Synthesis and Application of Low Molecular Weight PEI-Based Copolymers for siRNA Delivery with Smart Polymer Blends

Polyethylenimine (PEI) is a commonly used cationic polymer for small-interfering RNA (siRNA) delivery due to its high transfection efficiency at low commercial cost. However, high molecular weight PEI is cytotoxic and thus, its practical application is limited. In this study, different formulations of low molecular weight PEI (LMW-PEI) based copolymers polyethylenimine-g-polycaprolactone (PEI–PCL) (800 Da–40 kDa) and PEI–PCL–PEI (5–5–5 kDa) blended with or without polyethylene glycol-b-polycaprolactone (PEG–PCL) (5 kDa-4 kDa) are investigated to prepare nanoparticles via nanoprecipitation using a solvent displacement method with sizes ≈100 nm. PEG–PCL can stabilize the nanoparticles, improve their biocompatibility, and extend their circulation time in vivo. The nanoparticles composed of PEI–PCL–PEI and PEG–PCL show higher siRNA encapsulation efficiency than PEI–PCL/PEG–PCL based nanoparticles at low N/P ratios, higher cellular uptake, and a gene silencing efficiency of ≈40% as a result of the higher molecular weight PEI blocks. These results suggest that the PEI–PCL–PEI/PEG–PCL nanoparticle system could be a promising vehicle for siRNA delivery at minimal synthetic effort.     

Targeted Gastrointestinal Delivery of Nutraceuticals with Polysaccharide‐Based Coatings

Oral delivery is one of the facile methods for the administration of active ingredients (AIs) like nutraceuticals and drugs. However, its intrinsic disadvantages include poor absorption and bioavailability, degradation of the AI during transit through the gastrointestinal tract (GIT), and a lack of action specificity. Hence, a delivery system for targeted gastrointestinal delivery of AI using polysaccharide‐based polymers, that are generally recognized as safe and approved for use as a direct food additive, is proposed. In this regard, mucoadhesive chitosan nanoparticles that could adhere to the mucosa of the GIT are fabricated and encapsulated with AI. These particles are subsequently coated with polysaccharides that have different enzymatic susceptibilities, to allow for specific degradation in the small or large intestines. It is observed that the polysaccharide coating efficiently retarded the nonspecific release of the encapsulated agent until it is exposed to its intended environment of release. The cytotoxicity and uptake of chitosan nanoparticles is further evaluated on Caco2 cells. In conclusion, these polysaccharide‐coated nanoparticles can potentially be targeted to different organs in the GIT and to be taken up by the enterocytes for improved oral bioavailability.     

Electrosprayed maize starch and its constituents (amylose and amylopectin) nanoparticles

Starch consists of amylose and amylopectin. Properties such as being natural and highly hygroscopic as well as biodegradability have opened a considerable range of applications for amylose, amylopectin and starch. The performance of particles is highly dependent on their size which in turn determines the specific surface area. This work studies the application of electrospraying to fabricate maize starch and its constituents: amylose and amylopectin nanoparticles. This study showed that electrospraying technique is capable of producing amylose, amylopectin and starch nanopowder with an average particle size around 100 nm. FTIR analysis showed no reaction or interaction occurring in amylose, amylopectin and starch nanoparticle compared with their natural form. Basically, lower concentration, lower viscosity and lower surface tension of the electrospraying solution as well as higher nozzle–collector distance, higher voltage and lower feed rate lead to smaller nanoparticle size. Copyright © 2015 John Wiley & Sons, Ltd.     

Carrier recombination dynamics in anatase TiO2 nanoparticles

We present an experimental study of the radiative recombination dynamics in size-controlled TiO₂ nanoparticles in the range 20–130 nm. Time-integrated photoluminescence spectra clearly show a dominance of self-trapped exciton (STE) emission, with main features not dependent on the nanoparticle size and on its environment. From picosecond time-resolved experiments as a function of the excitation density and the nanoparticle size we address the STE recombination dynamics as the result of two main processes related to the direct STE formation and to the indirect STE formation mediated by non-radiative surface states.     

