Unmodified Silica Nanoparticles Research Articles

Unraveling the Complexities of Silica Nanoparticle Adsorption onto Polymer Latexes in Pickering Emulsion Polymerization.

Incorporating unmodified silica nanoparticles onto polymer latexes to fabricate aqueous polymer dispersions without relying on electrostatic attraction during the Pickering emulsion polymerization process still faces challenges. For negatively charged silica nanoparticles to successfully adsorb onto polymer latexes, particularly in an anionic initiator emulsion polymerization system, they have remained elusive without the use of auxiliary monomers and cationic initiators. This study investigates various experimental parameters, such as emulsion polymerization temperature, monomer solubility, salt concentration, and cation type, to elucidate the factors influencing the adsorption of unmodified silica nanoparticles in Pickering emulsion polymerization. While poly(methyl methacrylate) (PMMA)/SiO2 hybrid latexes can be obtained under pH conditions of 5-6 and at temperatures of 65 °C or below, the loading rate of silica nanoparticles decreases as the reaction temperature increases, resulting in bare PMMA latexes without silica nanoparticle adsorption at temperatures exceeding 70 °C. Introducing styrene (St) into the monomer mixture with methyl methacrylate in a ratio of up to 10 wt % leads to a gradual decrease in silica nanoparticle loading rate, from 27.3 to 8.2 wt %, attributed to the low solubility of St in water. Furthermore, the presence of sodium ions (Na+) is found to be crucial for silica nanoparticle adsorption onto PMMA latexes, as the sodium ions have a stabilizing effect on both the silica nanoparticles and the silica nanoparticle-armored latexes. These findings highlight the complex nature of Pickering emulsion polymerization in the presence of unmodified silica nanoparticles, demonstrating that the loading rate of silica nanoparticles onto polymer latexes is influenced by various factors. These insights pave the way for developing aqueous polymer dispersions with high silica nanoparticle loading rates onto polymer latexes, which is a desirable trait in the coating industry.

Impact of silica oxide and functionalized silica oxide nanoparticles on growth of Chlorella vulgaris and its physicochemical properties

In this study, silica oxide nanoparticles (SiO2 NPs) and methyl-functionalized SiO2 NPs were compared for their effects on the growth of Chlorella vulgaris, production of biomass, and lipid content. The synthesised nanoparticles were characterised by using techniques such as FTIR, XRD, UV-Vis, FESEM with EDX and TEM. The synthesised nanoparticles were used to enhance the gas-liquid interface areas, which increase the concentration of dissolved carbon dioxide in the growth medium in order to increase the accumulation of lipid content in C. vulgaris cultures. The most effective way to improve the gas-liquid interface area was to use SiO2 NPs at a concentration of 0.3 wt%. The hydrophobic functional group methyl was added to the hydrophilic surfaces of SiO2 NPs. Methyl-functionalized SiO2 NPs improved the gas-liquid interface area more effectively than unmodified silica nanoparticles. The concentration of dissolved CO2 was 316.66 mg L−1 with methyl-functionalized SiO2 NPs. During microalgae culture, methyl-functionalized SiO2 NPs at a concentration of 0.3 wt% considerably improved the production of dry biomass, lipid, protein, carbohydrate, and chlorophyll contents as compared to the control.

Tailoring nanocomposite membranes of cellulose acetate/silica nanoparticles for desalination

Herein, the fabrication of cellulose acetate (CA) silica-based nanocomposite membranes via the dry-wet phase inversion procedure for water desalination was investigated. The modified and unmodified silica nanoparticles (MSNPs and SNPs) were prepared by the sol-gel technique. The effect of the SNPs and MSNPs was investigated on the CA membrane's properties and their performance for water desalination. The CA nanocomposite membranes were characterized to study their structure, hydrophilicity, and morphology. The fabricated nanocomposite membranes showed hydrophilic surface properties. The performance of reverse osmosis (RO) membranes was measured using a crossflow RO unit at 10 bar (1 bar = 0.1 MPa). The membrane with 10 mg of SNPs enhanced permeate water flux compared to the pristine CA membrane by 1.6 L/(m2·h). The effect of MSNPs on the nanocomposites' performance was lower than their counterpart in the case of adding SNPs. The membrane with 30 mg of MSNPs showed the highest permeate water flux among other nanocomposite membranes with a value of 35.7 L/(m2·h) at 24 bar.

