Dual-functional antibiofilm polymer composite for biodegradable medical devices.

Urinary tract infections (UTI) represent one of the most common problem within the urological disorders, and it is mainly caused by biofilm formation which leads to bacterial infection. Anti-adhesion and antibacterial agents are two primary mechanisms to prevent biofilm formation; however, current strategies are insufficiently effective. In this study, we developed an effective antibiofilm biodegradable polymer with high biocompatibility. Here we embedded silver nanoparticles (AgNPs) in poly(glycerol sebacate) acrylate (PGSA) followed by superhydrophilic modification on the polymer surfaces. The modified surfaces were characterized using SEM, AFM and contact angle measurements. This anti-adhesive surface prevented the adhesion of E. coli and limited the biofilm coverage percentage to less than 3% in 24 h. In the in vitro degradation, the long-term antibiofilm performance was evaluated in Nowatzki-Stoodley artificial urine (NSAU). The surface modified AgNPs embedded PGSA (sPGSA-AgNPs) was able to effectively inhibit the formation of biofilm by reducing the biofilm coverage to less than 0.01%, and it also showed low cytotoxicity with human bladder carcinoma cell. With the effective antibiofilm, biocompatibility and biodegradability, it is possible to be applied in urological devices to ameliorate the situation of UTIs.

Assembly and Detachment of Hyaluronic Acid on a Protein-Conjugated Gold Nanoparticle.

The assembly-disassembly of hyaluronic acid (HA) with a bovine serum albumin-conjugated gold nanoparticle (BSA-AuNP) was demonstrated using a gas-phase electrophoresis approach, electrospray-differential mobility analysis (ES-DMA). Physical sizes, number and mass concentrations, and degrees of aggregation of HA, BSA, and AuNP were successfully quantified using ES-DMA hyphenated with inductively coupled plasma mass spectrometry. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was employed complementarily for an orthogonal characterization of the assembly of HA with BSA-AuNP and the subsequent HA detachment. The results show that the surface packing density of HA on BSA-AuNP was proportional to the concentration of HA (CHA) when CHA ≤ 5 × 10-3 µmol/L, and the equilibrium binding constant of HA on BSA-AuNP was identified as ≈ 4 × 105 L/mol at pH 3. The pH-sensitive and enzyme-induced detachments of HA from BSA-AuNP were both successfully characterized using ES-DMA and ATR-FTIR. In the absence of enzymatic catalysis, the rate constant of HA detachment (k) was shown to increase by at least 3.7 times on adjusting the environmental acidity from pH 3 to pH 7. A significant enzyme-induced HA detachment was identified at pH 7, showing a remarkable increase of k by at least two times in the presence of an enzyme. This work provides a proof of concept for assembly of HA-based hybrid colloidal nanomaterials through the tuning of surface chemistry in the aqueous phase with the ability of in situ quantitative characterization, which has shown promise for the development of a variety of HA-derivative biomedical applications (e.g., drug delivery).

Rapid trace element analysis of microgram soft materials with cryogenic milling and laser ablation spectroscopy.

Trace element analysis of soft materials, to determine the content of low concentration elements, is important in many industries such as food quality control and medical biopsy analysis. Many of these applications would benefit from faster analysis with smaller sample requirements. Further, some natural samples are soft and have high water content, which brings challenges to element analysis. Here, we develop a cryogenic pelletization pretreatment to address those challenges. The soft samples are cryogenically milled, freeze-dried, and pelletized before elemental analysis. Analysis is performed by laser ablation spectroscopy, the combination of laser-induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS), to rapidly analyze light and heavy analytes. For this initial study, aluminum (Al) content in soft samples is determined by LIBS and lead (Pb) content by LA-ICP-MS. The standard addition method is performed to build calibration curves for element quantification. The measurements are compared with a Hong Kong government certified acid digestion and ICP-MS procedure. The experiment is performed on standard reference materials and selected food samples. The relative errors compared with certified measurements are less than 10% for all samples, with Al content ranging from 63-1466 µg/g and Pb content from 0.37-2.35 µg/g (dry mass). Microscopy of pellets shows that laser ablation spectroscopy can be performed with 100 µg of sample (dry mass). Total analysis time from raw sample to final measurement, including preparation, is under 1 h. The results indicate that the laser ablation spectroscopy with cryogenic pelletization is a promising technique for many applications such as screening of small food samples for toxic metals and trace element analysis of millimeter biopsies.