Plant-Based Colloidal Delivery Systems for Bioactives

The supplementation of plant-based foods and beverages with bioactive agents may be an important strategy for increasing human healthiness. Numerous kinds of colloidal delivery systems have been developed to encapsulate bioactives with the goal of improving their water dispersibility, chemical stability, and bioavailability. In this review, we focus on colloidal delivery systems assembled entirely from plant-based ingredients, such as lipids, proteins, polysaccharides, phospholipids, and surfactants isolated from botanical sources. In particular, the utilization of these ingredients to create plant-based nanoemulsions, nanoliposomes, nanoparticles, and microgels is covered. The utilization of these delivery systems to encapsulate, protect, and release various kinds of bioactives is highlighted, including oil-soluble vitamins (like vitamin D), ω-3 oils, carotenoids (vitamin A precursors), curcuminoids, and polyphenols. The functionality of these delivery systems can be tailored to specific applications by careful selection of ingredients and processing operations, as this enables the composition, size, shape, internal structure, surface chemistry, and electrical characteristics of the colloidal particles to be controlled. The plant-based delivery systems discussed in this article may be useful for introducing active ingredients into the next generation of plant-based foods, meat, seafood, milk, and egg analogs. Nevertheless, there is still a need to systematically compare the functional performance of different delivery systems for specific applications to establish the most appropriate one. In addition, there is a need to test their efficacy at delivering bioavailable forms of bioactives using in vivo studies.     

Semi-elastic core-shell nanoparticles enhanced the oral bioavailability of peptide drugs

The rigidity of nanoparticles was newly reported to influence their oral delivery. Semi-elastic nanoparticles can enhance the penetration in mucus and uptake by epithelial cells. However, it is still challenging and unclear that the semi-elastic core-shell nanoparticles can enhance the oral bioavailability of peptide drugs. This study was for the first time to validate the semi-elastic core-shell poly(lactic-co-glycolic acid) (PLGA)-lipid nanoparticles (LNPs) as the carrier of the oral peptide drug. The antihypertensive peptide Val-Leu-Pro-Val-Pro (VP5) loaded LNPs (VP5-LNPs) were prepared by a modified thin-film ultrasonic dispersion method. Uptake experiment was performed in Caco-2 and HT-29 cells and monitored by high content screening (HCS) and flow cytometric (FCM). Pharmacokinetics of VP5-LNPs was carried out in Sprague-Dawley (SD) rats and analyzed by DAS 2.0. The optimal VP5-LNPs had an average particle size of 247.3 ± 3.8 nm, zeta potential of −6.57 ± 0.45 mV and excellent entrapment efficiency (EE) of 89.88% ± 1.23%. Transmission electron microscope (TEM) and Differential scanning calorimeter (DSC) further confirmed the core-shell structure. VP5-LNPs could increase the cellular uptake in vitro and have a 2.55-fold increase in AUC0-72 h, indicating a great promotion of the oral bioavailability. The semi-elastic LNPs remarkably improved the oral availability of peptide and could be a promising oral peptide delivery system for peptide drugs in the future.     

Luminescent amphiphilic nanogels by terpyridine-Zn(II) complexation of polymeric micelles

In this work, we investigated terpyridine (tpy)/Zn(II) complexation for the crosslinking of polymeric micelles of the branched poly(ethylene oxide)–poly(propylene oxide) block copolymer Tetronic® 1107 (T1107) in water and produce physically stable amphiphilic luminescent nanogels. Nanoparticles displayed a size of 235 ± 25 and 318 ± 57 nm before and after Zn(II) crosslinking, respectively, as measured by dynamic light scattering. High-resolution scanning electron microscopy analysis revealed the multimicellar nature of the crosslinked nanoparticles. In addition, Zn(II) complexation prevented nanoparticle disassembly after extreme dilution below the critical micellar concentration and reduced the minimum concentration required for the reverse thermal gelation of concentrated aqueous T1107 systems. The cell compatibility and uptake were initially assessed in the murine macrophage cell line RAW 264.7. Results showed that complexation increases the cell compatibility of the nanoparticles with respect to the non-complexed counterparts. In addition, non-crosslinked nanoparticles accumulated in the cell membrane, while the complexed ones were internalized, as observed by confocal laser scanning fluorescence microscopy. Then, the antiproliferative activity of the crosslinked nanoparticles was confirmed in the rhabdomyosarcoma cell line Rh30; their inhibitory concentration 50 (IC₅₀) being 101 μg/mL (6.7 μM). Finally, the encapsulation and release of the hydrophobic antiretroviral efavirenz was characterized in vitro. Complexation slightly reduced the release kinetics with respect to the pristine nanoparticles. Overall results demonstrate the promise of this simple modification strategy to produce amphiphilic nanogels with a set of advantageous physicochemical, optical, and biological properties.     