Effect of Surface Modification of Silica Nanoparticles with Thiol group on the Shear Thickening Behaviors of the Suspensions of Silica Nanoparticles in polyethylene glycol (PEG)

The Fine-tuning of Shear Thickening Fluids (STFs) by surface modification of silica particles has fascinated scientist’s interest worldwide as it results in performance enhancement of STF based on armor systems. In the current study, surface modified Silica nanoparticles (average diameter of 600 nm) possess thiol functional groups which were attained through a reaction with 3-mercaptopropyl-trimethoxysilane in absolute ethanol at 90 °C. Shear thickening fluid of Thiol functionalized Silica nanoparticles were prepared by sonochemical method in polyethylene glycol (PEG-200). The rheological parameters of STFs (modified and unmodified silica Nano particles) were measured using Rheometer MCR 52, Anton Par, Germany. The shear thickening behavior of thiol-based STF shows shear thickening at a higher shear rate compared to only silica-based STF with the decrease in viscosity maximum.

Efficient Encapsulation and Controlled Release of N,N-Diethyl-3-methylbenzamide (DEET) from Oil-in-Water Emulsions Stabilized by Cationic Nanocellulose and Silica Nanoparticles

Oil-in-water emulsions containing N,N-diethyl-3-methylbenzamide (DEET) were developed aiming to extend the sustained release of the active compound, by using two oppositely charged nanomaterials, namely silica nanoparticles (SiNP) and cationic cellulose nanofibrils (CCNF), as stabilizers, and a mixture of food-grade nonionic surfactants to avoid precipitation by electrostatic aggregation. The formulations were stable for more than four months at room temperature, and strongly resistant to destabilization upon centrifugal and thermal stress. The results were correlated with the effect of SiNP on strengthening the network formation of CCNF in the aqueous phase by electrostatic interactions, which increased the viscosity of the external phase and, hence, emulsion stability. There was a significant size reduction of the internal oil phase containing DEET in the presence of CCNF, which was attributed to the increased viscosity in the external aqueous phase, as well as to interfacial stabilization. The combined action of CCNF and unmodified SiNP in the stabilization of the DEET-containing oil phase significantly decreased the release rate of the active compound, compared to non-emulsified DEET. Moreover, in the emulsions containing the CCNF/SiNP mixture there was a more sustained release for the period of 6 h, demonstrating the potential of these formulations for extended protection.

Incorporation of alkyl‐functionalized silica nanoparticles into hydrophilic epoxy and hydrophobic polystyrene matrices

AbstractThe homogeneous dispersion of nanosized fillers in a polymeric matrix is crucial for improving the mechanical and thermal properties of composites. In this study, the dispersity of silica nanoparticles (SNPs) in the hydrophilic epoxy and hydrophobic polystyrene (PS) matrices was examined. As the unmodified SNPs were hydrophilic, they dispersed well in the epoxy matrix, but agglomerated in the PS matrix. We also explored the effects of different aliphatic chain lengths (hydrophilic vs. hydrophobic: unmodified, methyl, propyl, and octyl) on the dispersity of nanoparticles in the polymer. The alkyl‐functionalized SNPs were more uniformly dispersed than the unmodified SNPs in the PS matrix. Comparing the different alkyl chains, the propyl‐functionalized SNPs exhibited the most homogeneous dispersion in the polymer, thereby increasing the mechanical properties. The octyl‐functionalized SNPs agglomerated slightly, which might be due to their chain interaction (entanglement). The size of SNPs was controlled (60, 120, and 180 nm) via sol–gel synthesis, and the SNP with the smallest diameter (60 nm) showed the slight enhancement in mechanics and dispersion compared with SNPs with diameters of 120 and 180 nm. The SNP size, hydrophilicity, functionality, and aliphatic chain length on SNP surfaces investigated in this study can be useful for various nanocomposite applications.