Design of photocurable, biodegradable scaffolds for liver lobule regeneration via digital light process-additive manufacturing.

The regeneration of damaged or lost tissue is considered to be a critical step toward realizing full organ regeneration in modern medicine. Although surgical techniques continue to advance, treatment for missing tissues in irregular wounds remains particularly difficult. With increasing interest in the application of additive manufacturing in tissue engineering, the fabrication of customized scaffolds for the regeneration of missing tissue via three-dimensional (3D) printing has become especially promising. Amongst the work on the regeneration of many important organs, liver regeneration is particularly interesting because liver diseases are increasingly prevalent in many countries around the world, resulting in a greater need for liver transplantation. The generation of hexagonal scaffolds for the regeneration of liver lobules is highly demanding, but their 3D structure has been proved difficult to reproduce by traditional fabrication methods. In this work, various hexagonal scaffolds are developed for liver lobule regeneration via 3D printing using novel biodegradable polymeric materials, including poly(glycerol sebacate) acrylate and poly(ethylene glycol) diacrylate. Through fine-tuning of printing parameters, a series of hexagonal scaffolds were designed and printed to mimic liver lobule units. The scaffolds were printed with various structures together with varying surface areas and 3D structures to enhance cell seeding density and diffusivity of the culture medium. Analysis of cell metabolic activities showed that the high-diffusion staircase (HDS) scaffold could support potential differences in cell proliferation rate. Furthermore, the HDS scaffolds composed of different copolymers were cultured with cells for up to 16 days to investigate the relationship between physical properties and hepatocyte proliferation. The results indicate that the combination of the high flexibility 3D printing with biodegradable, photocurable copolymers shows great promise for the regeneration of 3D liver lobules.

Enhancing Boron Uptake in Brain Glioma by a Boron-Polymer/Microbubble Complex with Focused Ultrasound.

Boron neutron capture therapy (BNCT) is a promising radiotherapy for treating glioblastoma multiforme (GBM). However, the penetration of drugs (e.g., sodium borocaptate and BSH) for BNCT into brain tumors is limited by cerebral vesicular protective structures, the blood-brain barrier, and the blood-brain tumor barrier (BTB). Although BSH has been reported to be selectively taken up by tumors, it is rapidly excreted from the body and cannot achieve a high tumor-to-normal brain ratio (T/N ratio) and tumor-to-blood ratio (T/B ratio). Despite the development of large-molecular weight boron compounds, such as polymers and nanoparticles, to enhance the permeation and retention effect, their effects remain insufficient for clinical use. To improve the efficiency of boron delivery to the tumor site, we propose combinations of self-assembled boron-containing polyanion [polyethylene glycol- b-poly(( closo-dodecaboranyl)thiomethylstyrene) (PEG- b-PMBSH)] nanoparticles (295 ± 2.3 nm in aqueous media) coupled with cationic microbubble (B-MB)-assisted focused ultrasound (FUS) treatment. Upon FUS sonication (frequency = 1 MHz, pressure = 0.3-0.7 MPa, duty cycle = 0.5%, sonication = 1 min), B-MBs can simultaneously achieve safe BTB opening and boron drug delivery into tumor tissue. Compared with the MBs of the PEG- b-PMBSH mixture group (B + MBs), B-MBs showed 3- and 2.3-fold improvements in the T/N (4.4 ± 1.4 vs 1.3 ± 0.1) and T/B ratios (1.4 ± 0.6 vs 0.1 ± 0.1), respectively, after 4 min of FUS sonication. The spatial distribution of PEG- b-PMBSH was also improved by the complex of PEG- b-PMBSH with MBs. The findings presented herein, in combination with the expanding clinical application of FUS, may improve BNCT and treatment of GBM.

Laser-pattern induced contact guidance in biodegradable microfluidic channels for vasculature regeneration.