Development and characterization of new insulin containing polysaccharide nanoparticles

A nanoparticle insulin delivery system was prepared by complexation of dextran sulfate and chitosan in aqueous solution. Parameters of the formulation such as the final mass of polysaccharides, the mass ratio of the two polysaccharides, pH of polysaccharides solution, and insulin theorical loading were identified as the modulating factors of nanoparticle physical properties. Particles with a mean diameter of 500 nm and a zeta potential of approximately −15 mV were produced under optimal conditions of DS:chitosan mass ratio of 1.5:1 at pH 4.8. Nanoparticles showed spherical shape, uniform size and good shelf-life stability. Polysaccharides complexation was confirmed by differential scanning calorimetry and Fourier transformed infra-red spectroscopy. An association efficiency of 85% was obtained. Insulin release at pH below 5.2 was almost prevented up to 24 h and at pH 6.8 the release was characterized by a controlled profile. This suggests that release of insulin is ruled by a dissociation mechanism and DS/chitosan nanoparticles are pH-sensitive delivery systems. Furthermore, the released insulin entirely maintained its immunogenic bioactivity evaluated by ELISA, confirming that this new formulation shows promising properties towards the development of an oral delivery system for insulin.     

Chemosensitization of Cancer Cells via Gold Nanoparticle‐Induced Cell Cycle Regulation

We have previously shown that plasmonic nanoparticles conjugated with nuclear‐targeting and cytoplasm‐targeting peptides (NLS and RGD, respectively) are capable of altering the cell cycle of human oral squamous carcinoma cells (HSC‐3). In the present work, we show that this regulation of the cell cycle can be exploited to enhance the efficacy of a common chemotherapeutic agent, 5‐Fluorouracil, by pretreating cells with gold nanoparticles. Utilizing flow cytometry cell cycle analysis, we were able to quantify the 5‐Fluorouracil efficacy as an accumulation of cells in the S phase with a depletion of cells in the G2/M phase. Two gold nanoparticle sizes were tested in this work; 30 nm with a surface plasmon resonance at 530 nm and 15 nm with a surface plasmon resonance at 520 nm. The 30 nm nuclear‐targeted gold nanoparticles (NLS‐AuNPs) showed the greatest 5‐Fluorouracil efficacy enhancement when 5‐Fluorouracil treatment (500 μm , 48 h) is preceded by a 24‐h treatment with nanoparticles. In conclusion, we show that nuclear‐targeted 30 nm gold nanoparticles enhance 5‐Fluorouracil drug efficacy in HSC‐3 cells via regulation of the cell cycle, a chemosensitization technique that could potentially be expanded to different cell lines and different chemotherapies.     

Cytoplasmic delivery of quantum dots via microelectrophoresis technique

Nanoparticles with specific properties and functions have been developed for various biomedical research applications, such as in vivo and in vitro sensors, imaging agents and delivery vehicles of therapeutics. The development of an effective delivery method of nanoparticles into the intracellular environment is challenging and success in this endeavor would be beneficial to many biological studies. Here, the well-established microelectrophoresis technique was applied for the first time to deliver nanoparticles into living cells. An optimal protocol was explored to prepare semiconductive quantum dots suspensions having high monodispersity with average hydrodynamic diameter of 13.2–35.0 nm. Micropipettes were fabricated to have inner tip diameters of approximately 200 nm that are larger than quantum dots for ejection but less than 500 nm to minimize damage to the cell membrane. We demonstrated the successful delivery of quantum dots via small electrical currents (–0.2 nA) through micropipettes into the cytoplasm of living human embryonic kidney cells (roughly 20–30 μm in length) using microelectrophoresis technique. This method is promising as a simple and general strategy for delivering a variety of nanoparticles into the cellular environment.     

Functionalized surface as template for in situ generation of two-dimensional metal nanoparticle assembly

Two-dimensional gold nanoparticle assemblies with an average nanoparticle size of 6 nm are generated on silicon and indium tin oxide (ITO)-coated glass surfaces, functionalized with polyethylenimine (PEI) silane monolayer. Contact angle measurements show increased hydrophilic character of the surface due to nanoparticle formation. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) are used to monitor the chemical and structural development of these nanostructures, while UV–vis spectroscopy is used to follow the formation of the nanoparticle assemblies. This paper elucidates a simple route to in situ synthesis of surface immobilized gold nanoparticles under ambient conditions and also extends to the synthesis of other surface bound nanoparticles, like silver and platinum. Gold nanoparticle assemblies generated in this study are also catalytically active towards methanol oxidation reaction (MOR), which is relevant for direct methanol fuel cells (DMFCs).     

