A potential biological signature of 7-methylguanosine-related lncRNA to predict the immunotherapy effects in bladder cancer.

Background: Bladder urothelial carcinoma (BLCA) is the second prevalent genitourinary carcinoma globally. N7-methylguanosine (m7G) is important for tumorigenesis and progression. This study aimed to build a predictive model for m7G-related long non-coding RNAs (lncRNAs), elucidate their role in the tumor immune microenvironment (TIME), and predict immunotherapy response in BLCA. Methods: We first used univariate Cox regression and coexpression analyses to identify m7G-related lncRNAs. Next, the prognostic model was built by utilizing LASSO regression analysis. Then, the prognostic significance of the model was examined utilizing Kaplan-Meier survival analysis, receiver operating characteristic (ROC) curves, nomogram, and univariate, multivariate Cox regression. We also analyzed Gene set enrichment analyses (GSEA), immune analysis and principal component analysis (PCA) in risk groups. To further predict immunotherapy effectiveness, we evaluated the predictive ability for immunotherapy in 2 risk groups and clusters using tumor immune dysfunction and exclusion (TIDE) score and Immunophenoscore (IPS). Results: Seven lncRNAs related to m7G were used to create a model. The calibration plots for the model suggested a strong fit with the prediction of overall survival (OS). The area under the curve (AUC) for first, second, and third years was respectively, 0.722, 0.711, and 0.686. In addition, the risk score had strong correlation with TIME features and genes linked to immune checkpoint blockade (ICB). TIDE scores were dramatically different between two risk groups (p < 0.05), and IPS scores were markedly different between two clusters (p < 0.05). Conclusion: Our research constructed a novel m7G-related lncRNAs that could be used to predict patient outcomes and the effectiveness of immunotherapy in BLCA. Immunotherapy may be more effective for the low-risk group and cluster 2.

Endothelial cell infection and dysfunction, immune activation in severe COVID-19.

Rationale: Pulmonary vascular endotheliitis, perivascular inflammation, and immune activation are observed in COVID-19 patients. While the initial SARS-CoV-2 infection mainly infects lung epithelial cells, whether it also infects endothelial cells (ECs) and to what extent SARS-CoV-2-mediated pulmonary vascular endotheliitis is associated with immune activation remain to be determined. Methods: To address these questions, we studied SARS-CoV-2-infected K18-hACE2 (K18) mice, a severe COVID-19 mouse model, as well as lung samples from SARS-CoV-2-infected nonhuman primates (NHP) and patient deceased from COVID-19. We used immunostaining, RNAscope, and electron microscopy to analyze the organs collected from animals and patient. We conducted bulk and single cell (sc) RNA-seq analyses, and cytokine profiling of lungs or serum of the severe COVID-19 mice. Results: We show that SARS-CoV-2-infected K18 mice develop severe COVID-19, including progressive body weight loss and fatality at 7 days, severe lung interstitial inflammation, edema, hemorrhage, perivascular inflammation, systemic lymphocytopenia, and eosinopenia. Body weight loss in K18 mice correlated with the severity of pneumonia, but not with brain infection. We also observed endothelial activation and dysfunction in pulmonary vessels evidenced by the up-regulation of VCAM1 and ICAM1 and the downregulation of VE-cadherin. We detected SARS-CoV-2 in capillary ECs, activation and adhesion of platelets and immune cells to the vascular wall of the alveolar septa, and increased complement deposition in the lungs, in both COVID-19-murine and NHP models. We also revealed that pathways of coagulation, complement, K-ras signaling, and genes of ICAM1 and VCAM1 related to EC dysfunction and injury were upregulated, and were associated with massive immune activation in the lung and circulation. Conclusion: Together, our results indicate that SARS-CoV-2 causes endotheliitis via both infection and infection-mediated immune activation, which may contribute to the pathogenesis of severe COVID-19 disease.

Hydrophobe Containing Polypeptoids Complex with Lipids and Induce Fusogenesis of Lipid Vesicles.

