Luminescent Silicon Diatom Replicas: Self‐Reporting and Degradable Drug Carriers with Biologically Derived Shape for Sustained Delivery of Therapeutics

Current development of drug microcarriers is mainly based on spherical shapes, which are not biologically favorable geometries for complex interactions with biological systems. Scalable synthesis of drug carriers with nonspherical and anisotropic shapes featuring sustained drug‐releasing performances, biocompatibility, degradability, and sensing capabilities is challenging. These challenges are addressed in this work by employing Nature's optimized designs obtained from low‐cost diatomaceous earth mineral derived from single‐cell algae diatoms. Silica diatoms with unique shapes and 3D microcapsule morphology are converted into silicon diatom replicas with identical structure by a magnesiothermic reduction process. The results reveal that prepared silicon diatoms have a set of unique properties including favorable microcapsule structure with high surface area and micro/mesoporosity providing high drug loading, fast biodegradability, and intrinsic luminescence, which make them highly suitable for low‐cost production of advanced drug microcarriers. Their sustained drug release >30 days combined with self‐reporting function based on silicon luminescence properties using nonluminescent and luminescent drugs for intravitreal drug therapy is successfully demonstrated. These silicon diatoms offer promising potential toward scalable production of low‐cost and advanced microcarriers for broad medical therapies, including theranostics and microrobotic guided drug delivery devices.     

Novel PEGylated Nanoassemblies Made of Self‐Assembled Squalenoyl Nucleoside Analogues

This study describes a new simple method to obtain high loading of anticancer or antiviral nucleoside analogues into “stealth” poly(ethylene glycol) (PEG)‐coated nanoassemblies. These nanodevices are obtained by co‐nanoprecipitation in water of (i) squalenoyl prodrugs obtained by the bioconjugation of the natural lipid squalene with either the anticancer drug gemcitabine (Gem‐Sq) or the antiviral drug deoxycytidine (ddC‐Sq) with (ii) a PEG derivative of either cholesterol (Chol‐PEG) or squalene (Sq‐PEG). It was found that both PEG derivatives (Chol‐PEG or Sq‐PEG) were efficiently incorporated in the resulting composite nanoassemblies (CNAs), as shown by radioactivity studies, Zeta potential determination, and size measurements. Optimal compositions were defined for each PEG derivative to ensure the best stability in water and in buffer solutions. X‐ray diffraction and electron microscopy investigations revealed that depending on the structure of the squalenoyl nucleoside analogue used (Gem‐Sq or ddC‐Sq), these nanoassemblies might be toroids or cubosomes. Following PEGylation, the Gem‐Sq nanoassemblies displayed superior in vitro anticancer activity on gemcitabine‐resistant leukemia L1210 10K cells than either their non‐PEGylated counterparts or gemcitabine alone.     

Stability and magnetically induced heating behavior of lipid-coated Fe3O4 nanoparticles

Magnetic nanoparticles that are currently explored for various biomedical applications exhibit a high propensity to minimize total surface energy through aggregation. This study introduces a unique, thermoresponsive nanocomposite design demonstrating substantial colloidal stability of superparamagnetic Fe₃O₄ nanoparticles (SPIONs) due to a surface-immobilized lipid layer. Lipid coating was accomplished in different buffer systems, pH 7.4, using an equimolar mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and l-α-dipalmitoylphosphatidyl glycerol (DPPG). Particle size and zeta potential were measured by dynamic laser light scattering. Heating behavior within an alternating magnetic field was compared between the commercial MFG-1000 magnetic field generator at 7 mT (1 MHz) and an experimental, laboratory-made magnetic hyperthermia system at 16.6 mT (13.7 MHz). The results revealed that product quality of lipid-coated SPIONs was significantly dependent on the colloidal stability of uncoated SPIONs during the coating process. Greatest stability was achieved at 0.02 mg/mL in citrate buffer (mean diameter = 80.0 ± 1.7 nm; zeta potential = -47.1 ± 2.6 mV). Surface immobilization of an equimolar DPPC/DPPG layer effectively reduced the impact of buffer components on particle aggregation. Most stable suspensions of lipid-coated nanoparticles were obtained at 0.02 mg/mL in citrate buffer (mean diameter = 179.3 ± 13.9 nm; zeta potential = -19.1 ± 2.3 mV). The configuration of the magnetic field generator significantly affected the heating properties of fabricated SPIONs. Heating rates of uncoated nanoparticles were substantially dependent on buffer composition but less influenced by particle concentration. In contrast, thermal behavior of lipid-coated nanoparticles within an alternating magnetic field was less influenced by suspension vehicle but dramatically more sensitive to particle concentration. These results underline the advantages of lipid-coated SPIONs on colloidal stability without compromising magnetically induced hyperthermia properties. Since phospholipids are biocompatible, these unique lipid-coated Fe₃O₄ nanoparticles offer exciting opportunities as thermoresponsive drug delivery carriers for targeted, stimulus-induced therapeutic interventions.

