Current Nanoscience - Volume 11, Issue 2, 2015

This article aims at highlighting the most recent and promising research trends, the open challenges and the possible routes to follow in the field of targeted therapy. A highly interdisciplinary viewpoint has been used, trying to evidence and discuss the different opportunities deriving from recent evolutions of nanotechnology, polymer science, robotics and biotechnology. The most used vectors for nanomedicine applications are described, together with the different action strategies reported in the literature, such as passive targeting, site-directed targeting and remotely triggerable drug delivery. Special emphasis is given to magnetically triggered systems and ultrasound-responsive materials, identified as the most promising paradigms. Key competences and system integration strategies derived from robotics are also introduced, focusing the attention on the crucial issue of achieving high controllability of the vector at the micro- and nano-scale. Finally, biocomponents are described, highlighting their potential as functional sensing elements or smart mechanisms to be integrated on board of advanced micro-nano therapeutic devices. The conclusion aims at depicting the importance of novel and improved targeted therapy strategies, to be coupled with the emerging world of predicting and personalized medicine. To this aim, a real merging of skills and approaches, derived from the aforementioned research fields, is recognized as highly desirable and rich of opportunities.

Doughnut-like nanocomposite colloidal crystal particles with enhanced structural colors were fabricated from monodisperse silica microspheres using droplet templates on polytetrafluoroethylene (PTFE) superhydrophobic surfaces. The structural colors of the doughnut-like particles were greatly enhanced by incorporating carbon black nanoparticles (CB-NPs) into the voids of silica colloidal crystals in the drying self-assembly (DSA) process. The presence of CB-NPs in the structure did not lead to a shift of the reflection band, but enhanced the diffraction color by increased reflectance and suppressed transmission. The lack of physical contact and adhesion to the PTFE superhydrophobic surface allowed the easy detachment of the final assemblies from the substrate, which in turn made possible the large-scale production of the doughnut-like nanocomposite colloidal crystal particles.

Chitosan-silver nanoparticles (CS-AgNP’s) composite films have been synthesized by three different methods. Structure and relaxation properties of nanocomposites films have been analyzed by scanning electron microscopy, thermo-gravimetry analysis, infrared, dielectric spectroscopy and X-ray photoelectron spectroscopies. Two relaxation processes have been detected; in the wet films in the temperature range 25-70°C (with water content between 1-11 wt%, TGA measurements) the α-relaxation associated with the glass-rubber transition has been observed. The second relaxation was observed in the temperature range 80-160°C and it has been identified as the σ-relaxation which is often associated with the hopping motion of ions in the disordered structure of the composite. These relaxation processes and DC conductivity depend upon the method of preparation and concentration of AgNP’s. Based upon the results, a possible mechanism of interaction between AgNP’s and chitosan matrix and the influence of nanoparticles concentration on structure, relaxation and electrical properties have been proposed.

The new Pd-P catalysts for o-CNB hydrogenation obtained by interaction of Pd(acac)2 with white phosphorus in hydrogen, in N,N-dimethylformamide (DMF) under mild conditions were developed and studied. They exhibit higher selectivity to o-chloroaniline (74-94%) compared to Pd-black (56%). The introduction of phosphorus increases selectivity of palladium catalysts, however the activity values and P/Pd ratio are inversely related. The nature and the properties of Pd-P catalysts depend on P/Pd ratio. With the increase of the P/Pd ratio the average size of the particles decreases from 26 nm (for P/Pd = 0) to 5.6 nm (P/Pd = 0.3) and 4.8 nm (P/Pd = 1.0). Nanoparticles formed at P/Pd = 0.3 consist of palladium phosphide Pd6P and clusters Pd(0). Core-shell structure PdxP@Pdn was proposed for them. The Pd(0) clusters in the Pd-P catalyst (P/Pd = 0.3) possess higher electron density (Pd3d5/2 334.52 eV) compared to metallic palladium. With the increase of the P/Pd ratio the fraction of Pd(0) reduces and P-enriched palladium phosphides are formed. The Pd-P catalyst with P/Pd = 1.0 mainly consists of Pd5P2 and PdP2. The Pd(0) content for this catalyst is below 8%. Dimethylammonium dihydro- and hydrophosphates (phosphites) formed via the partial hydrolysis of the solvent – DMF contribute to the stabilization of Pd-P nanoparticles. We suggest that the nature of the catalyst nanoparticles consisting of Pd and PdxP as well as electronic state of Pd(0) clusters are the main factors determining catalytic properties of the Pd-P catalyst in o-CNB hydrogenation.