The hydrophobic effect of alkyl group insertion into phospholipid bilayers is exploited in modifying and modulating vesicle structure. We show that amphiphilic polypeptoids (peptide mimics) with n-decyl side chains, which we term as hydrophobe-containing polypeptoids (HCPs), can insert the alkyl hydrophobes into the membrane bilayer of phospholipid-based vesicles. Such insertion leads to disruption of the liposomes and the formation of HCP-lipid complexes that are colloidally stable in aqueous solution. Interestingly, when these complexes are added to fresh liposomes, remnant uncomplexed hydrophobes (the n-decyl groups) bridge liposomes and fuse them. The fusion leads to the engulfing of liposomes and the formation of multilayered vesicles. The morphology of the liposome system can be changed from stopping fusion and forming clustered vesicles to the continued formation of multilayered liposomes simply by controlling the amount of the HCP-lipid complex added. The entire procedure occurs in aqueous systems without the addition of any other solvents. There are several implications to these observations including the biological relevance of mimicking fusogenic proteins such as the SNARE proteins and the development of new drug delivery technologies to impact delivery to cell organelles.

Targeted and Stimulus-Responsive Delivery of Surfactant to the Oil-Water Interface for Applications in Oil Spill Remediation.

The use of chemical dispersants is a well-established approach to oil spill remediation where surfactants in an appropriate solvent are contacted with the oil to reduce the oil-water interfacial tension and create small oil droplets capable of being sustained in the water column. Dispersant formulations typically include organic solvents, and to minimize environmental impacts of dispersant use and avoid surfactant wastage it is beneficial to use water-based systems and target the oil-water interface. The approach here involves the tubular clay minerals known as halloysite nanotubes (HNTs) that serve as nanosized reservoir for surfactants. Such particles generate Pickering emulsions with oil, and the release of surfactant reduces the interfacial tension to extremely low values allowing small droplets to be formed that are colloidally stable in the water column. We report new findings on engineering the surfactant-loaded halloysite nanotubes to be stimuli responsive such that the release of surfactant is triggered by contact with oil. This is achieved by forming a thin coating of wax to stopper the nanotubes to prevent the premature release of surfactant. Surfactant release only occurs when the wax dissolves upon contact with oil. The system thus represents an environmentally benign approach where the wax coated HNTs are dispersed in an aqueous solvent and delivered to an oil spill whereupon they release surfactant to the oil-water interface upon contact with oil.

Amphiphilic Polypeptoids Serve as the Connective Glue to Transform Liposomes into Multilamellar Structures with Closely Spaced Bilayers.

We report the ability of hydrophobically modified polypeptoids (HMPs), which are amphiphilic pseudopeptidic macromolecules, to connect across lipid bilayers and thus form layered structures on liposomes. The HMPs are obtained by attaching hydrophobic decyl groups at random points along the polypeptoid backbone. Although native polypeptoids (with no hydrophobes) have no effect on liposomal structure, the HMPs remodel the unilamellar liposomes into structures with comparable diameters but with multiple concentric bilayers. The transition from single-bilayer to multiple-bilayer structures is revealed by small-angle neutron scattering (SANS) and cryo-transmission electron microscopy (cryo-TEM). The spacing between bilayers is found to be relatively uniform at ∼6.7 nm. We suggest that the amphiphilic nature of the HMPs explains the formation of multibilayered liposomes; i.e., the HMPs insert their hydrophobic tails into adjacent bilayers and thereby serve as the connective glue between bilayers. At higher HMP concentrations, the liposomes are entirely disrupted into much smaller micellelike structures through extensive hydrophobe insertion. Interestingly, these small structures can reattach to fresh unilamellar liposomes and self-assemble to form new two-bilayer liposomes. The two-bilayer liposomes in our study are reminiscent of two-bilayer organelles such as the nucleus in eukaryotic cells. The observations have significance in designing new nanoscale drug delivery carriers with multiple drugs on separate lipid bilayers and extending liposome circulation times with entirely biocompatible materials.