PACS

7550Mw; 7575Cd; 8185Qr     

Comparative durability study of CFRP strengthened tubular steel members under cold weather

In strengthening systems, the carbon fibre reinforced polymer (CFRP) materials typically have excellent resistance against environmental conditions; however, the performance of adhesives between CFRP and steel is generally affected by various environmental conditions such as marine environment, cold and hot weather. This paper presents the comparative durability study of CFRP strengthened tubular steel structures by using two different adhesives such as MBrace saturant and Araldite K630 under four-point bending. The program consisted of testing twelve CFRP strengthened specimens having treated with epoxy based adhesion promoter, untreated surface and one unstrengthened specimen and conditioned under cold weather for 3 and 6 months to determine the environmental durability. The beams were then loaded to failure in quasi-static manner under four-point bending. The structural responses of CFRP strengthened tubular steel beams were compared in terms of failure load, stiffness and modes of failure. The research findings show that the cold weather immersion had adversely affected the durability of CFRP strengthened steel members. Design factor is also proposed to address the short-terms durability performance under cold weather.     

Isolation and structure determination of new nematicidal triglyceride fromArgemone mexicana

The petroleum ether extract ofArgemone mexicana seeds was found to possess nematicidal activity against the plant parasitic nematodeMeloidogyne incognita. The active nematicidal compound has been isolated from the crude extract by column Chromatographic techniques and purified by TLC. Chemical structure has been determined by chemical and spectro-scopic methods to be that of a triglyceride, sn-glycerol-1-eicosa-9, 12-dien-oate-2-palmitoleate-3-linoleate.     

Synthesis and characterization of crosslinked chitosan immobilized on bentonite and its grafted products with polyaniline

Chitosan immobilized bentonite (CIB) namely chitosan‐coated bentonite (5% chitosan content) was synthesized in 2% acetic acid solution, followed by crosslinking, using epichlorohydrien (ECH). The so‐obtained crosslinked chitosan immobilized on bentonite (CIB‐ECH) and CIB composites were grafted with polyaniline (PANI) through oxidative‐radical copolymerization using ammonium peroxydisulfate in acidic medium to produce PANI‐grafted crosslinked chitosan immobilized on bentonite (PANI‐g‐CIB‐ECH) and PANI‐grafted‐chitosan immobilized on bentonite (PANI‐g‐CIB) composites, respectively. The resultant composites were characterized by using X‐ray diffraction (XRD), thermo gravimetric analysis/differential scanning calorimetry, scanning electron microscopy, Fourier transform infrared (FTIR), and electrical conductivity. XRD and FTIR analyses indicate that chitosan was not intercalated into the silicate layer. Also the electrical conductivity elucidates that the grafted composites fall in the range required for the application as electrostatic dissipation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41078.     

Assessment and Management of a Desert Basin in Kuwait

ABSTRACT

The study area, Umm Gudair, is located in the southwest corner of Kuwait. It occupies an area of ≈ 4.84 × 10⁹ ft². The brackish ground water is derived from the two main aquifers within the Cenozoic sequence. These are: the Kuwait Group aquifer (Miopleistocene) and the Dammam aquifer (Eocene). In the study area, the two aquifers are treated as a single reservoir Forty-one production wells, locally called “dual completion wells” were finished in the aquifers. This research identifies the hydrogeologic properties and the water quality of the aquifers. In addition, the article discusses the application of the surface electrical method Schlumberger configuration to correlate and delineate the areal distribution of the apparent resistivity with the aquifer salinity, and the occurrence of a water-bearing formation. The results will be use for assessment and management of the groundwater reservoir The water quality of the two aquifers is relatively poor The T.D.S. ranges between 3,130-4,740 mg/L. The hydrochemical facies are calcium-sodium cation facies and chloride-sulphate anion facies. The ground water is classified as a NaCl water type, however two genetic water types are identified: the MgCl₂ and CaCl₂ are of marine origin and are old marine formations. The aquifer is semiconfined to confined The average transmissivity, which increases toward the N and N-E, is 20,965 Igpd/ft. The geophysical studies conducted along seven profiles with 19 vertical electrical soundings reveal three distinct layers. The first layer is composed of dry gravel and has a resistivity of 80–220 m. For the second layer, the resistivity ranges between 5–9 Ωm. It is assumed to be a clayey layer saturated with brackish water; whereas the third layer corresponding to a limestone formation, has a resistivity of 25–700Ωm. The apparent resistivity decreases in the direction of the increasing salinity From the flow-net analysis, the amount of ground water entering the aquifer along the border with the Saudi Arabia is 2.3 × 10⁶ Igpd, while the average daily production from the Umm Gudair field is 13.5 × 10⁶ Igpd, It is obvious that the daily abstraction rate is higher than the daily flow toward the aquifer Therefore, in the future, if the daily abstractions continue to exceed the daily water flow through the aquifer a serious decline in the water level will result.