Self-assembled Core-shell Nanoparticles Research Articles

Self-assembled core-shell nanoparticles with embedded internal standards for SERS quantitative detection and identification of nicotine released from snus products.

Surface enhanced Raman spectroscopy (SERS) is a unique analytical technique with excellent performance in terms of sensitivity, non-destructive detection and resolution. However, due to the randomness and poor repeatability of hot spot distribution, SERS quantitative analysis is still challenging. Meanwhile, snus is a type of tobacco product that can release nicotine and other components in the mouth without burning, and the rapid detection technique based on SERS can reliably evaluate the amount of nicotine released from snus, which is of great significance for understanding its characteristics and regulating its components. Herein, the strategy was proposed to solve the feasibility of SERS quantitative detection based on self-assembled core-shell nanoparticles with embedded internal standards (EIS) due to EIS signal can effectively correct SERS signal fluctuations caused by different aggregation states and measurement conditions, thus allowing reliable quantitative SERS analysis of targets with different surface affinity. By means of process control, after the Au nanoparticles (Au NPs) were modified with 4-Mercaptobenzonitrile (4-MBN) as internal standard molecules, Ag shell with a certain thickness was grown on the surface of the AuNP@4-MBN, and then the Au@4-MBN@Ag NPs were used to regulate and control the assembly of liquid-liquid interface. The high-density nano-arrays assembled at the liquid-liquid interface ensure high reproducibility as SERS substrates, and which could be used for SERS detection of nicotine released from snus products. In addition, time-mapping research shows that this method can also be used to dynamically monitor the release of nicotine. Moreover, such destruction-free evaluation of the release of nicotine from snus products opens up new perspectives for further research about the impact of nicotinoids-related health programs.

Core-Shell Structures from the Coassembly of Lipoprotein-like Nanoparticles and Plasmid DNA for Gene Delivery.

We reported self-assembled core-shell nanoparticles (NPs) based on lipoprotein-like NPs and plasmid DNA (pDNA). Lipoprotein-like NPs were prepared using cholic acid (CA)-modified lipopeptides. We designed six different lipopeptides with different peptide segments to construct a series of NPs. It was proven that these NPs have different positive surface charges. These NPs could bind pDNA through electrostatic interaction to form core-shell complexes. The interactions between NPs and pDNA were systematically investigated. The number of NP charges determines the strength of the interaction between NPs and pDNA. Thus, various types of core-shell structures, such as loose and dense core-shell NPs, were found in this system. Cytotoxicity test confirmed that the carriers had no toxicity. We also proved that the core-shell structures have a good cell transfection effect. This study would expand the application of lipopeptide assemblies in the gene delivery field, which may lead to the development of peptide-based gene vectors for therapeutic application.

Injectable Supramolecular Polymer-Nanoparticle Hydrogels for Cell and Drug Delivery Applications.

These methods describe how to formulate injectable, supramolecular polymer-nanoparticle (PNP) hydrogels for use as biomaterials. PNP hydrogels are composed of two components: hydrophobically modified cellulose as the network polymer and self-assembled core-shell nanoparticles that act as non-covalent cross linkers through dynamic, multivalent interactions. These methods describe both the formation of these self-assembled nanoparticles through nanoprecipitation as well as the formulation and mixing of the two components to form hydrogels with tunable mechanical properties. The use of dynamic light scattering (DLS) and rheology to characterize the quality of the synthesized materials is also detailed. Finally, the utility of these hydrogels for drug delivery, biopharmaceutical stabilization, and cell encapsulation and delivery is demonstrated through in vitro experiments to characterize drug release, thermal stability, and cell settling and viability. Due to its biocompatibility, injectability, and mild gel formation conditions, this hydrogel system is a readily tunable platform suitable for a range of biomedical applications.

Injectable Supramolecular Polymer-Nanoparticle Hydrogels for Cell and Drug Delivery Applications

These methods describe how to formulate injectable, supramolecular polymer-nanoparticle (PNP) hydrogels for use as biomaterials. PNP hydrogels are composed of two components: hydrophobically modified cellulose as the network polymer and self-assembled core-shell nanoparticles that act as non-covalent cross linkers through dynamic, multivalent interactions. These methods describe both the formation of these self-assembled nanoparticles through nanoprecipitation as well as the formulation and mixing of the two components to form hydrogels with tunable mechanical properties. The use of dynamic light scattering (DLS) and rheology to characterize the quality of the synthesized materials is also detailed. Finally, the utility of these hydrogels for drug delivery, biopharmaceutical stabilization, and cell encapsulation and delivery is demonstrated through in vitro experiments to characterize drug release, thermal stability, and cell settling and viability. Due to its biocompatibility, injectability, and mild gel formation conditions, this hydrogel system is a readily tunable platform suitable for a range of biomedical applications.