Preparation of high-stable silver nanoparticle dispersion by using sodium alginate as a stabilizer under gamma radiation

Highly stable silver nanoparticles were successfully synthesized by gamma ray irradiation in the presence of sodium alginate. The silver nanoparticles were characterized by UV–vis spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). Their particle sizes were in the range of 6–30 nm. The as-obtained Ag nanoparticle dispersion was stable for over 6 months at room temperature.     

Layer-by-layer nanoparticle coatings on lignocellulose wood microfibers

The layer-by-layer (LbL) self-assembly technique was applied to deposit organized multilayers of TiO₂ or SiO₂ nanoparticles of 30–80 nm diameter, and 50-nm diameter halloysite clay nanotubes on softwood fibers. Fluorescent and scanning electron microscopy images showed complete nanoparticle coating on these fibers. The thickness of the two-layer coating was estimated as 46, 58, and 115 nm for TiO₂, SiO₂, and halloysite tubules, respectively, which corresponds to ca. 1 wt% nanoparticle loading of the fibers. The brightness test of paper handsheets prepared from nanocoated fibers showed that TiO₂ nanoparticle coating gave handsheet reflectance of 84% at 450 nm, which is 4% higher than the brightness of the control sample from virgin fibers. The paper handsheets prepared with nanoparticle-coated fibers had 30–50% higher porosity with tensile strength index retained close to the control sample.     

Production of Gold nanoparticles in aqueous solutions of cellulose derivatives

It is shown that gold nanoparticles can be produced using cellulose ethers, methylhydroxyethyl cellulose, and carboxymethyl cellulose as reducing agents that also play the role of nanoparticle stabilizers. Depending on the synthesis conditions, nanoparticle sizes vary in the range of 20–100 nm. The application of carboxymethyl cellulose as a stabilizer may give rise to the formation of a bimodal ensemble of nanoparticles with sizes of 4–5 and 30–40 nm. The differences in the mechanisms for the reduction and stabilization of gold nanoparticles in the presence of these cellulose derivatives are established by IR spectroscopy. The obtained colloidal dispersions of gold nanoparticles remain stable for a long time.     

Biosynthesis of Silver Nanoparticles by <Emphasis Type="Italic">Geotricum</Emphasis> sp.

Nanoparticles are usually 1–100 nm in each spatial dimension considered as building blocks of the next generation of optoelectronics, electronics, and various chemical and biochemical sensors. In the synthesis of nanoparticles use of microorganisms emerges as an eco-friendly and exciting approach that reduce waste products (ultimately leading to atomically precise molecular manufacturing with zero waste); the use of nanomaterials as catalysts for greater efficiency in current manufacturing processes by minimizing or eliminating the use of toxic materials (green chemistry principles); the use of nanomaterials and nanodevices to reduce pollution (e.g. water and air filters); and the use of nanomaterials for more efficient alternative energy production (e.g. solar and fuel cells). Fungi have many advantages for nanoparticle synthesis compared with other organisms. In this study, Geotricum sp. found to successfully produce Ag nanoparticles. Geotricum sp. was grown in SDA (Sabro Dextrose Agar) medium at 25 ± 1 °C for 96 h. The mycelia were used to convert silver nitrate solution into nano-silver. Silver nanoparticles were synthesized using these fungi (Geotricum sp.) extracellularly. UV–VIS spectroscopy, Atomic Force Microscopy (AFM) and Scanning Electron Microscopy images shows the nanoparticle formation in the medium. Energy-dispersive X-ray spectroscopy (EDX) also confirmed that silver nanoparticles in the range of 30–50 nm were synthesized extracellularly. FTIR analyses confirmed the presence of amide (I) and (II) bands of protein as capping and stabilizing agent on the surface of nanoparticles.     

Decoration of Gold Nanoparticles by a Double‐Armed Calix[4]pyrrole: A Receptor‐Decorated Nanoensemble for Anion Sensing and Extraction

Gold nanoparticles decorated with a double‐armed, deep‐cavity calix[4]pyrrole were prepared and fully characterized. Transmission electron microscopy imaging revealed that the average diameter of the particles was approximately 4 nm both before and after attachment of the receptor to the surface. The calix[4]pyrrole‐functionalized nanoparticles exhibited highly elevated sensing behavior (approximately 1000 times in dichloromethane) relative to its monomeric congener while maintaining its guest selectivity. The receptor–nanoparticle conjugate (nanoreceptor) showed significant aggregation upon addition of the biphenolate anion, an effect ascribed to anion‐mediated interparticle linking. The receptor–nanoparticle conjugate is also capable of extracting the fluoride anion (as its tetrabutylammonium salt) from an aqueous layer to an organic medium. Control experiments revealed that this extraction is not possible when using the analogous monomeric receptor.     

