University of Jordan

About: University of Jordan is a education organization based out in Amman, Jordan. It is known for research contribution in the topics: Population & Health care. The organization has 7796 authors who have published 13764 publications receiving 213526 citations.

Microparacrystals : the intermediate stage between crystalline and amorphous

Abstract: It has been established that “microparacrystals” are the building blocks of materials in the intermediate stage between crystalline and amorphous. A simplified review of the Theory of Paracrystallinity will be given. The analytical procedure for the determination of the paracrystalline distortion parameter,ghkl, and evidence of the existence of paracrystalline structure in various types of materials will be included.g-values > 0 and < 15% characterize the world of paracrystalline materials, which range from catalysts (g ≃ 1%) to polymers (g ≃ 3%), graphites (g ≃ 6%), glasses (g ≃ 12%) and molten metals (g ≃ 15%). Extensive studies ofg and-N, the average number of netplane layers which build up the paracrystal, have led to a fundamental empirical relationα*=N 1/2 g ≃ 0.15. This relation implies physically that the growth of paracrystals in a particular material is controlled appreciably by the level ofg in the netplane structure. Examples on the impact ofg on the behaviour of materials will be given. Relationships betweeng, the crystallinity, and the mechanical properties in polymers will be discussed. The results of our recent investigations on high-modulus Kevlar fibres will be used to demonstrate these relationships.

Stable Chitosan-Based Nanoparticles Using Polyphosphoric Acid or Hexametaphosphate for Tandem Ionotropic/Covalent Crosslinking and Subsequent Investigation as Novel Vehicles for Drug Delivery

Abstract: Chitosan nanoparticles (NPs) are widely studied as vehicles for drug, protein, and gene delivery. However, lack of sufficient stability, particularly under physiological conditions, render chitosan NPs of limited pharmaceutical utility. The aim of this study is to produce stable chitosan NPs suitable for drug delivery applications. Chitosan was first grafted to phthalic or phenylsuccinic acids. Subsequently, polyphosphoric acid (PPA), hexametaphosphate (HMP), or tripolyphosphate (TPP) were used to achieve tandem ionotropic/covalently crosslinked chitosan NPs in the presence of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC). Thermal and infrared traits confirmed phosphoramide bonds formation tying chitosan with the polyphosphate crosslinkers within NPs matrices. DLS and TEM size analysis indicated spherical NPs with size range of 120 to 350 nm. The generated NPs exhibited excellent stabilities under harsh pH, CaCl2, and 10% FBS conditions. Interestingly, DLS, NPs stability and infrared data suggest HMP to reside within NPs cores, while TPP and PPA to act mainly as NPs surface crosslinkers. Drug loading and release studies using methylene blue (MB) and doxorubicin (DOX) drug models showed covalent PPA- and HMP-based NPs to have superior loading capacities compared to NPs based on unmodified chitosan, generated by ionotropic crosslinking only or covalently crosslinked by TPP. Doxorubicin-loaded NPs were of superior cytotoxic properties against MCF-7 cells compared to free doxorubicin. Specifically, DOX-loaded chitosan-phthalate polyphosphoric acid-crosslinked NPs exhibited 10-folds cytotoxicity enhancement compared to free DOX. The use of PPA and HMP to produce covalently-stabilized chitosan NPs is completely novel.