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1.  PEGylated Single-Walled Carbon Nanotubes as Nanocarriers for Cyclosporin A Delivery 
AAPS PharmSciTech  2013;14(2):593-600.
Single-walled carbon nanotubes (SWCNTs) have attracted the attention of many researchers due to their remarkable physicochemical features and have been found to be a new family of nanovectors for the delivery of therapeutic molecules. The ability of these nanostructures to load large amounts of drug molecules on their outer surface has been considered as the main advantage by many investigators. Here, we report the development of a PEGylated SWCNT-mediated delivery system for cyclosporin A (CsA) as a potent immunosuppressive agent. The available OH group in the CsA structure was first linked to a bi-functional linker (i.e., succinic anhydride) in order to provide a COOH terminal group. CsA succinylation process was optimized by using the modified simplex method. The resulting compound, CsA–CO–(CH2)2–COOH, was then grafted onto the exterior surface of SWCNTs, previously PEGylated with phospholipid–PEG5000–NH2 conjugates, through the formation of an amide bond with the free amine group of PEGylated SWCNTs. Drug loading, stability of the PEGylated SWCNT–CsA complex, and in vitro release of the drug were evaluated. Loading efficiencies of almost 72% and 68% were achieved by UV spectrophotometry and elemental analysis methods, respectively. It was observed that 57.3% of cyclosporine was released from CsA–Pl–PEG5000–SWCNTs after 3 days. In this investigation, we conjugated CsA to an amine-terminated phospholipid–polyethylene glycol chain attached on SWCNTs via a cleavable ester bond and demonstrated the possible potential of PEGylated SWCNT-based systems for CsA delivery.
PMCID: PMC3666015  PMID: 23479049
carbon nanotubes; cyclosporin A; drug loading; elemental analysis; functionalization
2.  Study on the Effect of Solution Conditions on Heat Induced-Aggregation of Human Alpha Interferon  
A major problem in the formulation of therapeutic proteins is the irreversible protein aggregation. Recombinant human interferon alpha2b (rhIFNα2b) has poor stability and undergoes physical degradation. The aim of this study was to investigate the effect of solution conditions on the heat-induced aggregation of rhIFNα2b. The protein was incubated for 1 h at 40–70 °C and for up to 240 h at 50 °C and its aggregation tendency was then studied using optical density (at 350 nm), SE-HPLC, dynamic light scattering and SDS-PAGE methods. The effect of various pH (5, 6 and 7) and buffer concentrations (10, 55 and 100 mM) on the aggregation of protein following incubation at 50 °C for 72 h was also evaluated. The results obtained for samples incubated at 50 °C for up to 240 h showed that OD350 and the amount of higher molecular weight aggregates (HMW) increased and the monomer content decreased significantly (p<0.05) as the incubation time increased. Following incubation at various temperatures, a significant increase in OD350, drop in monomer content and increase in the amount of HMW aggregates were observed (p<0.05). Data obtained from incubation of samples at 50 °C for 72 h confirmed that regardless of the buffer concentration, the percentage of monomer at pH 6 was significantly higher than that at pH 7 and pH 5 (p<0.05). At constant pH, although not significant, the same trend was observed when the buffer concentration increased to 100 mM. In conclusion, the change in solution conditions can influence the aggregation extent of rhIFNα2b.
PMCID: PMC3977050  PMID: 24711826
Interferon alpha2b; Thermal aggregation; SE-HPLC; Optical density; SDS-PAGE
3.  Challenges to Design and Develop of DNA Aptamers for Protein Targets. I. Optimization of Asymmetric PCR for Generation of a Single Stranded DNA Library  
Aptamers, or single stranded oligonucleotides, are produced by systematic evolution of ligands by exponential enrichment, abbreviated as SELEX. In the amplification and regeneration step of SELEX technique, dsDNA is conversed to ssDNA. Asymmetric PCR is one of the methods used for the generation of ssDNA. The purpose of this study was to design a random DNA library for selection of aptamers with high affinity for protein targets and develop an efficient asymmetric PCR amplification. Thus, the influence of factors including annealing temperature, number of amplification cycles, primer ratio, Mg2+ concentration and the presence of a PCR enhancer on the amplification of the desired product were evaluated. Results obtained by agarose gel electrophoresis showed that the annealing temperature of 64 °C, Mg2+ concentration of 0.25 mM, reverse to forward primer ratio of 15:1, amplification cycle of 25 and the presence L-ectoin as a PCR enhancer with the concentration of 0.4 M were the optimal conditions. Our results supported that the yield of this type of ssDNA production is sufficient for combinatorial screening of aptamers.