Cover Image, Volume 138, Issue 24

This cover designed by Muhammad Bilal and colleagues represents the brittle fractured surface of unmodified silica microparticles, which are spherical with sharp boundaries and smooth surfaces, suggesting no chemical interaction between two boundaries. The silica particles seem to be out of their grooves, as there was no chemical interaction between the two phases i.e., organic, and inorganic. Wide gaps between polyimide matrix and silica microparticles expose the weak interfacial interaction between organic-inorganic components. This phase separation and immiscibility in the case of unmodified silica nanoparticles result in the stress amount defect instead of effective strengthening constituents. 10.1002/app.50646

Synthesis and physicochemical investigation of imide‐functionalized silica nanocomposites

AbstractThe incorporation of inorganic nanoparticles into polymers have gained significant attention to improving functional properties. The ultimate nanocomposite behaviors are influenced by many parameters, such as microstructural distribution that are produced during the treatment process. Herein, a hybrid material integrating a modified network into a polyimide PI matrix was produced via the sol–gel method by the reaction of pyromellitic dianhydride, 4, 4‐oxydianaline, and 1, 5‐diaminonaphthalene to synthesize copolyimides nanocomposite. The modified polyimide and unmodified polyimide silica (SiO2) nanoparticles were incorporated in the polyimide matrix to have polyimide silica nanocomposite. In modified silica nanoparticles, 3‐aminopropyltriethosilane was introduced to have better compatibility among inorganic–organic hybrid with similar chemical contact due to their flexible alkyl group. The surface morphology or structure of silica and polyimide was affirmed by scanning electron microscopy, Fourier transforms infrared spectroscopy confirmed the synthesis of pure polyimide, unmodified polyimide, and modified polyimide silica via presence and absence of certain peaks. Thermogravimetric analysis (TGA) results showed high thermal stability of nanocomposites as silica content increases. In contrast to unmodified silica, the modified silica provides more thermal stability to the nanocomposites. Dynamic mechanical analysis was used to investigate the tensile stress of pure polyimide, unmodified, and modified silica nanocomposites. Thermal stability, storage modulus, and moisture absorption of these hybrid materials were improved with silica nanoparticles. The TG mass spectrum confirms the successful synthesis of modified silica networks. The substituted silica nanoparticles show higher mechanical toughness and storage in modified compared to unmodified silica nanocomposite, which exhibits stronger binding attraction between silica nanoparticles and polyimide matrix.

Poly(ethylene oxide) grafted silica nanoparticles: efficient routes of synthesis with associated colloidal stability.

In this study, poly(ethylene oxide) monomethyl ether (MPEO) of molecular weight of 5000, 10 000, and 20 000 g mol-1 were grafted onto colloidal silica nanoparticles (NPs) of a 27.6 nm diameter using two distinct "grafting to" processes. The first method was based on the coupling reaction of epoxide-end capped MPEO with amine-functionalized silica NPs, while the second method was based on the condensation of triethoxysilane-terminated MPEO onto the unmodified silica NPs. The influence of PEO molecular weight, grafting process and grafting conditions (temperature, reactant concentration, reaction time) on the PEO grafting density was fully investigated. Thermogravimetric analysis (TGA) was used to determine the grafting density which ranged from 0.12 chains per nm2 using the first approach to 1.02 chains per nm2 when using the second approach. 29Si CP/MAS NMR characterization indirectly revealed that above a grafting density value of 0.3 PEO chains per nm2, a dendri-graft PEO network was built around the silica surface which was composed of PEO chains directly anchored to the silica surface and those grafted to silica NPs by intermediate of >CH-O-Si- bonds. The colloidal stability of the particles during different steps of the grafting process was characterized by small-angle X-ray scattering (SAXS). We have found that the colloidal systems are stable whatever the achieved grafting density due to the strong repulsions between the NPs, with the strength of repulsion increasing with the molecular weight of the grafted MPEO chains.

