Poly(glycerol sebacate) nanoparticles for ocular delivery of sunitinib: physicochemical,cytotoxic and allergic studies

Poly(glycerol sebacate) (PGS) is a new biodegradable polymer with good biocompatibility used in many fields of biomedicine and drug delivery. Sunitinib‐loaded PGS/gelatine nanoparticles were prepared by the de‐solvation method for retinal delivery and treatment of diabetic retinopathy. The nanoparticles were characterised by Fourier‐transform infrared and differential scanning calorimetry. The effects of different formulation variables including drug‐to‐carrier ratio, gelatine‐to‐PGS ratio, and glycerine‐to‐sebacate ratio were assessed on the encapsulation efficiency (EE%), particle size, release efficiency (RE), and zeta potential of the nanoparticles. The in vitro cytotoxicity of PGS/gelatine nanoparticles was studied on L929 cells. Draize test on rabbit eyes was also done to investigate the possible allergic reactions caused by the polymer. Glycerine/sebacic acid was the most effective parameter on the EE and RE. Gelatine‐to‐PGS ratio had the most considerable effect on the particle size while the RE was more affected by the glycerine/sebacic acid ratio. The optimised formulation (S₁ G_0.7 D_21.2) exhibited a particle size of 282 nm, 34.6% EE, zeta potential of −8.9 mV, and RE% of about 27.3% for drug over 228 h. The 3‐(4,5‐dimethylthuazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay indicated PGS/gelatine nanoparticles were not cytotoxic and sunitinib‐loaded nanoparticles were not toxic at concentrations <36 nM.Inspec keywords: polymers, differential scanning calorimetry, toxicology, drug delivery systems, solvation, eye, encapsulation, particle size, drugs, biodegradable materials, nanofabrication, nanomedicine, nanoparticles, gelatin, Fourier transform infrared spectraOther keywords: gelatine‐to‐PGS ratio, glycerine‐to‐sebacate ratio, particle size, zeta potential, sunitinib‐loaded nanoparticles, biodegradable polymer, retinal delivery, differential scanning calorimetry, drug‐to‐carrier ratio, allergic reactions, physicochemistry, cytotoxicity, poly(glycerol sebacate) nanoparticles, sunitinib ocular delivery, drug delivery, sunitinib‐loaded PGS‐gelatine nanoparticles, Fourier‐transform, in vitro cytotoxicity, biocompatibility, Draize test, rabbit eyes, 3‐(4,5‐dimethylthuazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay     

Asphalt colloidal types differentiated by Korcak distribution

Asphalt in a colloidal context can be considered as a sol, sol-gel or gel type where in all three cases the asphaltene particle plays an important role. Usually the three colloidal types can be differentiated by refinery processes or by rheological properties. The aggregation or clustering of the asphaltene particles (or micelles) from sol to sol-gel and finally to the gel state with a fixed lattice can follow the stochastic process of fractal Brownian motion which can fit a hyperbolic (or Korcak) distribution. A test was carried out using the same mass of various asphalts of different colloidal types for floc formation with a series of n-alkanes (dispersion media) of increasing characteristic lengths. Results from floc formation studies indicate that the value of the size distribution for the gel type is small, is higher for the sol-gel type, and is highest for the sol type. On the other hand, the surface irregularities for all three types of asphalt do not have any correlation. These observed facts are consistent with principles based on the fractal approach.     

A High Gain and Low Flicker Noise CMOS Mixer with Low Flicker Noise Corner Frequency Using Tunable Differential Active Inductor

This paper presents the design of a high conversion gain and low flicker noise down conversion CMOS double balanced Gilbert cell mixer using \(0.18\,\upmu \hbox {m}\) CMOS technology. The high conversion gain and low flicker noise mixer is implemented by using a differential active inductor (DAI) circuit and cross-coupled current injection technique within the conventional double-balanced Gilbert cell mixer. A cross-coupled current bleeding circuit is used to inject the current to the switching stage to decrease the flicker noise. Instead of spiral inductor, a DAI with high tunability of the inductor and quality factor is used to tune out the parasitic capacitance effect and decrease the leakage current that has a harmonic component and produce the flicker noise. By tuning the DAI, the flicker noise corner frequency is reduced to 150 Hz. The proposed circuit is simulated with Cadence Spectra and the simulation results shows the NF of 11.2 dB, conversion gain of 23.7 dB and IIP3 of \(-6\)  dB for an RF frequency of 2.4 GHz. The excellent LO-RF, LO-IF, RF-LO and RF-IF isolations of \(-60, -110, -52\) and \(-64\)  dB are achieved respectively. The total power consumption is 10.5 mW from a 1.8 V DC power supply.     