Ablative Focused Ultrasound Synergistically Enhances Thermally Triggered Chemotherapy for Prostate Cancer in Vitro.

High-intensity focused ultrasound (HIFU) can locally ablate biological tissues such as tumors, i.e., induce their rapid heating and coagulative necrosis without causing damage to surrounding healthy structures. It is widely used in clinical practice for minimally invasive treatment of prostate cancer. Nonablative, low-power HIFU was established as a promising tool for triggering the release of chemotherapeutic drugs from temperature-sensitive liposomes (TSLs). In this study, we combine ablative HIFU and thermally triggered chemotherapy to address the lack of safe and effective treatment options for elderly patients with high-risk localized prostate cancer. DU145 prostate cancer cells were exposed to chemotherapy (free and liposomal Sorafenib) and ablative HIFU, alone or in combination. Prior to cell viability assessment by trypan blue exclusion and flow cytometry, the uptake of TSLs by DU145 cells was verified by confocal microscopy and cryogenic scanning electron microscopy (cryo-SEM). The combination of TSLs encapsulating 10 µM Sorafenib and 8.7W HIFU resulted in a viability of less than 10% at 72 h post-treatment, which was significant less than the viability of the cells treated with free Sorafenib (76%), Sorafenib-loaded TSLs (63%), or HIFU alone (44%). This synergy was not observed on cells treated with Sorafenib-loaded nontemperature sensitive liposomes and HIFU. According to cryo-SEM analysis, cells exposed to ablative HIFU exhibited significant mechanical disruption. Water bath immersion experiments also showed an important role of mechanical effects in the synergistic enhancement of TSL-mediated chemotherapy by ablative HIFU. This combination therapy can be an effective strategy for treatment of geriatric prostate cancer patients.

Serially Transplanted Nonpericytic CD146(-) Adipose Stromal/Stem Cells in Silk Bioscaffolds Regenerate Adipose Tissue In Vivo.

Progenitors derived from the stromal vascular fraction (SVF) of white adipose tissue (WAT) possess the ability to form clonal populations and differentiate along multiple lineage pathways. However, the literature continues to vacillate between defining adipocyte progenitors as "stromal" or "stem" cells. Recent studies have demonstrated that a nonpericytic subpopulation of adipose stromal cells, which possess the phenotype, CD45(-) /CD31(-) /CD146(-) /CD34(+) , are mesenchymal, and suggest this may be an endogenous progenitor subpopulation within adipose tissue. We hypothesized that an adipose progenitor could be sorted based on the expression of CD146, CD34, and/or CD29 and when implanted in vivo these cells can persist, proliferate, and regenerate a functional fat pad over serial transplants. SVF cells and culture expanded adipose stromal/stem cells (ASC) ubiquitously expressing the green fluorescent protein transgene (GFP-Tg) were fractionated by flow cytometry. Both freshly isolated SVF and culture expanded ASC were seeded in three-dimensional silk scaffolds, implanted subcutaneously in wild-type hosts, and serially transplanted. Six-week WAT constructs were removed and evaluated for the presence of GFP-Tg adipocytes and stem cells. Flow cytometry, quantitative polymerase chain reaction, and confocal microscopy demonstrated GFP-Tg cell persistence, proliferation, and expansion, respectively. Glycerol secretion and glucose uptake assays revealed GFP-Tg adipose was metabolically functional. Constructs seeded with GFP-Tg SVF cells or GFP-Tg ASC exhibited higher SVF yields from digested tissue, and higher construct weights, compared to nonseeded controls. Constructs derived from CD146(-) CD34(+) -enriched GFP-Tg ASC populations exhibited higher hemoglobin saturation, and higher frequency of GFP-Tg cells than unsorted or CD29(+) GFP-Tg ASC counterparts. These data demonstrated successful serial transplantation of nonpericytic adipose-derived progenitors that can reconstitute adipose tissue as a solid organ. These findings have the potential to provide new insights regarding the stem cell identity of adipose progenitor cells.