Elongational behavior of silica nanoparticle-filled low-density polyethylene/polylactic acid blends and their morphology

We investigated the rheological behavior of linear low-density polyethylene (LLDPE)/polylactic acid (PLA) blends in the presence of modified and non-modified silica nanoparticles in extensional flow. Characterization methods were used as Fourier transform infrared spectroscopy, scanning electron microscopy, and rheometric measurements under shear and uniaxial extensional flows. The rheology behavior of LLDPE significantly was changed by the addition of PLA and silica nanoparticles. Extensional results showed that the elongational viscosity of the blends intensified by the incorporation of silica nanoparticles. Strain hardening was observed for LLDPE containing 2 wt.% of the unmodified silica nanoparticles, which disappeared by enhancement of the unmodified silica from 2 to 8 wt.%. Furthermore, elongation thinning was observed for the filled blends at high loading, which was more sensitive to the strain rate by increasing of PLA. Surface modification of silica was demonstrated in different elongational behavior. Indeed, a fracture took place by loading the modified silica nanoparticles in LLDPE; however, the intensity of this behavior dramatically increased for filled blends with a high loading of modified silica.

Cetyltrimethylammonium bromide functionalized silica nanoparticles (MSN) synthesis using a combined sol-gel and adsorption steps with enhanced adsorption performance of oxytetracycline in aqueous solution

The cetyltrimethylammonium bromide (CTAB)-functionalized silica nanoparticles (MSN) were prepared using a combined sol-gel and adsorption steps. The nitrogen adsorption-desorption surface analysis shows the MSN has a lower surface area than the unmodified (or free) silica nanoparticles (FSN). The energy dispersive X-ray (EDX) and Fourier transform infrared (FTIR) analysis confirmed the presence of CTAB in MSN with maximum CTAB coverage of (0.74 ± 0.04) mmol/g. The maximum adsorption capacity of oxytetracycline (OTC) onto MSN performed in the batch adsorption process, Qe.max is 449.89 µmol g−1, which is higher than FSN (57.06 µmol g−1). The adsorption depends on pH value, OTC concentration, temperature, and contact time. The thermodynamic parameters indicate the process as exothermic in nature and spontaneous. The isotherm data fits well with the Redlich-Peterson model, while the pseudo-second order (PSO) kinetic model is found to be suitable to describe the kinetic data with the film diffusion as the rate-limiting step. The electrostatic, hydrogen bonding and hydrophobic interactions are mainly responsible for the OTC adsorption onto the synthesized adsorbents. The reusability studies found that the adsorbent could be recycled without drastic adsorption capacity reduction. The successful decoration of the CTAB onto the surface of the silica nanoparticles provides an effective method in the development of promising adsorbents for antibiotic removal from wastewater.

Loss of membrane asymmetry alters the interactions of erythrocytes with engineered silica nanoparticles.

Disruption of plasma membrane integrity is a primary mechanism of nanoparticle toxicity in cells. Mechanistic studies on nanoparticle-induced membrane damage have been commonly performed using model membranes with a focus on symmetric bilayers, overlooking the fact that the membrane has an asymmetric phospholipid composition. In this study, erythrocytes with normal and scrambled membrane asymmetry were utilized to examine how the loss of membrane asymmetry and the resulting alterations in the outer leaflet lipid composition affect nanoparticle-membrane interactions. Unmodified, amine-modified, and carboxyl-modified silica (30 nm) were used as nanoparticle models. Loss of membrane asymmetry was achieved by induction of eryptosis, using a calcium ionophore. Erythrocyte membrane disruption (hemolysis) by unmodified silica nanoparticles was significantly reduced in eryptotic compared to healthy cells. Amine- and carboxyl-modified particles did not cause hemolysis in either cell. In agreement, a significant reduction in the binding of unmodified silica nanoparticles to the membrane was observed upon loss of membrane asymmetry. Unmodified silica particles also caused significant cell deformation, changing healthy erythrocytes into a spheroid shape. In agreement with findings in the cells, unmodified particles disrupted vesicles mimicking the erythrocyte outer leaflet lipid composition. The degree of disruption and nanoparticle binding to the membrane was reduced in vesicles mimicking the composition of scrambled membranes. Cryo-electron microscopy revealed the presence of lipid layers on particle surfaces, pointing to lipid adsorption as the mechanism for vesicle damage. Together, findings indicate an important role for the lipid composition of the membrane outer leaflet in nanoparticle-induced membrane damage in both vesicles and erythrocytes.