A magnetic Fe3O4/BiOCl nanocomposite has been prepared by a facile deposition–precipitation process. The microstructure and morphology of this nanocomposite were performed by transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and X-ray diffraction (XRD). The Fe3O4/BiOCl magnetic nanocomposite displays excellent catalytic activity for the photodegradation of RhB under simulated solar light irradiation. Introducing the magnetic materials Fe3O4 in the nanocomposite makes the Fe3O4/BiOCl nanocomposite photocatalyst easily being reused without loss of activity due to its magnetic property. The excellent activity, photo-stability and magnetic recyclability of the nanocomposite photocatalyst reveal that it is a promising candidate for environmental remediation.

In recent years, applications of metal oxide nanoparticles have become increasingly relevant ranging from semiconductor to medical health industries. In work presented here, Ni doped CuO nanoparticles with doping concentrations varying from 0% to 7% have been synthesized via sol-gel combustion route without adding any surfactants or templates. Detailed structural observations by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and Raman studies revealed a highly crystalline single phase monoclinic structure for as-synthesized nanoparticles. The decreasing particle size with increasing Ni content was confirmed by field emission scanning electron microscopy (FESEM) as observed by XRD analysis. An obvious increase of band gap estimated by UV-Vis spectrophotometer with increasing Ni dopant concentration was found. Additionally, an increase in the intensity of luminescent emission was observed with photoluminescence (PL) spectra which can be attributed to the defects in the doped samples. These changes in optical properties as a function of Ni doping could present novel strategies leading to tailored metal oxide nanoparticles for desired applications.

The ZnWO4 photocatalysts doped with different molar ratios of molybdenum ions have been successfully prepared by a facile and effective hydrothermal method. The photocatalytic activities of the as-prepared products were evaluated by the degradation of rhodamine B (RhB) in aqueous solution. The result showed that with the doping of molybdenum ions, the photocatalytic activity of the Mo-doped ZnWO4 photocatalysts were greatly improved. In addition, the best photoactivity was acquired when the Mo-doping molar ratio is 0.05. The doping effects on the properties of ZnWO4 nanoparticles such as particle size, specific surface area, band gap and the photocatalytic performance were systematically discussed.

In this study, two simple and sensitive methods for detection of tigecycline are developed based on thioglycolic acid-capped CdTe quantum dots (TGA-CdTe QDs) and unmodified gold nanoparticles (AuNPs), respectively. The first method was based on the fluorescence quenching of CdTe QDs by the addition of tigecycline. For the second method, the introduction of tigecycline could induce the aggregation of gold nanoparticles, displaying distinct changes in color and in UV-vis spectra. Under optimal conditions, the relative fluorescence intensity of CdTe QDs decreased linearly with the increasing concentration of tigecycline in the range of 0.11-35.56 ug mL-1 with a detection limit of 3.93×10-2 ug mL-1. While the colorimetric sensor could detect tigecycline in linear range from 5.98×10-3 to 1.44×10-1 ug mL-1 and from 0.30 to 2.99 ug mL-1 with a detection limit of 1.07×10-3 ug mL-1. Moreover, both the proposed methods were applied to real sample with satisfactory results. Finally, comparisons between these two methods were made.

In this paper, a facile method to fabricate two-dimensional (2D) Sn nanoparticles is demonstrated. Sn nanoparticles are deposited on porous anodic alumina membrane (PAA) by using thermal vapor deposition (TVD) technique. A set of PAA membranes fabricated under the same conditions was coated with Sn for different periods of time. SEM images showed the formation of hexagonal nanoarrays of Sn around each nanopore following a selective agglomeration growth mechanism on the active dots of the PAA surface. As the deposition time increased from 1 to 3 min, the agglomerated particles height increased from 20 to 75 nm. Moreover, Sn was thermally deposited for 2 min onto PAA substrates of different pore diameters. As the pore diameter increases, the formed Sn particles diameter decreases and their density distribution around each pore is improved, which may be attributed to the dimensions of the active area of the PAA surface. According to reflection spectra, it was found that the oscillation strength of the samples increased as the deposition time increased to 2 min. For the time greater than 2 min, the oscillation strength decreased due to the scattering of light, particularly in the short wavelength region, that caused by the increase of sample roughness.

Chronic wounds and ulcers denote a grave ubiquitous complication, and the bacterial contagions existing in such lesions further impede their successful and swift healing. Wound dressings currently used are far from being ideal. Consequently, there is a demand to design bio responsive material, which not only sets a mechanical aid but also cutbacks microbial load and modulates the complex events of tissue regeneration and morphogenesis by recruiting cells to the wound site. In the current scrutiny, PLGA/Gelatin 70:30 nanofibrous scaffolds laden with gentamicin were prepared by electrospinning. The compatibility between the constituents of the nanofibrous scaffolds was determined by Fourier Transform Infrared Spectroscopy, and the physical state of the constituents was studied by Thermogravimetric analysis. Porosity and swelling index were also calculated and the outcomes revealed a remarkable resemblance to the extracellular matrix. The in vitro drug release studies manifested a constant drug release deprived of burst effect designating that the drug was homogeneously dispersed in the scaffold matrix and there was no significant amount of drug adsorbed onto the surface. This study demonstrated that gentamicin loaded PLGA/Gelatin 70:30 nanofibrous scaffolds have potential to be used as a promising wound dressing material to prevent bacterial infection at the wound site.