PMCID: PMC3977063  PMID: 24711839
Aptamer; Single stranded DNA; Random pool; SELEX; Asymmetric PCR
4.  Challenges to Improve the Stability and Efficacy of an Intravesical BCG Product  
The aim of this investigation was to improve the storage stability and survival rate of an intravesical BCG product, manufactured with an attenuated strain of Mycobacterium bovis (Pasteur strain 1173P2 of BCG) in the presence of sodium glutamate. Formulations with various concentrations of trehalose (a known protectant) were developed as liquid and lyophilized forms. Formulations were evaluated by different methods, including optical density measurement, safety assessment, skin reaction test, moisture content determination, viability assay, bacterial and fungal contaminations and the results were compared with those obtained for sodium glutamate-containing formulations. The stability tests were also carried out in various storage durations and different temperatures. To develop the lyophilization protocol, glass transition temperatures in the presence of both stabilizers were determined using differential scanning calorimetry. In general, results showed that trehalose could considerably increase the stability of the product against freezing and drying processes, increase the survival rate even in the liquid formulations, as well as the production of an acceptable cake. However, further studies are required to optimize the product characteristics.
PMCID: PMC3977064  PMID: 24711840
Bacillus Calmette-Guérin; BCG; Intravesical; Lyophilization; Trehalose; Mycobacterium bovis
5.  A Reversed Phase High Performance Liquid Chromatographic Method for Determination of Rapamycin  
Easily degradating and various isomeric forms of rapamycin (Sirolimus) face the determination of this compound to many challenges. In this study, we developed and validated the isocratic reversed phase high performance liquid chromatographic (RP-HPLC) method for rapamycin. Separation was performed on a C8 column (MZ, 15 × 4.6 mm, 5 μm particle size) using methanol:water (80:20 v/v) as the mobile phase with the flow rate of 1 mL/min. The column temperature was set at 57°C and the detection was carried out at the wavelength of 277 nm. The method was linear over a concentration range of 0.025-2 μg/mL. The coefficient of variation of intra- and inter-day, assessed at three concentration levels of 0.075, 0.3 and 0.900 μg/mL, was less than 2%. Limit of quantification (LOQ) was found 25 ng/mL. The method with high percent recovery and short retention time of rapamycin, was found to be simple, rapid and reproducible.
PMCID: PMC3813370  PMID: 24250675
Rapamycin; Sirolimus; RP- HPLC; UV detection
6.  Halotolerant Ability and α-Amylase Activity of Some Saltwater Fungal Isolates  
Four halotolerant fungal isolates originating from the saltwater Lake Urmia in Iran were selected during a screening program for salt resistance and α-amylase activity. The isolates were identified based on sequencing the ITS region and a part of the β-tubulin gene, as Penicillium chrysogenum (isolate U1; CBS 132820), Fusarium incarnatum (isolate U2; CBS 132821), and Penicillium polonicum (isolate U3; CBS 132822, and isolate U4; CBS 132823). The growth of these isolates was determined by measuring the colony diameter and mycelia dry weight in Sabouraud dextrose agar and yeast nitrogen base medium supplemented with NaCl, KCl, and LiCl. Isolate U4 showed a growth up in 15% NaCl and U1 was the only isolate that could grow in 20% KCl. None of the strains grew in a media containing LiCl. The salt supplemented medium did not increase the size of colony diameter in all isolates (p > 0.05). The ability of the selected isolates for amylase production was quantitatively tested and showed that P. polonicum isolate U4 was the most potent producer of amylase with a yield of 260.9 U/L after 60 h, whereas P. polonicum isolate U3 was the lowest one with a production level of 97.9 U/L after 48 h. P. polonicum isolate U4 could be a suitable candidate for production of amylase on an industrial scale after optimization.
PMCID: PMC3813371  PMID: 24250679
Isolation; Amylase; Halotolerant; Fungi; Hypersaline environments
7.  Immobilization of Laccase in Alginate-Gelatin Mixed Gel and Decolorization of Synthetic Dyes 
Alginate-gelatin mixed gel was applied to immobilized laccase for decolorization of some synthetic dyes including crystal violet. The immobilization procedure was accomplished by adding alginate to a gelatin solution containing the enzyme and the subsequent dropwise addition of the mixture into a stirred CaCl2 solution. The obtained data showed that both immobilized and free enzymes acted optimally at 50°C for removal of crystal violet, but the entrapped enzyme showed higher thermal stability compared to the free enzyme. The immobilized enzyme represented optimum decolorization at pH 8. Reusability of the entrapped laccase was also studied and the results showed that ca. 85% activity was retained after five successive cycles. The best removal condition was applied for decolorization of seven other synthetic dyes. Results showed that the maximum and minimum dye removal was related to amido black 10B and eosin, respectively.