Resistive Sensors Based on Self-Assembled Core-Shell Nanoparticles

A gas sensor allows the detection thanks to the specific reactivity of its sensitive material towards the target gas. The use of resistive sensors is based on measuring the variation of their electrical conductivity when the target gas is in contact with the sensitive material. In our study, we chose to work with self assembled core-shell nanoparticles as sensing materials. The idea consists on decorating spherical gold nanoparticles, insensitive to the target gases, with a shell based on a different material. The latter provides the specific sensitivity to the sensor. Previous works in our laboratory focused on Au@Pd and Au@Pt nanoparticles as H2 sensors. These works were extended to other shell materials to examine their sensitivity towards H2 as well as other target gases including NH3. Au@ZnO, Au@SnO2 and Au@Ag nanoparticles were synthetized and then assembled by Langmuir Blodgett technique. The assembly resulted in close-packed core-shell nanoparticle monolayers. These layers were transferred, by simple dip-coating, to a glass slide supporting interdigitated electrodes. Sensing performances of the as fabricated sensors were evaluated through the resistivity changes in the discontinuous particle assemble. The sensitivity of Au@ZnO and Au@SnO2 based sensors was tested towards H2 while Au@Ag based sensors were tested under NH3. All sensors showed responses towards the target gases. The effect of humidity and the sensing temperature on the sensing performances were studied. Besides, among the main sensor proprieties requested and studied we note : sensitivity, selectivity, response and recovery times. Assembles of core-shell nanoparticles organized with Langmuir-Blodgett technique demonstrated attractive sensing performances towards H2 and NH3 in extended concentration ranges. Another important contribution concerns the elucidation of the sensing mechanisms. Various analytical techniques including Temperature Programmed Desorption, Temperature Programmed Reduction and Microcalorimetry were used to allow the discussion of the sensing performances towards mechanisms. Figure 1

Resistive Sensors Based on Self-Assembled Core-Shell Nanoparticles

Au@Ag, Au@ZnO and Au@SnO2 nanoparticles were synthetized and then assembled by Langmuir Blodgett technique. The resulting close-packed core-shell nanoparticle monolayers were transferred onto glass chips to fabricate NH3 and H2 resistive sensors. Sensing performances of the as fabricated sensors were evaluated through the resistivity changes in the discontinuous particle assemble. The sensitivity of Au@Ag based sensor was tested towards NH3 while Au@ZnO and Au@SnO2 based sensors were tested under H2. Assembles of core-shell nanoparticles organized by the Langmuir-Blodgett technique demonstrated attractive sensing performances towards the target gases in extended concentration ranges.

Nanoscale Coordination Polymers Codeliver Chemotherapeutics and siRNAs to Eradicate Tumors of Cisplatin-Resistant Ovarian Cancer.

Drug resistance impedes the successful treatment of many types of cancers, especially ovarian cancer (OCa). To counter this problem, we developed novel long-circulating, self-assembled core-shell nanoscale coordination polymer (NCP) nanoparticles that efficiently deliver multiple therapeutics with different mechanisms of action to enhance synergistic therapeutic effects. These NCP particles contain high payloads of chemotherapeutics cisplatin or cisplatin plus gemcitabine in the core and pooled siRNAs that target multidrug resistant (MDR) genes in the shell. The NCP particles possess efficient endosomal escape via a novel carbon dioxide release mechanism without compromising the neutral surface charge required for long blood circulation and effectively downregulate MDR gene expression in vivo to enhance chemotherapeutic efficacy by several orders of magnitude. Even at low doses, intraperitoneal injections of nanoparticles led to effective and long-lasting tumor regression/eradication in subcutaneous and intraperitoneal xenograft mouse models of cisplatin-resistant OCa. By silencing MDR genes in tumors, self-assembled core-shell nanoparticles promise a more effective chemotherapeutic treatment for many challenging cancers.

Millimeter-wave magneto-dielectric effects in self-assembled ferrite-ferroelectric core-shell nanoparticles

The magneto-dielectric effect (MDE) involves studies on the influence of an applied magnetic field on the dielectric constant of a material. MDEs in self-assembled core-shell nanoparticles of nickel ferrite and barium titanate have been investigated in the millimeter wave frequencies. The core-shell nanocomposites were synthesized by coating 15 nm nickel ferrite and 100 nm barium titanate nanoparticles with complementary coupling groups and allowing them to self-assemble in the presence of a catalyst forming heterogeneous nanocomposites. Studies on MDE in as-assembled particles have been carried out by measurements of the relative permittivity as a function of frequency f under an applied static magnetic field H over 16–24 GHz. Measurements show an H-induced decrease in permittivity by 0.8% for H = 4 kOe and is much stronger than MDE in single phase multiferroics. A model for the high frequency MDE has been discussed here.