We developed cyclic voltammetry (CV)-based screen-printed carbon nanotubes (SP-CNTs) electrode system for the measurement antidiabetic potential of medicinal plants. The antidiabetic potential was measured by the ability of medicinal plant extracts to inhibit α-glucosidase (AG) enzyme that hydrolyses Pnitrophenol- α-D-glucopyranoside (PNPG) to release para-nitrophenol (p-NP). The SP-CNTs electrode system directly measured the released p-NP without any separation and purification steps. The bioactive phenolic compounds of the medicinal plant extracts are implicated to inhibit the enzymatic reaction. The antidiabetic potential of three different medicinal plants, namely, Tebengau (Ehretis laevis), Cemumar (Micromelum pubescens), Kedondong (Sponbias dulcis) and one commercial antidiabetic drug (Acarbose) were measured using the electrode system and excellent sensitivity was obtained (limit of detection 0.5 mg/mL). The results were verified using conventional UV-Vis spectroscopic system and excellent correlation was found (R2 = 0.982, 0.986, 0.976, 0.987 for Tebengau, Cemumar, Kedondong and Acarbose respectively), suggesting the reliability of the system among the three plants. Tebengau plant extracts exhibited the highest inhibition, indicating its potential application as a natural antidiabetic drug. The method is suitable for field level screening of antidiabetic potentials of herbs.

Silicon nanowires based biosensors have garnered great potential in serving as highly sensitive, label-free and real-time response biosensing application. These biosensors are useful in detecting pH, DNA molecules, proteins and even single viruses. In this paper, we report the geometrical characteristics and performance of silicon nanowires array for pH level detection. The nanowires are designed for 40 nm, 50 nm and 60 nm diameter sizes. Top-Down Nanofabrication (TDN) is utilized in the development of resist mask and nanowires formation from silicon on insulator (SOI) wafer involving scanning electron microscope (SEM) based electron beam lithography (EBL). The smallest silicon nanowires structure achieved is 40 nm width and 30 nm height. The corresponding source and drain are fabricated via two aluminum (Al) electrodes on top of the silicon nanowires array using conventional lithography process. A 100 μm microfluidic channel is attached on the silicon nanowires for the sample solution transportation. pH level detection are performed based on several types of standard aqueous pH buffer solutions (pH 4, pH 7, pH 10 and pH 12) to test the electrical response of the sensor. Morphological and electrical responses have been proposed to verify the characteristics of the silicon nanowires array based pH sensor.

Biomaterials are essentially complex viscoelastic composites whose mechanical properties are related to their inter hierarchical structure. Nanoindentation can be used to investigate local material properties by employing a small probe to induce local surface deformation. This technique is recognized as an effective mechanical testing method for biomaterials, facilitating the measurement of time-dependent and viscoelastic mechanical properties. However, it is very difficult to acquire accurate mechanical properties for viscoelastic biomaterials using quasi- static nanoindentation testing techniques due to surface size effects, indenter shape, and force frequency and loading function. However, the dynamic nanoindentation approach has been successfully used to accurately investigate the viscoelastic mechanical properties of some materials. The application of small sinusoidal loading in nanoindentation has been used to investigate the dynamic characteristics of viscoelastic materials, including the storage modulus (E), loss modulus (E“) and loss tangent (tan δ). The objective of this study was to measure the viscoelastic properties of the cuticle of Harmonia axyridis Pallas (multicolored Asian lady beetle) by modulus mapping techniques on different color zones, the black spot region (BSR) and orange region (OR). Herein, the results are discussed in the context of the cuticle microstructure. Twodimensional (2-D) spatial distributions of E and E“ were mapped as functions of frequency in different color zones of Harmonia axyridis Pallas with the aim of shedding light on the nanomechanical properties of key structural features.

Tin oxide (SnO2) nanoparticles are prepared by simple and cost-effective biosynthesis method, wherein, tin chloride (SnCl4) reacts with Bengal gram bean (Cicer arietinum L.) extract. The assynthesized SnO2 nanoparticles were coated onto the glass substrates using doctor blade method to form thin films. The films were further annealed at 250°C and used for characterization and gas sensing applications. Alternatively, the SnO2 nanoparticles were biosynthesized using carbohydrate (starch) and also by chemical precipitation method. A comparative study of structural and morphological properties of chemical and biosynthesized SnO2 nanoparticles is also carried out. Further, room temperature ammonia gas sensing properties of the biosynthesized SnO2 nanoparticles thin films are studied.