Fungal spore adhesion on glycidoxypropyltrimethoxy silane modified silica nanoparticle surfaces as revealed by single cell force spectroscopy.

Thin film coatings prepared from commercially available glycidoxypropyltrimethoxysilane (GPS) modified silica nanoparticles (SiNPs) (Bindzil® CC301 and Bindzil® CC302) have previously shown excellent antifouling performance against a broad range of microbes [Molino et al., "Hydration layer structure of biofouling-resistant nanoparticles," ACS Nano 12, 11610 (2018)]. In this work, single cell force spectroscopy (SCFS) was used to measure the biological interactions between Epicoccum nigrum fungal spores and the same silica nanoparticle-based surfaces used in the aforementioned study, including a: glass coverslip, unmodified SiNP coatings, and both low (Bindzil® CC301) and high density (CC302) GPS functionalized SiNP coatings as a function of NaCl concentration. From the SCFS curves, the spore adhesion to the surface was greatest on the glass coverslip (20-80 nN) followed by the unmodified SiNP (3-5 nN) across all salt concentrations. Upon approach to both surfaces, the spores showed a long-range attraction generally with a profile characteristic of biointeractions and likely those of the outer cell wall structures or biological constituents. The attractive force allowed the spores to initially adhere to the surface and was found to be linearly proportional to the spore adhesion. In comparison, both high and low density GPS-SINP significantly reduced the spore adhesion (0.5-0.9 nN). In addition, the spore adhesion on high density GPS-SiNP occurred in only 14%-27% of SCFS curves (40%-48% for low density GPS-SiNP) compared to 83%-97% for the unmodified SiNP, indicating that in most cases the GPS functionalization completely prevented spore adhesion. The GPS-SiNP surfaces conversely showed a long-range electrostatic repulsion at low 1mM NaCl that was replaced by short-range repulsion at the higher salt concentrations. From the findings, it is proposed that the attractive force is a critical step in initial adhesion processes of the spore. The effective antifouling properties of the GPS are attributed to the ability to negate the attractive forces, either through electrostatic repulsion in low salt conditions and primarily from short-range repulsion correlating to the previously reported combined steric-hydration effect of the GPS functionalization on SiNP coatings.

Nanoscale Pattern Decay Monitored Line by Line via In Situ Heated Atomic Force Microscopy.

We combine in situ heated atomic force microscopy (AFM) with automated line-by-line spectral analysis to quantify the relaxation or decay phenomenon of nanopatterned composite polymer films above the glass-transition temperature of the composite material. This approach enables assessment of pattern fidelity with a temporal resolution of ≈1 s, providing the necessary data density to confidently capture the short-time relaxation processes inaccessible to conventional ex situ measurements. Specifically, we studied the thermal decay of nanopatterned poly(methyl methacrylate) (PMMA) and PMMA nanocomposite films containing unmodified and PMMA-grafted silica nanoparticles (SiO2 NP) of varying concentrations and film thicknesses using this new approach. Features imprinted on neat PMMA films were seen to relax at least an order of magnitude faster than the NP-filled films at decay temperatures above the glass transition of the PMMA matrix. It was also seen that patterned films with the lowest residual thickness (34 nm) filled with unmodified SiO2 NP decayed the slowest. The effect of nanoparticle additive was almost negligible in reinforcing the patterned features for films with the highest residual thickness (257 nm). Our in situ pattern decay measurement and the subsequent line-by-line spectral analysis enabled the investigation of various parameters affecting the pattern decay such as the underlying residual thickness, type of additive system, and temperature in a timely and efficient manner.