The direct cell control by surface topographic patterns in the micrometer and nanometer range has been proven to be important for the maintenance of tissue structures. This study presents the application of direct laser writing to fabricate micro-gratings on the biodegradable material 1,3-diamino-2-hydroxypropane-co-polyol sebacate (APS). The 193 nm excimer laser is applied to form microgrooves with widths of 2 to 10 µm and depths of 400 to 2884 nm. Two kinds of cells, fibroblasts of the rabbit synoviocyte cell line (HIG-82) and endothelial cells of human umbilical vein endothelial cells (HUVECs), were cultured on the flat and patterned APS to evaluate the biocompatibility of APS as well as the influence of contact guidance for cellular behaviours, respectively. The results show that both HIG-82 and HUVECs grow actively on APS scaffolds with directional growth, which was observed through cell morphology and proliferation rate, indicating their applicability in tissue regeneration. HIG-82 was observed to exhibit directional growth with the highest cell spreading area and density on the scaffolds with 7 µm width and 1350-1500 nm depth of gratings. Meanwhile, high cell spreading area and cell density of HUVECs were observed on laser ablated APS with 5 µm gratings and at depths greater than 1485 nm. The proposed microgrooves on APS could significantly enhance the cell growth, adhesion and even promote selective cell proliferation, which poses potential application for further tissue engineering studies.

Study of Physical and Degradation Properties of 3D-Printed Biodegradable, Photocurable Copolymers, PGSA-co-PEGDA and PGSA-co-PCLDA.

As acrylated polymers become more widely used in additive manufacturing, their potential applications toward biomedicine also raise the demand for biodegradable, photocurable polymeric materials. Polycaprolactone diacrylate (PCLDA) and poly(ethylene glycol) diacrylate (PEGDA) are two popular choices of materials for stereolithography (SLA) and digital light processing additive manufacturing (DLP-AM), and have been applied to many biomedical related research. However, both materials are known to degrade at a relatively low rate in vivo, limiting their applications in biomedical engineering. In this work, biodegradable, photocurable copolymers are introduced by copolymerizing PCLDA and/or PEGDA with poly(glycerol sebacate) acrylate (PGSA) to form a network polymer. Two main factors are discussed: the effect of degree of acrylation in PGSA and the weight ratio between the prepolymers toward the mechanical and degradation properties. It is found that by blending prepolymers with various degree of acrylation and at various weight ratios, the viscosity of the prepolymers remains stable, and are even more 3D printable than pure substances. The formation of various copolymers yielded a database with selectable Young's moduli between 0.67⁻10.54 MPa, and the overall degradation rate was significantly higher than pure substance. In addition, it is shown that copolymers fabricated by DLP-AM fabrication presents higher mechanical strength than those fabricated via direct UV exposure. With the tunable mechanical and degradation properties, the photocurable, biodegradable copolymers are expected to enable a wider application of additive manufacturing toward tissue engineering.

Development of biomimetic micro-patterned device incorporated with neurotrophic gradient and supportive Schwann cells for the applications in neural tissue engineering.

In these years, the artificial nerve guidance conduit (NGC) has been developed as an alternative way to repair peripheral nerve injury. Unlike autologous nerve graft, the artificial NGC without proper stimulating factors and guidance cues still cannot obtain satisfactory prognosis for clinical patients. In this study, a biodegradable polymer-based implantable device has been developed and characterized. By incorporating three stimulating factors: (1) micro-patterned surface that can directionally guide the axon as physical cue; (2) neurotrophic gradient membrane that can continually attract axon outgrowth from the proximal to distal stump as chemical cue; (3) Schwann cells (SCs) that can support the growth of neurite and form myelin sheath around axon as biological cue, we expect that this construct can be used as a promising NGC for peripheral nerve regeneration. The results showed that the micro-patterned surface with specific dimension of channels and chambers can be precisely fabricated by laser ablation. Attachment and directional extension of differentiated neural stem cells (NSCs) were observed in micro-channels. The gradient distribution of nerve growth factor 7S on gelatin membrane was successfully achieved. Significant improvement in neurite length and increase in neuronal gene expressions were also noticed in higher concentration region. When co-culturing with SCs, NSCs can differentiate toward neuronal cells with strong expression of mature neuronal markers: ßIII tubulin and microtubule-associated protein-2 (Map 2). Meanwhile, myelin basic protein was also observed, suggesting that SCs can provide biological support to neuronal cells in vitro. In the future, this advanced artificial NGC may be used as implantable prosthesis for the treatment of peripheral nerve injury with better functional recovery.