Comparison of sorafenib-loaded poly (lactic/glycolic) acid and DPPC liposome nanoparticles in the in vitro treatment of renal cell carcinoma.

The objective of this study is to develop and compare several Sorafenib-loaded biocompatible nanoparticle models in order to optimize drug delivery and tumor cellular kill thereby improving the quality of Sorafenib-regimented chemotherapy. Sorafenib-loaded poly (lactic-co-glycolic) acid (PLGA), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes, and hydrophobically modified chitosan (HMC)-coated DPPC liposomes were evaluated for several characteristics including zeta potential, drug loading, and release profile. Cytotoxicity and uptake trials were also studied using cell line RCC 786-0, a human metastatic clear cell histology renal cell carcinoma cell line. Sorafenib-loaded PLGA particles and HMC-coated DPPC liposomes exhibited significantly improved cell kill compared to Sorafenib alone at lower concentrations, namely 10-15 and 5-15 µM from 24 to 96 h, respectively. At maximum dosage and time (15 µM and 96 h), Sorafenib-loaded PLGA and HMC-coated liposomes killed 88.3 ± 1.8% and 98 ± 1.1% of all tumor cells, significant values compared with Sorafenib 81.8 ± 1.7% (p < 0.01). Likewise, HMC coating substantially improved cell kill for liposome model for all concentrations (5-15 µM) and at time points (24-96 h) (p < 0.01). PLGA and HMC-coated liposomes are promising platforms for drug delivery of Sorafenib. Because of different particle characteristics of PLGA and liposomes, each model can be further developed for unique clinical modalities.

Release of surfactant cargo from interfacially-active halloysite clay nanotubes for oil spill remediation.

Naturally occurring halloysite clay nanotubes are effective in stabilizing oil-in-water emulsions and can serve as interfacially-active vehicles for delivering oil spill treating agents. Halloysite nanotubes adsorb at the oil-water interface and stabilize oil-in-water emulsions that are stable for months. Cryo-scanning electron microscopy (Cryo-SEM) imaging of the oil-in-water emulsions shows that these nanotubes assemble in a side-on orientation at the oil-water interface and form networks on the interface through end-to-end linkages. For application in the treatment of marine oil spills, halloysite nanotubes were successfully loaded with surfactants and utilized as an interfacially-active vehicle for the delivery of surfactant cargo. The adsorption of surfactant molecules at the interface serves to lower the interfacial tension while the adsorption of particles provides a steric barrier to drop coalescence. Pendant drop tensiometry was used to characterize the dynamic reduction in interfacial tension resulting from the release of dioctyl sulfosuccinate sodium salt (DOSS) from halloysite nanotubes. At appropriate surfactant compositions and loadings in halloysite nanotubes, the crude oil-saline water interfacial tension is effectively lowered to levels appropriate for the dispersion of oil. This work indicates a novel concept of integrating particle stabilization of emulsions together with the release of chemical surfactants from the particles for the development of an alternative, cheaper, and environmentally-benign technology for oil spill remediation.

Encapsulating gold nanomaterials into size-controlled human serum albumin nanoparticles for cancer therapy platforms.

Progress has been made in using human serum albumin nanoparticles (HSAPs) as promising colloidal carrier systems for early detection and targeted treatment of cancer and other diseases. Despite this success, there is a current lack of multi-functional HSAP hybrids that offer combinational therapies. The size of the HSAPs has crucial importance on drug loading and in vivo performance and has previously been controlled via manipulation of pH and cross-linking parameters. Gold nanomaterials have also gained attention for medicinal use due to their ability to absorb near-infrared light, thus offering photothermal capabilities. In this study, the desolvation and cross-linking approach was employed to encapsulate gold nanorods, nanoparticles, and nanoshells into HSAPs. Incorporation of gold nanomaterials caused some changes in HSAP sizes, but the general size trends remained. This encasement strategy facilitated size-controlled HSAPs, in the range of 100-300 nm, loaded with gold nanostructures; providing composite particles which incorporate photothermally active components.

