe-acyl bonds, which is representative of a new type of polymer. Furthermore, PFpP is tested to be soluble in a wide range of organic solvents and shown to possess reactive Fp end groups. PFpP amphiphiles have therefore been prepared via an end group migration insertion reaction in the presence of oligoethylene phosphine.

Malignant peripheral nerve sheath tumor of tongue: a case report.

Malignant peripheral nerve sheath tumor (MPNST) is a rare neurogenic malignant tumor. MPNST has aty-pical clinical symptoms and imaging presentations, difficult diagnosis, a high degree of malignancy, and poor prognosis. It usually occurs in the trunk, approximately 20% in the head and neck, and rarely in the mouth. This paper reports a case of MPNST of the tongue. A summary of the clinical features, diagnosis, and treatment of MPNST is presented in combination with a literature review to provide a reference for the diagnosis and treatment of this disease.

Mucin-targeting-aptamer functionalized liposomes for delivery of cyclosporin A for dry eye diseases.

Traditional eye drops are convenient to use; however, their effectiveness is limited by their poor retention time and bioavailability in the eyes due to ocular barriers. Therefore, strategies to enhance ocular drug delivery are required. Herein, we constructed a mucin-1 aptamer-functionalized liposome and loaded it with cyclosporin A, a common ocular drug in eye drops used to treat dry eye diseases (DED). Drug encapsulation slightly reduced the liposome size without changing the surface potential of liposomes. Approximately 90% of the cholesterol-modified aptamers were inserted to the liposomes. We evaluated the cytotoxicity, anti-inflammatory effects, cell permeability regulation, and retention time of liposomes in human corneal epithelial cells under dry eye conditions. These results suggest that the aptamer-functionalized liposomes are more efficient as nanocarriers than non-functionalized liposomes and drug-free liposomes. They restore inflammation levels by 1-fold and remain in the cells for up to 24 h. An in vivo study was also performed in a rat DED model, which demonstrated the efficacy of aptamer-functionalized liposomes in restoring tear production and corneal integrity. The present study demonstrated the capability of aptamer-functionalized liposomes in the delivery of ocular drugs for the management of ocular diseases.

Meta-analysis of the survival rate and postoperative infection rate of primary and secondary implants after vascularized fibula transplantation for reconstruction of jaw defects.

OBJECTIVES: Vascularized fibula flap transplantation is the most effective and common method to repair the jaw defects. In addition, implantation is the first choice to restore dentition on the graft fibula. Implants are usually implanted at least 6 months after fibula transplantation. Primary implantation of implants during surgery can restore the dentition earlier, but whether this method can achieve the same restorative effect as secondary implantation is still uncertain. This article aims to compare the survival rate and complications between primary and secondary implantation through meta-analysis. METHODS: This meta-analysis was conducted according to PRISMA protocol and the Cochrane Handbook of Systematic Reviews of Interventions. According to the inclusion and exclusion criteria, we selected the PubMed, Embase, Web of Science, Cochrane Library, Chinese National Knowledge Infrastructure (CNKI), Chinese BioMedical Literature Database (CBM) according to established inclusion and exclusion criteria. The Newcastle-Ottawa Scale (NOS) was used to assess the quality of the included studies. Meta-analysis was conducted to compare the survival rate and postoperative infection rate of primary and secondary implantation. RESULTS: Seven studies were involved in our research, involving 186 patients. Five of the studies detailed implant success in 106 patients (primary implantation 50, secondary implantation 56), and four studies documented infection after implantation in 117 patients (primary implantation 52, secondary implantation 65); the survival rate of the primary implantation was 93.3%, and the incidence of postoperative infection was 17.3%. The survival rate of the secondary implantation was 93.4%, and 23.1% had postoperative infection. Meta-analysis showed that there was no significant difference in the survival rate between primary implantation and secondary implantation, OR = 0.813 (95% CI 0.383-1.725, P = 0.589 > 0.05), and there was no significant difference in the incidence of postoperative infection, OR = 0.614 (95% CI 0.239-1.581, P = 0.312 > 0.05). CONCLUSIONS: Based on the results of this study, the research found no significant difference in the survival rate or infection rates between primary and secondary implantation. After appropriate indications selection, primary implantation can be used to reconstruct the dentition with less waiting time, reduce the impact of radiotherapy, and bring a higher quality of life for patients.