PMCID: PMC3415199  PMID: 22899898
8.  Optimization of single-walled carbon nanotube solubility by noncovalent PEGylation using experimental design methods 
In this study, noncovalent functionalization of single-walled carbon nanotubes (SWCNTs) with phospholipid-polyethylene glycols (Pl-PEGs) was performed to improve the solubility of SWCNTs in aqueous solution. Two kinds of PEG derivatives, ie, Pl-PEG 2000 and Pl-PEG 5000, were used for the PEGylation process. An experimental design technique (D-optimal design and second-order polynomial equations) was applied to investigate the effect of variables on PEGylation and the solubility of SWCNTs. The type of PEG derivative was selected as a qualitative parameter, and the PEG/SWCNT weight ratio and sonication time were applied as quantitative variables for the experimental design. Optimization was performed for two responses, aqueous solubility and loading efficiency. The grafting of PEG to the carbon nanostructure was determined by thermogravimetric analysis, Raman spectroscopy, and scanning electron microscopy. Aqueous solubility and loading efficiency were determined by ultraviolet-visible spectrophotometry and measurement of free amine groups, respectively. Results showed that Pl-PEGs were grafted onto SWCNTs. Aqueous solubility of 0.84 mg/mL and loading efficiency of nearly 98% were achieved for the prepared Pl-PEG 5000-SWCNT conjugates. Evaluation of functionalized SWCNTs showed that our noncovalent functionalization protocol could considerably increase aqueous solubility, which is an essential criterion in the design of a carbon nanotube-based drug delivery system and its biodistribution.
PMCID: PMC3084320  PMID: 21556348
phospholipid-PEG; D-optimal design; loading efficiency; Raman spectroscopy; scanning electron microscopy; theromogravimetric analysis; carbon nanotubes
9.  Preparing Poly (Lactic-co-Glycolic Acid) (PLGA) Microspheres Containing Lysozyme-Zinc Precipitate Using a Modified Double Emulsion Method 
Lysozyme, as a model protein, was precipitated through the formation of protein-Zn complex to micronize for subsequent encapsulation within poly (lactic-co-glycolic acid) (PLGA) microspheres. Various parameters, including pH, type and concentration of added salts and protein concentration, were modified to optimize the yield of protein complexation and precipitation. The resulting protein particles (lysozyme-Zn complex as a freshly prepared suspension or a freeze-dried solid) were then loaded into PLGA (Resomer® 503H) microspheres, using a double emulsion technique and microspheres encapsulation efficiency and their sizes were determined. It was observed that salt type could significantly influence the magnitude of protein complexation. At the same conditions, zinc chloride was found to be more successful in producing pelletizable lysozyme. Generally, higher concentrations of protein solution led also to the higher yields of complexation and at the optimum conditions, the percentage of pelletizable lysozyme reached to 80%. Taking advantage of this procedure, a modified technique for preparation of protein-loaded PLGA microspheres was established, although it is also expected that this technique increases the protein drugs stabilization during the encapsulation process.
PMCID: PMC3828917  PMID: 24250344
Lysozyme; Microencapsulation; Poly (lactic-co-glycolic acid); Protein micronization; Zinc complexation
10.  An Approach to the Design of a Particulate System for Oral Protein Delivery .II. Preparation and Stability Study of rhGH-Loaded Microspheres in Simulated Gastrointestinal Fluids 
The delivery of therapeutic proteins has gained momentum with development of biotechnology. However, large molecular weight, hydrophilic nature and susceptibility to harsh environment of gastrointestinal tract (GIT) resulted in low absorption. The main objective of this work was the design of a particulate system for oral delivery of recombinant human growth hormone (rhGH) on the basis of particle uptake mechanism in GIT. Biodegradable protein-loaded microspheres were prepared using Resomers (RG207, RG756 and RG505) by double emulsion methods. Aqueous solution of protein and freshly prepared rhGH-zinc complex were used for loading process. Various analytical methods, including fluorescence spectroscopy, SDS-PAGE electrophoresis and reversed-phase chromatography, were set up for the quantification and qualification of rhGH before and after the formulation and fabrication procedures. At the optimum conditions, microspheres were mostly below 10 μm with relatively high protein loading (> 50%). Obtained data showed that the stability of protein did not change during the formulation and microencapsulation processes. Results also showed that the encapsulation process in the presence of zinc caused no detectable change in the protein chemical stability. In-vitro stability study of microspheres in different simulated GI media indicated that the entrapped protein was physically stable. Less than 20% of rhGH was released from the microspheres incubated in both simulated stomach and intestine fluids for 3 and 6 h, respectively.
PMCID: PMC3828920  PMID: 24250342
Microencapsulation; Oral protein delivery; Biodegradable polymer; Microparticle; Resomer®

Results 1-10 (10)