The combined effect of encapsulating curcumin and C6 ceramide in liposomal nanoparticles against osteosarcoma.

This study examines the antitumor potential of curcumin and C6 ceramide (C6) against osteosarcoma (OS) cell lines when both are encapsulated in the bilayer of liposomal nanoparticles. Three liposomal formulations were prepared: curcumin liposomes, C6 liposomes and C6-curcumin liposomes. Curcumin in combination with C6 showed 1.5 times enhanced cytotoxic effect in the case of MG-63 and KHOS OS cell lines, in comparison with curcumin liposomes alone. Importantly, C6-curcumin liposomes were found to be less toxic on untransformed primary human cells (human mesenchymal stem cells) in comparison to OS cell lines. In addition, cell cycle assays on a KHOS cell line after treatment revealed that curcumin only liposomes induced G2/M arrest by upregulation of cyclin B1, while C6 only liposomes induced G1 arrest by downregulation of cyclin D1. C6-curcumin liposomes induced G2/M arrest and showed a combined effect in the expression levels of cyclin D1 and cyclin B1. The efficiency of the preparations was tested in vivo using a human osteosarcoma xenograft assay. Using pegylated liposomes to increase the plasma half-life and tagging with folate (FA) for targeted delivery in vivo, a significant reduction in tumor size was observed with C6-curcumin-FA liposomes. The encapsulation of two water insoluble drugs, curcumin and C6, in the lipid bilayer of liposomes enhances the cytotoxic effect and validates the potential of combined drug therapy.

Receptor interacting protein kinase-mediated necrosis contributes to cone and rod photoreceptor degeneration in the retina lacking interphotoreceptor retinoid-binding protein.

Interphotoreceptor retinoid-binding protein (IRBP) secreted by photoreceptors plays a pivotal role in photoreceptor survival with an unknown mechanism. A mutation in the human IRBP has been linked to retinitis pigmentosa, a progressive retinal degenerative disease. Mice lacking IRBP display severe early and progressive photoreceptor degeneration. However, the signaling pathway(s) leading to photoreceptor death in IRBP-deficient mice remains poorly understood. Here, we show that amounts of tumor necrosis factor-α (TNF-α) in the interphotoreceptor matrix and retinas of Irbp(-/-) mice were increased more than 10-fold and fivefold, respectively, compared with those in wild-type mice. Moreover, TNF-α receptor 1, an important membrane death receptor that mediates both programmed apoptosis and necrosis, was also significantly increased in Irbp(-/-) retina, and was colocalized with peanut agglutinin to the Irbp(-/-) cone outer segments. Although these death signaling proteins were increased, the caspase-dependent and independent apoptotic pathways were mildly activated in the Irbp(-/-) retinas, suggesting that other cell death mechanism(s) also contributes to the extensive photoreceptor degeneration in Irbp(-/-) retina. We found that receptor interacting protein 1 and 3 (RIP1 and RIP3) kinases, the intracellular key mediators of TNF-induced cellular necrosis, were elevated at least threefold in the Irbp(-/-) retinas. Moreover, pharmacological inhibition of RIP1 kinase significantly prevented cone and rod photoreceptor degeneration in Irbp(-/-) mice. These results reveal that RIP kinase-mediated necrosis strongly contributes to cone and rod degeneration in Irbp(-/-) mice, implicating the TNF-RIP pathway as a potential therapeutic target to prevent or delay photoreceptor degeneration in patients with retinitis pigmentosa caused by IRBP mutation.

Attachment of a hydrophobically modified biopolymer at the oil-water interface in the treatment of oil spills.

