Solid lipid nanoparticles prepared by solvent diffusion method in a nanoreactor system

In this study, water-in-oil (W/O) miniemulsion was used as nanoreactor to prepare solid lipid nanoparticles (SLN) by solvent diffusion method. n-Hexane, Tween 80 and Span 80 were used as the oil phase and surfactant combination for preparation of W/O miniemulsion, respectively. The stable miniemulsion with the particle size of 27.1 ± 7.6 nm was obtained when the composition of water/Tween 80/Span 80/n-hexane was 1 ml/18 mg/200 mg/10 ml. Clobetasol propionate (CP) was used as a model drug. The physicochemical properties of the SLN, such as particle size, zeta potential, surface morphology, drug entrapment efficiency, drug loading capacity and in vitro drug release behaviors were investigated, comparing with those of SLN prepared by conventional aqueoethod. The SLN prepared by the novel method displayed smaller particles size and higher dus solvent diffusion mrug entrapment efficiency than those of SLN prepared by the conventional method. The drug entrapment efficiency decreased with increasing of charged amount of drug, and 15.9% of drug loading was achieved as the charged amount of drug was 20%. The in vitro drug release tests indicated that the drug release rate was faster than that of SLN prepared by the conventional method, and the drug content in SLN did not affect the in vitro drug release profile.     

Studies on crystallinity state of puerarin loaded solid lipid nanoparticles prepared by double emulsion method

In this work, solid lipid nanoparticles (SLN) have been prepared from water-in-oil-in-water double emulsion, using monocaprate as solid lipid, sorbitan monooleate (Span 80) and polyoxyethylene sorbitan monolaurate (Tween 20) as emulsifier, and puerarin as target drug. The morphology of SLN with drug loaded or not was investigated by the transmission electron microscope (TEM). The crystal order and structure of particles were studied by differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD), respectively. The results indicate that the diameters of SLN with puerarin inside are larger than those without drugs. The analysis of WAXD and DSC shows that the state of crystallinity SLN prepared by double emulsion method was worse than that of SLN prepared by microemulsion. And also the drug-loaded SLN presents a less ordered crystallinity than the drug-free SLN. But both the drug-free and drug-loaded SLN exist in an amorphous state. The reasons of the phenomenon have been discussed.     

Evaluation of surface charge density and surface potential by electrophoretic mobility for solid lipid nanoparticles and human brain-microvascular endothelial cells

Electrophoretic mobility, zeta potential, surface charge density, and surface potential of cacao butter-based solid lipid nanoparticles (SLN) and human brain-microvascular endothelial cells (HBMEC) were analyzed in this study. Electrophoretic mobility and zeta potential were determined experimentally. Surface charge density and surface potential were evaluated theoretically via incorporation of ion condensation theory with the relationship between surface charge density and surface potential. The results revealed that the lower the pH value, the weaker the electrostatic properties of the negatively charged SLN and HBMEC. A higher content of cacao butter or a slower stirring rate yielded a larger SLN and stronger surface electricity. On the contrary, storage led to instability of SLN suspension and weaker electrical behavior because of hydrolysis of ionogenic groups on the particle surfaces. Also, high H+ concentration resulted in excess adsorption of H+ onto HBMEC, rendering charge reversal and cell death. The largest normalized discrepancy between surface potential and zeta potential occurred at pH = 7. For a fixed biocolloidal species, the discrepancy was nearly invariant at high pH value. However, the discrepancy followed the order of electrical intensity for HBMEC system at low pH value because mammalian cells were sensitive to H+. The present study provided a practical method to obtain surface charge properties by capillary electrophoresis.     

Small angle X-ray scattering study of surface modified tin oxide nanoparticles prepared by sol-gel route

The surface properties of SnO₂ nanoparticles were modified by grafting ionic (Tiron®_, (OH)₂C₆H₂(SO₃Na)₂·H₂O) or non-ionic (Catechol®_, C₆H₄-1,2-(OH)₂) capping molecules during aqueous sol-gel processing to improve the redispersibility of powdered xerogel. The effect of the amount of grafted organic molecules on the redispersibility of powders in aqueous solution at several basic pH values was studied. The nanostructural features of the colloidal suspensions were analyzed by small angle X-ray scattering (SAXS) measurements. Irrespective of the nature and amount of grafted molecules, complete redispersion was obtained in aqueous solution at pH = 13. The redispersion at pH = 11 results in a mixture of dispersed primary particles and aggregates. The proportion of well dispersed nanoparticles and aggregates (and their average size) can be tuned by the quantity of grafted ionic molecules.     