The Influence of Surface Modified Silica Nanoparticles: Properties of Epoxy Nanocomposites

Abstract The influence of the surface-modified (CCS) and un-modified (UCS) silica nanoparticles on epoxy nanocomposites were studied. Two different nanocomposites systems were synthesized using tetraethylorthosilicate (TEOS) and 3-(triethoxysilyl) propylamine APTES as a precursor and coupling agent, respectively. In the uncoupled composite system (UCS) the silica particles were solely generated using TEOS as a precursor. The APTES was used as a coupling agent to chemically link the silica (SiO2) particles to the matrix in the coupled composite system (CCS). Both composite systems were fabricated as thin films. The SiO2 epoxy nanocomposites thin films were characterized by Differential Scanning Calorimetry (DSC), RAMAN, Fourier Transform Infra-Red (FT-IR), Scanning Electron Microscopy (SEM) and Thermal Gravimetric (TGA) analysis. RAMAN and FT-IR analysis confirmed the curing of epoxy resin and the generation of the inorganic structural network formation. SEM analysis of these nanocomposites revealed that silica particles were uniformly dispersed in the epoxy matrix. DSC analysis of the nano-composites revealed an increase in glass transition (T g) temperature with the addition of nanofiller. TGA analysis shows enhanced thermal stability of the coupled composite system in comparison to the neat and uncoupled epoxy composite system.

RhB-encapsulating silica nanoparticles modified with PEG impact the vascular endothelial function in endothelial cells and zebrafish model

Silica nanoparticles (SiNPs) have been widely used in human health related products, such as food additives, cosmetics and even drug delivery, gene therapy or bioimaging. Recently, a first-in-human clinical trial based on polyethylene glycol (PEG)-modified SiNPs had been approved by US FDA to trace melanoma. However, as a nano-based drug delivery system, its biocompatibility and vascular toxicity are still largely unknown. Thus, we synthesized the fluorescent SiNPs to explore the biocompatibility and vascular endothelial function, and compare different biological effects caused by PEG-modified and unmodified SiNPs in cells and zebrafish model. The characterizations of SiNPs and PEG-modified SiNPs were analyzed by TEM, SEM, AFM and DLS, which exhibited relatively good stable and dispersive. Compared with SiNPs, PEG-modified SiNPs had markedly reduced the inflammatory response and vascular damage in Tg (fli-1: EGFP) and Tg (mpo: GFP) transgenic zebrafish lines, respectively. Consistent with the in vivo results, the PEG-modified SiNPs had been found to significantly decline the levels of ROS, inflammatory cytokines and mitochondrial-mediated apoptosis in vascular endothelial cells compared to SiNPs, and the ROS scavenger NAC could effectively alleviate the above adverse effects induced by nanoparticles. Our results suggested that the PEG-modified SiNPs could become more safety via increasing the biocompatibility and decreasing cellular toxicities in living organisms.

Preparation of UV-opaque, Vis-transparent acrylic–silica nanocomposite coating with promising physico-mechanical properties via miniemulsion polymerization

Here, waterborne coatings with enhanced physico-mechanical properties were prepared by incorporation of modified silica nanoparticles into an acrylic matrix through miniemulsion polymerization. In order to circumvent the inherent incompatibility of organic and inorganic portions, methylene diphenyl diisocyanate and 2-hydroxyethyl methacrylate molecules were chemically coupled to the surface of silica nanoparticles to alter the hydrophilic nature of inorganic nanoparticles to hydrophobic ones. Also, for investigating the effect of the exploited surface modification process, unmodified silica nanoparticles were used in preparing acrylic latex via miniemulsion polymerization. The optical and physico-mechanical properties of the acrylic–silica nanocomposite films with 0–10 wt% of unmodified and modified SiO2 were characterized by measuring their surface roughness, haziness, gloss values, UV–Vis transmittance, scratch resistance, tensile, and pendulum hardness. It was found that by using modified SiO2 nanoparticles, due to their better dispersion state and ability for establishing covalent linkage with acrylic polymer chains, it is possible to obtain nanocomposite coatings with improved physico-mechanical properties, high transparency in Vis region, considerable UV adsorption, and comparable surface roughness, glossiness, and haziness with pure acrylic film. However, unmodified silica nanoparticles formed many aggregates in the polymer matrix which deteriorated optical and different physico-mechanical properties of acrylic latex. It was found that the greatest improvement in properties is achieved by incorporation of 7 wt% modified silica nanoparticles in acrylic polymer.

