Preparation,Characterization and Controlled Release Investigation of Biocompatible pH-Sensitive PVA/PAA Hydrogels

In the present research hydrogel films based on polyvinyl alcohol (PVA) and polyacrylic acid (PAA) blend, with various crosslink densities, have been prepared through different thermal treatment. The results of FTIR and DSC confirmed quality and quantity of conclusion on miscibility of PVA/PAA blends, respectively. Besides, biocompatibility of the samples has been proved in cytotoxicity tests using L929 cells, according to ISO10993–5. Water uptake of the hydrogel blends is measured. pH sensitivity properties of blends are studied with and without boiling in NaOH solutions where the effect of swelling in water before boiling has also been investigated. Preswellings in water and NaOH concentration have been found to be mainly effective on pH sensitivity of PVA/PAA blends. Biocompatibility and pH sensitivity behavior make these hydrogels appropriate candidates to orally deliver drugs such as insulin and peptides that can be released in basic pH of intestine. The stability of these films in acidic solutions and its expansion and also the consequent release of drugs in basic solutions have been studied by using Teofilin as a model drug by UV-spectrophotometeric measurements.     

Bone regeneration based on nano-hydroxyapatite and hydroxyapatite/chitosan nanocomposites: an in vitro and in vivo comparative study

Surface morphology, surface wettability, and size distribution of biomaterials affect their in vitro and in vivo bone regeneration potential. Since nano-hydroxyapatite has a great chemical and structural similarity to natural bone and dental tissues, incorporated biomaterial of such products could improve bioactivity and bone bonding ability. In this research, nano-hydroxyapatite (23 ± 0.09 nm) and its composites with variety of chitosan content [2, 4, and 6 g (45 ± 0.19, 32 ± 0.12, and 28 ± 0.12 nm, respectively)] were prepared via an in situ hybridization route. Size distribution of the particles, protein adsorption, and calcium deposition of powders by the osteoblast cells, gene expression and percentage of new bone formation area were investigated. The highest degree of bone regeneration potential was observed in nano-hydroxyapatite powder, while the bone regeneration was lowest in nano-hydroxyapatite with 6 g of chitosan. Regarding these data, suitable size distribution next to size distribution of hydroxyapatite in bone, smaller size, higher wettability, lower surface roughness of the nano-hydroxyapatite particles and homogeneity in surface resulted in higher protein adsorption, cell differentiation and percentage of bone formation area. Results obtained from in vivo and in vitro tests confirmed the role of surface morphology, surface wettability, mean size and size distribution of biomaterial besides surface chemistry as a temporary bone substitute.     

Highly stretchable,self-adhesive,and self-healable double network hydrogel based on alginate/polyacrylamide with tunable mechanical properties

A number of synthetic hydrogels suffer from low mechanical strength. Despite of the recent advances in the fabrication of tough hydrogels, it is still a great challenge to simultaneously construct high stretchability, and self-adhesive and self-healing capability in a hydrogel. Herein, a new type of double network hydrogel was prepared based on irreversible cross-linking of polyacrylamide chains and Schiff-base reversible cross-linking between glycidyl methacrylate-grafted ethylenediamine and oxidized sodium alginate (OSA). The combination of both cross-linkings and their synergistic effect provided a novel hydrogel with high strength, stretchable, rapid self-healing, and self-adhesiveness to different material. Besides, the hydrogels with diverse OSA content could maintain their original shapes after loading–unloading tensile test. The resulting hydrogel has a great potential in various fields for supporting and load-bearing substance.     

