A simple and sensitive HPLC-fluorescence method for the determination of moxifloxacin in human plasma and its application in a pharmacokinetic study.

A simple sample preparation technique coupled with the specific and sensitive fluorescence detection for the determination of moxifloxacin in human plasma was developed and fully validated. Levofloxacin was chosen as an internal standard. Chromatographic separation was achieved using a Shiseido C18 MGII (250×4.6mm i.d.; 5 µm) column under an isocratic mobile phase comprising of 50 mM potassium dihydrogen phosphate (pH 2.4) - acetonitrile (77:23, v/v) at a flow rate of 1.5 mL/min. Fluorescence detection was optimized for the determination of moxifloxacin in human plasma at an excitation wavelength of 296 nm and an emission wavelength of 504 nm. The total chromatographic run time was 8 min with the retention times of moxifloxacin and internal standard at 6.5 and 3.0 min, respectively. Calibration curves were established over the dynamic range of 20-3000 ng/mL. The analytical method was validated as per US-FDA and EMA guidelines for specificity, sensitivity, linearity, accuracy, precision, recovery, hemolytic effect, lipemic effect, dilution integrity and stability. The validated analytical method was successfully applied in a pharmacokinetic study of a single-dose oral administration of a moxifloxacin 400 mg tablet in Thai healthy volunteers.

Curcumin diethyl disuccinate encapsulated in chitosan/alginate nanoparticles for improvement of its in vitro cytotoxicity against MDA-MB-231 human breast cancer cells.

Curcumin diethyl disuccinate (CDD) is a succinate prodrug of curcuminoids that has better stability in human plasma and improved in vitro cytotoxicity compared to curcumin. Therefore, CDD has the potential for further development as an anticancer agent. In this study, we focused on optimization of the formulation of CDD-loaded chitosan/alginate nanoparticles using Box-Behnken statistical design to enhance the therapeutic efficacy of CDD. Oil-in-water emulsification followed by ionotropic gelification was used to prepare the CDD-loaded chitosan/ alginate nanoparticles. A formulation with a 0.05:1 chitosan/alginate mass ratio, 0.65% (w/v) Pluronic F127 and 1.5 mg/ml CDD was found to be optimal. FTIR, TGA and XRD confirmed the encapsulation of CDD molecules in the nanoparticles. In vitro cytotoxicity and cellular uptake studies showed that CDD-loaded chitosan/alginate nanoparticles had significantly higher cytotoxicity and cellular uptake in human breast adenocarcinoma MDA-MB-231 cells, compared to free CDD. Physical and chemical stability studies indicated that the optimally formulated CDD-loaded chitosan/alginate nanoparticles were stable at 4 °C for 3 months.

Biopolymeric alginate-chitosan nanoparticles as drug delivery carriers for cancer therapy.

Nanoparticulate drug delivery systems enhance cancer treatment by direct entry of nanometer particles into the fenestration in the vasculature of cancer cells. Nanoparticles for encapsulation of anticancer drugs are preferably prepared using natural polymers as carriers, with polysaccharides being particularly favorable. Alginate and chitosan polysaccharides have been widely used in nanoparticulate drug delivery systems because of their biodegradable, biocompatible, non-toxic and bioadhesive properties. In this review, we present an overview of drug delivery systems for cancer treatment, describe the use of biopolymeric alginate-chitosan nanoparticles for anticancer drug delivery, and discuss the important characteristics of these nanoparticles for use in drug delivery.

Preparation of curcuminoid niosomes for enhancement of skin permeation.

Curcuminoids (curcumin, desmethoxycurcumin, and bisdesmethoxycurcumin) are major bioactive substances found in turmeric (Curcuma longa L.) extracts and possess antioxidant, anti-inflammatory, antimicrobial and anticancer properties. In this study, curcuminoid niosomes prepared with a series of Span non-ionic surfactants were developed to enhance the skin permeation of curcuminoids. Formulations were evaluated based on aggregation of niosomes, curcuminoid loading, % entrapment efficiency and in vitro permeation of curcuminoids through shed snake skin. Optimal formulations of curcuminoid niosomes including sorbitan monooleate, cholesterol, and Solulan C-24 at a mole ratio of 47.5:47.5:5 were obtained. Up to 11 micromoles of curcuminoids could be loaded in the niosome with a % entrapment efficiency of 83%. About 90% of the niosomes had a diameter of 12.25 +/- 5.00 microm. The niosomes significantly enhanced permeation of curcuminoids compared with a methanolic solution of curcuminoids: 4% of entrapped curcuminoids traversed the shed snake skin, whereas permeation from the methanolic solution was undetectable. The fluxes of curcumin, desmethoxycurcumin, and bisdesmethoxycurcumin were 1.117, 0.263, and 0.057 microg/(cm2h), respectively, consistent with the relative hydrophobicity of curcumin > desmethoxycurcumin > bisdesmethoxycurcumin. In conclusion, our data show that curcuminoids can be successfully formulated as niosomes and that such formulations have improved properties for transdermal delivery.