Electrochemical biosensors for detection of point mutation based on surface ligation reaction and oligonucleotides modified gold nanoparticles

An electrochemical method for point mutation detection based on surface ligation reaction and oligonucleotides (ODNs) modified gold nanoparticles (AuNPs) was demonstrated. Point mutation identification was achieved using Escherichia coli DNA ligase. This system for point mutation detection relied on a sandwich assay comprising capture ODN immobilized on Au electrodes, target ODN and ligation ODN. Because of the sequence-specific surface reactions of E. coli DNA ligase, the ligation ODN covalently linked to the capture ODN only in the presence of a perfectly complementary target ODN. The presence of ligation products on Au electrode was detected using chronocoulometry through hybridization with reporter ODN modified AuNPs. The use of AuNPs improved the sensitivity of chronocoulometry in this approach, a detection limit of 0.9 pM complementary ODN was obtained. For single base mismatched ODN (smODN), a negligible signal was observed. Even if the concentration ratio of complementary ODN to smODN was decreased to 1:1000, a detectable signal was observed. This work may provide a specific, sensitive and cost-efficient approach for point mutant detection.     

Inorganic nanoparticles prepared in miniemulsion

The defined synthesis of inorganic nanoparticles is the crucial step for their successful application. Thus, preparation methods to control composition, shape, size, and aggregation behavior are of high interest and relevance. Here, the possibilities that the miniemulsion technique offers for the generation of inorganic nanoparticles are reviewed. Several of the traditional synthetic methods as the controlled precipitation or sol–gel chemistry were confined to the droplets of a miniemulsion, leading to new structures and morphologies. Furthermore, the focus is put on polymer- and latex-assisted mineralization and a miniemulsion-based approach to nonconventional colloidal lithography.     

Reconstitution of the voltage-gated K+ channel KAT1 in planar lipid bilayers

The single-channel current has been recorded for the voltage-gated K⁺ channel from Arabidopsis thaliana, KAT1, reconstituted in the planar bilayer lipid membrane (BLM). Channel-like current was observed between two aqueous phases after the addition of the proteoliposomes into one aqueous phase. In the potential range from 60 to 120 mV, the single-channel current was recorded and the conductance was calculated to 10.0–12.5 pS. The open channel probability increased with an increase of the applied membrane potential. These characteristics of the reconstituted channels are close to those of KAT1 reported by Hoshi et al. and Hedrich et al. with the patch clamp technique. This is the first work in which the isolated ion channel from higher plants was reconstituted in the planar BLM system.     

Monosized cationic nanoparticles prepared by emulsifer-free emulsion polymerization

Monosized poly(styrene/N-[3-(dimethylamino)propyl]methacrylamide/poly(ethylene glycol) ethyl ether methacrylate) [poly(St/PEG-EEM/DMAPM)] cationic nanoparticles were synthesized by emulsifier-free emulsion polymerization conducted in the presence of a cationic initiator, 2,2-azobis(2-methylpropionamidine) dihydrochloride (APDH or V-50). Particle sizes and surface charge densities were measured with a Zeta Sizer. The structure of the terpolymers was determined by Fourier transform IR and ¹H NMR spectroscopies. The amounts of the main monomer (St), cationic comonomer (DMAPM), stabilizer (PEG-EEM), and initiator (APDH), and the water-to-monomer phase ratio were all effective on both the average size and the surface charge of the nanoparicles. The average particle size was in the range 75–400 nm depending on the recipe applied; it decreased on increasing the amount of DMAP or PEG-EEM or the water-to-monomer phase ratio in the feed, while it increased with increasing St or APDH content. These nanoparticles were quite monodisperse with a polydispersity index of 1.008–1.14.     

Peptide dendrimer enzyme models for ester hydrolysis and aldolization prepared by convergent thioether ligation

Peptide dendrimers with multiple histidines or N-terminal prolines efficiently catalyze ester hydrolysis or aldol reactions in aqueous medium. Part of the catalytic proficiency of these dendritic enzyme models stems from multivalency effects observed in G2, G3 and G4 dendrimers displaying multiple catalytic groups in their branches. To study multivalency in higher generation systems, G4, G5 and G6 peptide dendrimers were prepared by a convergent assembly. Thus, peptide dendrimers bearing four or eight chloroacetyl groups at their N-termini underwent multiple thioether ligation with G2 and G3 peptide dendrimers with a cysteine residue at their focal point, to give G4, G5 and G6 dendrimers containing up to 341 amino acids, including multiple histidines or N-terminal prolines. While the efficiency of the esterase catalysts was comparable to that of their lower generation analogs, a remarkable reactivity increase was observed in G5 and G6 aldolase dendrimers.     