Effects of silver nanoparticles on the interactions of neuron- and glia-like cells: Toxicity, uptake mechanisms, and lysosomal tracking.

Silver nanoparticles (AgNPs) are commonly used nanomaterials in consumer products. Previous studies focused on its effects on neurons; however, little is known about their effects and uptake mechanisms on glial cells under normal or activated states. Here, ALT astrocyte-like, BV-2 microglia and differentiated N2a neuroblastoma cells were directly or indirectly exposed to 10 nm AgNPs using mono- and co-culture system. A lipopolysaccharide (LPS) was pretreated to activate glial cells before AgNP treatment for mimicking NP exposure under brain inflammation. From mono-culture, ALT took up the most AgNPs and had the lowest cell viability within three cells. Moreover, AgNPs induced H2 O2 and NO from ALT/activated ALT and BV-2, respectively. However, AgNPs did not induce cytokines release (IL-6, TNF-α, MCP-1). LPS-activated BV-2 took up more AgNPs than normal BV-2, while the induction of ROS and cytokines from activated cells were diminished. Ca2+ -regulated clathrin- and caveolae-independent endocytosis and phagocytosis were involved in the AgNP uptake in ALT, which caused more rapid NP translocation to lysosome than in macropinocytosis and clathrin-dependent endocytosis-involved BV-2. AgNPs directly caused apoptosis and necrosis in N2a cells, while by indirect NP exposure to bottom chamber ALT or BV-2 in Transwell, more apoptotic upper chamber N2a cells were observed. Cell viability of BV-2 also decreased in an ALT-BV-2 co-culturing study. The damaged cells correlated to NP-mediated H2 O2 release from ALT or NO from BV-2, which indicates that toxic response of AgNPs to neurons is not direct, but indirectly arises from AgNP-induced soluble factors from other glial cells.

Direct Micromachining of Microfluidic Channels on Biodegradable Materials Using Laser Ablation.

Laser patterning on polymeric materials is considered a green and rapid manufacturing process with low material selection barrier and high adjustability. Unlike microelectromechanical systems (MEMS), it is a highly flexible processing method, especially useful for prototyping. This study focuses on the development of polymer surface modification method using a 193 nm excimer laser system for the design and fabrication of a microfluidic system similar to that of natural vasculatures. Besides from poly(dimethyl siloxane) (PDMS), laser ablation on biodegradable polymeric material, poly(glycerol sebacate) (PGS) and poly(1,3-diamino-2-hydroxypropane-co-polyol sebacate) (APS) are investigated. Parameters of laser ablation and fabrication techniques to create microchannels are discussed. The results show that nano/micro-sized fractures and cracks are generally observed across PDMS surface after laser ablation, but not on PGS and APS surfaces. The widths of channels are more precise on PGS and APS than those on PDMS. Laser beam size and channel depth are high correlation with a linear relationship. Repeated laser ablations on the same position of scaffolds reveal that the ablation efficiencies and edge quality on PGS and APS are higher than on PDMS, suggesting the high applicability of direct laser machining to PGS and APS. To ensure stable ablation efficiency, effects of defocus distance into polymer surfaces toward laser ablation stability are investigated. The depth of channel is related to the ratio of firing frequency and ablation progression speed. The hydrodynamic simulation of channels suggests that natural blood vessel is similar to the laser patterned U-shaped channels, and the resulting micro-patterns are highly applicable in the field of micro-fabrication and biomedical engineering.

Enhanced photoelectrochemical water splitting efficiency of hematite electrodes with aqueous metal ions as in situ homogenous surface passivation agents.

