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A hydrated tungsten oxide (WO3·nH2O)-embedded aniline–formaldehyde condensate (AFC/WO3·nH2O) nanocomposite thin film was prepared on an indium tin oxide (ITO)-coated glass surface via vacuum-deposition technique. The resulting AFC/WO3·nH2O/ITO thin film was characterized using ultraviolet–visible spectroscopy (UV–Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), and electron microscopy (SEM). The composite thin film exhibited a crystalline surface morphology containing nanocrystals of WO3·nH2O with a diameter ranging from 15 to 20 nm. The AFC/WO3·nH2O/ITO film allowed for the low potential detection of NO2 gas at a concentration range from 0 to 9000 ppm. The NO2 gas sensing characteristics were studied by measuring the change in the current with respect to concentration and time. The current of the AFC/WO3·nH2O/ITO film linearly increased with an increase in concentration of NO2 gas with a response of ~20 s. [ABSTRACT FROM AUTHOR]

Amphiphilic guar gum grafted with poly(ε-caprolactone) (GG-g-PCL) was fabricated as a drug-delivery carrier using microwave irradiation. The structure of the GG-g-PCL co-polymer was characterized by 1H-NMR spectroscopy. By microwave irradiation, GG-g-PCL with high grafting percentage (>200%) was obtained in a short reaction time. The GG-g-PCL co-polymer is capable of self-assembling into nanosized spherical micelles in aqueous solution with the diameter of around 75–135 nm and 60–100 nm, as determined by DLS and TEM, respectively. The critical micelle concentration (CMC) of GG-g-PCL was found to be approx. 0.56 mg/l in a phosphate buffer solution. The drug-release profile showed that the GG-g-PCL micelles provided an initial burst release followed by a sustained release of the entrapped hydrophobic model drug, ketoprofen, over a period of 10–68 h. Under physiological conditions, the GG-g-PCL co-polymer hydrolytically degraded into lower-molecular-weight fragments within a 7-week period. These results suggest that the GG-g-PCL micelles could be used as a nanocarrier for in vitro controlled drug delivery. [ABSTRACT FROM AUTHOR]

Abstract: Gold (Au) nanoparticles (NPs) stabilized with a monolayer of folate-conjugated poly(l-aspartate-doxorubicin)-b-poly(ethylene glycol) copolymer (Au-P(LA-DOX)-b-PEG-OH/FA) was synthesized as a tumor-targeted drug delivery carrier. The Au-P(LA-DOX)-b-PEG-OH/FA NPs consist of an Au core, a hydrophobic poly(l-aspartate-doxorubicin) (P(LA-DOX)) inner shell, and a hydrophilic poly(ethylene glycol) and folate-conjugated poly(ethylene glycol) outer shell (PEG-OH/FA). The anticancer drug, doxorubicin (DOX), was covalently conjugated onto the hydrophobic inner shell by acid-cleavable hydrazone linkage. The DOX loading level was determined to be 17wt%. The Au-P(LA-DOX)-b-PEG-OH/FA NPs formed stable unimolecular micelles in aqueous solution. The size of the Au-P(LA-DOX)-b-PEG-OH/FA micelles were determined as 24–52 and 10–25nm by dynamic light scattering (DLS) and transmission electron microscopy (TEM), respectively. The conjugated DOX was released from the Au-P(LA-DOX)-b-PEG-OH/FA micelles much more rapidly at pH 5.3 and 6.6 than at pH 7.4, which is a desirable characteristic for tumor-targeted drug delivery. Cellular uptake of the Au-P(LA-DOX)-b-PEG-OH/FA micelles facilitated by the folate-receptor-mediated endocytosis process was higher than that of the micelles without folate. This was consistent with the higher cytotoxicity observed with the Au-P(LA-DOX)-b-PEG-OH/FA micelles against the 4T1 mouse mammary carcinoma cell line. These results suggest that Au-P(LA-DOX)-b-PEG-OH/FA NPs could be used as a carrier with pH-triggered drug releasing properties for tumor-targeted drug delivery. [Copyright &y& Elsevier]