Recent progress in the detection and treatment of atherosclerosis by nanoparticles

Cardiovascular diseases (CVDs) have high mortality and morbidity in the US and presently rank as one of the leading causes of death. Atherosclerosis (AS) acts as one of the CVDs, playing an important role in mortality because of many lethal complications. The common cause of AS is that low-density lipoprotein (LDL) in the blood circulation enters the intima through endothelial cells that have been broken for various reasons. Under the action of inflammatory factors secreted by damaged endothelial cells, monocytes also enter the inner membrane and differentiate into macrophages. Macrophages engulf the oxidized LDL and become foam cells which eventually become apoptotic. However, recent studies have shown that LDL entry into the intima, an important step in AS, may be associated with endothelial cells actively inhaling LDL through the receptor. Nanotechnology is a promising technology that can be applied in the noninvasive imaging and therapy of AS. Nanoparticles (NPs) have the ability to passively target AS because of their inherent small diameter. They can also be loaded with chemicals for targeting lesions, contrast agents for imaging, and drugs for treatment to achieve accurate diagnosis and treatment of AS. This review consequently highlights the recent progress in the detection and treatment of AS by NPs.     

Conformational study of CdS nanoparticles prepared by ultrasonic waves

CdS nanoparticles of about 5 nm in size have been prepared with the aid of ultrasound irradiation to ethylenediamine solution of cadmium acetate dehydrate and elemental S in presence of 1-decanthiol under air and normal laboratory conditions. X-ray diffraction (XRD) and selected area electron diffraction (SAED) studies indicate that the products are nanocrystallites in hexagonal structure. High resolution transmission electron microscopy (HRTEM) image reveals that lattice fringes are clearly visible, conforming their crystallinity with lattice space of 0.27 nm corresponding to (1 0 2) plane of hexagonal CdS. Energy-dispersive X-ray analysis (EDAX) shows that the product are entirely pure and atomic percentage ratio of Cd to S is about 53:47. UV–vis absorption spectroscopy of the as prepared nanoparticles reveals an energy band gap of about 3.8 eV compared to 2.42 eV corresponding to its bulk value; a blue shift of about 1.38 eV, which is understood as quantum size effect due to confinement of electron and hole in a small volume.     

Disruption of supported lipid bilayers by semihydrophobic nanoparticles

Understanding the interaction between functional nanoparticles and cell membranes is critical to use nanomaterials for broad biomedical applications with minimal cytotoxicity. In this work, we have investigated the effect of adsorbed semihydrophobic nanoparticles (NPs) on the dynamics and morphology of model cell membranes. We have systematically varied the degree of surface hydrophobicity of carboxyl end-functionalized polystyrene NPs of varied size in buffer solutions with varied ionic strength. It is observed that semihydrophobic NPs can readily adsorb on neutral SLBs and drag lipids from SLBs to NP surfaces. Above a critical NP concentration, the disruption of SLBs is observed, accompanied with the formation and rapid growth of lipid-poor regions on NP-adsorbed SLBs. In the study of the effect of solution ionic strength on NP surface hydrophobic degree and the growth of lipid-poor regions, we have concluded that the hydrophobic interaction enhanced by screened electrostatic interaction underlies the envelopment of NPs by lipids that are attracted from SLBs to the surface of NPs or their aggregates. Hence, the formation and growth of lipid-poor regions, or vaguely referred as "pores" or "holes" in the literature, can be controlled by NP concentration, size, and surface hydrophobicity, which is critical to design functional nanomaterials for effective nanomedicine while minimizing possible cytotoxicity.     

Light-up lipid droplets for the visualization of lipophagy and atherosclerosis by coumarin-derived bioprobe

Lipid droplets(LDs) are intracellular lipid-metabolism organelles that involved in many physiological processes,metabolic disorders as well as diseases such as atherosclerosis.However,the specific probes that can visually locate abnormal LDs-rich tissues and track LDs-associated behavior to the naked eye with adequate biosafety still are rare.Herein,we develop a new design strategy of LDs-targeted probe based on the solvatochromism of coumarin derivatives.The results revealed that the emission wavelength of coumarin fluorophores gradually red shift in different solvents with increasing polarity,while absorption wavelength almost unchanged.As a result,the enlarged stokes shift of coumarin was emerged from oil to water.Furthermore,properly reducing water solubility and adding electronic donor at the structure of coumarins can enlarge this type of solvatochromism.This discovery was utilized to develop suitable probe for the image of LDs and LDs-rich tissues with high resolution and biosafety.Therefore,LDs-associated behavior was visible to the naked eye during the process of lipophagy and atherosclerosis.We deem that the developed probe here offers a new possibility to accurately diagnosis and analyse LDs-related diseases in clinic and preclinical study.     