Passivation of surface states is known to reduce the onset photocurrent potential by removing the Fermi level pinning effect at the Helmholtz layer and enhance the photocurrent plateau by suppressing recombination loss in the space charge region. We report for the first time that metal ions can effectively passivate surface states in situ that improves the photoelectrochemical (PEC) performance of hematite electrodes. Among metal ions studied, Cr(iii), Mn(ii), Fe(ii), Co(ii), Cu(ii) and Zn(ii) were found to enhance the photocurrent by 30-300%; whereas photocurrent density significantly dropped by 90% in Ni(ii) solution after 90 min of illumination. We further hypothesized that the surface states might be the high affinity adsorption sites on hematite surfaces. Once the surface states are occupied by metal ions, along with the Schottky barrier effect at the hematite/electrolyte interface formed by adsorbed metal ions, the PEC performance is enhanced. Our results also enable the design of a potential PEC based water treatment method to extract additional energy, for example, in the brines (containing concentrated metal ions and electrolyte) of membrane processed wastewater.

Indirect effects of TiO2 nanoparticle on neuron-glial cell interactions.

Although, titanium dioxide nanoparticles (TiO2NPs) are nanomaterials commonly used in consumer products, little is known about their hazardous effects, especially on central nervous systems. To examine this issue, ALT astrocyte-like, BV-2 microglia and differentiated N2a neuroblastoma cells were exposed to 6 nm of 100% anatase TiO2NPs. A lipopolysaccharide (LPS) was pre-treated to activate glial cells before NP treatment for mimicking NP exposure under brain injury. We found that ALT and BV-2 cells took up more NPs than N2a cells and caused lower cell viability. TiO2NPs induced IL-1ß in the three cell lines and IL-6 in N2a. LPS-activated BV-2 took up more TiO2NPs than normal BV-2 and released more intra/extracellular reactive oxygen species (ROS), IL-1ß, IL-6 and MCP-1 than did activated BV-2. Involvement of clathrin- and caveolae-dependent endocytosis in ALT and clathrin-dependent endocytosis and phagocytosis in BV-2 both had a slow NP translocation rate to lysosome, which may cause slow ROS production (after 24 h). Although TiO2NPs did not directly cause N2a viability loss, by indirect NP exposure to the bottom chamber of LPS-activated BV-2 in the Transwell system, they caused late apoptosis and loss of cell viability in the upper N2a chamber due to H2O2 and/or TNF-α release from BV-2. However, none of the adverse effects in N2a or BV-2 cells was observed when TiO2NPs were exposed to ALT-N2a or ALT-BV-2 co-culture. These results demonstrate that neuron damage can result from TiO2NP-mediated ROS and/or cytokines release from microglia, but not from astrocytes.

Element distribution over the surface of fish scales and its connection to the geochemical environment of habitats: a potential biogeochemical tag.

The elemental content of fish scales is known to be a reliable biogeochemical tag for tracing the origin of fishes. In this study, this correlation is further confirmed to exist on the surface of fish scales using a novel environmental analytical method, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), which bypasses several complicated sample preparation procedures such as acid digestion and pre-concentration. The results suggest that the elemental ratios of Sr/Ca, Ba/Ca, and Mn/Ca on the surface of fish scales are strongly correlated with the geochemical environment of their original habitat. This correlation is further demonstrated to be sensitive to variation of water in the habitat due to the adsorbed inorganic ions. In this sense, the limitation of fish scales as a biogeochemical tag is the sensitivity of LA-ICP-MS toward the studied elements. Graphical abstract Illustration of the connection between element distribution pattern over the surface of fish scales and biogeochemical environment of its habitat.

Effect of interactions between Co(2+) and surface goethite layer on the performance of α-FeOOH coated hollow fiber ceramic ultrafiltration membranes.

The consideration of water energy nexus inspires the environmental engineering community to pursue a more sustainable strategy in the wastewater treatment. One potential response would be to enhance the performance of the low-pressure driven filtration system. To reach this objective, it is essential to have a better understanding regarding the surface interaction between the target substance and the surface of membrane. In this study, the hollow fiber ceramic membranes were coated with a goethite layer in order to enhance the Co(2+) rejection. Experimental results indicate that higher Co(2+) rejections are always accompanied with the significant reduction in the permeability. Based on the consideration of electroviscous effect, the surface interactions including the induced changes in viscosity, pore radius and Donnan effect in the goethite layer are likely responsible for the pH dependent behaviors in the rejection and permeability. These results could be valuable references to develop the filtration system with high rejection along with acceptable degree of permeability in the future.