Abstract: Folate-conjugated unimolecular micelles based on amphiphilic hyperbranched block copolymer, Boltorn® H40-poly(l-aspartate-doxorubicin)-b-poly(ethylene glycol)/FA-conjugated poly(ethylene glycol) (H40-P(LA-DOX)-b-PEG-OH/FA), were synthesized as a carrier for tumor-targeted drug delivery. The anticancer drug DOX was covalently conjugated onto the hydrophobic segments of the amphiphilic block copolymer arms by pH-sensitive hydrazone linkage. The size of the unimolecular micelles was determined as ∼17–36 and 10–20nm by dynamic light scattering (DLS) and transmission electron microscopy (TEM), respectively. The release profiles of the DOX from the H40-P(LA-DOX)-b-PEG-OH/FA micelles showed a strong dependence on the environmental pH values. The DOX release rate increased in the acidic medium due to the acid-cleavable hydrazone linkage between the DOX and micelles. Cellular uptake of the H40-P(LA-DOX)-b-PEG-OH/FA micelles was found to be higher than that of the H40-P(LA-DOX)-b-PEG-OH micelles because of the folate-receptor-mediated endocytosis, thereby providing higher cytotoxicity against the 4T1 mouse mammary carcinoma cell line. Degradation studies showed that the H40-P(LA-DOX)-b-PEG-OH/FA copolymer hydrolytically degraded into polymer fragments within six weeks. These results suggest that H40-P(LA-DOX)-b-PEG-OH/FA micelles could be a promising nanocarrier with excellent in vivo stability for targeting the drugs to cancer cells and releasing the drug molecules inside the cells by sensing the acidic environment of the endosomal compartments. [Copyright &y& Elsevier]

Abstract: Folate-conjugated amphiphilic hyperbranched block copolymer (H40–PLA-b-MPEG/PEG–FA) with a dendritic Boltorn® H40 core, a hydrophobic poly(l-lactide) (PLA) inner shell and a hydrophilic methoxy poly(ethylene glycol) (MPEG) and folate-conjugated poly(ethylene glycol) (PEG–FA) outer shell was synthesized as a carrier for tumor-targeted drug delivery. The block copolymer was characterized using 1H NMR and gel permeation chromatography (GPC) analysis. Due to its core–shell structure, this block polymer forms unimolecular micelles in aqueous solutions. The micellar properties of H40–PLA-b-MPEG/PEG–FA block copolymer were extensively studied by dynamic light scattering (DLS), fluorescence spectroscopy, and transmission electron microscopy (TEM). An anticancer drug, doxorubicin in the free base form (DOX) was encapsulated into H40–PLA-b-MPEG/PEG–FA micelles. The DOX-loaded micelles provided an initial burst release (up to 4h) followed by a sustained release of the entrapped DOX over a period of about 40h. Cellular uptake of the DOX-loaded H40–PLA-b-MPEG/PEG–FA micelles was found to be higher than that of the DOX-loaded H40–PLA-b-MPEG micelles because of the folate-receptor-mediated endocytosis, thereby providing higher cytotoxicity against the 4T1 mouse mammary carcinoma cell line. In vitro degradation studies revealed that the H40–PLA-b-MPEG/PEG–FA block copolymer hydrolytically degraded into polymer fragments within six weeks. These results indicated that the micelles prepared from the H40–PLA-b-MPEG/PEG–FA block copolymer have great potential as tumor-targeted drug delivery nanocarriers. [Copyright &y& Elsevier]

Abstract: Multi-arm star amphiphilic block copolymers (SABCs) with approximately 32 arms were synthesized and characterized for drug delivery applications. A hyperbranched polyester, boltorn® H40 (H40), was used as the macroinitiator for the ring-opening polymerization of ɛ-caprolactone (ɛ-CL). The resulting multi-arm H40-poly(ɛ-caprolactone) (H40-PCL-OH) was further reacted with carboxyl terminated methoxy poly(ethylene glycol) (MPEG-COOH) to form H40-PCL-b-MPEG copolymers. The resulting SABCs were characterized by 1H NMR spectroscopy and gel permeation chromatography (GPC). The critical aggregation concentration (CAC) of H40-PCL-b-MPEG was 3.8mg/L as determined by fluorescence spectrophotometry. Below the CAC, stable unimolecular micelles were formed with an average diameter of 18nm as measured by TEM. Above the CAC, unimolecular micelles exhibited agglomeration with an average diameter of 98nm. The hydrodynamic diameter of these agglomerates was found to be 122nm, as measured by dynamic light scattering (DLS). The drug loading efficacy of the H40-PCL-b-MPEG micelles was 26wt%. Drug release study showed an initial burst followed by a sustained release of the entrapped hydrophobic model drug, 5-fluorouracil, over a period of 9–140h. These results indicate that the H40-PCL-b-MPEG micelles have great potential as hydrophobic drug delivery carriers. [Copyright &y& Elsevier]