The ultratrace detection of crystal violet using surface enhanced Raman scattering on colloidal Ag nanoparticles prepared by electrolysis

Highly active,stable and affordable surface enhanced Raman scattering(SERS) substrates were obtained by electrolyzing a mixture of AgNO_3(4×10~(-4) mol/L) and Na_3C_6H_5O_7·H_2O(6×10~(-5) mol/L) for 1,2,3 and 4h at 7V.With crystal violet(CV) as a test molecule,a portable Raman spectrometer with 785 nm laser excitation was employed to carry out the SERS detection.Colloidal Ag nanoparticles prepared by electrolyzing for 3 h with the particle size of(65±17) nm is a perfect SERS substrate for the ultratrace ...     

Polyaniline nanoparticles prepared in rodlike micelles

The effect of aniline hydrochloride (AHC) on the size and shape of sodium dodecyl sulfate (SDS) micelles has been investigated by dynamic light scattering. A monotonic decrease in the diffusion coefficient of the micelles was observed with an increase in AHC at fixed SDS concentration. This was ascribed to prolate ellipsoidal growth of the micelles due to decrease of the effective headgroup area/molecule by adsorption of AHC on SDS micelles. The length of the micelles can be tuned by controlling the ratio of concentrations of AHC to SDS. Polymerization of aniline in micelles of different sizes leads to the formation of colloidal polyaniline with variable sizes. A direct correlation between size ofmicelles and size ofpolyaniline particles was observed. Combination of static and dynamic light scattering experiments reveal that the conformations of the polymer do not change significantly with size of the colloid.     

Strategic approaches for improving entrapment of hydrophilic peptide drugs by lipid nanoparticles

In order to introduce hydrophilic peptide drugs into solid lipid nanoparticles (SLN), a technique of combining hydrophobic ion pairing (HIP) and non-aqueous oil-in-oil (O/O) emulsion-evaporation was developed. Leuprolide (LR) was selected as the model drug, while sodium stearate (SA-Na) was used as the negative charged ion pairing material. The formation of leuprolide-sodium stearate (LR-SA-Na) complex was confirmed by differential scanning calorimetry (DSC). It was observed that when the molar ratio of SA-Na/LR reached 2/1, ca 88.5% LR was incorporated into the hydrophobic ion complexes with SA-Na. Compared with the conventional method of solvent diffusion in an aqueous system, the efficiency of LR drug entrapment with SLN increased from 28.0% to 74.6% by the combined technique of HIP and O/O emulsion-evaporation. In vitro drug release tests revealed that employing technique of HIP obviously reduced the burst release and slowed down the rate of drug release. At meanwhile, applying the method of non-aqueous O/O emulsion-evaporation, the longer time of drug release but relatively higher drug burst release ratio was observed in comparison with those by the solvent diffusion method in an aqueous system. The drug entrapment and release behaviors of LR-SA-Na SLN prepared by the O/O emulsion-evaporation method suggested that it could potentially be exploited as an oral delivery system for leuprolide.     

Electromagnetic nanocomposites prepared by cryomilling of polyaniline and Fe nanoparticles

The polyaniline (PANI)/iron nanocomposites have been prepared by high‐energy ball milling under cryogenic temperatures, namely cryomilling, of PANI with Fe nanoparticles. It takes 5 h to refine the Fe into an average grain size of 20 nm and to get homogeneously dispersed in PANI matrix. The obtained PANI/Fe nanocomposites have a maximum conductivity of 0.78 S cm^?1 after 2‐h cryomilling, whereas its coercivity increases monotonously with time in the range of experiment up to 10 h. It is found that the sizes of Fe particles have obvious effects on both electrical and magnetic properties. When compared with micrometer Fe particles as raw materials, Fe nanoparticles result in somewhat lower conductivity but a much higher coercivity exceeding 400 Oe. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1571–1576, 2008     

Neoglycolipid probes prepared via oxime ligation for microarray analysis of oligosaccharide-protein interactions

Neoglycolipid technology is the basis of a microarray platform for assigning oligosaccharide ligands for carbohydrate-binding proteins. The strategy for generating the neoglycolipid probes by reductive amination results in ring opening of the core monosaccharides. This often limits applicability to short-chain saccharides, although the majority of recognition motifs are satisfactorily presented with neoglycolipids of longer oligosaccharides. Here, we describe neoglycolipids prepared by oxime ligation. We provide evidence from NMR studies that a significant proportion of the oxime-linked core monosaccharide is in the ring-closed form, and this form selectively interacts with a carbohydrate-binding protein. By microarray analyses we demonstrate the effective presentation with oxime-linked neoglycolipids of (1) Lewis(x) trisaccharide to antibodies to Lewis(x), (2) sialyllactose analogs to the sialic acid-binding receptors, siglecs, and (3) N-glycans to a plant lectin that requires an intact N-acetylglucosamine core.