Trojan-horse mechanism in the cellular uptake of silver nanoparticles verified by direct intra- and extracellular silver speciation analysis.

The so-called "Trojan-horse" mechanism, in which nanoparticles are internalized within cells and then release high levels of toxic ions, has been proposed as a behavior in the cellular uptake of Ag nanoparticles (AgNPs). While several reports claim to have proved this mechanism by measuring AgNPs and Ag ions (I) in cells, it cannot be fully proven without examining those two components in both intra- and extracellular media. In our study, we found that even though cells take up AgNPs similarly to (microglia (BV-2)) or more rapidly than (astrocyte (ALT)) Ag (I), the ratio of AgNPs to total Ag (AgNPs+Ag (I)) in both cells was lower than that in outside media. It could be explained that H2O2, a major intracellular reactive oxygen species (ROS), reacts with AgNPs to form more Ag (I). Moreover, the major speciation of Ag (I) in cells was Ag(cysteine) and Ag(cysteine)2, indicating the possible binding of monomer cysteine or vital thiol proteins/peptides to Ag ions. Evidence we found indicates that the Trojan-horse mechanism really exists.

CO2 uptake performance and life cycle assessment of CaO-based sorbents prepared from waste oyster shells blended with PMMA nanosphere scaffolds.

In this paper, we demonstrate a means of simultaneously solving two serious environmental issues by reutilization of calcinated mixture of pulverized waste oyster shells blending with poly(methyl methacrylate) (PMMA) nanospheres to prepare CaO-based sorbents for CO2 capture. After 10 cycles of isothermal carbonation/calcination at 750°C, the greatest CO2 uptake (0.19 g CO2/g sorbent) was that for the sorbent featuring 70 wt% of PMMA, which was almost three times higher than that (0.07 g CO2/g sorbent) of untreated waste oyster shell. The greater CO2 uptake was likely a result of particle size reduction and afterwards surface basicity enhancement and an increase in the volume of mesopores and macropores. Following simplified life cycle assessment, whose all input values were collected from our experimental results, suggested that a significant CO2 emission reduction along with lesser human health and ecosystems impacts would be achieved immediately once waste is reutilized. Most importantly, the CO2 uptake efficiency must be greater than 20% or sorbents prepared from limestone mining would eventually produce a net positive CO2 emission.

Influence of sodium halides (NaF, NaCl, NaBr, NaI) on the photocatalytic performance of hydrothermally synthesized hematite photoanodes.

It has been suggested that a high concentration of Fe(3+) in solution, a low pH, and noncomplexing ions of high ionic strength are all essential for developing a high-quality hematite array. Our curiosity was piqued regarding the role of the electrolyte ions in the hydrothermal synthesis of hematite photoanodes. In this study, we prepared hematite photoanodes hydrothermally from precursor solutions of 0.1 M FeCl3 at pH 1.55 with a background electrolyte of 1.0 M sodium halide (NaF, NaCl, NaBr, or NaI). We compared the structures and properties of the as-obtained hematite photoanodes with those of the material prepared in 1.0 M NaNO3, the most widely adopted electrolyte in previous studies. Among our studied systems, we found that the hematite photoanode prepared in NaCl solution was the only one possessing properties similar to those of the sample obtained from the NaNO3 solution-most importantly in terms of photoelectrochemical performance (ca. 0.2 mA/cm(2) with +0.4 V vs SCE). The hematites obtained from the NaF, NaBr, and NaI solutions exhibited much lower (by approximately 2 orders of magnitude) photocurrent densities under the same conditions, possibly because of their relatively less ordered crystallinity and the absence of rodlike morphologies. Because the synthetic protocol was identical in each case, we believe that these two distinct features reflect the environments in which these hematite photoanodes were formed. Consistent with the latest studies reported in the literature of the X-ray photoelectron spectra of fast-frozen hematite colloids in aqueous solutions, it appears that the degree of surface ion loading at the electrolyte-hematite interface (Stern layer) is critical during the development of hematite photoanodes. We suspect that a lower ion surface loading benefits the hematite developing relatively higher-order and a rodlike texture, thereby improving the photoelectrochemical activity.

