Iron cross-linked carboxymethyl cellulose—gelatin complex coacervate beads for sustained drug delivery

The formation and smooth recovery of ibuprofen encapsulated in microcapsules using gelatin and carboxymethyl cellulose (CMC) complex coacervation without glutaraldehyde were the objectives of this investigation. The microcapsules were recovered as ionically cross-linked beads using aqueous ferric chloride in 50 vol.% of 2-propanol. A physical mixture of CMC/gelatin (FP1) and CMC alone (FP2) beads was also prepared for comparison. The drug-entrapment efficiency of complex coacervate beads (FP3-FP5) was dependent on the drug-to-polymer ratio and was in the range of 86–92 mass %. Beads prepared with the highest ratio of the drug (FP5) exhibited the lowest entrapment. FP1 and FP2 beads exhibited an entrapment efficiency of 98.5 mass % and 91.3 mass %, respectively. Infrared spectroscopy (FTIR) revealed different functional groups in complex coacervate, physical mixture and FP2 beads. Optical and scanning electron microscopy revealed the distinct appearance and surface morphology of the various beads. The stable and crystalline nature of ibuprofen in the beads was confirmed by FTIR and differential scanning calorimetry (DSC), respectively. Ibuprofen release from FP1 and FP2 beads was very slow and unsuitable for oral delivery. The bead prepared by complex coacervation (FP5) showed a better release profile over 48 h and could be developed as a sustained drug delivery system.     

Miniaturization of capillary isoelectric focusing.

Miniaturization of whole-column imaging capillary isoelectric focusing (CIEF) is discussed. A 1.2 cm capillary was used as a separation column for CIEF. The experimental results for the analysis of two pI markers and the protein myoglobin showed that good CIEF separation results could be obtained. Secondly, a light-emitting diode (LED) was used as the light source for the whole-column absorbance imaging detection. The focusing of both the pI markers and myoglobin were observed with the LED light source. The whole-column imaging CIEF instrument was simplified and miniaturized by the use of the LED. Further developments are also discussed.     

Synthesis of polyimides containing triphenylamine‐substituted triazole moieties for polymer memory applications

A series of thermally stable aromatic polyimides containing triphenylamine‐substituted triazole moieties ( AZTA‐PI )s were prepared and characterized. The glass transition temperatures (T_g) of the polyimides were found to be in the range of 262–314 °C. The polyimides obtained by chemical imidization had inherent viscosities of 0.25–0.44 dL g^?1 in N‐methyl‐2‐pyrrolidinone. The number average molecular weights (M_n) and weight average molecular weights (M_w) were 1.9–3.2 × 10⁴ and 3.2–5.6 × 10⁴, respectively, and the polydispersity indices (PDI = M_w/M_n) were in the range of 1.70–1.78. A resistive switching device was constructed from the 4,4′‐hexafluoroisopropylidenediphthalic dianhydride‐based soluble polyimide ( AZTA‐PIa ) in a sandwich structure of indium‐tin oxide/polymer/Al. The as‐fabricated device can be switched from the initial low‐conductivity (OFF) state to the high‐conductivity (ON) state at a switching threshold voltage of 2.5 V under either positive or negative electrical sweep, with an ON/OFF state current ratio in the order of 10⁵ at ?1 V. The device is able to remain in the ON state even after turning off the power or under a reverse bias. The nonvolatile and nonrewritable natures of the ON state indicate that the device is a write‐once read‐many times (WORM) memory. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Upper and lower bounds on subcarrier collision for inter-cell interference scheduler in OFDMA-based systems: Voice traffic

This study investigates upper and lower bounds on subcarrier collision for inter-cell interference (ICI) schedulers in orthogonal frequency division multiple access (OFDMA)-based wireless systems carrying voice traffic. It is shown that the amount of knowledge regarding the reserved resources in the neighboring cell plays a crucial role in the performance of ICI schedulers. Also, it is proven that the upper bound of subcarrier collision for ICI schedulers corresponds to the case which is driven by the absence of knowledge about the reserved resources in the neighboring cell. On the other hand, the lower bound of subcarrier collision for ICI schedulers corresponds to the case which is driven by the perfect knowledge about the reserved resources in the neighboring cell. Based on the lower bound analysis, a minimum expected number of collision scheduler is developed and its performance is investigated as well. Moreover, the impact of scheduling period on the performance of schedulers is examined. Numerical results are presented along with related discussions.     

A bilateral study for the establishment of comparability in the measurement of ethanol in bioethanol fuel using isotope dilution mass spectrometry

A bilateral comparative study between two metrology institutes was conducted for the determination of ethanol in bioethanol fuel by isotope dilution mass spectrometry. Measurement procedures were independently developed by the Health Sciences Authority (Singapore) and the National Institute of Metrology (People??s Republic of China). The methods used included headspace gas chromatography?Chigh-resolution mass spectrometry, headspace gas chromatography?Cmass spectrometry (GC-MS) and direct injection to GC-MS. An investigation of all potential sources of uncertainty, including a component of uncertainty due to the effect of using different instruments such as gas chromatography?Cflame ionization detector method, commonly adopted for the analysis of organic volatiles, was carried out. The results of the analyses are consistent within the associated measurement uncertainty of each laboratory, reported at approximately 95% confidence level.     

Combined ATRP and 'click' chemistry for designing stable tumor-targeting superparamagnetic iron oxide nanoparticles

Important issues in the design of superparamagnetic iron oxide nanoparticles (SPIONs) for cancer diagnosis include stability under physiological conditions and specificity in targeting the cancer cells. In the present study, atom transfer radical polymerization (ATRP) was used to graft SPIONs with poly(glycidyl methacrylate-co-poly(ethylene glycol) methyl ether methacrylate) (SPIONs-P(GMA-co-PEGMA)). The PEGMA in the copolymer chain confers high stability to the nanoparticles in aqueous medium, and prevents recognition by macrophages with the aim of prolonging their in vivo circulation time. The GMA groups were used for conjugating the cancer targeting ligand, folic acid (FA), via 'click' chemistry. Using this method, the amount of FA conjugated to the nanoparticles (SPIONs-P(GMA-co-PEGMA)-FA) can be readily controlled. The specificity of cellular uptake of the nanoparticles by three different cell lines was investigated. The cellular iron uptake by KB cells (human epidermoid carcinoma) after 24 h of incubation is about thirteen and five times higher than those by 3T3 fibroblasts and macrophages, respectively. No significant cytotoxicity was observed with these three types of cells. The high targeting efficiency and biocompatibility of these nanoparticles are promising features for in vivo specific targeting and detection of tumor cells which overexpress the folate receptor.