Investigation of a Biosensor Based on Phenylalanine Dehydrogenase Immobilized on a Polymer‐Blend Film for Phenylketonuria Diagnosis

We investigated a L ‐phenylalanine (L ‐phe) biosensor, functionalized through enzyme immobilization on a polymer‐blend film. The electron mediator 3,4‐dihydroxybenzaldehyde (3,4‐DHB) was employed at the electrode surface to improve direct oxidation of NADH to NAD⁺ and no additional reagents is required to be added to the sample solution. The bioactivated electrode was coated with a semi‐permeable cellulose acetate membrane in order to prevent dissolution of biofunctionalized polymer‐blend film. This constructed enzyme electrode is the first selective biosensor for phenylketonuria (PKU) detection. The sensitivity of the enzyme electrode was determined as 12.014 mA/M cm². The Michaelis–Menten and current responses as well as sensitivity of the electrode showed improved values than those of previous works. This selective biosensor presented an excellent electroanalytical response for L ‐phe, with a high steady‐state current being obtained after 20 s. The sensitivity of our biodevice is quite sufficient for the purpose of PKU detection because the reference range of clinical concern for L ‐phenylalanine concentration is C_{L ‐phe}>0.5 mM. This surface‐bioactivated enzyme electrode retained more than 80 % of its electrocatalytic activity after 16 days.     

Sampling from complex networks with high community structures

In this paper, we propose a novel link-tracing sampling algorithm, based on the concepts from PageRank vectors, to sample from networks with high community structures. Our method has two phases; (1) Sampling the closest nodes to the initial nodes by approximating personalized PageRank vectors and (2) Jumping to a new community by using PageRank vectors and unknown neighbors. Empirical studies on several synthetic and real-world networks show that the proposed method improves the performance of network sampling compared to the popular link-based sampling methods in terms of accuracy and visited communities.     

Experimental Scale Photocatalytic Oxidation SO2 from Simulated Flue Gas in the Presence of Mn/Copper Slag as a Novel Nanocatalyst: Optimizations by Hybrid Box-Behnken Experimental Design and Genetic Algorithm

Russian Journal of Applied Chemistry - One of the most important air pollutants from simulated flue gas is sulfur dioxide (SO2). In this work, experimental scale photocatalytic oxidation of SO2 as...     

Synthesis and Characterization of Doxorubicin-Loaded Poly(Lactide-co-glycolide) Nanoparticles as a Sustained-Release Anticancer Drug Delivery System

The objective of the present study was to prepare a polymeric drug delivery system with no burst effect. To attain this goal, doxorubicin (Dox) as an effective anticancer drug was loaded into poly(lactide-co-glycolide) (PLGA) nanoparticles (NPs) to improve the drug performance and also maximize the release period. After the synthesis process, the freshly made PLGA NPs with two different lactide-to-glycolide ratios (75:25 and 50:50) were evaluated physically and chemically. To determine the encapsulation efficiency, a centrifugation method was applied. Also, the drug loading effect on particle size, polydispersity index, and zeta potential was examined. The results indicated that the NPs had nearly the same diameters around 360?nm, and the entrapment efficiencies for 75:25 PLGA and 50:50 PLGA were reported around 39 and 48?%, respectively. A slight increase in all parameters was observed due to the increase of the drug loading content. The primary release was 7.91?% (w/w) and 14.70?% (w/w) for 75:25 and 50:50 drug-loaded NPs, respectively; no burst effect was observed. After 20?days, the drug release was around 70.98 and 62.22?% of the total entrapped drug for 75:25 and 50:50 drug-loaded NPs, respectively. Finally, it was found that Dox was an appropriate anticancer agent with good capability to be encapsulated in polymeric NPs and could be released from the carriers with no burst effect and favor rate.     

A robust algorithm for computing fluid flows on highly non‐smooth staggered grids

A new method for computing the fluid flow in complex geometries using highly non‐smooth and non‐orthogonal staggered grid is presented. In a context of the SIMPLE algorithm, pressure and physical tangential velocity components are used as dependent variables in momentum equations. To reduce the sensitivity of the curvature terms in response to coordinate line orientation change, these terms are exclusively computed using Cartesian velocity components in momentum equations. The method is then used to solve some fairly complicated 2‐D and 3‐D flow field using highly non‐smooth grids. The accuracy of results on rough grids (with sharp grid line orientation change and non‐uniformity) was found to be high and the agreement with previous experimental and numerical results was quite good. Copyright © 2008 John Wiley & Sons, Ltd.