Abstract: A novel thiolated carboxymethyl chitosan-g-β-cyclodextrin (CMC-g-β-CD) drug delivery carrier was synthesized and characterized. Thiolated CMC-g-β-CD was synthesized using two steps. First, carboxymethyl β-cyclodextrin (CM β-CD) was grafted onto carboxymethyl chitosan (CMC) using water-soluble 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) as the condensing agents. Next, the resultant product was further grafted with cysteine methyl ester hydrochloride (CMEH). Its structure was confirmed by FT-IR and 1H NMR spectral analysis. X-ray diffraction (XRD) analysis on the resulting product showed that the peaks at 2θ =10° and 20° decreased greatly in thiolated polymers, indicating that these polymers are more amorphous in nature. The swelling study showed that the water uptake of thiolated CMC-g-β-CD was higher than that of the unmodified chitosan control. The adhesive properties of thiolated CMC-g-β-CD were evaluated in vitro on a freshly excised mouse mucosa, and a fivefold increase in the adhesion time was found in thiolated CMC-g-β-CD when compared with the unmodified chitosan control. The drug release profile showed that thiolated CMC-g-β-CD tablets provided a slower release of the entrapped hydrophobic model drug, ketoprofen, than the chitosan control, and the release behavior was influenced by the amounts of thiol groups present on the polymer chains. These results suggest that thiolated CMC-g-β-CD with improved mucoadhesive properties may potentially become an effective hydrophobic drug delivery system with controlled drug release capability. [Copyright &y& Elsevier]

Chitosan, a natural based-polymer obtained by alkaline deacetylation of chitin, is nontoxic, biocompatible, and biodegradable. These properties make chitosan a good candidate for the development of conventional and novel drug delivery systems. Chitosan has been found to be used as a support material for gene delivery, cell culture, and tissue engineering. However, practical use of chitosan has been mainly confined to the unmodified forms. For a breakthrough in utilization, especially in the field of controlled drug delivery, graft copolymerization onto chitosan will be a key point, which will introduce desired properties and enlarge the field of the potential applications of chitosan by choosing various types of side chains. Chemical modification of chitosan is useful for the association of bioactive molecules to polymer and controlling the drug release profile. This paper reviews the various methods of preparation of chitosan derivatives intended for controlled drug delivery. From the studies reviewed it is concluded that chitosan derivatives are promising materials for controlled drug and nonviral gene delivery. [ABSTRACT FROM AUTHOR]

Abstract: A 20-mer single-stranded oligodeoxyribonucleotide (ssODNs) was covalently probed onto the nanocomposite electrode, made up of an indium-tin oxide (ITO) glass surface coated with chitosan (CHIT), which is bonded with carboxyl functionalized thiol capped gold nanoparticles (gold-mercaptopropionic acid, Au-MPA NPs). The prepared CHIT/Au-MPA/ITO and the ssODNs/CHIT/Au-MPA/ITO electrodes were characterized with FTIR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry (CV). TEM micrograph of the composite electrode showed that Au-MPA NPs had the diameter ranging from 4 to 16nm. The ssODNs/CHIT/Au-MPA/ITO electrode showed a linear increase in the amperometric current with an increasing concentration of the single-stranded target complementary ODNs (cODNs) within the range of 0.03–325fM. The ssODNs/CHIT/Au-MPA/ITO electrode exhibited a sensitivity of 0.572μA/fM with a response time of 12s. The ssODNs/CHIT/Au-MPA/ITO electrode had a shelf life of ∼182 days, when stored at 4°C. [Copyright &y& Elsevier]