Chitosan-alginate nanocapsules for encapsulation of turmeric oil.

Turmeric oil is widely used in pharmaceutical and cosmetic applications because of its antibacterial, antifungal, antioxidant, and insect-repellent properties. However, turmeric oil is volatile, insoluble in water and unstable in certain environments, which causes difficulties with formulation development and stability of new products. One approach to overcome these problems is to encapsulate turmeric oil in carriers formed from naturally occurring polysaccharides. Among such polysaccharides, chitosan and alginate have been widely used as particulate carriers for encapsulation and controlled release of bioactive compounds. The potential for size reduction of the carriers to the nanometer scale is of particular interest for delivery systems. In this review, we provide an overview of the versatile properties of turmeric oil and discuss the use of alginate and chitosan for capsule formation and encapsulation of turmeric oil in chitosan-alginate nanocapsules. We also discuss the in vitro skin permeation of turmeric oil from nanocapsules.

Extrahelical cytosine bases in DNA duplexes containing d[GCC](n).d[GCC](n) repeats: detection by a mechlorethamine crosslinking reaction.

The cytosine-cytosine (C-C) pair is one of the least stable DNA mismatch pairs. The bases of the C-C mismatch are only weakly hydrogen bonded, and previous work has shown that, in certain sequence contexts, they can become unstacked from the core helix, and adopt an 'extrahelical' location. Here, using DNA duplexes with d[GCC](n).d[GCC](n) fragments containing C-C mismatches in a 1,4 bp relationship, we show that cytosine bases of different formal mismatch pairs can be crosslinked by mechlorethamine. For example, in the duplex d[CTCTCGCCGCCGCCGTATC].d[GATACGCCGCCGCCGAGAG], where underlined cytosine bases are present as the formal C-C mismatch pairs C(7)-C(32), C(10)-C(29) and C(13)-C(26), we show that two mechlorethamine crosslinks form between C(13) and C(29) and between C(10) and C(32), in addition to crosslinks at C(7)-C(32), C(10)-C(29) and C(13)-C(26) (we have reported previously the crosslinking of formal C-C pairs by mechlorethamine). We interpret the formation of the C(13)-C(29) and C(10)-C(32) crosslinks as evidence of an extrahelical location of the crosslinkable cytosines. Such extrahelical cytosine bases have been observed previously for a single C-C mismatch pair (in the so-called E-motif conformation). In the E-motif, the extrahelical cytosines are folded back towards the 5'-end of the duplex, consistent with our crosslinking data, and also consistent with the absence of C(7)-C(29) and C(10)-C(26) crosslinks in the current work. Hence, our data provide evidence for an extended E-motif DNA (eE-DNA) conformation in short d[GCC](n).d[GCC](n) repeat fragments, and raise the possibility that such structures might occur in much longer d[GCC](n).d[GCC](n) repeat tracts.

DNA interstrand crosslink formation by mechlorethamine at a cytosine-cytosine mismatch pair: kinetics and sequence dependence.

Expansion of the triplet repeat DNA sequence d[CGG]n.d[CCG]n is a characteristic of Fragile X syndrome, a human neurodegenerative disease. Stable intrastrand conformations formed by both d[CGG]n and d[CCG]n, and involving G-G and C-C mismatch pairs, respectively, are believed to be of importance in the development of the disease. We have shown previously that C-C mismatch pairs can be crosslinked covalently by mechlorethamine, a nitrogen mustard alkylating agent, and hence this reaction may be of value as a probe for conformers of d[CCG]n. To characterize the mechlorethamine C-C crosslink reaction further, here we report the kinetics and sequence dependence of formation of the crosslink species, using a series of model duplexes. The rate of reaction depends on the base sequence proximal to the C-C mismatch pair. Hence, in 19mer duplexes containing a central d[M4M3M2M1Cn1n2n3n4].d[N4N3N2N1Cm1m2m3m4] sequence, where M-m and N-n are complementary base pairs, the amount of crosslink increased with increasing G-C content of the eight base pairs neighboring the C-C mismatch and with the proximity of the G-C pairs to the C-C mismatch. Molecular dynamics simulations of the solvated duplexes provided an explanation of these data. Hence, for a C-C pair flanked by G-C base pairs the mismatched cytosine bases remain stacked within the duplex, but for a C-C pair flanked by A-T base pairs, the simulations suggested local opening of the duplex around the C-C pair, making it a less effective target for mechlorethamine.