High frequency magneto-dielectric effects in self-assembled ferrite-ferroelectric core-shell nanoparticles

Magneto-dielectric effects in self-assembled core-shell nanoparticles of nickel ferrite (NFO) and barium titanate (BTO) have been investigated in the millimeter wave frequencies. The core-shell nano-composites were synthesized by coating 100 nm nickel ferrite and 50 nm barium titanate nanoparticles with complementary coupling groups and allowing them to self-assemble in the presence of a catalyst forming heterogeneous nanocomposites. Magneto-electric (ME) characterization of as-assembled particles has been carried out by measurements of the relative permittivity ɛr as a function of frequency f under an applied static magnetic field H over 16–24 GHz. Measurements show an H-induced decrease in ɛr of 1 to 1.5%. But a giant magneto-dielectric effect with an H-induced change in permittivity as high as 28% is measured under dielectric resonance in the samples. A strong ME coupling was also evident from H-tuning of dielectric resonance in the composites. A theory for the high frequency magneto-dielectric effect has been developed and consists of the following steps. First the Bruggeman model is used to estimate the effective dielectric constant for the shell consisting of the BTO particles and voids considered as spherical air-pores. Then the permittivity for the core and shell is estimated taking into consideration the sample porosity. Finally the H-dependence of the permittivity due to ME interactions is calculated from the free energy considerations. Estimated ɛr vs. H and dielectric resonance frequency vs. H characteristics are in general agreement with the data.

Superstructures of self-assembled multiferroic core-shell nanoparticles and studies on magneto-electric interactions

Superstructures of linear chains and arrays of chemically self-assembled core-shell nanoparticles of nickel ferrite and barium titanate have been obtained by magnetic-field-assisted assembly (MFAA). Studies on strain mediated magneto-electric (ME) effects by ME voltage coefficient (MEVC) measurements reveal higher MEVC for MFAA samples than for unassembled films and is higher for magnetic fields parallel to the array orientation than for transverse fields. The strongest ME effect is measured in MFAA-films with a maximum MEVC of 8 mV/cm Oe, one of the highest reported for as-assembled nanocomposite. A model is discussed for the ME coupling in the MFA samples.

Encapsulation of low molecular weight heparin (bemiparin) into polymeric nanoparticles obtained from cationic block copolymers: properties and cell activity.

Bemiparin (fractionated low molecular weight heparin)-loaded nanoparticles were prepared by two consecutive w/o emulsions and an inversion to an o/w emulsion for various polymer systems as controlled release formulations. New synthetic block copolymers, poly(methyl methacrylate-b-trimethyl aminoethyl methacrylate) (PMMA-b-PMAETMA), with controlled microstructure and molecular weight, were prepared by RAFT (Reversible Addition-Fragmentation chain-Transfer) polymerization creating a set of polymers with different amounts of cationic charges. For comparison, a non-biodegradable positively charged polymer, Eudragit® RS PO, and a biodegradable polymer poly(lactic-co-glycolic acid), PLGA, were used. The microstructural arrangement of MMA and MAETMA sequences in PMMA-b-PMAETMA results in self-assembled core-shell nanoparticles in water with a positively charged surface, which interacts with bemiparin. The formulations were evaluated in terms of particle size, zeta potential and morphology by scanning electron microscopy (SEM). The entrapment of bemiparin molecules was confirmed by a negatively increased zeta potential value and the detection of a sulfur signal by energy dispersive X-ray spectroscopy (EDAX). High encapsulation efficiency was reached with all the polymeric matrices, ranging from 89 to 98%. Systems prepared with synthetic block copolymers PMMA-b-PMAETMA and PLGA showed higher in vitro bemiparin release than Eudragit® RS PO systems. For each formulation, bemiparin released from nanoparticles preserved its biological activity as shown by the BaF32 cell proliferation assay in the presence of fibroblast growth factor (FGF2).

Structural Iridescent Tuned Colors from Self-Assembled Polymer Opal Surfaces

Structural colors are the object of a wide scientific interest, not only for the potential technical applications of their intriguing optical properties but also for the need of coloring agents to replace toxic and carcinogenic dyes. We present a simple methodology to obtain polymer opal surfaces of self-assembled core-shell nanoparticles with different degree of order for structural color applications. Polymer nanospheres prepared by surfactant-free emulsion radical copolymerization of an hydrophobic and an hydrophilic comonomer (styrene and methacrylic acid) spontaneously assemble into core-shell particles. Nanoparticles with identical composition and different diameters were prepared by modulating the degree of ionization of the weakly acidic comonomer. We report experimental results revealing how the synthesis parameters affect the properties of the core-shell particles and their influence on the optical properties of the final polymer opal surfaces, which depend on size, charge, and packing arrangement of the constituent nanoparticles.