Delivery of ROS Generating Anthraquinones Using Reduction‐Responsive Peptide‐Based Nanoparticles

In order to limit the side effects associated with antitumor drugs such as doxorubicin, nanosized drug‐delivery systems capable of selectively delivering and releasing the drug in the diseased tissue are required. We describe nanoparticles (NPs), self‐assembled from a reduction responsive amphiphilic peptide, capable of entrapping high amounts of a redox active anticancer drug candidate and releasing it in presence of a reducing agent. This system shows a high entrapment efficiency with up to 15 mg drug per gram of peptide (5.8 mol‐%). Treatment of the NPs with reducing agent results in the disassembly of the NPs and release of the drug molecules. A reduction in cell viability is observed at drug concentrations above 250 nm in HEK293T and HeLa cell lines. This drug delivery system has potential for targeting tumor sites via the EPR effect while taking advantage of the increased reduction potential in tumor microenvironment.     

Amplified Production of Singlet Oxygen in Aqueous Solution Using Metal Enhancement Effects

Studies involving metal enhancement effects have gained popularity, and enhancement of fluorescence due to the close proximity of a dye molecule to a metal nanoparticle is well documented. Although enhancement of singlet oxygen production by metal has been reported, studies are relatively scarce and so far only stationary silver island films have been proven to be adequate to do so. Herein, we describe the synthesis and characterization of core–shell nanoparticles on which a photosensitizer acting as source of singlet oxygen has been covalently attached to the nanoparticle surface. As a proof of concept, silver nanoparticles with a diameter around 68 nm were chosen as the metallic core, and were coated by a silica shell of about 22 nm in thickness. The silica shell plays a dual role as a spacer and a medium onto which the photosensitizer, rose bengal (RB), has been covalently attached. These novel core–shell nanoparticles allow for the amplification of singlet oxygen production by 3.8 times, which is similar to the amplification found for RB in proximity of silver island films.     

Experimental investigation of nanoparticle dispersion by beads milling with centrifugal bead separation

A new type of beads mill for dispersing nanoparticles into liquids has been developed. The bead mill utilizes centrifugation to separate beads from nanoparticle suspensions and allows for the use of small sized beads (i.e. 15-30 microm in diameter). The performance of the beads mill in dispersing a suspension of titanium dioxide nanoparticle with 15 nm primary particles was evaluated experimentally. Dynamic light scattering was used to measure titania particle size distributions over time during the milling process, and bead sizes in the 15-100 microm range were used. It was found that larger beads (50-100 microm) were not capable of fully dispersing nanoparticles, and particles reagglomerated after long milling times. Smaller beads (15-30 microm) were capable of dispersing nanoparticles, and a sharp peak around 15 nm in the titania size distribution was visible when smaller beads were used. Because nanoparticle collisions with smaller beads have lower impact energy, it was found by X-ray diffraction and transmission electron microscopy that changes in nanoparticle crystallinity and morphology are minimized when smaller beads are used. Furthermore, inductively-coupled plasma spectroscopy was used to determine the level of bead contamination in the nanoparticle suspension during milling, and it was found that smaller beads are less likely to fragment and contaminate nanoparticle suspensions. The new type of beads mill is capable of effectively dispersing nanoparticle suspensions and will be extremely useful in future nanoparticle research.     

AgSbS2 semiconductor-sensitized solar cells

We present a ternary semiconductor nanoparticle sensitizer – AgSbS₂ – for solar cells. AgSbS₂ nanoparticles were grown using a two-stage successive ionic layer adsorption and reaction process. First, Ag₂S nanoparticles were grown on the surface of a nanoporous TiO₂ electrode. Secondly, a Sb–S film was coated on top of the Ag₂S. The double-layered structure was transformed into AgSbS₂ nanoparticles ~ 40 nm in diameter, after post-deposition heating at 350 °C. The AgSbS₂-sensitized TiO₂ electrodes were fabricated into liquid-junction solar cells. The best cell yielded a power conversion efficiency of 0.34% at 1 sun and 0.42% at 0.1 sun. The external quantum efficiency (EQE) spectrum covered the range of 380–680 nm with a maximal EQE of 10.5% at λ = 470 nm. The method can be applied to grow other systems of ternary semiconductor nanoparticles for solar absorbers.