Low-density lipoprotein-decorated and Adriamycin-loaded silica nanoparticles for tumor-targeted chemotherapy of colorectal cancer.

Chemotherapy for colorectal cancer remains an unsatisfactory method of treatment and requires the development of more advanced drug delivery systems (DDSs). Among inorganic materials, silica nanoparticles (SLNs) have been considered a suitable candidate to be developed as versatile carriers for drug delivery and imaging applications. Low-density lipoprotein (LDL) is a widespread material that is responsible for cholesterol transport in plasma. The concept of employing LDL-modified nanoparticles for tumor-targeted drug delivery has been widely adopted. The objective of this study was to develop and test a new DDS for effective chemotherapy of colorectal cancer. We successfully developed an Adriamycin (Adr)-loaded DDS based on LDL-modified SLNs (LDL/SLN/Adr). The tumor-homing property of LDL and the drug-loading capability of SLNs were combined to prepare LDL/SLN/Adr that can specifically deliver Adr to the cancer site to achieve effective chemotherapy of HT-29 colorectal cancer. In vitro analysis showed that LDL/SLN/Adr consisted of nano-sized particles and was capable of targeting the low-density lipoprotein receptors (LDLR) which were overexpressed in many cancer cell lines. As a result, LDL/SLN/Adr exerted better cytotoxicity than unmodified SLNs and free drugs. In vivo imaging and anticancer assays also confirmed the preferable tumor-homing and enhanced anticancer effect of LDL/SLN/Adr. LDL/SLN/Adr might be a promising DDS for effective chemotherapy of colorectal cancer.

Core-shell red silica nanoparticles based immunochromatographic assay for detection of Escherichia coli O157:H7

In this paper, a new type immunochromatographic assay (ICA) based on core-shell red silica nanoparticles (core-shell red SiO2NPs) was proposed and used to detect Escherichia coli O157:H7 (E. coli O157:H7). This is the first report of qualitative ICA for detecting E. coli O157:H7 in phosphate buffer saline (PBS) and food sample using core-shell red SiO2NPs. Monodispersed red SiO2NPs were synthesized in the aqueous solution by modifying amino silane and C.I Reactive Red 136 on unmodified silica nanoparticles. The limit of detection (LOD) of this core-shell red SiO2NPs based ICA for E. coli O157:H7 was 4.5 × 105 CFU/mL in sterile PBS within 20 min. The LOD of this ICA strip for E. coli O157:H7 in milk and pork samples both were 4.5 × 106 CFU/mL. The core-shell red SiO2NPs based ICA for detection of E. coli O157:H7 has no cross activity with other bacteria. All these results show that this new kind of core-shell colored SiO2NPs is promising for the practical applications in ICA and other rapid detection fields.

Photo-crosslinkable polyurethanes reinforced with coumarin modified silica nanoparticles for photo-responsive coatings

Coumarin and poly-ε-(caprolactone) diol (PCL)-based polyurethanes (PUs), were reinforced with modified silica nanoparticles (mSiNPs), in which a novel coumarin molecule was synthetized. The behavior as photo-responsive coatings of these materials was studied. The silica nanoparticles (SiNPs) modification was analyzed by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and UV spectroscopy. The yield of photo-crosslinking in nanocomposites loaded with mSiNPs was studied by UV–vis spectroscopy, which showed higher conversion degree than nanocomposites with unmodified SiNPs and non-reinforced PUs. The dispersion of mSiNPs on segregated microdomains was observed by transmission electron microscopy (TEM). The presence of coumarin grafted on the SiNPs surface (mSiNPs) leads to an improvement on the thermal stability of PU matrix. Meanwhile, they were able to maintain the mechanical performance before and after the irradiation process mainly due to the improved nanofiller-matrix interaction. Contact angle measurements were also assayed to study the hydrophobicity changes on the surface of modified nanocomposites. The observed phase segregation was associated with the mechanical and thermal properties of the materials and the photo-crosslinking of coumarin moieties bring to the final material high responsiveness to be employed as photo-switchable coatings.