The stability of crude oil droplets formed by adding chemical dispersants can be considerably enhanced by the use of the biopolymer, hydrophobically modified chitosan. Turbidimetric analyses show that emulsions of crude oil in saline water prepared using a combination of the biopolymer and the well-studied chemical dispersant (Corexit 9500A) remain stable for extended periods in comparison to emulsions stabilized by the dispersant alone. We hypothesize that the hydrophobic residues from the polymer preferentially anchor in the oil droplets, thereby forming a layer of the polymer around the droplets. The enhanced stability of the droplets is due to the polymer layer providing an increase in electrostatic and steric repulsions and thereby a large barrier to droplet coalescence. Our results show that the addition of hydrophobically modified chitosan following the application of chemical dispersant to an oil spill can potentially reduce the use of chemical dispersants. Increasing the molecular weight of the biopolymer changes the rheological properties of the oil-in-water emulsion to that of a weak gel. The ability of the biopolymer to tether the oil droplets in a gel-like matrix has potential applications in the immobilization of surface oil spills for enhanced removal.

Superparamagnetic iron oxide nanoparticles with variable size and an iron oxidation state as prospective imaging agents.

Magnetite nanoparticles in the size range of 3.2-7.5 nm were synthesized in high yields under variable reaction conditions using high-temperature hydrolysis of the precursor iron(II) and iron(III) alkoxides in diethylene glycol solution. The average sizes of the particles were adjusted by changing the reaction temperature and time and by using a sequential growth technique. To obtain γ-iron(III) oxide particles in the same range of sizes, magnetite particles were oxidized with dry oxygen in diethylene glycol at room temperature. The products were characterized by DLS, TEM, X-ray powder diffractometry, TGA, chemical analysis, and magnetic measurements. NMR r(1) and r(2) relaxivity measurements in water and diethylene glycol (for OH and CH(2) protons) have shown a decrease in the r(2)/r(1) ratio with the particle size reduction, which correlates with the results of magnetic measurements on magnetite nanoparticles. Saturation magnetization of the oxidized particles was found to be 20% lower than that for Fe(3)O(4) with the same particle size, but their r(1) relaxivities are similar. Because the oxidation of magnetite is spontaneous under ambient conditions, it was important to learn that the oxidation product has no disadvantages as compared to its precursor and therefore may be a better prospective imaging agent because of its chemical stability.

Curcumin-loaded γ-cyclodextrin liposomal nanoparticles as delivery vehicles for osteosarcoma.

The delivery of curcumin, a broad-spectrum anticancer drug, has been explored in the form of liposomal nanoparticles to treat osteosarcoma (OS). Curcumin is water insoluble and an effective delivery route is through encapsulation in cyclodextrins followed by a second encapsulation in liposomes. Liposomal curcumin's potential was evaluated against cancer models of mesenchymal (OS) and epithelial origin (breast cancer). The resulting 2-Hydroxypropyl-γ-cyclodextrin/curcumin - liposome complex shows promising anticancer potential both in vitro and in vivo against KHOS OS cell line and MCF-7 breast cancer cell line. An interesting aspect is that liposomal curcumin initiates the caspase cascade that leads to apoptotic cell death in vitro in comparison with DMSO-curcumin induced autophagic cell death. In addition, the efficiency of the liposomal curcumin formulation was confirmed in vivo using a xenograft OS model. Curcumin-loaded γ-cyclodextrin liposomes indicate significant potential as delivery vehicles for the treatment of cancers of different tissue origin. FROM THE CLINICAL EDITOR: Curcumin-loaded γ-cyclodextrin liposomes were demonstrated in vitro to have significant potential as delivery vehicles for the treatment of cancers of mesenchymal and epithelial origin. Differences between mechanisms of cell death were also evaluated.

Multifunctional iron-carbon nanocomposites through an aerosol-based process for the in situ remediation of chlorinated hydrocarbons.