Effects of freeze-thaw dynamics and microplastics on the distribution of antibiotic resistance genes in soil aggregates.

This is the first study investigating the effects of freeze-thaw (FT) and microplastics (MPs) on the distribution of antibiotic resistance genes (ARGs) in soil aggregates (i.e., soil basic constituent and functional unit) via microcosm experiments. The results showed that FT significantly increased the total relative abundance of target ARGs in different aggregates due to the increase in intI1 and ARG host bacteria. However, polyethylene MPs (PE-MPs) hindered the increase in ARG abundance caused by FT. The host bacteria carrying ARGs and intI1 varied with aggregate size, and the highest number of hosts was observed in micro-aggregates (<0.25 mm). FT and MPs altered host bacteria abundance by affecting aggregate physicochemical properties and bacterial community and enhanced multiple antibiotic resistance via vertical gene transfer. Although the dominant factors affecting ARGs varied with aggregate size, intI1 was a co-dominant factor in various-sized aggregates. Furthermore, other than ARGs, FT, PE-MPs, and their integration promoted the proliferation of human pathogenic bacteria in aggregates. These findings suggested that FT and its integration with MPs significantly affected ARG distribution in soil aggregates. They amplified antibiotic resistance environmental risks, contributing to a profound understanding of soil antibiotic resistance in the boreal region.

Targeted liposomal drug delivery: a nanoscience and biophysical perspective.

Liposomes are a unique platform for drug delivery, and a number of liposomal formulations have already been commercialized. Doxil is a representative example, which uses PEGylated liposomes to load doxorubicin for cancer therapy. Its delivery relies on the enhanced permeability and retention (EPR) effect or passive targeting. Drug loading can be achieved using both standard liposomes and also those containing a solid core such as mesoporous silica and poly(lactide-co-glycolide) (PLGA). Developments have also been made on active targeted delivery using bioaffinity ligands such as small molecules, antibodies, peptides and aptamers. Compared to other types of nanoparticles, the surface of liposomes is fluid, allowing dynamic organization of targeting ligands to achieve optimal binding to cell surface receptors. This review article summarizes development of liposomal targeted drug delivery systems, with an emphasis on the biophysical properties of lipids. In both passive and active targeting, the effects of liposome size, charge, fluidity, rigidity, head-group chemistry and PEGylation are discussed along with recent examples. Most of the examples are focused on targeting tumors or cancer cells. Finally, a few examples of commercialized formulations are described, and some future research opportunities are discussed.

Hybrid nanomaterials of WS2 or MoS2 nanosheets with liposomes: biointerfaces and multiplexed drug delivery.

Lipid containing hybrid materials are of significant interest for biointerface research and drug delivery applications, and a large number of previous studies have focused on graphene oxide (GO). In this work, novel hybrid materials made of transition metal dichalcogenides (TMDCs) and phosphocholine (DOPC) liposomes were prepared and compared with GO. All these inorganic materials are 2D nanosheets. DOPC liposomes are adsorbed by tungsten disulfide (WS2) as intact liposomes as indicated by cryo-TEM and liposome leakage assays. WS2 likely uses van der Waals forces for liposome adsorption as determined from urea, salt, and surfactant washing experiments. In addition, WS2 adsorbed doxorubicin (DOX) and DOPC liposomes synergistically. The adsorption capacity of DOPC on bare WS2 was 22.5% of the weight of WS2. After adsorbing DOX on WS2, the liposome adsorption capacity increased to ∼110%. Hydrogen bonding also contributed to liposome adsorption on DOX-loaded WS2. Confocal fluorescence microscopy confirmed the uptake of the DOPC/WS2 hybrid material by HeLa cells, and the co-delivery of DOX and calcein was achieved by loading calcein inside the liposomes. This study provides fundamental insights into the interaction between PC liposomes and WS2. Furthermore, preliminary biomedical applications of this hybrid material were explored.