Synthesis of aluminium nanoparticles by arc evaporation of an aluminium cathode surface

Aluminium nanoparticles (Al Nps) are synthesized using arc discharge method by applying direct current between aluminium electrodes in liquid environment without any use of vacuum equipment, heat exchangers, high temperatures furnaces and inert gases. After synthesis of Al Nps, in situ coating process on the nanoparticles was performed immediately. The effects of media on the yield and morphology of aluminium nanoparticles were investigated. Analysis result of the samples indicated that particle size was less than 30 nm, when 120 A/cm² arc current was used. In addition, coating agent can affect arc velocity, arc stability, morphology and composition of the nanoparticles. Resultant nanoparticles were identified using X-ray powder diffraction (XRD), also their surface morphology was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and finally the accuracy of coating was assessed with infrared (IR) spectroscopy.     

Dosimetric characteristic of a new 125I brachytherapy source

A new brachytherapy (125)I source has been investigated at Iranian Agricultural, Medical and Industrial Research School. Dosimetric characteristics [dose-rate constant Λ, radial dose function g(l)(r) and anisotropy function F(r,)] of IRA-(125)I were theoretically determined in terms of the updated AAPM task group 43 (TG-43U1) recommendations. Versions 5 and 4C of the Monte Carlo radiation transport code were used to calculate the dosimetry parameters around the source. The Monte Carlo calculated dose-rate constant of the (125)I source in water was found to be 92×10(-4) Gy h(-1) U(-1) with an approximate uncertainty of ±3 %. Brachytherapy seed model, 6711-(125)I, carrying (125)I radionuclides, was modelled and benchmarked against previously published values. Finally, the calculated results were compared with the published results of those of other source manufacturers.     

Preparation and characterization of foamed polyurethane/silicone rubber/graphite nanocomposite as radio frequency wave absorbing material: The role of interfacial compatibilization

A novel method for the preparation of radio frequency (RF) wave absorber polyurethane foam (PU) has been developed by impregnation of PU foam in n-hexane solution of room temperature vulcanizing (RTV) silicone rubber (SR) hybridized with graphite nanosheets (GNs) called doping solution. Extent of the GNs dispersion was optimized by the incorporation of a specific type of bifunctional compatibilizer. Insulator to conductive transition threshold as well as electromagnetic wave absorption characteristics of the fabricated nanocomposites was shown to be dependent upon the compatibilizer functionality. All PU/SR/GN nanocomposites generated from bifunctional compatibilizer exhibited higher electrical conductivity with enhanced permittivity implying enhanced formation of conductive networks by GN platelets. Permittivity of the PU/SR/GN nanocomposite based on bifunctional compatibilizer showed to be higher than uncompatibilized counterpart. Electromagnetic reflection loss behavior of the PU/SR/GN nanocomposites exhibited a non-linear correlation with the electrical conductivity. Although all PU/SR/GN prepared nanocomposites exhibited electromagnetic wave reflection loss behavior, but this revealed to be affected by the GN level as well as the size and dispersion state of the graphite nanosheets.     

Optical and electrical characterization of CdS thin films

Thin CdS films have been grown by chemical bath (CdCl₂, thiourea, ammonia) deposition (CBD) on SnO₂ (TO)-coated glass substrate for use as window materials in CdS/CdTe solar cells. High-resolution transmission electron microscopy revealed grains with an average size of 10 nm. The structure was predominantly hexagonal with a high density of stacking faults. The film crystallinity improved with annealing in air. Annealing in a CdCl₂ flux increased the grain size considerably and reduced the density of stacking faults. The optical transmission of the as-deposited films indicated a band gap energy of 2.41 eV. Annealing in air reduced the band gap by 0.1 eV. Annealing in CdCl₂ led to a sharper optical absorption edge that remained at 2.41 eV. Similar band gap values were obtained by photocurrent spectroscopy and electroabsorption spectroscopy (EEA) using an electrolyte contact. EEA spectra were broad for the as-deposited and air-annealed samples, but narrower for the CdCl₂-annealed films, reflecting the reduction in stacking fault density. Donor densities of ca. 10¹⁷ cm ^–3 were derived from the film/electrolyte junction capacitance.     

A density-based fuzzy clustering technique for non-destructive detection of defects in materials

In non-destructive testing and evaluation of materials, defects contain visible aggregations of similar levels of brightness with large scale of correlation between them. In most cases, these brightnesses have no notable contrast relative to non-defect counterparts. However, the density and the size of the defect are visually the most notable features. In this paper, we have utilized human conception for classifying defects by the fusion of fuzzy clustering method and fuzzy logic rules based on the density and the size of the defect. The probability of detection and the probability of error are compared with the Bayes classifier. The proposed approach shows that there is less dependency between the variation of density and size of a defect and variations of noise density and distribution. Experimental images from eddy current, ultrasonic and radiography techniques are investigated. It is shown that the new approach reduces the noise and drift, leading to a better detection of defects.