Spatial distributions of inorganic elements in honeybees (Apis mellifera L.) and possible relationships to dietary habits and surrounding environmental pollutants.

In this study, the laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was adopted to determine the distribution of inorganic elements, including Ca, Cu, Fe, Mg, Mn, S, P, Pb, and Zn, in honeybees (Apis melifera L.). Two features are particularly noteworthy. First, it was found there is a significant amount of Fe located at the fringe of the abdomen in worker bees; ultrasonic imaging, scanning electron microscopy, and magnetic resonance imaging revealed that it arose from magnetic Fe-bearing nanoparticles (NPs) having an average diameter of approximately 40 nm. Interestingly, only worker bees contained these magnetic Fe-bearing NPs; no similar features appeared in larvae, pupae, wasps, or drones. Second, a detectable amount of Pb accumulated particularly in the alimentary canals of worker bees. Again, no detectable amounts of Pb in larvae, pupae, drones, or wasps, yet a level of 0.24 ± 0.05 mg/kg of Pb in pollen; therefore, the diet appears to be the primary pathway for environmental pollutants entering the honeybees' food chain.

The in vivo biodistribution and fate of CdSe quantum dots in the murine model: a laser ablation inductively coupled plasma mass spectrometry study.

Understanding the cytotoxicity of quantum dots strongly relies upon the development of new analytical techniques to gather information about various aspects of the system. In this study, we demonstrate the in vivo biodistribution and fate of CdSe quantum dots in the murine model by means of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). By comparing the hot zones of each element acquired from LA-ICP-MS with those in fluorescence images, together with hematoxylin and eosin-stained images, we are able to perceive the fate and in vivo interactions between quantum dots and rat tissues. One hour after intravenous injection, we found that all of the quantum dots had been concentrated inside the spleen, liver and kidneys, while no quantum dots were found in other tissues (i.e., muscle, brain, lung, etc.). In the spleen, cadmium-114 signals always appeared in conjunction with iron signals, indicating that the quantum dots had been filtered from main vessels and then accumulated inside splenic red pulp. In the liver, the overlapped hot zones of quantum dots and those of phosphorus, copper, and zinc showed that these quantum dots have been retained inside hepatic cells. Importantly, it was noted that in the kidneys, quantum dots went into the cortical areas of adrenal glands. At the same time, hot zones of copper appeared in proximal tubules of the cortex. This could be a sign that the uptake of quantum dots initiates certain immune responses. Interestingly, the intensity of the selenium signals was not proportional to that of cadmium in all tissues. This could be the result of the decomposition of the quantum dots or matrix interference. In conclusion, the advantage in spatial resolution of LA-ICP-MS is one of the most powerful tools to probe the fate, interactions and biodistribution of quantum dots in vivo.

Using laser ablation/inductively coupled plasma mass spectrometry to bioimage multiple elements in mouse tumors after hyperthermia.

In this study, we employed laser ablation/inductively coupled plasma mass spectrometry (LA-ICP-MS) to map the spatial distribution of Gd-doped iron oxide nanoparticles (IONPs) in one tumor slice that had been subjected to magnetic fluid hyperthermia (MFH). The mapping results revealed the high resolution of the elemental analysis, with the distribution of Gd atoms highly correlated with that of the Fe atoms. The spatial distributions of C, P, S, and Zn atoms revealed that the effect of MFH treatment was significantly dependent on the diffusion of the magnetic fluid in the tissue. An observed enrichment of Cu atoms after MFH treatment was probably due to inflammation in the tumor. The abnormal distribution of Ni atoms suggests a probable biochemical reaction in the tumor. Therefore, this LA-ICP-MS mapping technique can provide novel information regarding the spatial distribution of elements in tumors after cancer therapy.