Non-invasive controlled release from gold nanoparticle integrated photo-responsive liposomes through pulse laser induced microbubble cavitation.

Drug-carriers, capable of releasing the drug at the target sites upon external stimuli, are attractive for theranostic applications. In recent years, photo-responsive nanoparticles (NPs) have received considerable attention because of their potentials in providing spatial, temporal, and dosage control over the drug release. However, most of the relevant technologies are still in the process of development and are unprocurable by the clinics. Here, we demonstrated facile fabrication of these photo-responsive NPs by loading hydrophilic gold NPs within thermo-responsive liposomes. Calcein was used as a model drug to evaluate the encapsulation efficiency and the release kinetic profile upon heat/light stimulation. Furthermore, we characterized their size, morphology, phase transition temperature and stability. Finally, we demonstrated that this photo-triggered release might be due to the membrane disruption caused by microbubble cavitation.

A construction of novel iron-foam-based calcium phosphate/chitosan coating biodegradable scaffold material.

Slow corrosion rate and poor bioactivity restrict iron-based implants in biomedical application. In this study, we design a new iron-foam-based calcium phosphate/chitosan coating biodegradable composites offering a priority mechanical and bioactive property for bone tissue engineering through electrophoretic deposition (EPD) followed by a conversion process into a phosphate buffer solution (PBS). Tensile test results showed that the mechanical property of iron foam could be regulated through altering the construction of polyurethane foam. The priority coatings were deposited from 40% nano hydroxyapatite (nHA)/ethanol suspension mixed with 60% nHA/chitosan-acetic acid aqueous solution. In vitro immersion test showed that oxidation-iron foam as the matrix decreased the amount of iron implanted and had not influence on the bioactivity of this implant, obviously. So, this method could also be a promising method for the preparation of a new calcium phosphate/chitosan coating on foam construction.

Calcium phosphate embedded PLGA nanoparticles: a promising gene delivery vector with high gene loading and transfection efficiency.

In the purpose of increasing incorporation efficiency and improving the release kinetics of plasmid DNA (pDNA) from poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles, a facile method for the fabrication of calcium phosphate (CaPi) embedded PLGA nanoparticles (CaPi-pDNA-PLGA-NPs) was developed. The effect of several preparation factors on the particle size, incorporation efficiency, pDNA release and transfection efficiency in vitro was studied by Single Factor Screening Method. These preparation factors included the molecular weight (MW), hydrolysis degree (HD) of polyvinyl alcohol (PVA), sonication power and time, composition of organic phase, initial concentration of calcium phosphate and calcium (Ca) to phosphate ion (P) ratio (Ca/P ratio), etc. The CaPi-pDNA-PLGA-NPs made according to the optimal formulation were spherical in shape observed by transmission electron microscopy (TEM) with a mean particle size of 207±5 nm and an entrapment efficiency of 95.7±0.8%. Differential scanning calorimetry (DSC) suggested that there existed interaction between the DNA-calcium-phosphate (CaPi-pDNA) complexes and the polymeric matrices of PLGA. X-ray diffractometry (XRD) further proved the conclusion and indicated that the CaPi-pDNA was in weak crystallization form inside the nanoparticles. The Brunauer-Emmett-Teller (BET) surface area measurement demonstrated that the CaPi-pDNA-PLGA-NPs are mesoporous with specific surface area of 57.5m(2)/g and an average pore size of 96.5 Å. The transfection efficiency of the CaPi-pDNA-PLGA-NPs on human embryonic kidney 293 (HEK 293) cells in vitro was 22.4±1.2%, which was much higher than those of both the pDNA loaded PLGA nanoparticles (pDNA-PLGA-NPs) and the CaPi-pDNA embedded PLGA microparticles (CaPi-pDNA-PLGA-MPs). The CaPi-pDNA-PLGA-NPs are promising vectors for gene delivery.