Spherical iron-carbon nanocomposites were developed through a facile aerosol-based process with sucrose and iron chloride as starting materials. These composites exhibit multiple functionalities relevant to the in situ remediation of chlorinated hydrocarbons such as trichloroethylene (TCE). The distribution and immobilization of iron nanoparticles on the surface of carbon spheres prevents zerovalent nanoiron aggregation with maintenance of reactivity. The aerosol-based carbon microspheres allow adsorption of TCE, thus removing dissolved TCE rapidly and facilitating reaction by increasing the local concentration of TCE in the vicinity of iron nanoparticles. The strongly adsorptive property of the composites may also prevent release of any toxic chlorinated intermediate products. The composite particles are in the optimal range for transport through groundwater saturated sediments. Furthermore, those iron-carbon composites can be designed at low cost, the process is amenable to scale-up for in situ application, and the materials are intrinsically benign to the environment.

Titanium dioxide nanoparticles cause apoptosis in BEAS-2B cells through the caspase 8/t-Bid-independent mitochondrial pathway.

To understand the underlying mechanism for apoptosis induced by titanium dioxide nanoparticles (TNP), human airway epithelial cell line was cultured to investigate the relevant apoptosis pathways. Our results showed that the levels of reactive oxygen species and morphological apoptosis increased in a dose-dependent manner whereas cell viability decreased in a similar manner in response to TNP exposure in the BEAS-2B cells. The activities of caspase 3 and PARP were also increased in parallel to the morphological apoptosis. Levels of caspase 9 increased significantly whereas there were no detectable changes in caspase 8 and t-Bid in the TNP treated cells. Caspase 9 inhibition blocked the TNP-induced activation of caspase 3 significantly. The levels of bax, cytochrome C, p53 and bcl-2 also changed reflecting the activation of intrinsic apoptosis pathway. Our results provide solid evidence that apoptosis in BEAS-2B cells exposed to TNP occurred via a mitochondrial apoptosis pathway independent of caspase 8/t-Bid pathway.

Reactivity characteristics of nanoscale zerovalent iron--silica composites for trichloroethylene remediation.

Spherical silica particles containing nanoscale zerovalent iron were synthesized through an aerosol-assisted process. These particles are effective for groundwater remediation, with the environmentally benign silica particles serving as effective carriers for nanoiron transport. Incorporation of iron into porous sub-micrometer silica particles protects ferromagnetic iron nanoparticles from aggregation and may increase their subsurface mobility. Additionally, the presence of surface silanol groups on silica particles allows control of surface properties via silanol modification using organic functional groups. Aerosolized silica particles with functional alkyl moieties, such as ethyl groups on the surface, clearly adsorb solubilized trichloroethylene (TCE) in water. These materials may therefore act as adsorbents which have coupled reactivity characteristics. The nanoscale iron/silica composite particles with controlled surface properties have the potential to be efficiently applied for in situ source depletion and in the design of permeable reactive barriers.

Surfactant templating effects on the encapsulation of iron oxide nanoparticles within silica microspheres.

Hollow silica microspheres encapsulating ferromagnetic iron oxide nanoparticles were synthesized by a surfactant-aided aerosol process and subsequent treatment. The cationic surfactant cetyltrimethyl ammonium bromide (CTAB) played an essential role in directing the structure of the composite. Translation from mesoporous silica particles to hollow particles was a consequence of increased loading of ferric species in the precursor solution and the competitive partitioning of CTAB between silicate and ferric colloids. The hypothesis was that CTAB preferentially adsorbed onto more positively charged ferric colloids under acidic conditions. At a critical Fe/Si ratio, most of the CTAB was adsorbed onto ferric colloids and coagulated the colloids to form larger clusters. During the aerosol process, a silica shell was first formed due to the preferred silicate condensation on the gas-liquid interface of the aerosol droplet. Subsequent drying concentrated the ferric clusters inside the silica shell and resulted in a silica shell/ferric core particle. Thermal treatment of the core shell particle led to encapsulation of a single iron oxide nanoparticle inside each silica hollow microsphere.